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1. Spatiotemporal Variability in the Hydrological Regimes and Water Resources of the Ouham River Basin at Batangafo, Central African Republic

Author

Cyriaque Rufin Nguimalet and Didier Orange

Subjects
spatiotemporal variability, hydrological regimes, water resources, Ouham at Batangafo, Bozoum, Bossangoa, Geology, QE1-996.5
Abstract

This paper examines the effect of rainfall decline on water resources in each sub-basin (Bozoum: 8100 km2 and Bossangoa: 22,800 km2) and at the outlet of Batangafo (43,650 km2) over the 1951–1995 period, due to a lack of measurements since 1996. Annual, monthly, and daily series of rainfall and discharges were subjected to statistical tests (rainfall and flow indices, SPI, search for ruptures/breaks, depletion coefficient, and potential groundwater discharge) to present and discuss the rainfall variability impact on the water resources of the whole basin. The average rainfall per sub-basin decreases from the west to the east according to the Ouham river direction: 1423 mm at Bozoum, 1439 mm at Bossangoa, and 1393 mm at Batangafo, the main outlet. The SPI approach provides evidence of a moderate to normal drought in the whole basin in the 1980s, mainly compared to the 1970s. Thus, deficient breaks in the rainfall series of the Ouham Basin at Batangafo were noticed in 1967 (Bossangoa and Batangafo) and 1969 (Bozoum). A declining rainfall of −5% on average tended to have the highest impact on the runoff deficit, from about −30 to −43%. The deficit seems more important from west to east, and is also high over the groundwater in each outlet (−33% at Bozoum, −29% at Bossangoa, and −31% at Batangafo) in the 1986–1995 period, despite rainfall recovery in 1991 having generated a flow increase in 1995 at Bossangoa as well as at Batangafo. At the same time, Chari/Logone at Ndjamena recorded critical discharges in both 1987 (313 m3/s) and 1990 (390 m3/s) before they increased, such as on the Ouham. These results demonstrate the decline in water resources in the Ouham River, and their direct impact on the water level of the Chari River and Lake Chad in the targeted period.

Published
2023
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2. Community Approach for Public Flower Garden Renovation in Hanoi Center: Perspective for Building a Green City

Author

Thai Huyen Nguyen and Didier Orange

Subjects
public flower garden (PFG), Hanoi, landscape design, Blue-Green Infrastructure (BGI), landscape approach, urban living lab (ULL), Hydraulic engineering, TC1-978, Water supply for domestic and industrial purposes, TD201-500
Abstract

Public gardens in urban areas play an important role in the development of physical and mental health of the people. These spaces are also social spaces, where people meet to interact, exchange, and organize collective activities. They create a unique identity for each residential area in the city, which is a premise for green urban development. In Hanoi, public flower gardens (PFGs) were formed and developed from the French colonial period, mainly those in the historic city centre. Facing the forceful urbanization process and the changing of urban structure, in order to evaluate the role of all public flower gardens in the historic city centre area, we carried out a systematic survey from 2019 to 2022. We surveyed all 30 PFGs in five central districts of Hanoi, and interviewed 229 users at these gardens. We also conducted research on relevant documents regarding the management and planning of green space and water infrastructure in the city. Moreover, we implemented an experimental workshop, combining an urban living lab (ULL) approach and an in situ landscape approach, to develop urban landscape design ideas with community participation. Based on the data from this research, this paper analyzes the potential for the establishment of urban blue-green infrastructure (BGI) from these PFGs and aims to evaluate the role of community participation in landscape design for the city. Data from multiple collection methods provide a multi-faceted understanding of the original characteristics of the PFGs in Hanoi and their importance in urban life. The project results supply experimental lessons from urban landscape design activities through community participation, which opens up the potential for developing sustainable urban spaces based on existing natural structures in the city. The main result proves that active community participation until the end of the research project raises public awareness and ensures the social acceptance of the final design. These lessons allow the improvement of urban landscape design practices and the establishment of BGIs from PFGs in an efficient and sustainable manner for green cities in the future.

Published
2023
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3. What Inspiring Elements from Natural Services of Water Quality Regulation Could Be Applied to Water Management?

Author

Magali Gerino, Didier Orange, José Miguel Sánchez-Pérez, Evelyne Buffan-Dubau, Sophie Canovas, Bertrand Monfort, Claire Albasi, and Sabine Sauvage

Subjects
biomimicry, water, natural regulation service, management, Hydraulic engineering, TC1-978, Water supply for domestic and industrial purposes, TD201-500
Abstract

Theoretical and functional ecology is a source of useful knowledge for ecological engineering. The better understanding of the natural service of water quality regulation is now inspiring for optimization of water resource management, restoration and bioremediation practices. This transfer with a biomimicry approach applies particularly well in the urban, rural and agricultural areas, but is yet underexplored for water quality purposes. This natural service intensely involves the benthic boundary layer as a biogeochemical hot spot with living communities. A selection of processes related to the bioturbation phenomena is explored because of their influence on properties of the aquatic environment. The applications are valuable in a range of fields, from water treatment technology to management of ecosystems such as constructed and natural wetlands, streams, rivers, lagoons and coastal ecosystems. This paper gathers the more obvious cases of potential applications of bioturbation research findings on the biomimicry of natural services to water practices. These include pollution pumping by bioturbated sediment, water column oxygen saving during early diagenesis of deposits under conveyors transport and conservation of macroporous as well as fine sediment. Some applications for constructed devices are also emerging, including infiltration optimization and sewage reduction based on cross-biological community involvement.

Published
2022
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4. Density Effect of Eisenia sp. Epigeic Earthworms on the Hydraulic Conductivity of Sand Filters for Wastewater Treatment

Author

Océane Gilibert, Magali Gerino, Dan-Tâm Costa, Sabine Sauvage, Frédéric Julien, Yvan Capowiez, and Didier Orange

Subjects
Eisenia sp., hydraulic conductivity, sand filter, wastewater treatment, Hydraulic engineering, TC1-978, Water supply for domestic and industrial purposes, TD201-500
Abstract

Inside sand filters, as inside other microporous substrates, several invertebrates create temporary burrows that impact on water movement through the filter. Lumbricids Eisenia fetida and Eisenia andrei live under a wide range of environmental conditions and have a high reproduction rate so they are good candidates for ecological engineering tests. We assessed the impact of these species at different densities (0, 100, 500, 1000 g m−2) on the hydraulic conductivity of small-sized experimental filters made of columns filled with filter sand classically used for sanitation mixed with 5% organic matter. The hydraulic conductivity was recorded every 7 days over 37 days in non-saturated conditions. On day 23, 40 g of peat bedding was added at the column surfaces to simulate a surface clogging organic matter pulse input. Columns with an earthworm density equal or superior to 500 g m−2 revealed the highest hydraulic conductivities during the first 21 days. At these densities, the hydraulic conductivity was also restored in less than 7 days after the addition of the surface organic matter, showing the influence of the earthworm species on the resilience capacity of the hydraulic conductivity. It was also highlighted that the hydraulic flow was dependent on the lumbricid densities with an optimal density/effect around 500 g m−2 in this specific substrate composition. This study showed that the feeding habits and burrowing activity of both Eisenia species significantly enhanced the hydraulic flow in a sandy substrate, providing a sustainable solution to limit the clogging of the substrate similar to the one used in filters to treat wastewater.

Published
2022
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5. Are the Fouta Djallon Highlands Still the Water Tower of West Africa?

Author

Luc Descroix, Bakary Faty, Sylvie Paméla Manga, Ange Bouramanding Diedhiou, Laurent A. Lambert, Safietou Soumaré, Julien Andrieu, Andrew Ogilvie, Ababacar Fall, Gil Mahé, Fatoumata Binta Sombily Diallo, Amirou Diallo, Kadiatou Diallo, Jean Albergel, Bachir Alkali Tanimoun, Ilia Amadou, Jean-Claude Bader, Aliou Barry, Ansoumana Bodian, Yves Boulvert, Nadine Braquet, Jean-Louis Couture, Honoré Dacosta, Gwenaelle Dejacquelot, Mahamadou Diakité, Kourahoye Diallo, Eugenia Gallese, Luc Ferry, Lamine Konaté, Bernadette Nka Nnomo, Jean-Claude Olivry, Didier Orange, Yaya Sakho, Saly Sambou, and Jean-Pierre Vandervaere

Subjects
Fouta Djallon, water tower, depletion (or recession) coefficient, runoff coefficient, soil water holding capacity, basement, Hydraulic engineering, TC1-978, Water supply for domestic and industrial purposes, TD201-500
Abstract

A large share of surface water resources in Sahelian countries originates from Guinea’s Fouta Djallon highlands, earning the area the name of “the water tower of West Africa”. This paper aims to investigate the recent dynamics of the Fouta Djallon’s hydrological functioning. The evolution of the runoff and depletion coefficients are analyzed as well as their correlations with the rainfall and vegetation cover. The latter is described at three different space scales and with different methods. Twenty-five years after the end of the 1968–1993 major drought, annual discharges continue to slowly increase, nearly reaching a long-term average, as natural reservoirs which emptied to sustain streamflows during the drought have been replenishing since the 1990s, explaining the slow increase in discharges. However, another important trend has been detected since the beginning of the drought, i.e., the increase in the depletion coefficient of most of the Fouta Djallon upper basins, as a consequence of the reduction in the soil water-holding capacity. After confirming the pertinence and significance of this increase and subsequent decrease in the depletion coefficient, this paper identifies the factors possibly linked with the basins’ storage capacity trends. The densely populated areas of the summit plateau are also shown to be the ones where vegetation cover is not threatened and where ecological intensification of rural activities is ancient.

