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• A citizen science (CS)-based method was applied to monitor rainfall in a test region. • A step-by-step approach was used to engage citizens from different generations. • Field training was provided to volunteers to guarantee consistent monitoring. • Statistical analysis validated the quality of the CS data compared to reference ones. Citizen Science (CS) has been emerging in the last decade as a new field of environmental monitoring involving a direct collaboration between everyday citizens and scientists. In Tunisia, several recent governmental efforts aimed at reinforcing and renovating the existing official water monitoring systems. However, the lack of reliable hydrological data is still an issue, which could be better addressed through integrating a CS approach. The latter approach is tested for rainfall monitoring in the Medjerda catchment in Tunisia using cost-effective and publicly available manual rain gauges. We used a step-by-step approach to target, engage and train citizens on using the monitoring tools and transmitting the data to a user-friendly online platform. The ongoing approach involved 7 citizens from different generations and different educational backgrounds. The collected daily CS data are compared with data from reference stations. Results yield a significant correlation between CS data collected at 3 different sites and the reference stations with r (Pearson Correlation Coefficient (PCC)) ranges between 0.91 and 0.98 for all citizens. Student's t -test was applied to evaluate the significance of the agreement between the CS and reference data. In addition, the variability of the CS data is compared with the variability associated with the official governmental data. The CS approach delivered consistent outcomes to complement existing Tunisian monitoring systems, and also to enhance innovation, adaptation, and local capacity building in the Tunisian water sector. [ABSTRACT FROM AUTHOR]

This study assessed the vulnerability of groundwater against pollution in the Kinshasa region, DR Congo, as a support of a groundwater protection program. The parametric vulnerability model (DRASTIC) was modified and calibrated to predict the intrinsic vulnerability as well as the groundwater pollution risk. The method uses groundwater body specific parameters for the calibration of the factor ratings and weightings of the original DRASTIC model. These groundwater specific parameters are inferred from the statistical relation between the original DRASTIC model and observed nitrate pollution for a specific period. In addition, site-specific land use parameters are integrated into the method. The method is fully embedded in a Geographic Information System (GIS). Following these modifications, the correlation coefficient between groundwater pollution risk and observed nitrate concentrations for the 2013–2014 survey improved from r = 0.42, for the original DRASTIC model, to r = 0.61 for the calibrated model. As a way to validate this pollution risk map, observed nitrate concentrations from another survey (2008) are compared to pollution risk indices showing a good degree of coincidence with r = 0.51. The study shows that a calibration of a vulnerability model is recommended when vulnerability maps are used for groundwater resource management and land use planning at the regional scale and that it is adapted to a specific area. [ABSTRACT FROM AUTHOR]

Abstract: Many different expressions for irrigation efficiency exist. A popular expression is the engineers’ irrigation efficiency (IE) that can be separated into conveyance efficiency (ec) and application efficiency (ea). ea is often seen as the key parameter to optimize, leading to the promotion of application techniques associated to a high ea value. Unfortunately, the processes that determine the overall efficiencies are not yet well understood. In this paper, we aim to assess and model technical irrigation performance (IP) for the Triffa's irrigation perimeter in East Morocco. IP is modeled in terms of technical, agronomic and socio-economical parameters as a way to understand the underlying processes that determine efficiencies. IP calculation shows that actual performance values are much more variable than literature reference values. IP variability is indeed related not only to application technology but also to agronomic, technical, socio-economical and even nearly psychological factors, highlighting the need to include such socio-economic considerations into the irrigation evaluation process. [Copyright &y& Elsevier]

Abstract: This study analyses the sources of atrazine contamination in the Brusselian sandy aquifer of central Belgium. Atrazine has in the past been used for both agricultural and non-agricultural applications, but it is difficult to distinguish the contamination originating from these two sources. The spatial and temporal covariance of atrazine concentrations was studied by fitting semi-variogram models to monitoring data. Correlation ranges were found to be 600 m and 600–700 days, respectively. The results were used to apply a declustering algorithm before examining the distribution of atrazine concentrations measured in groundwater. Monitoring data appeared to follow a pseudo-lognormal distribution, as a lognormality test was negative. An inflexion point on the cumulative density function was thought to indicate the two different pollution processes, i.e., agricultural and non-agricultural contamination sources. A non-parametric one-way analysis of variance suggested that the vast majority of atrazine in groundwater was from non-agricultural, point sources. This was supported by the strong relationship between mean concentrations and land use, whilst other environmental variables, such as soil organic matter or groundwater depth, produced less meaningful results. [Copyright &y& Elsevier]

