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[EN] Exploitation of groundwater resources with no proper characterization of water reserves jeopardizes the quantity and quality of water available in the future. A major challenge is finding appropriate methods or coefficients to evaluate the carrying capacity of the aquifer. The objective of this study was to quantitatively and qualitatively characterize water reserves to provide information and management strategies for the rational use of available water resources in an alluvial aquifer in the Brazilian Northeastern semi-arid region. Shallow and medium-depth wells were analyzed. Water tables were monitored in the dry and wet seasons to calculate water reserves. Groundwater samples were collected for the determination of water quality for irrigation purposes. The increase in agricultural activities is jeopardizing the sustainability of the aquifer’s water, as reserves are not sufficient to meet this demand. Groundwater quality is not limiting for agricultural use. Converting surface irrigation into localized methods will potentially increase water productivity and consequently the irrigated area. This study provides data and makes it possible to recommend appropriate strategies for the exploitation of groundwater resources for the maintenance of agricultural activities under semi-arid conditions, and to avoid overexploitation., [PT] A explotação dos recursos hídricos subterrâneos sem a caracterização adequada das reservas hídricas compromete a quantidade e a qualidade da água disponível no futuro. Um grande desafio é encontrar métodos ou coeficientes apropriados para avaliar a capacidade de recarga do aquífero. Objetivou-se caracterizar qualiquantitativamente as reservas hídricas, com vistas a disponibilizar informações e estratégias de gerenciamento para o uso racional dos recursos hídricos disponíveis em um aquífero aluvial no semiárido do Nordeste brasileiro. Foram analisados poços rasos e de média profundidade. Os níveis estáticos dos poços foram monitorados nos períodos secos e chuvosos para calcular as reservas hídricas. Foram coletadas amostras de água para a determinação da qualidade da água para fins de irrigação. A constante ampliação de áreas para atividades agropecuárias está comprometendo a sustentabilidade hídrica do aquífero, uma vez que as reservas não são suficientes para atender a essa demanda. A qualidade das águas subterrâneas não é limitante para uso agropecuário. A conversão da irrigação por superfície em métodos localizados irá proporcionar o aumento da produtividade da água e, consequentemente, a área irrigada. O estudo fornece dados e permite recomendar estratégias apropriadas para a explotação dos recursos hídricos subterrâneos, com vistas à manutenção das atividades agropecuárias em condições semiáridas, de modo a evitar a superexplotação., This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). Acknowledgments are also due to the Agência Estadual de Desenvolvimento do Ceará (ADECE), Secretaria de Desenvolvimento Econômico e Trabalho do Ceará (SEDET), Centro do Instituto de Educação Tecnológica (CENTEC), Fundação de Amparo à Pesquisa Científica e Desenvolvimento Tecnológico do Ceará (FUNCAP), and Chief Scientist Program, Brazil, for the financial support provided for this research and the award of scholarships.

Variable rate irrigation (VRI) shows attractive cost/benefit ratios, as compared to drip irrigation, when implemented in large orchards with suitable field and planting geometries. To evaluate the effectiveness of apparent electrical conductivity (ECa), elevation (Z), topographic wetness index (TWI) and time-series of Sentinel-2 NDVI imagery for delimiting VRI zones in olive groves, a study was conducted in a 40-ha commercial plot in southern Spain (Ecija, Seville), equipped with a linear move sprinkler irrigation system and with trees on a 4 × 7 m grid. Soil samples were collected at 140 points on a regular grid with depth intervals of 0.3 m down to 1.2 m and analyzed for soil texture. Relationships between soil texture, topography, ECa and NDVI were analyzed using correlation analysis and regression trees. Time series of correlation between ECa and NDVI showed a seasonal pattern because of the growth-decline pattern of the grass soil cover. The regression tree analysis showed that ECa and elevation were most relevant for classifying NDVI (R2=0.70). Fuzzy k-means classification using ECa+Z yielded 4 classes while for ECa, ECa+Z+TWI and ECa+Z+TWI+NDVI 2 classes were obtained. The zoning based on ECa+Z classified clay content and the 0.95 percentile NDVI successfully. This classification was adopted for VRI since the involved variables can be related to soil water availability. Confounding effects of coarse fragments and soil water content on the clay-ECa relationship could be resolved in future studies by measuring theses variables to improve further the classification.AcknowledgementThis work is funded by the Spanish State Agency for Research through grants PID2019-104136RR-C21 and PID2019-104136RR-C22/AEI/10.13039/501100011033 and by IFAPA/FEDER through grant AVA2019.018.

Solar photovoltaic (PV) irrigation is increasingly used in agriculture, driven by its low operation cost and virtually zero emissions, providing electricity access in rural areas. However, the high investment cost requires an optimal design. The objective of this work was to develop a user-friendly tool to optimally size a PV generator that satisfies crop irrigation needs under local constrictions. The ODSIS (Optimal Design of Solar Irrigation System) tool, was organized in three calculation modules, preceded by two complements, which determine the daily crop irrigation needs and power demand of the pumping system. Then, the first module sizes the PV plant, considering a multiplication factor, and provides the PV production potential throughout each day of the season. The second and third modules evaluate the total investment cost and equivalent greenhouse gas emissions avoided by comparison with traditional energy sources. This tool was applied to a case study in Senegal for which a multiplication factor of 1.4 was obtained for the optimal PV plant size. Between 22% to 64% of the investment cost corresponded to the PV pumping system, depending on the irrigation technique. The use of PV energy in the case study would represent an annual economic saving for the farmer after 5 to 8 years of payback period, avoiding the emission of between 29.8 and 37.9 tCO2eq/year for the case study area.

Many governments and international agencies have promoted irrigation management transfer (IMT) in order to reduce operations and maintenance costs and satisfy farmers' willingness to improve their irrigation service by self-management. However, IMT has produced both satisfactory and unsatisfactory results. This paper presents a participatory research-based assessment of IMT in a case study in Northwest Argentina. The study combined conventional irrigation performance assessment and a survey of farmers' perception of the water delivery service and willingness to participate in water users associations. The assessment compared two subsystems in the Río Dulce Irrigation District with different levels of management transfer. Water service in the subsystem where management had been transferred allowed flexible delivery schedules that facilitated a diversified cropping pattern, greater irrigation intensity, and resulted in more water use. Farmers in the transferred subsystem were more aware of the problems of the irrigation service than farmers in the non-transferred subsystem. The perception of problems in the non-transferred subsystem increased with the level of the farmer's professionalism and technical knowledge. The transmission of requests and complaints from farmers to managers was more transparent in the transferred subsystem than in the non-transferred one., The first author acknowledges the grant funded by INTA to develop his PhD at the Instituto de Agricultura Sostenible (CSIC) in Spain, APAZ-IV, and UER.