Published
2020
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6. Recent Budget of Hydroclimatology and Hydrosedimentology of the Congo River in Central Africa

Author

Alain Laraque, Guy D. Moukandi N’kaya, Didier Orange, Raphael Tshimanga, Jean Marie Tshitenge, Gil Mahé, Cyriaque R. Nguimalet, Mark A. Trigg, Santiago Yepez, and Georges Gulemvuga

Subjects
hydroclimatology, hydrosedimentology, hydrogeochemical, Congo River Basin, Hydraulic engineering, TC1-978, Water supply for domestic and industrial purposes, TD201-500
Abstract

Although the Congo Basin is still one of the least studied river basins in the world, this paper attempts to provide a multidisciplinary but non-exhaustive synthesis on the general hydrology of the Congo River by highlighting some points of interest and some particular results obtained over a century of surveys and scientific studies. The Congo River is especially marked by its hydrological regularity only interrupted by the wet decade of 1960, which is its major anomaly over nearly 120 years of daily observations. Its interannual flow is 40,500 m3 s−1. This great flow regularity should not hide important spatial variations. As an example, we can cite the Ubangi basin, which is the most northern and the most affected by a reduction in flow, which has been a cause for concern since 1970 and constitutes a serious hindrance for river navigation. With regard to material fluxes, nearly 88 × 106 tonnes of material are exported annually from the Congo Basin to the Atlantic Ocean, composed of 33.6 × 106 tonnes of TSS, 38.1 × 106 tonnes of TDS and 16.2 × 106 tonnes of DOC. In this ancient flat basin, the absence of mountains chains and the extent of its coverage by dense rainforest explains that chemical weathering (10.6 t km−2 year−1 of TDS) slightly predominates physical erosion (9.3 t km−2 year−1 of TSS), followed by organic production (4.5 t km−2 year−1 of DOC). As the interannual mean discharges are similar, it can be assumed that these interannual averages of material fluxes, calculated over the longest period (2006–2017) of monthly monitoring of its sedimentology and bio-physical-chemistry, are therefore representative of the flow record available since 1902 (with the exception of the wet decade of 1960). Spatial heterogeneity within the Congo Basin has made it possible to establish an original hydrological classification of right bank tributaries, which takes into account vegetation cover and lithology to explain their hydrological regimes. Those of the Batéké plateau present a hydroclimatic paradox with hydrological regimes that are among the most stable on the planet, but also with some of the most pristine waters as a result of the intense drainage of an immense sandy-sandstone aquifer. This aquifer contributes to the regularity of the Congo River flows, as does the buffer role of the mysterious “Cuvette Centrale”. As the study of this last one sector can only be done indirectly, this paper presents its first hydrological regime calculated by inter-gauging station water balance. Without neglecting the indispensable in situ work, the contributions of remote sensing and numerical modelling should be increasingly used to try to circumvent the dramatic lack of field data that persists in this basin.

Published
2020
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7. Temporal Variability of Sediments, Dissolved Solids and Dissolved Organic Matter Fluxes in the Congo River at Brazzaville/Kinshasa

Author

Guy Dieudonne Moukandi N’kaya, Didier Orange, Sandra Murielle Bayonne Padou, Pankyes Datok, and Alain Laraque

Subjects
discharge, TSS, TDS, DOC, matter fluxes, Congo River, Geology, QE1-996.5
Abstract

For three decades, the solid and dissolved fluxes of the Congo River have been regularly monitored on a monthly basis, despite 12 years of deficiencies (1994–2005). Two programs successively carried out these follow-ups: PEGI/GBF (1987–1993) and SO HYBAM (2006–2017), upstream and downstream, respectively, of the Malebo Pool near Brazzaville, the main hydrometric station of the Congo River. The objective of this study is to examine the temporal dynamic of TSS, TDS and DOC, to explore how these descriptors change over time. Comparison with the two time programs will shed more light on how these descriptors are related to discharge. Afterward, we then find a relationship between total TSS in the water column and that measured in surface for eventual estimation of TSS by remote sensing. In the last decade, compared to the PEGI/GBF period, the discharge of the Congo River was mainly marked by a 4% increase, leading to a significant change on TDS and DOC behaviors. The TSS was quite stable (from 8.2 and 9.3 t km−2 yr−1) due to the low physical erosion well known in this region. The TDS concentrations decreased slightly, by a simple dilution effect. However, the mineral dissolved fluxes (from 11.6 and 10.1 t km-2 yr-1) due to the chemical weathering and atmospheric inputs still predominate over the solid fluxes. Therefore, there was no radical change in the monthly geochemical regime of Congo River Basin (CRB) during these last 30 years. Contrariwise, the DOC concentration marking the biogeochemical processes significantly increased, from 9.0+/−3.0 mg L−1 to 12.7+/−5.0 mg L−1, due to more flooding events in the central part of the CRB. The change for the DOC fluxes is more relevant, with an increase of 45% between the two studied periods, from 11.1 × 106 to 16.2 × 106 t yr−1. This highlights the continuous and actual importance of the “Cuvette Centrale” in the heart of the CRB for dissolved organic matter transport by the Congo River.

Published
2020
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8. A Modeling Approach to Diagnose the Impacts of Global Changes on Discharge and Suspended Sediment Concentration within the Red River Basin

Author

Xi Wei, Sabine Sauvage, Thi Phuong Quynh Le, Sylvain Ouillon, Didier Orange, Vu Duy Vinh, and José-Miguel Sanchez-Perez

Subjects
Red River, SWAT model, hydrology, suspended sediment, dam impacts, climate, Hydraulic engineering, TC1-978, Water supply for domestic and industrial purposes, TD201-500
Abstract

The Red River basin is a typical Asian river system affected by climate and anthropogenic changes. The purpose of this study is to build a tool to separate the effect of climate variability and anthropogenic influences on hydrology and suspended sediments. A modeling method combining in situ and climatic satellite data was used to analyze the discharge (Q) and suspended sediment concentration (SSC) at a daily time scale from 2000 to 2014. Scenarios of natural and actual conditions were implemented to quantify the impacts of climate variability and dams. The modeling gained satisfactory simulation results of water regime and SSC compared to the observations. Under natural conditions, the Q and SSC show decreasing tendencies, and climate variability is the main influence factor reducing the Q. Under actual conditions, SSC is mainly reduced by dams. At the outlet, annual mean Q got reduced by 13% (9% by climate and 4% by dams), and annual mean SSC got reduced to 89% (13% due to climate and 76% due to dams) of that under natural conditions. The climate tendencies are mainly explained by a decrease of 9% on precipitation and 5% on evapotranspiration, which results in a 13% decrease of available water for the whole basin.

Published
2019
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10. Spatio-temporal analysis of soil surface hydraulic properties in a semi-arid agroforestry system of the Senegalese groundnut basin

Author

Waly Faye, Didier Orange, Seydou Talla, Frederic Do, Christophe Jourdan, Olivier Roupsard, Abdoulaye Faty, Awa Niang, Alioune Kane, Simone Di prima, Raphael Angulo-Jaramillo, and Laurent Lassabatere

Abstract

In Senegal, the groundnut basin is the main agricultural region under a semi-arid climate, heavily cultivated in an agrarian system combining agricultural rotation and agroforestry dominated by Faidherbia albida trees. The soils of the groundnut basin, essentially sandy, have a low water retention capacity. In this area, water is a limiting factor, and the climate variability represents an additional constraint on an already precarious agricultural production system. It is therefore essential to improve knowledge on water saving practices and soil humidity dynamics. The management of water resources in agricultural fields requires reliable information about soil hydraulic properties, which control the partition of rainfall into infiltration and runoff, and their spatio-temporal variability. To investigate the variability of soil hydraulic parameters we have carried out infiltration measurement in open space without tree and below tree canopies. A total of 24 infiltration measurements were carried out using an automatic single-ring infiltrometer in the nearby of each plot (4 measurements × 6 plots), and after removing the first 10 cm of uncompacted sand. The infiltration tests were carried out in June, October and December, respectively before, during and after the crop season. We used the Beerkan Estimation of Soil Transfer Parameters (BEST) method to retrieve the soil hydraulic parameters from infiltrometer data and field measurements of soil porosity, initial and saturated soil water contents and soil bulk density. The statistical analysis of the data showed a high variability during the cultivating period, both in time and space, especially of the saturated soil hydraulic conductivity Ks. However, the Ks seems higher under tree cover, around 0.186 mm/s, for 0.167mm/s without any tree canopy influence. Despite the expected homogeneity of the investigated sandy soil, the presence of the perennials triggered a patchy distribution of soil hydraulic conditions. These preliminary results evidenced the importance of taking into account parameters variability and landscape structure when simulating soil water dynamics in the Senegalese groundnut basin.