We estimated vulnerability and pollution risk of groundwater at the pan-African scale. We therefore compiled the most recent continental scale information on soil, land use, geology, hydrogeology and climate in a Geographical Information System (GIS) at a resolution of 15 km × 15 km and at the scale of 1:60,000,000. The groundwater vulnerability map was constructed by means of the DRASTIC method. The map reveals that groundwater is highly vulnerable in Central and West Africa, where the watertable is very low. In addition, very low vulnerability is found in the large sedimentary basins of the African deserts where groundwater is situated in very deep aquifers. The groundwater pollution risk map is obtained by overlaying the DRASTIC vulnerability map with land use. The northern, central and western part of the African continent is dominated by high pollution risk classes and this is very strongly related to shallow groundwater systems and the development of agricultural activities. Subsequently, we performed a sensitivity analysis to evaluate the relative importance of each parameter on groundwater vulnerability and pollution risk. The sensitivity analysis indicated that the removal of the impact of vadose zone, the depth of the groundwater, the hydraulic conductivity and the net recharge causes a large variation in the mapped vulnerability and pollution risk. The mapping model was validated using nitrate concentration data of groundwater as a proxy of pollution risk. Pan-African concentration data were inferred from a meta-analysis of literature data. Results shows a good match between nitrate concentration and the groundwater pollution risk classes. The pan African assessment of groundwater vulnerability and pollution risk is expected to be of particular value for water policy and for designing groundwater resources management programs. We expect, however, that this assessment can be strongly improved when better pan African monitoring data related to groundwater pollution will be integrated in the assessment methodology. [ABSTRACT FROM AUTHOR]

The present work deals with modeling of the fate of nitrogen through a vertical flow constructed wetland (VFCW) using gravel, treating directly domestic raw wastewater. The experimental design of the work involved lab-scale and full-scale experiments to calibrate the multi-component reactive transport model for constructed wetlands (CW2D). Besides measured values for the hydraulic parameters and the maximum autotrophic growth rate, we calibrated two other parameters (oxygen re-aeration rate and adsorption coefficients of ammonium) to reduce the difference between predictions and measurements. The obtained model determined the time-variation of nitrogen concentrations in the effluent with reasonable performances. With the use of the model we demonstrate that, during feeding period, the ammonium was significantly adsorbed onto organic matter besides conversion into nitrates; the adsorbed mass of ammonium was nitrified during the rest period provoking high nitrates concentrations during the first two subsequent batches. We also demonstrated that heterotrophic biomass was mainly present in the sludge layer (first 20 cm), whereas autotrophic biomass was located in the first 50 cm of the VFCW (sludge and 30 cm biomat). [ABSTRACT FROM AUTHOR]

Abstract: We developed an original method to measure nitrification rates at different depths of a vertical flow constructed wetland (VFCW) with variable contents of organic matter (sludge, colonized gravel). The method was adapted for organic matter sampled in constructed wetland (sludge, colonized gravel) operated under partially saturated conditions and is based on respirometric principles. Measurements were performed on a reactor, containing a mixture of organic matter (sludge, colonized gravel) mixed with a bulking agent (wood), on which an ammonium-containing liquid was applied. The oxygen demand was determined from analysing oxygen concentration of the gas passing through the reactor with an on-line analyzer equipped with a paramagnetic detector. Within this paper we present the overall methodology, the factors influencing the measurement (sample volume, nature and concentration of the applied liquid, number of successive applications), and the robustness of the method. The combination of this new method with a mass balance approach also allowed determining the concentration and maximum growth rate of the autotrophic biomass in different layers of a VFCW. These latter parameters are essential inputs for the VFCW plant modelling. [Copyright &y& Elsevier]