Solar irrigation pumps are considered as an alternative to the use of diesel and electric pumps due to the high cost of energy. These pumps are now increasingly used in the Niayes area. Thus, a more in-depth knowledge about the components of a solar pumping system and their characteristics available on the market as well as prices can be beneficial. This study was conducted to have an idea on the baseline of the use of solar irrigation pumps in this area. To perform this study, surveys were conducted among 12 suppliers and 10 service providers located in Dakar, Thies, Louga and Saint-Louis region and among 53 users located in Potou area which is in Louga region. Results show a wide range of pump brands and characteristics. Brands found were Lorentz, LIKOU, SHIMGE, Grundfos, Solar pump, Feili, Difful, JUQIANG, Solar tech, and Asaman. The pumps’ flow rate varies between 2.5 m3/h and 45 m3/h, the pressure ranges from 15 m to 160 m and the power is between 0.072 kW and 10 kW. The price of these pumps varies depending on the brand used and their characteristics. In addition, other materials are available, such as panels with power ranging from 80 W to 330 W and electric cables. The price of these components varies according on the type used. Thus, the investment cost for implementation varies between 640 euros (420,000 CFA) and 25,087 euros (16,455,919 CFA). The cost of installation varies between 76.3 euros (50,000 CFA) and 1219.6 euros (800,000 CFA). Concerning maintenance, it is generally free during the warranty period when the equipment is supplied and installed by the same company. However, the cost of maintenance varies between 152.5 euros and 457.4 euros/year or is estimated at 45.7 euro/maintenance after the warranty years. Investigations conducted among users show that farmers in general do not perform pump maintenance due to a lack of knowledge and financial means. Thus, according to farmers, factors that impact pumps operation are the low sunshine that occurs between December and January and the iron in the water and low well discharge.

Northern Niayes is an area where agriculture is the main activity. Water used for irrigation in this area comes exclusively from groundwater. Farmers do not have access to electricity, thus fuel is the main source of energy used, which is very expensive. The objective of this study was to assess the techno-economic feasibility of solar irrigation pumps. Regarding technical feasibility, pump sizing was carried out on the basis of irrigation management, irrigation techniques, and water distribution. Also, the economic feasibility was studied on the basis of the Net Present Value, Benefit-Cost Ratio, Internal Rate of Return and Payback Period. Results showed for cultivated area ranging from 0.05 ha to 1.91 ha, pumps’ flow rate does not vary greatly from one irrigation technique to another. It varies between 2.5 m3/h and 31 m3/h. However, pressure and power are higher when using drip and sprinkler irrigation techniques, ranging from 27.8 m to 39.9 m for drip and 40.1 m to 58.5 m for sprinkler irrigation. The power varies between 0.05 kW and 1.6 kW for manual, between 0.05 kW and 2.5 kW for drip and between 0.1 kW and 4.75 kW for sprinkler irrigation. The investment cost is variable (669 euros to 21,400 euros), depending on the cultivated area, pump brands and characteristics, and irrigation techniques. Results show that the investment cost ranges from 669 euros (438,500 CFA) to 4090 euros (2,683,000 CFA) when using the manual irrigation technique, from 1281 euros to 20,600 euros when using the drip irrigation technique and from 819 euros to 21,403 euros when using sprinkler irrigation technique for individual pumps. The investment cost is higher when using reservoirs. In this case, the investment cost varied between €722 and €6062 for manual irrigation, €1532 and €25,882 for drip irrigation and €900 and €28,000 for sprinkling. However, the total investment cost at the entire lowland scale is higher when farmers use the pumps individually and lower when farmers use the pumps in groups when using manual and drip irrigation techniques. NPV varies between 15,993€ (0.75 ha) and 103,139€ (1.41 ha) and between 13,064€ and 86,139€ when using sprinkler irrigation techniques with PVC pipes and when using the drip irrigation technique, respectively. BCR is estimated to average 2.2, 2, and 2 respectively when using manual, drip, and sprinkler irrigation techniques. In addition, PBP is reached more rapidly when using the manual irrigation technique.

Ameliorer l’efficience de l’eau d’irrigation dans les exploitations agricoles presente de nombreux avantages tant sur les plans economiques qu’environnementaux. Cependant, comme le demontre l’auteur de cet article, cela peut induire des effets negatifs, dont notamment des « effets rebonds » bien connus dans le domaine des economies d’energie, qui peuvent induire en erreur les politiques visant a accroitre la disponibilite de l'eau a l'echelle des bassins versants.

Irrigation is expanding in the tropics and could make an important contribution to the intensification of production in those tropical areas where a dry season limits productivity. A study was carried out to characterize irrigation performance and the yield gaps of a tropical irrigation scheme that covers more than 41 000 ha in northern Costa Rica. The study covered a 5-year period, from 2014 to 2018. The performance indicator relative irrigation supply (RIS) ranged between 2.48 and 3.78, values higher than those typically observed in schemes of temperate areas, but in the low range of those documented in the tropics. Despite the excess of water usage, it was found that there were farms with water shortages, especially in the canal tails during the dry season, but there was also damage caused by excess of water in the rainy season. The potential yield of the two main crops (rice and sugar cane) was determined with the AquaCrop simulation model. Actual yields were determined via a farmers' survey that also inquired about irrigation management issues. Yield gaps were determined for each of the two sectors that make up the irrigation scheme (South and West canals). The mean yield gap of rice in the South Canal sector (3.34 t ha−1) was smaller than that of the West Canal sector (4.84 t ha−1). The highest yield gap of rice occurred in the rainy season in the West canal sector. The yield gap of sugar cane in the West canal sector was significantly larger than that in the South canal sector (170 and 148 t ha−1, respectively). A farmers' survey, combined with an examination of soil maps, revealed that poor drainage through the heavy soils that predominate in the West canal sector is one of the main causes of the large yield gap, in both rice and sugar cane. While users are relatively satisfied with the provision of irrigation water and its cost, several opportunities (e.g. water delivery, amount of fertilizer in sugar cane, water supply and irrigation system on farms) for improving scheme performance and for closing the yield gaps are discussed., University of Córdoba; University of Costa Rica.

Performance evaluation of irrigated agriculture is an important tool that assists in decision-making on water management in the river basin, particularly in tropical semiarid regions. This study was carried out using information from the Jaguaribe River basin, located in the Northeast region of Brazil, which has an important restriction in the availability of water resources and high competition for water use. From a set of indicators (production, water, economic, and social), the overall performance index of irrigated agriculture was estimated (ranging from zero to 1.0) for two scenarios: high water scarcity and low water scarcity. The performance index used was based on the mean value of these security criteria normalized with respect to the maximum value of the indicator for the crop obtained in the sub-basin. A low performance index of irrigated agriculture (less than 0.3) has always been associated with inadequacy of more than one security indicator. Crops with significant cultivated areas and, therefore, requiring a high volume of irrigation, such as rice, sugar cane, banana, and green coconut, require technical interventions related to the management of the soil–water–plant system aiming at improving yield with less water. Under conditions of water restrictions, crops with performance indexes higher than 0.3 should be prioritized. The study presented here for Jaguaribe River basin may support public policies related to irrigation and agronomic techniques necessary to improve the performance of agricultural under tropical dry lands., This research was funded by Ceará State Development Agency (ADECE) and Cearense Foundation to Support Scientific and Technological Development (FUNCAP). The APC was funded by Institute of Technological Education Center (CENTEC).