Published
2023

13. Estimating water fluxes in the critical zone using water stable isotope approaches in the Groundnut and Ferlo basins of Senegal

Author

Djim M. L. Diongue, Christine Stumpp, Olivier Roupsard, Didier Orange, Frederic C. Do, Serigne Faye, Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), Universität für Bodenkultur Wien = University of Natural Resources and Life [Vienne, Autriche] (BOKU), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro Montpellier, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Département Performances des systèmes de production et de transformation tropicaux (Cirad-PERSYST), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), LMI IESOL Intensification Ecologique des Sols Cultivés en Afrique de l’Ouest [Dakar] (IESOL), Institut de recherche pour le développement (IRD [Sénégal]), CIRAD/IRD/EDEQUE, U-LEAP-Agri (RAMSES II),EU-DESIRA (CASSECS), TOTAL Foundations (DSCATT), CGIAR (GLDC), ANR-11-LABX-0010,DRIIHM / IRDHEI,Dispositif de recherche interdisciplinaire sur les Interactions Hommes-Milieux(2011), and European Project: 861974, H2020,SOCIETAL CHALLENGES - Food security, sustainable agriculture and forestry, marine, maritime and inland water research, and the bioeconomy,SustainSahel(2020)

Subjects
water balance, recharge, semi-arid, evapotranspiration, stable isotopes, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Water Science and Technology
Abstract

Sustainable water management in semi-arid agriculture practices requires quantitative knowledge of water fluxes within the soil-vegetation-atmosphere system. Therefore, we used stable-isotope approaches to evaluate evaporation (Ea), transpiration (Ta), and groundwater recharge (R) at sites in Senegal's Groundnut basin and Ferlo Valley pasture region during the pre-monsoon, monsoon, and post-monsoon seasons of 2021. The approaches were based upon (i) the isothermal evaporation model (for quantifyingEa); (ii) water and isotope mass balances (to partitionEaandTafor groundnut and pasture); and (iii) the piston displacement method (for estimating R).Ealosses derived from the isothermal evaporation model corresponded primarily to Stage II evaporation, and ranged from 0.02 to 0.09 mm d−1in the Groundnut basin, versus 0.02–0.11 mm d−1in Ferlo. At the groundnut site,Earates ranged from 0.01 to 0.69 mm d−1;Tawas in the range 0.55–2.29 mm d−1; and theTa/ETaratio was 74%–90%. At the pasture site, the ranges were 0.02–0.39 mm d−1forEa; 0.9–1.69 mm d−1forTa; and 62–90% forTa/ETa. TheETavalue derived for the groundnut site via the isotope approach was similar to those from eddy covariance measurements, and also to the results from the previous validated HYDRUS-1D model. However, the HYDRUS-1D model gave a lowerTa/ETaratio (23.2%). The computed groundwater recharge for the groundnut site amounted to less than 2% of the local annual precipitation. Recommendations are made regarding protocols for preventing changes to isotopic compositions of water in samples that are collected in remote arid regions, but must be analysed days later. The article ends with suggestions for studies to follow up on evidence that local aquifers are being recharged via preferential pathways.

Published
2023

15. Ecohydrologie urbaine et changement climatique

Author

Didier Orange, Pascal Breil, and Abdoulaye Faty

Subjects
QE1-996.5, education.field_of_study, Population, Climate change, Geology, General Medicine, Environmental sciences, Water resources, Urban planning, Effects of global warming, Ecohydrology, Environmental science, GE1-350, Land use, land-use change and forestry, Surface runoff, education, Environmental planning
Abstract

Due to global change, cities of the future will have to deal with more intense runoff and longer drought sequences, in addition to a growing urban and peri-urban population. French Mediterranean cities, such as Toulon, are already densely urbanised and exposed to the effects of global warming. The adaptation of their infrastructures is problematic. Cities with high development potential, such as Dakar, offer the opportunity to imagine other solutions for the management of water resources and its extremes in the context of global change. In particular, it is a question of managing the flows of water and substances linked to intense runoff events according to an ecohydrological logic that makes it possible to reduce environmental risks and increase social and economic benefits. To do this, we use a hydrologically-based geomatics model (IRIP) that produces predictive maps of areas of generation, transfer and accumulation of intense runoff and associated nutrients. This allows us to target effective intervention areas to reduce risks and increase water resources, for example by simulating land use change in appropriate locations and at the same time stimulating specific biological processes. The fundamental principle of ecohydrology is to balance energy flows with biological metabolic flows at the sub-catchment scale. The mapping of intense runoff processes is a first step illustrated in this article for the cities of Toulon and Dakar. This first step is part of the Dakar'2030 project, which aims to rethink urban development and adapt it to climate change.

Published
2021

17. Comparing the performances of Pedotransfer Functions with Hydrus 1D Inverse Parameters Estimation in a deep cultivated sahelian soil

Author

Djim M L Diongue, Frederic C Do, Christine Stumpp, Didier Orange, Christophe Jourdan, Sidy Sow, Serigne Faye, and Olivier Roupsard

Subjects
sahel, soil water balance, soil
Abstract

Knowledge about soil water balance and ecosystem water partitioning is crucial for managing soils in semi-arid areas like the Sahel, but hydraulic parameters are hardly available to run either parsimonious or detailed process models. This study aims at bridging this parameterization gap in a typical deep (> 2m) loamy sand soil from the groundnut basin in Senegal[1]. Five approaches of soil hydraulic parameterization with a range of different complexity were compared: (1) the lookup table of Carsel and Parrish (1988) that use only the soil texture class known as “Class PTFs”, (2) Rosetta PTFs from only topsoil characterization, (3) Rosetta PTFs with a detailed multilayer soil characterization, and inverse estimation from soil moisture using Hydrus-1D, considering the soil column either as (4) a single soil material and (5) with three-layered soil material. We compared the predicted (i) soil water content (SWC) with high-frequency measurements from 15 cm down to 200 cm deep and (ii) actual evapotranspiration (ET) with Eddy Covariance (EC) data during four consecutive growing seasons under a rotation of pearl millet and peanut crops. The simplest methods (1 & 2) resulted in a significant bias of the predicted SWC, with, however, some predictive ability of Method 2 to simulate the general trends of Swc, especially under peanut crops. Method 3 behaved reasonably with average RMSE for SWC, varying between 0.029 and 0.023 cm-3 cm-3. Method 4 further improved the predictions with RMSE ranging from 0.013 to 0.020 cm-3 cm-3. The best agreement was found under peanut using Method 5 (RMSE ≤ 0.013 cm3 cm-3). Methods 3, 4 or 5 behaved satisfactorily for predicting ET whatever the crop, e.g. Method 4 (RMSE= 0.05 cm day-1, NSE= 0.9 and R²= 0.93) for pearl millet.We showed that inverse modelling should be preferred over using PTFs when studying water fluxes and evapotranspiration in cultivated Sahelian soils. [1] Faidherbia-Flux (FLUXNET: SN-Nkr): https://lped.info/wikiObsSN/?Faidherbia-Flux

Published
2022

18. Evaluation of parameterisation approaches for estimating soil hydraulic parameters with HYDRUS-1D in the groundnut basin of Senegal

Author

Djim M. L. Diongue, Olivier Roupsard, Frederic C. Do, Christine Stumpp, Didier Orange, Sidy Sow, Christophe Jourdan, Serigne Faye, Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro Montpellier, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Département Performances des systèmes de production et de transformation tropicaux (Cirad-PERSYST), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), LMI IESOL Intensification Ecologique des Sols Cultivés en Afrique de l’Ouest [Dakar] (IESOL), Institut de recherche pour le développement (IRD [Sénégal]), Universität für Bodenkultur Wien = University of Natural Resources and Life [Vienne, Autriche] (BOKU), Université Gaston Berger de Saint-Louis Sénégal (UGB), scholarship from CIRAD, Faidherbia-Flux received funding from EU-LEAP-Agri (RAMSES II), EU-DESIRA (CASSECS), EU- H2020 (SustainSahel), AGROPOLIS and TOTAL Foundations (DSCATT), CGIAR (GLDC), European Project: 861974, H2020,SOCIETAL CHALLENGES - Food security, sustainable agriculture and forestry, marine, maritime and inland water research, and the bioeconomy,SustainSahel(2020), and European Project: 32851,RAMSES II

Subjects
[SDV.SA]Life Sciences [q-bio]/Agricultural sciences, evapotranspiration, soil hydraulic parameters, loamy sand soil, Propriété hydraulique du sol, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, Évapotranspiration, Sahelian cropping system, soil moisture, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, P10 - Ressources en eau et leur gestion, Teneur en eau du sol, HYDRUS-1D, Hydrologie, Water Science and Technology
Abstract

Soil hydraulic parameters (SHPs) required as inputs for numerical models are scarce in Sahelian regions. Instead, they are estimated using pedotransfer functions (PTFs), but their ability to simulate soil water dynamics has not been evaluated. This study aims to parameterize SHPs with seven different PTFs and inverse modelling to examine their ability to simulate water fluxes in Senegal’s Groundnut basin. We used four years of field measurements of soil water content (SWC) and actual evapotranspiration (ETa) under pearl millet and groundnut crop rotation for model evaluation. Inverse modelling for SWC (root mean square error [RMSE] ≤ 0.015 cm3 cm−3) and ETa (RMSE ≤ 0.62 mm d−1) yielded the best model performance compared to PTFs (0.024–0.175 cm3 cm−3 and 0.68–0.96 mm d−1, respectively). Where field measurements are lacking for inverse estimation, three of the seven tested PTFs yielded good modelling results and could be used as a parsimonious approach for cultivated Sahelian soils.