Abstract: In this study, sulphur transport processes and effect of flow rate on sulphate breakthrough curves (BTCs) were studied on six undisturbed large soil monoliths (each having roughly a volume of 0.5m3), collected from two different agricultural soils being loamy and sandy loam. In the laboratory, each monolith was equipped with different measuring devices to monitor soil water content, bulk soil electrical conductivity (ECa), soil temperature, pressure head, outlet flux, and pH. Four unsaturated steady state experiments were carried out on each monolith using two different imposed fluxes (referred to as low and high). First a chloride breakthrough experiment was performed to identify the basic transport processes followed by sulphate breakthrough experiment for the identification of the important sulphate transport processes. Water and solute (chloride and sulphate) mass balances were made to evaluate effective sulphate transformations at the scale of the monolith. The relative water mass balance errors ranged between −4.0% and 5.0%. The chloride mass balances were almost as good as those obtained for water, whereas the sulphate mass balance revealed that sulphate was subjected to adsorption and immobilization during the transport. The high flux sulphate experiments resulted in relatively large mass balance discrepancies compared to the low flux sulphate experiments. The sulphate breakthrough curves (BTCs) were somewhat retarded in the loamy monoliths whereas both chloride and sulphate BTCs were significantly affected by preferential flow in the sandy loam monoliths. Standard batch experiments showed that the adsorption isotherm was linear and immobilization occurred in both soils studied whereas net mineralization was essentially low. The effect of flow rate on the BTCs and influence of water content on immobilization process was not apparent. [Copyright &y& Elsevier]

The recently adopted UN Sustainable Development Goals (SDGs) encompasses a specific goal for water (SDG-6). The target 6.4 deals with water scarcity and refers to two main indicators: water use efficiency and water stress (WS), monitored by the UN statistical services yearly at the country level. Yet, for more efficient development planning, indicators should also be provided with higher spatial and temporal resolutions. This study presents a data-driven method allowing to disaggregate the WS indicator at higher spatial and temporal resolution. We applied the method for the Medjerda catchment in Tunisia, known as being severely water-stressed. We disaggregated the WS indicator from the overall catchment to the administrative regional level at yearly and monthly scales. In order to overcome poorly documented irrigation water withdrawals, two approaches were adopted: 1) we used yearly governmental data at both catchment and regions scales; 2) we replaced governmental irrigation data by remote sensing-based irrigation estimation. First Order Uncertainty Analysis (FOUA) was performed to characterize the uncertainty associated with the assessment of WS. Results reveal that the WS at the scale of the catchment increases considerably in recent years, exceeding 50% from 2005 and surpassing the 100% threshold in 2015 and 2016 (102%, 108% respectively). The two adopted approaches result in similar WS trends. However, the second approach yields higher WS values compared to the first approach (144% versus 108% in 2016). The monthly-disaggregated WS at catchment scale exhibits a similar increasing trend. The highest WS values are at the end of the fall and during the summer season, which is mainly due to the increasing demand for irrigation and drinking water. Siliana region is the most affected by WS, while Beja is the least affected. The FOUA shows that the integration of remote sensing-based irrigation data reduces the WS uncertainty. Unlabelled Image • A data-driven method is presented to assess the UN SDG-6 water stress indicator. • The method allows the spatial and temporal disaggregation of the indicator. • Remotely sensed irrigation data was used as surrogate to governmental data. • The Medjerda basin reached an increasingly sever water scarcity in recent years. [ABSTRACT FROM AUTHOR]

• The study evaluate the impact of cover cropping in soil properties on the long term. • Soil water content was continuously monitored during 10 years by capacitance probes. • Soil hydraulic properties were estimated yearly inverting WAVE hydrological model. • Minimum tillage and cover crop affected macro-micro porosity and hydraulic properties. • Water depleted by cover crops was compensated with a larger water retention capacity. Cover cropping in agriculture is expected to enhance many agricultural and ecosystems functions and services. Yet, few studies are available allowing to evaluate the impact of cover cropping on the long term change of soil hydrologic functions. We assessed the long term change of the soil hydraulic properties due to cover cropping by means of a 10-year field experiment. We monitored continuously soil water content in non cover cropped and cover cropped fields by means of capacitance probes. We subsequently determined the hydraulic properties by inverting the soil hydrological model WAVE, using the time series of the 10 year monitoring data in the object function. We observed two main impacts, each having their own time dynamics. First, we observed an initial compaction as a result of the minimum tillage. This initial negative effect was followed by a more positive cover crop effect. The positive cover crop effect consisted in an increase of the soil micro- and macro-porosity, improving the structure. This resulted in a larger soil water retention capacity. This latter improvement was mainly observed below 20 cm, and mostly in the soil layer between 40 and 80 cm depth. This study shows that the expected cover crop competition for water with the main crop (evapotranspiration) can be compensated by an improvement of the water retention in the intermediate soil layers and a reduction of drainage loses. This may enhance the hydrologic functions of agricultural soils in arid and semiarid regions which often are constrained by water stress. [ABSTRACT FROM AUTHOR]