Applying pruning residues in the lanes of olive groves has become a popular practice because it is economical and accrues benefits for soil and water management. This study presents an analysis of the impact of different rates of pruning residue on soil properties, in particular related with soil quality. Over 4 annual campaigns, chopped pruning residues used as a mulch were analyzed in terms of composition, coverage and moisture content to evaluate their effects on the amount of soil organic carbon (−10 cm and −20 cm) and CO2 emissions, temperature and moisture. The experiment was carried out in a super-intensive olive orchard in Cordoba (SE, Spain) and used four amounts of fresh pruning residue: 7.5 t ha⁻1(T1), 15.0 t ha⁻1 (T2) and 30.0 t ha⁻1 (T3), with a control T0 = 0.0 t ha1. Mulch mean leaf fraction was 46.0 ± 17.5% (±SD) and initial water content, 24.8 ± 8.6%. The mulching benefits for soil moisture were observed in amounts of pruning residue >7.5 t ha⁻1, which are only produced in super-intensive olive groves or in orchards with high tree densities. The low impact of the treatments on soil moisture was explained by the dramatic annual variations in residue moisture contents, caused by the regimes of high temperatures and rainfall-evapotranspiration deficits inherent to the Mediterranean Basin climate. Thus, the mulching capacity only resulted efficient when the residues were still humid in spring. In addition, 15.0 t ha⁻1 of pruning residues was the threshold to provide significant increases in soil organic carbon at depths of 0–20 cm. Thus, accumulating pruning residue in lanes at rates of over 15 t ha⁻1 (T2 and T3) is more convenient than a uniform distribution with lower amounts, due to the low mineralization rates occurring during warm seasons and the larger inputs of OM increasing the annual balance of SOC., This research was supported by the research projects CGL 2015-64284-C2-2-R, funded by the MINECO-FEDER (Spanish Ministery of Economy and Competitiveness).

This article also appears in: A tribute to Edward P. Glenn (1947-2017): a legacy of scientific environmental assessment and applications in hydrological processes., Evapotranspiration (ET) is an important parameter in hydrologic processes and modelling. In agricultural watersheds with competing uses of fresh water including irrigated agriculture, estimating crop evapotranspiration (ETc) accurately is critical for improving irrigation system and basin water management. The use of remote sensing-based basal crop coefficients is becoming a common method for estimating crop evapotranspiration for multiple crops over large areas. The Normalized Difference Vegetation Index (NDVI) and the Soil Adjusted Vegetation Index (SAVI), based on reflectance in the red and near-infrared bands, are commonly used for this purpose. In this paper, we examine the effects of row crop orientation and soil background darkening due to shading and soil surface wetness on these two vegetation indices through modelling, coupled with a field experiment where canopy reflectance of a cotton crop at different solar zenith angles, was measured with a portable radiometer. The results show that the NDVI is significantly more affected than the SAVI by background shading and soil surface wetness, especially in north–south oriented rows at higher latitudes and could lead to a potential overestimation of crop evapotranspiration and irrigation water demand if used for basal crop coefficient estimation. Relationships between the analysed vegetation indices and canopy biophysical parameters such as crop height, fraction of cover and leaf area index also were developed for both indices., Daugherty Water for Food Global Institute; Department of Biological and irrigation Engineering, Utah State University; Institute for Sustainable Agriculture-CSIC, Cordoba, Spain; Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Grant/Award Number: RTA2005-047; Programa Nacional de Ayudas Para La Movilidad de Profesores de Universidad e Investigadores Españoles y Extranjeros of The Ministerio de Educacion Y Ciencia, Grant/Award Number: SAB2004-0200.

In the assessment of irrigation schemes, the accuracy of performance indicators related to the water balance could be improved by estimating crop evapotranspiration (ETc) using remote sensing techniques. The two main remote sensing approaches to estimating ETc are the surface energy balance and the FAO56-based approach, that uses the ability of vegetation indices (VI) to trace the crop coefficient. Both approaches were evaluated comparatively at the Río Dulce irrigation scheme in Argentina (where the predominant crops are cotton, alfalfa, and maize) using products from the Landsat 7 and 8 sensors provided by the EEFlux application. The first analysis used field-specific, VI-derived basal crop coefficients obtained for 1743 fields using series of 9–29 satellite images along the 2014−15 irrigation campaign. The second analysis used 30 fields (grown with cotton and maize) where the actual irrigation schedules in the 2014−15 irrigation campaign were known. A root zone soil water balance was computed in these fields using the FAO56 dual approach with field-specific, VI-derived basal crop coefficients. The ETc obtained from the water balance was compared with the ETc estimated using a single crop coefficient approach that uses field-specific VI and takes into account soil evaporation (herein called synthetic approach), and with the ETc obtained with the METRIC surface energy balance model as facilitated by the EEFlux application. The third analysis was a simulation analysis of errors in the estimation of the ETc due to the interpolation to daily values of single crop coefficients and basal crop coefficients determined at hypothetical satellite overpass intervals of longer than one day. The VI-derived basal crop coefficient curves obtained for the 1743 fields of the first analysis were below the locally adopted standard (not field-specific) basal crop coefficient. Crop evapotranspiration in the 8005 ha covered by this analysis was about 20 % higher when applying standard non-field specific curves than when applying VI-derived curves. This difference pointed to the importance of using field-specific estimations of ETc. In the analysis carried out on the 30 selected fields, the ETc estimated using the VI-based approach agreed well with the ETc obtained from the water balance except under water deficit conditions. The crop coefficients obtained for these fields using the METRIC model correlated with those obtained by applying the VI-based method, although the former tended to be higher than the latter in the lower value range. The analysis of interpolation errors showed that when satellite overpass frequency is greater than one week and water deficit is mild or inexistent, the interpolation of crop coefficients (for instance, of those derived from an energy balance) gives errors of ETc estimations that are greater than those resulting from the VI-based approach. Under water deficit conditions, the VI-based approach systematically overestimates evapotranspiration., The first author acknowledges the grant funded by INTA to develop his PhD at the Instituto de Agricultura Sostenible (CSIC) in Spain.