Published
2022
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20. Influence of trees and topography on soil water content in semi-arid region, the case of an agro-silvo-pastoral ecosystem dominated by Faidherbia albida (Senegal)

Author

Christophe Jourdan, Serigne Faye, Djim M. L Diongue, Frederic C. Do, Olivier Roupsard, Waly Faye, Christine Stumpp, Awa Niang Fall, and Didier Orange

Subjects
biology, Faidherbia albida, Agroforestry, Soil water, Environmental science, Ecosystem, biology.organism_classification, Arid
Abstract

Vegetation strongly affects the water cycle, and the interactions between vegetation and soil moisture are fundamental for ecological processes in semiarid regions. Therefore, characterizing the variation in soil moisture is important to understand the ecological sustainability of cropping systems towards food security. The present study aims at exploring factors and mechanisms influencing soil moisture variability in the Faidherbia albida (FA) parkland at Sob basin located in the center of Senegal [1]. Volumetric soil moisture content at multiple depths was monitored at 15 locations distributed along a transect (upper slope, mid-slope and lower slope) and different FA tree position (under, at the limit and outside canopy) from August to October 2020. A portable TRIME Time Domain Reflectometry (TDR) Tube Probe (IMKO, Germany) was used to determine soil volumetric moisture content while being placed at specific depth intervals inside a PVC access tube set up at each location. Soil moisture was monitored at 10 cm interval from 20 to 420 cm during the rainy season from July to October 2020. Results of soil moisture profiles along the transects exhibit two main zones based on the standard deviation (SD) and the inflection of the coefficient of variation (CV): shallow soil moisture (SSM) and deep soil moisture (DSM). For SSM observed at 20-60 cm of the soil layer, both mean soil moisture and SD increase with depth, the lowest mean value (8%) being observed at the top surface. This soil layer is influenced by rainfall infiltration and daily evaporation. For DSM observed at 70-420 cm, the moisture pattern can be further divided into 4 soil sublayers taking the mean soil moisture vertical distribution as reference: (i) a rainfall infiltration layer (70-160 cm) which appears mainly influenced by cumulative rainfall infiltration in addition to transpiration of grassland and crops (shallow root system); (ii) a rainfall-transpiration layer (170-250 cm) which is still an infiltration layer but more influenced by crops transpiration; (iii) a transpiration layer (260-350 cm) which can be recharged by rainfall infiltration during heavy rainfall and supply deep root system; and (iv) deep transpiration layer (360-400 cm) which has DSM that can be influenced by extremely deep root vegetation such as FA. The factors influencing the soil water content varied with the topography. The soil water content SWC (mean and median value of 27.2 and 29.6% respectively) in the lower slope was significantly higher than that at middle (mean and median value of 14.4 and 13.2 % respectively) and upper slope (mean and median value of 16.8 and 18.4 % respectively). At last, soil water content was positively correlated with the distance from the FA, regardless the slope. The higher water content for both SSM and DSM was observed outside the FA canopy. This result refutes the initial hypothesis of higher SWC under trees and support a more detailed analysis of the infiltration capacity in relationship with the FA position. [1] Faidherbia-Flux : https://lped.info/wikiObsSN/?Faidherbia-Flux

Published
2021

21. Potential impact of Faidherbia albida tree on soil infiltration in a semi-arid agroforestry system of the Senegalese groundnut basin: role of preferential flows?

Author

Simone Di Prima, Olivier Roupsard, Djim M. L Diongue, Christophe Jourdan, Laurent Lassabatere, Alioune Kane, Serigne Faye, Waly Faye, Awa Niang Fall, Frederic C. Do, Rafaele Angulo-Jaramillo, and Didier Orange

Subjects
Potential impact, Tree (data structure), biology, Faidherbia albida, Agroforestry, Soil infiltration, Environmental science, Structural basin, biology.organism_classification, Arid
Abstract

The soil hydraulic properties controlling infiltration are dynamic depending on interrelated factors such as soil texture and structure, climate (rainfall intensity), land use, vegetation cover and plant root systems. These physical and biological factors directly influence the size and geometry of the conductive pores, and therefore the bulk density, soil structure and finally water infiltration at surface. In the Sahelian zone, the slightest modification of the physical properties of the soil has severe consequences on the soil properties and thus on hydrological processes. It is therefore essential to improve knowledge on the spatial distribution of the hydraulic behavior of soils for optimization of agricultural uses.We used the BEST method (Beerkan Estimation of Soil Transfer parameters) on a toposequence of the Senegalese groundnut basin (Fatick region) in the Faidherbia-Flux observatory[1] where the average rainfall is 590 mm/yr. The studied toposequence (400 m long) is representative of a common agroforestry zone with annual cultivation of millet and peanuts and a sparse density of Faidherbia albida. The slope is low (1%) with small lowland areas made up of sandy soil with more clay (clay soil), while the glacis is represented by more or less compacted sand. The infiltrometry measurements were made with the automatic single-ring infiltrometer developed by Di Prima et al. (2016), used here for the first time in West Africa. The explicative variables tested are the type of soils, including: clay soils under tree (CLUT) and outside tree (CLOT), sandy soils under tree (SSUT) and outside trees (SSOT), and cattle trampled soils outside trees (TSOT) particularly compacted and largely present in the study area. BEST algorithms were applied to the experimental data to determine the hydraulic properties of the soils of the different variables and to draw water retention and hydraulic conductivity curves.There are significant differences in infiltration rates between the sampled zones and in relation with the studied factors. The highest infiltration rate is found on sandy soils under tree (SSUT) with an average infiltration rate of 14.0 mm/min, followed by SSOT with 11.6 mm/min. Then the clay soils CLUT and CLOT are characterized by similar lower hydraulic responses with average infiltration rates of 6.9 mm/min and 6.2 mm/min, respectively. The average infiltration rate is the lowest on the compacted sandy soils TSOT, with only 5.4 mm/min. The study of the variability of the infiltration rates measured by class of variable shows a large variability for CLOT, CLUT and SSUT (decreasing order of variability). These results are in agreement with the measured values of dry soil bulk density. The high infiltration rates in the clay soils outside and under trees can be explained by the higher content of organic matter observed on the sampling, and probably by the existence of preferential flow activated by the macropores particularly present on clay soils (CLOT and CLUT) and on sandy soils under tree (SSUT).Di Prima, S., et al., 2016. Testing a new automated single ring infiltrometer for Beerkan infiltration experiments. Geoderma, 262, 20–34. doi:10.1016/j.geoderma.2015.08.006 [1] Faidherbia-Flux : https://lped.info/wikiObsSN/?Faidherbia-Flux

Published
2021

22. Functional role of earthworms to control the hydraulic conductivity of constructed wetlands

Author

Frédéric Julien, Dan Tam Costa, Sabine Sauvage, Magali Gerino, Yvan Capowiez, Didier Orange, and Océane Gilibert

Subjects
Functional role, Hydrology, geography, geography.geographical_feature_category, Hydraulic conductivity, Environmental science, Wetland
Abstract

Wetlands are known for their natural service of water quality regulation. The hyporheic zones of the rivers filter and purify the surface water from the stream and infiltrated waters in soil nearby through the riparian zone. This purification service occurs because of a synergy between the substrate and its biodiversity (including plants, bacteria and other invertebrates). Our study deals with constructed wetlands (CW) as a nature-based solution mimicking wetlands water purification process, to purify wastewaters. The REUSE technology of CW is based on the use of specific layers of gravels and sands inside a close concrete structure, planted with specific sub-aquatic plants, where wastewaters or runoff of stormwaters are introduced to be filtered. The technology of Vertical Flow Constructed Wetlands (VFCW) reproduces the water flux observed in the riparian zone with a gravity flow of water. It is composed of reeds planted on a sandy layer (Ø 0-4 mm) and succession of gravel layers. This substrate can be saturated or unsaturated to reproduce the functioning of the hyporheic zone or the riparian zone respectively. By the time, the substrate is colonized by a community of bacteria producing biofilms which capture the residual organic matter from wastewaters to mineralize them. However, the VFCW substrates tend to clog over time due to the accumulation of organic matter and biofilms. Many studies consider earthworms as one of the solutions to alleviate this clogging, thanks to their burrows recreating macropores and preferential channels which help to improve the dispersion of water into the deep soil. The main goal of this study is to assess the impact of earthworm activities on the hydraulic conductivity of columns composed with the same substrate used in the VFCW. Different densities of earthworms (Eisenia fetida) were introduced (0, 100, 500, 1000 g of earthworms/m²) in these columns to be monitored for 37 days. The hydraulic conductivity was measured every 7 days, aside from day 23 with the addition of 40 g of peat bedding on column surfaces to simulate a high organic matter input. Columns with earthworm density superior to 500 g/m² shows an amelioration of their hydraulic conductivity after 21 days. These densities are also able to restore the hydraulic conductivity of the column in less than 7 days after the setting of clogged condition due to the organic matter input (peat bedding) at the sediment surface. This study showed that the burrowing activity of E. fetida improves the hydraulic flux of a sandy substrate and this impact is dependent on the earthworm density introduced. So, the addition of earthworms in the VFCW could serve as a prevention against clogging.