The termination date is recognized as a key management factor to enhance cover crops for multiple benefits and to avoid competition with the following cash crop. However, the optimum date depends on annual meteorological conditions, and climate variability induces uncertainty in a decision that needs to be taken every year. One of the most important cover crop benefits is reducing nitrate leaching, a major concern for irrigated agricultural systems and highly affected by the termination date. This study aimed to determine the effects of cover crops and their termination date on the water and N balances of an irrigated Mediterranean agroecosystem under present and future climate conditions. For that purpose, two field experiments were used for inverse calibration and validation of the WAVE model (Water and Agrochemicals in the soil and Vadose Environment), based on continuous soil water content data, soil nitrogen content and crop measurements. The calibrated and validated model was subsequently used in advanced scenario analysis under present and climate change conditions. Under present conditions, a late termination date increased cover crop biomass and subsequently soil water and N depletion. Hence, preemptive competition risk with the main crop was enhanced, but a reduction of nitrate leaching also occurred. The hypothetical planting date of the following cash crop was also an important tool to reduce preemptive competition. Under climate change conditions, the simulations showed that the termination date will be even more important to reduce preemptive competition and nitrate leaching. [ABSTRACT FROM AUTHOR]

Catchment flow regimes alteration is likely to be a prominent consequence of climate change projections in the Mediterranean. Here we explore the potential effects of climatic change on the flow regime of the Thau and the Chiba catchments which are located in Southern France and Northeastern Tunisia, respectively. The Soil and Water Assessment Tool (SWAT) hydrological model is forced with projections from an ensemble of 4 climate model (CM) to assess changes and uncertainty in relevant hydrological indicators related to water balance, magnitude, frequency and timing of the flow between a reference (1971–2000) and future (2041–2071) periods. Results indicate that both catchments are likely to experience a decrease in precipitation and increase in temperature in the future. Consequently, runoff and soil water content are projected to decrease whereas potential evapotranspiration is likely to increase in both catchments. Yet uncertain, the projected magnitudes of these changes are higher in the wet period than in the dry period. Analyses of extreme flow show similar trend in both catchments, projecting a decrease in both high flow and low flow magnitudes for various time durations. Further, significant increase in low flow frequency as a proxy for hydrological droughts is projected for both catchments but with higher uncertainty in the wet period than in the dry period. Although no changes in the average timing of maximum and minimum flow events for different flow durations are projected, substantial uncertainty remains in the hydrological projections. While the results in both catchments show consistent trend of change for most of the hydrologic indicators, the overall degree of alteration on the flow regime of the Chiba catchment is projected to be higher than that of the Thau catchment. The projected magnitudes of alteration as well as their associated uncertainty vary depending on the catchment characteristics and flow seasonality. [ABSTRACT FROM AUTHOR]

Reaching the Sustainable Development Goal (SDG) 6 on water and sanitation is fundamentally important and conditional to the achievement of all the other SDGs. Nonetheless, achieving this goal by 2030 is challenging, especially in the Global South. Science lies at the root of sustainable development and is a key to new solutions for addressing SDG 6. However, SDG 6-related scientific outputs are often unknown, forming disconnections between academic world and practitioners implementing solutions. This study proposed a bibliometric and text mining method to qualitatively and quantitatively characterize the contribution of water research to the achievement of SDG 6. The method was applied for water research produced by Belgian-affiliated authors with a focus on the Global South collaboration. Despite accounting for less than one percent of the total global publications, Belgian water research has had a relatively high publication rate compared to its neighboring countries. We observed longstanding collaborations between Belgian and scientists from worldwide countries, and an increasing collaboration rate with countries from the Global South. The biggest share of publications focused on topics related to the targets 6.3, 6.4, 6.5, and 6.6, with the main hotspots for Belgian water research being water treatment, water stress, water pollution, climate change, and water modeling. The findings of the bibliometric search have been integrated into an online, user-friendly dashboard to facilitate the identification of research body and experts for practitioners and policy makers. The presented methodology is sufficiently generic and can be used to optimize other science programs in relation to the 2030 Agenda in other countries and regions. In this case study, the findings support shaping the Belgian cooperation and development policy in the water sector, and creating appropriate synergies between Belgian water researchers and their counterparts in the Global South. • New method to extract and analyze the publications supporting SDG 6 & its targets. • Belgian water research had a high publication rate compared to its neighbors. • A raising collaboration rate between Belgium and the Global South countries. • Biggest share of Belgian water research has focused on targets 6.3, 6.4, 6.5 & 6.6 • Findings and dashboard are important for optimizing the development of SDGs. [ABSTRACT FROM AUTHOR]