Water sowing and harvesting (WS&H) consists of a series of ancestral procedures by which humans collect and infiltrate (sow) rainwater and runoff underground, so as to recover (harvest) it downgradient at some later time. This management of the water has made it possible for various regions of Ibero-America that is, Latin America plus the Iberian Peninsula to overcome dramatic cultural and climatic changes over the centuries. The principles governing WS&H coincide with those pursued under the present paradigm of Integrated Water Resource Management. Moreover, WS&H implies a better use of water and enhanced conservation of the environment and patrimony, as well as recognition of rural communities as vital custodians of the land and of its relevant cultural aspects. The main WS&H systems that serve Ibero-American countries are described here, emphasizing the principles underlying this means of water management as exemplary of hydrogeoethical systems.

The performance of irrigation schemes around the world has been below expectations. The assessment of irrigation performance is an essential step towards improving agricultural water use. One of the primary performance indicators is the relative irrigation supply (RIS, the ratio between the amount of water delivered and the crop net irrigation requirements). This study presents a worldwide analysis of irrigation scheme performance by evaluating key attributes that influence the RIS. The analysis was based on a review of reports and scientific papers that yielded 264 cases belonging to 25 countries in six world regions. The database was subjected to two types of statistical analysis: k-means clustering and analysis of covariance (ANCOVA). The cluster grouped irrigation schemes which were characterized by low RIS and advanced irrigation technology. The ANCOVA showed that the RIS co-varied significantly with the variation in precipitation, delivery schedule, on-farm irrigation systems, distribution network, and region, but not with the crop. The ANCOVA also showed that modern pressurized on-farm irrigation systems and on-demand distribution systems significantly improve RIS. The ANCOVA general linear model had a good capacity to predict RIS with a coefficient of determination of R2 = 0.83., The first author acknowledges the financial support of the University of Costa Rica to carry out his doctoral degree at the University of Córdoba, Spain.

18th LACCEI International Multi-Conference for Engineering, Education, and Technology: “Engineering, Integration, and Alliances for a Sustainable Development” “Hemispheric Cooperation for Competitiveness and Prosperity on a Knowledge-Based Economy”, July 27-31, 2020, Virtual Edition., [ES] El rescate de la siembra y cosecha de agua, técnica ancestral de las civilizaciones, cada vez alcanza un mayor apogeo en los albores del siglo XXI, debido a su practicidad y eficiencia, pero sobre todo por los principios de sostenibilidad. La gestión del agua es un reto apremiante del siglo, ante el crecimiento de la población y la consecuente mayor demanda de agua y las acciones antrópicas que la contaminan, siendo el agua subterránea una alternativa al problema, y la siembra y cosecha de agua se presenta como una solución en diferentes zonas de la geografía regional. El presente trabajo tiene como objetivo analizar los sistemas de Siembra y Cosecha de Agua (SyCA) mediante las experiencias de los diferentes casos en Iberoamérica que configuran un mecanismo de cooperación y transferencia del rescate de estas técnicas ancestrales. La metodología comprende i) análisis comparativo de las técnicas de SyCA y sus características en varios países, ii) análisis FODA del proceso de rescate de SyCA mediante participación de cinco expertos internacionales, iii) estrategias para la sostenibilidad de los procesos de SyCA en países iberoamericanos. Actualmente se registran muchos casos de SyCA en Iberoamérica que presentan novedosos casos, trabajados preferencialmente por comunidades rurales que solucionan problemas de abastecimiento de agua del siglo XXI con técnicas ancestrales sostenibles de siembra y cosecha de agua., [EN] The rescue of water sowing and harvesting, an ancestral technique, is becoming increasingly popular at the dawn of the 21st century, due to its practicality and efficiency, but above all due to the sustainability principles. Water management is the challenge of the century, given the population growth and the consequent increased demand for water and the anthropic actions that pollute it, with groundwater being an alternative to the problem, and water sowing and harvesting is presented as a solution in different areas of the regional geography. The present work aims to analyze the systems of Water Sowing and Harvesting (SyCA, by its acronym in Spanish) through the study of the different cases in Iberoamerica that configure a mechanism of cooperation and transfer of the rescue of these ancestral techniques. The methodology includes i) matrix of comparative analysis of SyCA techniques and their characteristics, ii) SWOT analysis of the SyCA rescue process through the participation of five international experts, iii) strategies for the sustainability of SyCA processes in Iberoamerican countries. Currently, there are many cases of SyCA inIberoamerica presenting novel cases, worked by rural communities that have a sustainability approach.

This article belongs to the Special Issue Feature-Based Methods for Remote Sensing Image Classification., The application of satellite single-pass interferometric data to crop-type mapping is demonstrated for the first time in this work. A set of nine TanDEM-X dual-pol pairs of images acquired during its science phase, from June to August 2015, is exploited for this purpose. An agricultural site located in Sevilla (Spain), composed of fields of 13 different crop species, is employed for validation. Sets of input features formed by polarimetric and interferometric observables are tested for crop classification, including single-pass coherence and repeat-pass coherence formed by consecutive images. The backscattering coefficient at HH and VV channels and the correlation between channels form the set of polarimetric features employed as a reference set upon which the added value of interferometric coherence is evaluated. The inclusion of single-pass coherence as feature improves by 2% the overall accuracy (OA) with respect to the reference case, reaching 92%. More importantly, in single-pol configurations OA increases by 10% for the HH channel and by 8% for the VV channel, reaching 87% and 88%, respectively. Repeat-pass coherence also improves the classification performance, but with final scores slightly worse than with single-pass coherence. However, it improves the individual performance of the backscattering coefficient by 6–7%. Furthermore, in products evaluated at field level the dual-pol repeat-pass coherence features provide the same score as single-pass coherence features (overall accuracy above 94%). Consequently, the contribution of interferometry, both single-pass and repeat-pass, to crop-type mapping is proved., This work was funded by the Spanish Ministry of Science and Innovation, the State Agency of Research (AEI) and the European Funds for Regional Development (EFRD) under Project TEC2017-85244-C2-1-P, and by the European Commission, H2020 Programme, under Project MOSES (Managing crOp water Saving with Enterprise Services).

Agricultural policies and social change influence irrigation management decisions and their associated effects. The changes in the Common Agricultural Policy of the European Union have deeply affected irrigated agriculture in the Mediterranean region. In this region, hydrology is rather complex and the environment particularly vulnerable. We monitored cropping patterns and the water balance in a sprinkler-irrigated catchment in Central Portugal over thirteen irrigation seasons and twelve rainfall seasons. There was wide variation in annual rainfall (from 283 mm to 667 mm) and in the intensity of rainfall events from year to year. A monitoring station at the catchment outlet was installed to measure runoff which, together with field observations, allowed us to compute a water balance for both the rainfed and the irrigation seasons. Changes in cropping intensity led to changes in the depth of irrigation. Irrigation runoff followed irrigation depth and both followed the trend of cropping intensity. Less intensive cropping also reduced the off-site effects of agricultural activities. The runoff coefficient was 0.28 in the rainfed seasons and 0.02 in the irrigation seasons. The changes in the irrigation hydrology and in the off-site effects of agricultural activities in the catchment were caused by changes in cropping intensity induced by the European Union Common Agricultural Policy reforms, rather than by environmental or technical factors.