Published
2021

23. A modelling-based assessment of suspended sediment transport related to new damming in the Red River basin from 2000 to 2013

Author

Sylvain Ouillon, Thi Phuong Quynh Le, José-Miguel Sánchez-Pérez, Sabine Sauvage, Didier Orange, Marine Herrmann, Xi Wei, Centre National de la Recherche Scientifique (CNRS), Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Echanges Côte-Large (ECOLA), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), University of sciences and technologies of hanoi (USTH), Vietnam Academy of Science and Technology (VAST), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Land-Ocean-aTmosphere regional coUpled System study center (LOTUS), an international joint Vietnamese/French laboratory (http://lotus.usth.edu.vn/) funded by the Institut de Recherche pour le Développement (IRD)., China Scholarship Council (CSC), grant number 201606240088., Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), University of Science and Technology of Hanoi (USTH), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, and Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)

Subjects
Short-term climate, Delta, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Drainage basin, Flux, Short-term climate variability, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, Structural basin, 01 natural sciences, Modelling, Tributary, The Red River, Precipitation, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, Hydrology, geography, geography.geographical_feature_category, Dam, variability, Sediment, 04 agricultural and veterinary sciences, 15. Life on land, [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation, 6. Clean water, 13. Climate action, Suspended sediment, Soil erosion, 040103 agronomy & agriculture, 0401 agriculture, forestry, and fisheries, Environmental science, Sediment transport
Abstract

International audience; The Red River is an Asian river system strongly affected by global changes. This paper aims to characterize and quantify the suspended sediment flux (SF) over the basin under the influences of short-term climate variability and dam constructions. SF was evaluated at the outlets of main tributaries and along the main course of the Red River from 2000 to 2013 based on daily simulations from a modelling study. A reference scenario (without dams) was carried out to disentangle the impacts of short-term climate variability and damming by comparing to actual conditions. Without dams (reference scenario), the basin would generate 106.9 Mt yr−1 of SF to the downstream delta from 2000 to 2013, with a specific sediment yield (SSY) of 778.8 t km−2 yr−1. However, under the impacts of short-term climate variability and dams, the mean annual SSY decreased to 84.5 t km−2 yr−1. At the outlet of the basin, the annual mean SF of 2008–2013 (after new dam constructions) got reduced by 90% (10% related to short-term climate or atmospheric variability and 80% to dam constructions) compared to the reference scenario (without dams) during 2000–2007. The Thao tributary is the most sensitive to short-term climate variability while the Da tributary is mostly affected by the huge-capacity dams. Mean annual retentions of sediment by dams ranged from 7.1 to 111.0 Mt yr−1. Simple rating curves between monthly mean discharge (Q) and SF were established for estimating SF at the outlet of the tributaries and the Red River. High soil erosion (above 2000 t km−2 yr−1) occurred in the middle Thao and the lower Da tributaries. Precipitation, slope and agriculture practices are the key influence factors for soil erosion in the basin.

Published
2021

25. The UNESCO FRIEND-Water program : Accelerates, shares and transfers knowledge and innovation in hydrology across the world in the frame of the Intergovernmental Hydrological Program (IHP)

Author

Anil Mishra, Raphael Tshimanga, Didier Orange, Mohamed Meddi, Oula Amrouni, Ernest Amoussou, Gil Mahé, Ahmed El Tayeb, Stephan Dietrich, Henny A. J. Van Lanen, Patrick Valimba, Thi Phuong Quynh Le, Télesphore Yao Brou, Andrew Ogilvie, Santiago Yepez, Gamal M. Abdo, Hydrosciences Montpellier (HSM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), University of Khartoum, Université de Parakou (UP), Université de La Réunion (UR), Federal Institute of Hydrology, Wageningen University and Research [Wageningen] (WUR), Ecole Nationale Superieure d'Hydraulique [Blida, Algérie], UNESCO PARIS, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Hanoi University of Science and Technology (HUST), University of Kinshasa (UNIKIN), University of Dar es Salaam (UDSM), Universidad de Concepción - University of Concepcion [Chile], Gestion de l'Eau, Acteurs, Usages (UMR G-EAU), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, and Université de Carthage - University of Carthage

Subjects
QE1-996.5, WIMEK, [SDV]Life Sciences [q-bio], Member states, Frame (networking), Network data, Geology, General Medicine, Hydrology and Quantitative Water Management, Environmental sciences, Thematic map, Political science, Regional science, Life Science, GE1-350, Center (algebra and category theory), Hydrologie en Kwantitatief Waterbeheer
Abstract

The FRIEND-Water program (FWP) is the oldest and the most transverse program (i.e. Flagship Initiative) within the Hydrological Intergovernmental Program (IHP) from UNESCO. FRIEND means “Flow Regimes from International and Experimental Network Data”. The FWP is dedicated to allow large communities of hydrologists and associated disciplines to collaborate across borders on common shared data and scientific topics which are addressed through large world regions. The program has evolved in its 35 years of existence. There are 8 large regions in the world which gather tenths of hundreds of researchers, and organize events following several research topics defined according to each region priorities. The FWP is chaired by a scientific committee gathering regional coordinators and thematic experts. Each region gives its research priorities which evolve according to the projections given by the member States during the IHP council every year. The future activities of the FWP are defined by the upcoming IHP IX program and with the support of the newly created Montpellier UNESCO Category II Center ICIREWARD, acting as FWP Secretariat.

Published
2021

26. Are the Fouta Djallon Highlands Still the Water Tower of West Africa?

Author

Julien Andrieu, Yves Boulvert, Jean-Louis Couture, Bachir Tanimoun, Luc Ferry, Gwenaelle Dejacquelot, Aliou Barry, Luc Descroix, Fatoumata Binta Sombily Diallo, Ange Bouramanding Diedhiou, Jean-Pierre Vandervaere, Ababacar Fall, Lamine Konaté, Mahamadou Diakité, Bernadette Nka Nnomo, Amirou Diallo, Safietou Soumaré, Eugenia Gallese, Honoré Dacosta, Yaya Sakho, Kadiatou Diallo, Sylvie Paméla Manga, Ansoumana Bodian, Jean Albergel, Gil Mahé, Kourahoye Diallo, Jean-Claude Bader, Didier Orange, Bakary Faty, Jean-Claude Olivry, Nadine Braquet, Andrew Ogilvie, Laurent Lambert, Ilia Amadou, Saly Sambou, Patrimoines locaux, Environnement et Globalisation (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU), Patrimoines et Territoires de l'eau (LMI PATEO), Patrimoines Locaux et Gouvernance (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Direction de la Gestion et la Planification des Ressources en Eau (DGPRE), Université Assane SECK de Ziguinchor (UASZ), Université de Lorraine (UL), Université Félix Houphouët-Boigny (UFHB), School of Public Administration and Development Economics, Doha Institute for Graduate Studies, Ecole polytechnique de Thiès, Ecole Polytechnique de Thiès, Études des Structures, des Processus d’Adaptation et des Changements de l’Espace (ESPACE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Avignon Université (AU)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Université Côte d'Azur (UCA), Université Côte d'Azur (UCA), Gestion de l'Eau, Acteurs, Usages (UMR G-EAU), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Centre de recherche pluridisciplinaire en Lettres, Langues, Sciences Humaines et des Sociétés (Pléiade), Université Paris 13 (UP13), Hydrosciences Montpellier (HSM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université Gamal Abdel Nasser de Conakry, Institut Universitaire des Hautes Etudes de Guinée (IUHEG), Laboratoire d'étude des Interactions Sol - Agrosystème - Hydrosystème (UMR LISAH), Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, NBA Niger Basin Authority, Direction Nationale de l'Hydraulique [Guinée], Girardel - Laboratoire Leïdi (Leïdi), Université Gaston Berger de Saint-Louis Sénégal (UGB), Institut de Recherche pour le Développement (IRD), Independent Consultant, Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), Grdr Migrations, Citoyenneté, Développement, Organisation Pour la Mise en Valeur du Bassin du Fleuve Sénégal (OMVS), Institut de Recherches Géologiques et Minières (IRGM), Organisation pour la Mise en Valeur du Bassin du Fleuve Gambie (OMVG), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, Service National des Sols (SENASOLS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), European Union, via AICS (Agenzia Italiana de Cooperazione per il Sviluppo) ENV/2017/383-744/AP n, Sorbonne Université (SU)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Université Côte d'Azur (UCA)-Avignon Université (AU)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), and Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )

Subjects
Fula society, lcsh:Hydraulic engineering, depletion (or recession) coefficient, 010504 meteorology & atmospheric sciences, Geography, Planning and Development, 0207 environmental engineering, 02 engineering and technology, Aquatic Science, 01 natural sciences, Biochemistry, Natural (archaeology), West africa, Vegetation cover, lcsh:Water supply for domestic and industrial purposes, lcsh:TC1-978, basement, sandstone, runoff coefficient, 020701 environmental engineering, soil water holding capacity, 0105 earth and related environmental sciences, Water Science and Technology, lcsh:TD201-500, geography, Plateau, geography.geographical_feature_category, Fouta Djallon, 15. Life on land, 6. Clean water, Basement (geology), 13. Climate action, Threatened species, [SDE]Environmental Sciences, Physical geography, Surface runoff, Tower, water tower
Abstract

A large share of surface water resources in Sahelian countries originates from Guinea&rsquo, s Fouta Djallon highlands, earning the area the name of &ldquo, the water tower of West Africa&rdquo, This paper aims to investigate the recent dynamics of the Fouta Djallon&rsquo, s hydrological functioning. The evolution of the runoff and depletion coefficients are analyzed as well as their correlations with the rainfall and vegetation cover. The latter is described at three different space scales and with different methods. Twenty-five years after the end of the 1968&ndash, 1993 major drought, annual discharges continue to slowly increase, nearly reaching a long-term average, as natural reservoirs which emptied to sustain streamflows during the drought have been replenishing since the 1990s, explaining the slow increase in discharges. However, another important trend has been detected since the beginning of the drought, i.e., the increase in the depletion coefficient of most of the Fouta Djallon upper basins, as a consequence of the reduction in the soil water-holding capacity. After confirming the pertinence and significance of this increase and subsequent decrease in the depletion coefficient, this paper identifies the factors possibly linked with the basins&rsquo, storage capacity trends. The densely populated areas of the summit plateau are also shown to be the ones where vegetation cover is not threatened and where ecological intensification of rural activities is ancient.

Published
2020

27. Hydroclimatic variability in Tomi at Sibut, Gribingui at Kaga-Bandoro and Fafa at Bouca basins, in the Central African Republic

Author

Didier Orange and C.R. Nguimalet

Subjects
lcsh:GE1-350, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Range (biology), lcsh:QE1-996.5, 0208 environmental biotechnology, Drainage basin, Central africa, 02 engineering and technology, General Medicine, Structural basin, 01 natural sciences, 020801 environmental engineering, lcsh:Geology, Period (geology), Spatial variability, Physical geography, lcsh:Environmental sciences, Geology, 0105 earth and related environmental sciences
Abstract

The research of ruptures on rainfall and discharge serial data from 1950 to 1995 of three small catchments (from 2000 to 6000 km2) of the Central African Republic, at the boundary between Chad and Congo basins, has shown a high spatial variability. The rupture observed in 1970 at the subcontinental scale, which started the drought period in West and Central Africa, is observed only on the Northward basin, the driest. Then it was difficult to compare the hydroclimatic periods from a basin to another one. However, all the studied basins have shown a degradation of the hydrological regime from the end of the 1980s onward, with a severe level since the end of 1980s. The depletion coefficients have the same range for the 3 studied basins than for the Ubangi River basin, widening the drought impact.

Published
2020

28. Temporal Variability of Sediments, Dissolved Solids and Dissolved Organic Matter Fluxes in the Congo River at Brazzaville/Kinshasa

Author

Sandra Murielle Bayonne Padou, Alain Laraque, Pankyes Datok, Guy Dieudonne Moukandi N’Kaya, Didier Orange, Université Marien Ngouabi, Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Géosciences Environnement Toulouse (GET), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), AUF, grant number DRACGL-2019-4100', Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)

Subjects
Change over time, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Drainage basin, Weathering, DOC, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, 010502 geochemistry & geophysics, 01 natural sciences, Water column, discharge, Dissolved organic carbon, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, TDS, 0105 earth and related environmental sciences, Hydrology, Congo River, geography, geography.geographical_feature_category, lcsh:QE1-996.5, matter fluxes, Total dissolved solids, 6. Clean water, Dilution, TSS, lcsh:Geology, 13. Climate action, General Earth and Planetary Sciences, Environmental science
Abstract

For three decades, the solid and dissolved fluxes of the Congo River have been regularly monitored on a monthly basis, despite 12 years of deficiencies (1994&ndash, 2005). Two programs successively carried out these follow-ups: PEGI/GBF (1987&ndash, 1993) and SO HYBAM (2006&ndash, 2017), upstream and downstream, respectively, of the Malebo Pool near Brazzaville, the main hydrometric station of the Congo River. The objective of this study is to examine the temporal dynamic of TSS, TDS and DOC, to explore how these descriptors change over time. Comparison with the two time programs will shed more light on how these descriptors are related to discharge. Afterward, we then find a relationship between total TSS in the water column and that measured in surface for eventual estimation of TSS by remote sensing. In the last decade, compared to the PEGI/GBF period, the discharge of the Congo River was mainly marked by a 4% increase, leading to a significant change on TDS and DOC behaviors. The TSS was quite stable (from 8.2 and 9.3 t km&minus, 2 yr&minus, 1) due to the low physical erosion well known in this region. The TDS concentrations decreased slightly, by a simple dilution effect. However, the mineral dissolved fluxes (from 11.6 and 10.1 t km-2 yr-1) due to the chemical weathering and atmospheric inputs still predominate over the solid fluxes. Therefore, there was no radical change in the monthly geochemical regime of Congo River Basin (CRB) during these last 30 years. Contrariwise, the DOC concentration marking the biogeochemical processes significantly increased, from 9.0+/&minus, 3.0 mg L&minus, 1 to 12.7+/&minus, 5.0 mg L&minus, 1, due to more flooding events in the central part of the CRB. The change for the DOC fluxes is more relevant, with an increase of 45% between the two studied periods, from 11.1 &times, 106 to 16.2 &times, 106 t yr&minus, 1. This highlights the continuous and actual importance of the &ldquo, Cuvette Centrale&rdquo, in the heart of the CRB for dissolved organic matter transport by the Congo River.

Published
2020

29. Preface : Hydrological processes and water security in a changing world

Author

Dazheng Yu, Chunhui Lu, Henny A. J. Van Lanen, Didier Orange, Abou Amani, Zhongbo Yu, Gil Mahé, Jianyuan Cai, Anil Mishra, Christophe Cudennec, Hohai University, Ministry of Water Resources of the People's Republic of China, Hydrosciences Montpellier (HSM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), United Nations Educational, Scientific and Cultural Organization (UNESCO), INSTITUT AGRO Agrocampus Ouest, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Wageningen University and Research [Wageningen] (WUR), Institut Agro - Montpellier SupAgro, FRIEND-Water (Flow Regime from International Experimental and Network Data), and International Association of Hydrological Sciences (PIAHS)

Subjects
lcsh:GE1-350, lcsh:Geology, Water security, WIMEK, lcsh:QE1-996.5, Environmental science, Life Science, General Medicine, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Water resource management, Hydrology and Quantitative Water Management, lcsh:Environmental sciences, Hydrologie en Kwantitatief Waterbeheer
Published
2020

30. Recent budget of hydroclimatology and hydrosedimentology of the Congo River in Central Africa

Author

Santiago Yepez, Gil Mahé, Georges Gulemvuga, Raphael Tshimanga, Guy Dieudonne Moukandi N’Kaya, C.R. Nguimalet, Didier Orange, Jean Marie Tshitenge, Mark A. Trigg, Alain Laraque, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), University Marien Ngouabi of Brazzaville (umng), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), University of Kinshasa (UNIKIN), Hydrosciences Montpellier (HSM), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université de Bangui, University of Leeds, Universidad de Concepción [Chile], Commission Internationale du Bassin Congo-Oubangui-Sangha (CICOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Universidad de Concepción - University of Concepcion [Chile]

Subjects
lcsh:Hydraulic engineering, 010504 meteorology & atmospheric sciences, Geography, Planning and Development, 0207 environmental engineering, Drainage basin, Aquifer, 02 engineering and technology, Aquatic Science, Structural basin, 01 natural sciences, Biochemistry, Water balance, Hydrology (agriculture), lcsh:Water supply for domestic and industrial purposes, lcsh:TC1-978, Tributary, hydroclimatology, hydrosedimentology, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, 020701 environmental engineering, hydrogeochemical, 0105 earth and related environmental sciences, Water Science and Technology, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, geography, lcsh:TD201-500, geography.geographical_feature_category, Plateau, 15. Life on land, 6. Clean water, 13. Climate action, Erosion, Environmental science, Congo River Basin, Physical geography
Abstract