Smallholder farming is the basis of agricultural production in developing regions. Irrigation improves the household livelihood and welfare of smallholders. Furrow irrigation is the most common type of irrigation on the small farms of public irrigation schemes set up in the Northeast of Brazil during the 1970s and 1980s. However, furrow irrigation triggers environmental problems related to deep percolation, runoff and soil erosion. The objective of this research was to determine how soil was lost from irrigation furrows as a result of their management and performance. Experiments were carried out in the Curú-Pentecoste irrigation scheme located in the state of Ceará, Brazil. Three inflow rates (corresponding to the three sizes of syphons used to apply water to the furrows) were compared on 60-m long furrows in the two predominant soil classes (sandy loam and silty clay loam) during 4 or 5 irrigation events throughout the irrigation season. Runoff represented between 20 and 70% of the water applied, carrying sediments amounting up to 2.8 Mg ha−1 in 4 irrigation events. Simple irrigation practices that could improve furrow irrigation performance in the scheme are suggested. However, the environmental problems of the furrow irrigation in practice seem inherent to the irrigation method used under those conditions. The paper discusses the adoption and performance of traditional and modern irrigation technology in smallholdings in developing regions., The contribution of L. Mateos was partially funded by the project "Bases Científicas do Assessoramento na Melhoria da Irrigação", Programa Ciência Sem Fronteiras, 61/2011 MEC/MCTI/CAPES/CNPQ/FAPs, Brazil.

Regions and basins suffering from water scarcity have promoted the modernization of irrigation systems, defined as irrigation efficiency enhancement as a measure for the adaptation to a growing demand and a limited supply of water resources. In the period 2002–2015, Spain carried out an intense irrigation modernization process with the aim of achieving significant water savings and higher flexibility and to guarantee supply, among other favourable outcomes (e.g. environmental and socio-economic). Nevertheless, certain unfavourable effects of irrigation modernization also need to be discussed. This study analyses these effects in Spain based upon a DPSIR (Driving forces, Pressures, States, Impacts, and Responses) framework and a wide-ranging review of the existing empirical literature. Our findings are highly relevant to inform decision-makers in the planning of future irrigation modernization programmes worldwide., The authors have received financial support from MINECO-Grant: AGL-2014-53417-R.

Este artículo contiene 16 páginas, 6 figuras, 2 tablas., Soil degradation by water is a serious environmental problem worldwide, with specific climatic factors being the major causes. We investigated the relationships between synoptic atmospheric patterns (i.e. weather types, WTs) and runoff, erosion and sediment yield throughout the Mediterranean basin by analyzing a large database of natural rainfall events at 68 research sites in 9 countries. Principal Component Analysis (PCA) was used to identify spatial relationships of the different WTs including three hydro-sedimentary variables: rainfall, runoff, and sediment yield (SY, used to refer to both soil erosion measured at plot scale and sediment yield registered at catchment scale). The results indicated 4 spatial classes of rainfall and runoff: (a) northern sites dependent on North (N) and North West (NW) flows; (b) eastern sites dependent on E and NE flows; (c) southern sites dependent on S and SE flows; and, finally, (d) western sites dependent on W and SW flows. Conversely, three spatial classes are identified for SY characterized by: (a) N and NE flows in northern sites (b) E flows in eastern sites, and (c) Wand SW flows in western sites. Most of the rainfall, runoff and SY occurred during a small number of daily events, and just a few WTs accounted for large percentages of the total. Our results confirm that characterization by WT improves understanding of the general conditions under which runoff and SY occur, and provides useful information for understanding the spatial variability of runoff, and SY throughout the Mediterranean basin. The approach used here could be useful to aid of the design of regional water management and soil conservation measures., This research was supported by projects funded by the MINECOFEDER: CGL2014-52135-C3-3-R, CGL2014-59946-R, CGL2015-65569- R, CGL2015-64284-C2-2-R, and PCIN-2017-061/AEI. When this manuscript was first submitted Estela Nadal-Romero and Damià Vericat received a “Ramón y Cajal” postdoctoral contract (RYC-2013-14371 and RYC‐2010‐06264, Spanish Ministry of Economy and Competitiveness, MEC). Damià Vericat is now a Serra Húnter Fellow at the University of Lleida. María Fernández-Raga received a “José Castillejo” postdoctoral grant (Spanish Ministry of Education, Culture and Sports). Carla Ferreira was supported by a post-doctoral research grant from the Portuguese Science and Technology Foundation (SFRH/ BPD/120093/2016). Mariano Moreno-de las Heras received a Juan de la Cierva postdoctoral contract (IJCI-2015-26463) from the MEC. José Andrés López-Tarazón received a Vicenç Mut postdoctoral fellowship from the Autonomous Balearic Government (CAIB PD/038/2016). José Andrés López-Tarazón and Ramon Batalla also acknowledge the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUSFluvial Dynamics Research Group), and the CERCA Programme. This paper has benefited from the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306).

Conventional irrigation schedules are typically based on portions of the field where root zones hold the least available soil water. This leaves undepleted available water in areas with larger water holding capacities. The undepleted water could be used through variable-rate irrigation (VRI) management; however, the benefits of VRI without in-field mapping are unexamined. In this research, the field-averaged amount of undepleted available soil water in the root zone was calculated from the NRCS Soil Survey Geographic database for 49,224 center-pivot irrigated fields in Nebraska. Potential reductions in pumpage from mining undepleted available water were then estimated. Results of the analysis show that widespread adoption of zone control VRI technology based only on the pumping savings from mining undepleted available water may be unwarranted for current VRI costs and average pumping energy expenses in the Central Plains ($0.0026 m -3 to $0.0947 m -3 ). Pumpage reductions exceeded 51 mm year -1 for only 2% of the fields and exceeded 25 mm year -1 for 13% of the fields; thus, reductions may be small compared to annual pumpage requirements. If VRI were implemented on all fields with a potential pumpage reduction greater than 51 or 25 mm year -1 , the volume of pumpage reduction would be approximately 0.35% or 1.3%, respectively, of the total irrigation pumpage in Nebraska. These data may be a conservative estimate of pumpage reduction in fields where the measured variability in soil properties exceeds that described by the NRCS Soil Survey, or if undepleted water is mined early in the season and the soil water profile is refilled by precipitation, allowing undepleted water to be mined again. Adoption of zone control VRI for mining undepleted available water is most feasible for fields where the pumpage reduction from VRI is large and pumping costs are above normal. Pivot fields with high undepleted water were sparsely distributed across Nebraska and were often located along streams and or in associated alluvial areas. The prevalence of fields with large quantities of undepleted water differed among and within soil associations. We were unable to assign feasibility of VRI based on the soil association, as the occurrence of undepleted water varied significantly within a soil association. These findings should assist producers and other entities interested in VRI technology; however, pumpage reduction through use of undepleted soil water is only one benefit of VRI technology and management. Producers are encouraged to consider all potential benefits when analyzing VRI investments.

P. Cid was supported by a JAE Predoc (CSIC) grant. The study was financed by projects P08-AGR-03925 (Andalusia Government) and RESEL (Spanish Ministry of Agriculture, Food, and Environment).

The snow pack of Sierra Nevada, southern Spain, melts during spring and early summer, feeding ancestral irrigation channels in the region known as the Alpujarra. This simulation study compares the traditional irrigation water supply, based on proportional division, with the actual supply, based on up-downstream priority, in one watershed in the Alpujarra. A combination of three models was used for the analysis. Water supply was simulated using the snowmelt-runoff model. The snow cover required by that model was determined using satellite images. A second model simulated the distribution of water based on proportional division and on up-downstream priority. Irrigation requirements and return flows were simulated using a soil–water balance. Proportional division is an inherently equitable mechanism for distributing water, but can lead to water deficits for different crops in a command area. The analysis demonstrated this premise not be true. The superiority of proportional division was magnified in dry years. Because of the internal reuse of return flows, irrigation consumptive use coefficient (the ratio of irrigation water that is evapotranspirated by the crops to the total amount of irrigation water that leaves the area of concern during the period of analysis) at the watershed scale was significantly greater than at the irrigation-channel scale. This result illustrated, based on tradition in ancestral irrigation community, the notion of integrated water resources management.

In water-scarce environments, water conservation is a means to increase agricultural production and preserve the environment. Water conservation can be approached at different scales with different objectives. Water productivity (the ratio between crop production and water use or water consumption) is increased by reducing non-beneficial use and by regulating water applications as to reduce transpiration in smaller proportion than yield. Water productivity can also be modified through other agronomical practices and breeding. The consumptive use coefficient (consumptive use to supply ratio) can be enhanced through various engineering solutions that reduce the use of irrigation water and energy although they do not necessarily reduce consumptive use. Therefore, engineering solutions for water conservation at farm level do not imply basin-scale water conservation. However, agronomical solutions such as regulated deficit irrigation are directly linked to basin water conservation because they goal is to reduce transpiration with little or no yield penalty. Optimising water productivity is a plausible goal in some situations; however, in others it clashes with profit maximization, food production and food security. Concerning breeding, past evidence shows that except for very harsh environments, selection for greater transpiration efficiency, evaluated physiologically as the ratio of photosynthetic assimilation versus transpiration or indirectly through the stable carbon isotope signature of plant dry matter, may have a negative effect by limiting yield potential as well as productivity under a wide range of water stress conditions., Contribution of J.L. Araus was supported in part by the Spanish Project AGL2013-44147-R.

The vegetation index (VI)-reference evapotranspiration (ETo) method incorporates the estimation of basal crop coefficients from spectral VIs into the FAO56 guidelines for computing crop evapotranspiration (ET). Previous research pointed to the possibility of the differential spectral response of some Mediterranean crops, specifically olive trees. To evaluate this hypothesis and the potential related effects on the VI-ETo method, this work studied the spectral response of four Mediterranean canopies under full vegetation coverage: three fruit trees (olive, orange and almond trees), and the holm oak trees of the dehesa ecosystem. Spectral measurements were taken on dense vegetation placed on a workbench and over dense treetops, avoiding in both cases the effect of soil background. The results showed that the soil adjusted vegetation index (SAVI) for full-cover olive trees was significantly lower than for other fruit trees (0.57 for olive trees vs. 0.71 for orange tree and 0.70 for almond tree). SAVI of olive vegetation measured on the workbench was lower than that measured over treetops, probably due to the effects of canopy architecture and shadowing. SAVI obtained on oak treetops (0.51) was even lower than that on olive treetops. This differential spectral response of olive and oak trees influenced the estimation of ET (and water stress). The validation using ET measurements obtained with the eddy covariance method in the olive orchards showed a reduction of root mean square deviation (RMSD) from 0.73 to 0.6 mm day−1 when daily ET was estimated assuming SAVImax = 0.57 in comparison with a generic value for Mediterranean crops., The authors would like to acknowledge funding supplied by the FPU subprogram - Ministerio de Educación, Cultura y Deporte - Gobierno de España. Additional support was provided by the project LIFE AGROgestor (LIFE16ENV/ES/287) and SensDehesa (PP.PEI.IDF201601.16), co-funded at 80% by the European Regional Development Fund (ERDF), as part of the Andalusian operational programme2014-2020. Dr. Andreu work has been funded by the European Union’s Horizon 2020 Research and Innovation programme under the Marie Skłodowska-Curie grant agreement No703978.

Micro irrigation has been claimed to be the world's most valued irrigation innovation. However, both its potential to save water and its adaptability to smallholders’ needs are being questioned, while its energy requirement implies financial and environmental costs that are not affordable everywhere. This paper contributes to this debate with a field performance assessment of smallholder micro irrigation systems in the Baixo Acarau Irrigation District, Ceara, Brazil, and a novel analysis model that depicts the energy-water-yield nexus by linking irrigation performance with energy efficiency and yield gap. Irrigation system performance was evaluated in a sample of 40 family lots and compared to design performance in a fairly homogeneous subset of them. Pumping inefficiency and inappropriate filtering have been at the root of system deficiencies. The great variability of irrigation performance indicated a wide margin for improvement and the possibility of using prominent farmers as benchmarks. Although there has been “technology translation” in the irrigation district that included local innovation in the filtering system, the process has not been completed. It is concluded that the adoption of foreign irrigation technology could be accelerated with the collaboration between local innovators and publicly-supported irrigation advisory services using integrated performance assessment approaches like the one presented here.

Several decision support systems have been developed and many of them are focused on efficient use of water and energy resources. These include the Irrigation Advisory Service, combined with the use of benchmarking techniques and energy audits. In Brazil, the pioneer project called the Irrigation Advisory Service has been developed in Baixo Acarau irrigation district, located in the north-east of Brazil. The main goal of the project is to transfer information about irrigation to farmers. The aim of this paper is to present the results of the Irrigation Advisory Service activities in Baixo Acarau irrigation district, during the 2011, 2012 and 2013 irrigation seasons. Moreover, the results from the estimation of several performance indicators and from energy: audits carried out are shown as a complementary activity developed by the Irrigation Advisory Service. At the beginning of the irrigation season, on-field emission of uniformity was close to 67%. During the following evaluations, after recommendations of the Irrigation Advisory Service about the necessity of corrections to the systems, emission of uniformity reached 85%. With regard to the use of performance indicators, some problems relating to maintenance of equipment were noted, resulting in malfunctioning pumps. Copyright © 2015 John Wiley & Sons, Ltd.