Although the Congo Basin is still one of the least studied river basins in the world, this paper attempts to provide a multidisciplinary but non-exhaustive synthesis on the general hydrology of the Congo River by highlighting some points of interest and some particular results obtained over a century of surveys and scientific studies. The Congo River is especially marked by its hydrological regularity only interrupted by the wet decade of 1960, which is its major anomaly over nearly 120 years of daily observations. Its interannual flow is 40,500 m3 s−1. This great flow regularity should not hide important spatial variations. As an example, we can cite the Ubangi basin, which is the most northern and the most affected by a reduction in flow, which has been a cause for concern since 1970 and constitutes a serious hindrance for river navigation. With regard to material fluxes, nearly 88 × 106 tonnes of material are exported annually from the Congo Basin to the Atlantic Ocean, composed of 33.6 × 106 tonnes of TSS, 38.1 × 106 tonnes of TDS and 16.2 × 106 tonnes of DOC. In this ancient flat basin, the absence of mountains chains and the extent of its coverage by dense rainforest explains that chemical weathering (10.6 t km−2 year−1 of TDS) slightly predominates physical erosion (9.3 t km−2 year−1 of TSS), followed by organic production (4.5 t km−2 year−1 of DOC). As the interannual mean discharges are similar, it can be assumed that these interannual averages of material fluxes, calculated over the longest period (2006–2017) of monthly monitoring of its sedimentology and bio-physical-chemistry, are therefore representative of the flow record available since 1902 (with the exception of the wet decade of 1960). Spatial heterogeneity within the Congo Basin has made it possible to establish an original hydrological classification of right bank tributaries, which takes into account vegetation cover and lithology to explain their hydrological regimes. Those of the Batéké plateau present a hydroclimatic paradox with hydrological regimes that are among the most stable on the planet, but also with some of the most pristine waters as a result of the intense drainage of an immense sandy-sandstone aquifer. This aquifer contributes to the regularity of the Congo River flows, as does the buffer role of the mysterious “Cuvette Centrale”. As the study of this last one sector can only be done indirectly, this paper presents its first hydrological regime calculated by inter-gauging station water balance. Without neglecting the indispensable in situ work, the contributions of remote sensing and numerical modelling should be increasingly used to try to circumvent the dramatic lack of field data that persists in this basin.

Published
2020

33. More C uptake during the dry season? The case of a semi-arid agro-silvo-pastoral ecosystem dominated by Faidherbia albida, a tree with reverse phenology (Senegal)

Author

Roupsard, Olivier, primary, Frederic, Do, additional, Alain, Rocheteau, additional, Christophe, Jourdan, additional, Didier, Orange, additional, Laure, Tall, additional, Sidy, Sow, additional, Waly, Faye, additional, Djimm M.L., Diongue, additional, Khalisse, Diouf, additional, Yélognissé, Agbohessou, additional, Seydou, Diatta, additional, Serigne, Faye, additional, Mame Sokhna, Sarr, additional, Diaminatou, Sanogo, additional, Guerric, le Maire, additional, Remi, Vezy, additional, Josiane, Seghieri, additional, and Laurent, Cournac, additional

Published
2020
Full Text
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35. 'Faidherbia-Flux': adapting crops to climate changes in a semi-arid agro-sylvo-pastoral open observatory (Senegal)

Author

Olivier Roupsard, Cathy Clermont-Dauphin, Alain Audebert, Sanou, J., Koala, J., Christophe Jourdan, Didier Orange, Frédéric Do, Alain Rocheteau, Isabelle Bertrand, Emile Faye, Laure Tall, Gaglo, E., Tounkara, A., Gabriela Demarchi, Thierry Brévault, Rémi Vezy, Guerric le Maire, Josiane Seghieri, Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Institut de recherche pour le développement (IRD [Sénégal]), Institut de l'Environnement et Recherches Agricoles [Ouagadougou] (INERA), Institut de Recherche pour le Développement (IRD), and Institut Sénégalais de Recherches Agricoles [Dakar] (ISRA)

Subjects
[SDV.SA]Life Sciences [q-bio]/Agricultural sciences, Yield, Pests, Faidherbia effect, LER_M, Drone
Abstract

National audience; The adaptation of semi-arid crops to climate changes is theoretically possible through agroforestry, provided that the trees exert little competition, or even increase the multifunctional LER (LER_M). We monitored microclimate, net primary productivity (NPP), CO2 and H2O fluxes in a semiarid agro-sylvo-pastoral system (Niakhar, Senegal), dominated by the multipurpose Faidherbia albida (FA) tree. Undercrops were mainly millet and peanut, under annual rotation. We scanned a 1.24 ha millet under FA plot with UAV photogrammetry in RGB, thermal infrared and multispectral bands. At harvest, we collected 12 subplots of 15 millet holes each, distributed either below the crown of FA, or at 2.5 x crown radius, or at 5 x crown radius. We separated all organs. The whole millet root system (0-200 cm) was sampled also in 2 m trenches, totalizing 4 millet holes, where all roots were sorted by layer. The whole plot harvest will allow extrapolating yield from subplots, through UAV images. Millet yield per unit ground area was about 3 times higher below FA, with still a positive influence at 2.5 x crown radius and less impacts of pests close to FA. In the trenches, we noted higher soil humidity and SOC close to the FA trunks. This observatory is open for collaboration.

Published
2019

36. International Conference FRIEND-Water, 6-8 November 2018, Beijing Minute of the side-event on 'Collaboration between FRIEND & EcoHydrology networks'

Author

Breil, Pascal, Didier, Orange, RiverLy (UR Riverly), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Institut d'écologie et des sciences de l'environnement de Paris (iEES), Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), INRAE, and Breil, Pascal

Subjects
[SDE] Environmental Sciences, [SDE]Environmental Sciences
Published
2018

37. Impact of anthropogenic activities on water quality and plankton communities in the Day River (Red River Delta, Vietnam)

Author

Kien T. Nguyen, Thi Thuy Duong, Kim Dinh Dang, Hang Thi Thu Hoang, Anh Hung Le, Quynh Thi Phuong Le, Cuong Tu Ho, Judith Klein, Didier Orange, Julien Némery, Minh T. N. Luu, Duc Anh Trinh, MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Vietnam Academy of Science and Technology (VAST), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP), Institute of Ecology and Environmental Sciences, University Pierre et Marie Curie, Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Institut National de la Recherche Agronomique (INRA)-Institut de Recherche pour le Développement (IRD)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Institut d'écologie et des sciences de l'environnement de Paris (iEES), Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), and Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)

Subjects
0106 biological sciences, PHYTOPLANCTON, Rain, FONCTIONNEMENT DE L'ECOSYSTEME, QUALITE DE L'EAU, Day River, 010501 environmental sciences, 01 natural sciences, Chlorophyta, Biomass, Plankton communities, TEMPERATURE, General Environmental Science, Biomass (ecology), River delta, geography.geographical_feature_category, Ecology, Phosphorus, General Medicine, Plankton, Cladocera, Pollution, 6. Clean water, Water quality, Vietnam, Seasons, Environmental Monitoring, Food Chain, Nitrogen, [SDE.MCG]Environmental Sciences/Global Changes, Management, Monitoring, Policy and Law, Cyanobacteria, Zooplankton, FACTEUR ANTHROPIQUE, Tropical, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, AZOTE, Rivers, Aquatic plant, Phytoplankton, Animals, 14. Life underwater, Ecosystem, ANALYSE DE DONNEES, 0105 earth and related environmental sciences, Diatoms, geography, Red River Delta, TRAITEMENT DE DONNEES, 010604 marine biology & hydrobiology, Water Pollution, fungi, ECHANTILLON, PHOSPHORE, HYDROBIOLOGIE, NUTRIMENT, COURS D'EAU, Environmental science, ZOOPLANCTON, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Eutrophication, PLANCTON, METHODOLOGIE
Abstract

International audience; Plankton are a major component of food web structure in aquatic ecosystems. Their distribution and community structure are driven by the combination and interactions between physical, chemical, and biological factors within the environment. In the present study, water quality and the community structure of phytoplankton and zooplankton were monthly investigated from January to December 2015 at 11 sampling sites along the gradient course of the Day River (Red River Delta, northern Vietnam). The study demonstrated that the Day River was eutrophic with the average values of total phosphorus concentration 0.17 mg/L, total nitrogen concentration 1.98 mg/L, and Chl a 54 mu g/L. Microscopic plankton analysis showed that phytoplankton comprised 87 species belonging to seven groups in which Chlorophyceae, Bacillariophyceae, and Cyanobacteria accounted for the most important constituents of the river's phytoplankton assemblage. A total 53 zooplankton species belonging to three main groups including Copepoda, Cladocera, and Rotatoria were identified. Plankton biomass values were greatest in rainy season (3002.10-3 cell/L for phytoplankton and 12.573 individuals/m(3) for zooplankton). Using principal correspondence and Pearson correlation analyses, it was found that the Day River was divided into three main site groups based on water quality and characteristics of plankton community. Temperature and nutrients (total phosphorus and total nitrogen) are key factors regulating plankton abundance and distribution in the Day River.