Groundwater governance has acquired relevant economic, social and political importance in the last decades, especially for developing countries where groundwater abstractions have become critical to sustain its growth. Nowadays there are few examples of effective groundwater governance. Despite the fact that most water policies target sustainability in the use of groundwater, a majority of aquifers are still overdraft as it is the case in the Mediterranean region and elsewhere. Good governance of groundwater resources should be capable to offer effective responses to achieve stated goals as well as to solve conflicts and avoid the “tragedy of the commons”. This paper discusses effective governance of groundwater including the description of the recent evolution in the governance of two specific neighboring aquifers located in the North of Granada province (Andalusia, southeastern Spain). Both aquifers are representative of a semi-arid geographical context with Mediterranean climatic conditions and an intense irrigated agricultural development occurred in last decades based on groundwater abstractions. The aquifers are contiguous and share similar socioeconomic and natural characteristics, although both aquifers have developed different governance models and thus have achieved different sustainability results, what makes this case study of special interest.

Fittings called start connectors are usually employed to attach each lateral to its corresponding manifold in microirrigation systems. The protrusion of start connectors’ barbs into the manifold induces pressure losses due to contraction and subsequent enlargement of streamlines. In addition, when water flows from a manifold toward a lateral through a start connector, a sudden contraction followed by expansions of flow streamlines cause pressure loss whose intensity is influenced by connector’s geometry. Minor losses along manifolds or at laterals inlet due to start connectors may be significant and might be considered on subunits design or while undertaking hydraulic simulations. The objectives of this research were: (a) to develop equations based on dimensional analysis to estimate minor losses due to start connectors; (b) to compare the accuracy of the developed models against models that are currently used for estimating minor losses; (c) to undertake simulations to assess the relevance of minor losses due to start connectors in hydraulics of subunits. Minor losses due to start connectors were separated into two components. A model was developed and validated to estimate minor losses due to the protrusion of start connectors inserted along a manifold. Two models were developed and validated to estimate minor losses that occur when water flows from a manifold into a lateral line through a start connector. The required data to develop and validate the models were obtained experimentally in laboratory. Although minor losses due to start connectors represented a relative small percentage of total head losses, such effects may be significant while undertaking rigorous hydraulic simulations that require accurate estimation of pressure losses., The authors are grateful to the following Brazilian institutions for their financial support: the Federal Department of Science and Technology (MCT); the National Scientific and Technological Development Council (CNPq); the Sao Paulo State Scientific Foundation (FAPESP) and the National Institute of Science and Technology in Irrigation Engineering (INCTEI)

This deliverable aims to collect information about the data sources that the DIANA project consortium will work with. More specifically, for each work package the partners have to define the data sources they will use and create a Data Management Plan (DMP). The DMP includes a description of data management life cycle for all data sets and specifies which data will be findable, openly accessible, interoperable and re-usable. It also includes information about legal issues, privacy and maintenance. The DMP is a live document and it will be regularly updated as more information becomes available and data issues are resolved.

Accurate spatial characterization of field capacity (FC) and root zone available water capacity (R) can enhance site-specific management practices—such as variable rate irrigation—to lower input costs, reduce contaminant leaching, and/or improve crop yield. Measuring the volumetric water content after wet soils drain following substantial precipitation can provide a field estimate of FC. The average FC (FCa) for the managed root zone was determined at thirty-two locations in a topographically variable field in south central Nebraska. The difference between FC and permanent wilting point estimates—computed using a pedotransfer function—yielded values for R for the observation locations. Sampling locations were too sparse for reliable interpolation across the field. Therefore, relationships between a surrogate, or predictor, variable and soil water properties were used to provide spatial distributions of FC and R for the field. Field estimates of FCa and R were more strongly correlated to elevation (correlation coefficient, r = -0.77 and -0.76, respectively) than to deep soil apparent electrical conductivity (r = -0.46 and -0.39, respectively). Comparing maps of FCa and R from gSSURGO to maps from field characterization yielded a root mean squared difference of 0.031 m3 m-3 for FCa and 34 mm for R. Sampling seven locations across the elevation range in this field produced FCa and R prediction functions that achieved 95% and 87%, respectively, of the reduction in the standard error achievable with a larger number of sampling locations. Spatial characterization of FCa and R depends on identifying a suitable predictor variable(s) based on field knowledge and available spatial data. Well-chosen variables may allow satisfactory predictions using several sampling locations that are distributed over the entire field. Ultimately, the costs and benefits of spatial characterization should be considered when evaluating site-specific water management.

Although canal control automation has been generally disregarded in the irrigation modernization projects in Spain, regulation reservoirs formed part of most projects. Recent projects combining storage reservoirs with automatic canal control lack clear design criteria, although they are influenced by the evident benefits from the construction of reservoirs at the tail of large canals with upstream control. A case study is presented herein that evaluates the effects of enlarging the downstream pool of one of the few irrigation canals that is operated automatically in Spain using distant downstream control. The study used an unsteady flow hydraulic model that proved to be a very useful tool for demonstrating to district managers the advantages and disadvantages of alternative control strategies, including the construction of a reservoir at the canal tail.

Hydrological signatures are indices that help to describe the behavior of catchments. These indices can also be used to transfer information from gauged to ungauged catchments. In this study, different approaches were evaluated to determine volumetric runoff coefficients in 18 small/medium experimental gauged catchments of the Iberian Peninsula and to fit runoff calculations based on precipitation data for gauged and ungauged catchments. Using data derived from 1962 events, rainfall-runoff relationships were characterized and compared in order to evaluate the various hydrological response patterns. Volumetric runoff coefficients and cumulative runoff and precipitation ratios of the events that generated runoff (R cum ) minimized the root mean square error. A linear fit for the estimation of R cum in ungauged catchments was based on mean annual precipitation, rates of infiltration, the fraction of forest-land use, and the catchment channel length. Despite high catchment heterogeneity, R cum resulted in a suitable parameter to evaluate hydrological variability in rural gauged and ungauged catchments. In 50% of the catchments, the precipitation accounted for less than 50% of the runoff variation. Annual precipitation, antecedent rainfall, and base flow did not have a high significance in rainfall-runoff relationships, which illustrates the heterogeneity of hydrological responses. Our results highlight the need for signature characterizations of small/medium rural catchments because they are the sources of runoff and sediment discharge into rivers, and it is more economical and efficient to take action to mitigate runoff in rural locations., This research was supported by the research projects CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R, CGL2014-52135-C3-3-R, CGL2015-65569-R, CGL2014-56907-R, and AGL2015-65036-C3-1 funded by the MINECO-FEDER (Spanish Ministry of Economy and Competitiveness). E.N.-R. is the beneficiary of a Ramón y Cajal postdoctoral contract (Spanish Ministry of Economy and Competitiveness).