Published
2018

38. Bioturbation effects on bioaccumulation of cadmium in the wetland plant Typha latifolia: A nature-based experiment

Author

Sabina Bassil, Franck Gilbert, Jean Kallerhoff, Anne Probst, Thi Thuy Duong, Trung Kien Hoang, Magali Gerino, François Laurent, Arnaud Elger, Didier Orange, Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées, International Water Management Institute - South East Asia (IWMI-SEA), IWMI, Laboratoire Agronomie - Environnement - Ecotoxicologie (A2E), Ecole Nationale Supérieure Agronomique-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, ToxAlim (ToxAlim), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Ecole Nationale Vétérinaire de Toulouse (ENVT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Ecole d'Ingénieurs de Purpan (INPT - EI Purpan), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National de la Recherche Agronomique (INRA), Chimie Agro-Industrielle (CAI), Institut National de la Recherche Agronomique (INRA)-Ecole nationale supérieure des ingénieurs en arts chimiques et technologiques-Institut National Polytechnique (Toulouse) (Toulouse INP), University of sciences and technologies of hanoi (USTH), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes (UMR Eco&Sols), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA), Vietnam Academy of Science and Technology (VAST), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Ecole Nationale Supérieure Agronomique d'Alger, Métabolisme et Xénobiotiques (ToxAlim-MeX), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National de la Recherche Agronomique (INRA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Ecole nationale supérieure des ingénieurs en arts chimiques et technologiques-Institut National de la Recherche Agronomique (INRA), NUCOWS project University of Science and Technology of Hanoi (USTH), 'Programme de Bourses d'Excellence de l'Ambassade de France au Vietnam'., Centre de Coopération Internationale en Recherche Agronomique - CIRAD (FRANCE), Centre National de la Recherche Scientifique - CNRS (FRANCE), Ecole Nationale Vétérinaire de Toulouse - ENVT (FRANCE), Institut National Polytechnique de Toulouse - INPT (FRANCE), Institut National de la Recherche Agronomique - INRA (FRANCE), Institut de Recherche pour le Développement - IRD (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Université des Sciences et des Technologies de Hanoi - USTH (VIETNAM), Graduate University of Science and Technology - GUST (VIETNAM), Vietnam Academy of Science and Technology - VAST (VIETNAM), Laboratoire Ecologie fonctionnelle et Environnement - EcoLab (Toulouse, France), and Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)

Subjects
Geologic Sediments, 010504 meteorology & atmospheric sciences, 010501 environmental sciences, Typhaceae, 01 natural sciences, Riparian plants, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Waste Management and Disposal, ComputingMilieux_MISCELLANEOUS, Cadmium, biology, [SDE.IE]Environmental Sciences/Environmental Engineering, Pollution, 6. Clean water, Bioaccumulation, [SDV.TOX.ECO]Life Sciences [q-bio]/Toxicology/Ecotoxicology, Bioturbation, Microcosm, Environmental Engineering, [SDE.MCG]Environmental Sciences/Global Changes, chemistry.chemical_element, Cadmium-Sediment, [SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study, Bioremediation, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Environmental Chemistry, Animals, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Oligochaeta, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Ecosystem, 0105 earth and related environmental sciences, Ecologie, Environnement, Pollutant, Environmental engineering, Sediment, 15. Life on land, biology.organism_classification, Ecological engineering, Phytoremediation, chemistry, 13. Climate action, Tubifex tubifex, Wetlands, Environmental science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Water Pollutants, Chemical
Abstract

International audience; The development of efficient bioremediation techniques to reduce aquatic pollutant load in natural sediment is one of the current challenges in ecological engineering. A nature-based solution for metal bioremediation is proposed through a combination of bioturbation and phytoremediation processes in experimental indoor microcosms. The invertebrates Tubifex tubifex (Oligochaeta Tubificidae) was used as an active ecological engineer for bioturbation enhancement. The riparian plant species Typha latifolia was selected for its efficiency in phyto-accumulating pollutants from sediment. Phytoremediation efficiency was estimated by using cadmium as a conservative pollutant known to bio-accumulate in plants, and initially introduced in the overlying water (20 μg Cd/L of cadmium nitrate – Cd(NO3)2·4H2O). Biological sediment reworking by invertebrates' activity was quantified using luminophores (inert particulates). Our results showed that bioturbation caused by tubificid worms' activity followed the bio-conveying transport model with a downward vertical velocity (V) of luminophores ranging from 16.7 ± 4.5 to 18.5 ± 3.9 cm·year− 1. The biotransport changed the granulometric properties of the surface sediments, and this natural process was still efficient under cadmium contamination. The highest value of Cd enrichment coefficient for plant roots was observed in subsurface sediment layer (below 1 cm to 5 cm depth) with tubificids addition. We demonstrated that biotransport changed the distribution of cadmium across the sediment column as well as it enhanced the pumping of this metal from the surface to the anoxic sediment layers, thereby increasing the bioaccumulation of cadmium in the root system of Typha latifolia. This therefore highlights the potential of bioturbation as a tool to be considered in future as integrated bioremediation strategies of metallic polluted sediment in aquatic ecosystems.

Published
2017

40. Identification des voies de recherche et d’action pour une gestion durable des ZIT

Author

Didier Orange

Abstract

Durant ces vingt dernieres annees, la perception des rapports entre gestion de l'eau, gestion des ressources naturelles, environnement naturel, contraintes sociales et economiques a change fondamentalement (Marino et Simonovic, 2001). Un schema multicausal des impacts environnementaux faisant intervenir avec une egale importance les facteurs sociaux, economiques et ecologiques est maintenant admis. Aussi les politiques de planification retenues durant le siecle dernier ne font plus loi, mais les nouveaux modeles d'organisation sont encore a inventer (Heathcote, 1998 ; Schumann et ai, 2001). Mettre en ouvre les connaissances scientifiques et les qualites de l'expertise pour la resolution de problemes a la fois environnementaux et societales est maintenant un defi majeur a l'echelle du monde entier. Une litterature abondante d'origine multiple explore d'ailleurs le sujet (Sdage RMC, 1996; Nunes et Auge, 1999; Faucheux et Hue, 2000 ; Kalaora et Charles, 2000 ; Dunbar et Acreman, 2001 ; Josselin, 2001 ; Millenium Ecosystem Assessment, 2001 ; Pohl, 2001 ; Temple, 2001 ; Teniere-Buchot, 2001 ; etc.)

Published
2017

44. Liste des référés

Author

Marcel Kuper, Yveline Poncet, Pierre Morand, Didier Orange, and Robert Arfi

Published
2017

47. Hydrologie, agro-écologie et superficies d’inondation dans le delta intérieur du Niger

Author

Didier Orange, Marcel Kuper, Cheik Hamalla Diakité, Jean-Claude Olivry, Gil Mahé, and Lamine Dembélé

Abstract

Dans cette etude, nous reprenons un modele d'extension maximale annuelle d'inondation du delta interieur construit a partir d'un decoupage agro-ecologique que nous testons a partir de donnees hydrologiques recentes. Les resultats sont compares a ceux obtenus par un modele d'inondation base uniquement sur une approche hydrologique. Notre propos est de preciser le fonctionnement hydrologique des plaines d'inondation du sud, de l'erg inonde du nord et des lacs peripheriques en confrontant ces deux approches independantes, afin de determiner les superficies d'inondation de ces grandes composantes geographiques du delta en fonction des volumes d'eau provenant du bassin amont. (Resume d'auteur)

Published
2017

50. Gestion intégrée des ressources naturelles en zones inondables tropicales

Author

Abdourhamane Soumaguel, Bertrand Marieu, Fantagoma Bamba, Marcel Kuper, Lamine Fofana, Navon Cissé, Didier Orange, Gil Mahé, Orange, Didier (ed.), Arfi, Robert (ed.), Kuper, M. (ed.), Morand, Pierre (ed.), Poncet, Yveline (ed.), and Témé, B. (préf.)

Subjects
PLUVIOMETRIE, irrigation, VARIATION TEMPORELLE, gestion de l’environnement, fonctionnement de l’écosystème, développement intégré, P10 - Ressources en eau et leur gestion, ECOULEMENT, TEMPERATURE, DELTA, EVAPOTRANSPIRATION POTENTIELLE, Climat, environnement, NUAGE, milieu deltaïque, VARIATION INTERANNUELLE, Bilan hydrique, Delta, politique de l’environnement, BILAN HYDROLOGIQUE, FACTEUR CLIMATIQUE, HYDROCLIMAT, VARIATION SPATIALE, développement durable, plaine inondable, Ressource en eau, exploitation des ressources naturelles
Abstract

Les activites economiques - agricoles, pastorales et halieutiques - du delta interieur du Niger, tres liees a la montee et a la descente des eaux, se trouvent en cette periode de longue secheresse d'autant plus soumises a la variabilite hydroclimatique spatio-temporelle interannuelle. Aussi dans le cadre du projet Gihrex, il s'est agi de construire une grille spatio-temporelle des donnees hydroclimatiques pertinente pour comprendre les contraintes liees aux variabilites saisonniere et interannuelle du bilan de l'eau sur la productivite des milieux - et donc sur les choix strategiques d'exploitation. Dans un premier temps, nous presentons la variabilite spatiale recente des parametres climatiques constitutifs du bilan de l'eau et discutons du comportement hydrologique par grandes regions geomorphologiques du delta. Dans une seconde partie, nous abordons la variabilite interannuelle de la ressource en eau depuis le debut du siecle, en faisant la part entre la variabilite des ecoulements provenant des bassins versants amont du delta et celle de la pluviometrie recue par le delta. (Resume d'auteur)

Published
2017

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