Water management at different decision levels may be supported by the assessment of evapotranspiration (ET) on large spatial scales. In this study, a previously validated approach to estimating unstressed ET, based on the ability of vegetation indices to trace crop growth and thus to derive basal crop coefficients, has been applied to the irrigated areas of the Guadalquivir river basin in southern Spain. Vegetation indices, provided by a series of high spatial resolution satellite images for 2007, 2008 and 2009, supported the assessment of daily to seasonal ET of individual fields, enabling crop-oriented and individual water use to be analysed. The segmentation of the basin into zones with homogeneous climate and crop-growth patterns was the first step towards crop identification based on temporal trends in the Soil-Adjusted Vegetation Index (SAVI). Non-permanent crops were classified with good accuracy. Existing spatial databases of permanent crops enabled land use to be determined. The applied methodology has been compiled in a planning and operational tool named MINARET (MonitorINg irrigated AgricultuRe ET) for routinely monitoring crop water consumption in the irrigated lands of the Guadalquivir basin and it is now available for the Guadalquivir river authority.

Crop coefficients (the ratio of actual and reference evapotranspiration, ET/ETo) can be derived from vegetation indices (VIs) obtained by remote sensing. If ground meteorological stations are available to calculate ETo, then the FAO method for estimating the ET of actual crops may be applied in combination with series of satellite images if it is assumed that the crops are not water stressed. This approach was evaluated for two annual crops (cotton and garlic) and three tree crops (mandarin, olive, and peach) using measurements of evapotranspiration, made with the eddy covariance method, as ground truth. Thirty images acquired by the Landsat 5 TM and Landsat 7 ETM+ sensors were used to calculate VIs and derive crop coefficients. The assessment (based on 557 data pairs) led to an overall positive valuation of the method. The root-mean-square deviation over all estimates was 0.75 mm day−1. It was concluded that the VI-ETo method is valid and robust for estimating spatially distributed evapotranspiration in large, irrigated areas. Weaknesses of the method were identified and new research to overcome these deficiencies is proposed.

Degradation of irrigation schemes, low and variable land productivity, and inefficient use of production inputs are major concerns in Mauritania. That prompted this benchmarking analysis of 17 small and 3 large irrigation schemes located along the River Senegal. The objectives were to establish benchmarks for both productivity and performance of irrigation schemes along the valley, and to inquire whether small schemes function better than large schemes. Cluster and data envelopment analyses enabled, respectively, grouping and ranking of irrigation schemes according to a set of pre-determined performance indicators: viz. energy costs, relative irrigation supply, irrigation intensity related to irrigable and equipped area, adequacy, and land productivity. Land productivity, which was highly variable, was compared to simulated land productivity for non-limiting conditions in order to determine yield gap variations. Few early sown crops were close to the simulated yield frontier of 10.6tha-1 and the mean yield was similar for large and small schemes (3.50tha-1 and 3.77tha-1, respectively). The analysis of the indicators revealed that, on average, large schemes performed similarly to small-scale schemes, but small schemes were more variable, particularly in input-use efficiency. Analysis of clusters identified three groups of irrigation schemes: viz. consuming and productive, precarious, and productive and economic. According to data envelopment analysis, four irrigation schemes were identified as technically efficient. Their average land productivity was relatively high (4.75tha-1) and energy costs were contained (59€ha-1). Data envelopment analysis also identified the particular efficient schemes that should be taken as reference for improvement of each inefficient scheme. © 2013 Elsevier B.V., This study was supported by the Spanish Agency for International Cooperation for Development and the Mauritanian Ministry for Rural Development.

The N balance allows the calculation of the fertilizer requirement which depends on the amount of N absorbed by the crop, the amount of inorganic N in the soil or produced by mineralization and N losses of the system, which are quantified by the Recovery Efficiency. A fertilization plan should take into account the variability of environmental factors, especially rain, to distribute the N with flexibility to match the specific conditions of each year. Doing so we will avoid yield reductions due to N deficiency and the negative environmental impacts by excess application. Fertilization of trees should be based on the nutrient balance (mature trees) or the growth rate expected from actual transpiration.

The soil temperature regime depends on its thermal properties (specific heat, thermal conductivity, thermal diffusivity and thermal admittance). The main factors affecting the thermal regime are water content, soil texture and compaction. The rate of heating (or cooling) of the soil is proportional to its diffusivity which is higher in sandy soils. The amount of energy stored in the soil is proportional to its thermal admittance. Soil heating occurs as a wave train with the amplitude decreasing with depth and a phase shift that also increases with depth.

Air temperature shows unstable profiles during the day and stable profiles during the night. Therefore, canopy temperature is generally higher than that of the air during the day and lower during the night. Heat transfer between the crop and the atmosphere is sustained by turbulence and will be more effective the higher the wind speed, i.e. when aerodynamic resistance is low. In situations of unstable atmosphere, turbulence is enhanced (by added thermal turbulence) while in a stable condition turbulence is reduced. The water vapor content of the atmosphere can be expressed by different variables (vapor pressure, relative humidity, vapor pressure deficit, mixing ratio, vapor density). The flow of water vapor (equivalent to energy spent as latent heat) between the crop and the atmosphere is directly proportional to the vapor pressure difference and inversely proportional to the sum of the canopy and aerodynamic resistances.

Solar radiation (short wave) is the energy source for photosynthesis, warming and evaporation in agricultural systems. Its value can be calculated as a function of latitude, time of year and cloud cover. Fifty percent of solar radiation is available to photosynthesis and is called photosynthetically active radiation (PAR), although only a very small fraction is actually used in this process. Net radiation is obtained by discounting the reflected solar radiation (which depends on the albedo) and longwave losses that depend on air temperature, humidity and cloud cover. Plants intercept all the radiation fluxes. Shortwave radiation interception is modulated by leaf angle distribution that varies with LAI and plant type. The fraction of radiation intercepted by trees can be calculated assuming simple geometrical forms (spheroids).

Nitrogen is the most important nutrient in agricultural production. The natural input of N is due to N fixation, especially by Rhizobium bacteria that infect the roots of legumes. Organic N becomes inorganic through mineralization, and then inorganic N is absorbed by plants. Often soil microorganisms “capture” temporarily inorganic N when residue with high C/N ratio decompose (immobilization process). The ammonium in the soil is converted to NO3− through nitrification which is greatly reduced in waterlogged soils. In the latter denitrification generates gaseous N forms that are lost (oxides of N and N2). Major losses of N may occur by nitrate leaching which is proportional to deep percolation and to nitrate concentration in the soil solution. A Leaching Index may be calculated as a function of rainfall and soil type to quantify the risk of leaching.

The simplest and most robust method for irrigation scheduling, i.e. deciding the dates and amounts of irrigation, is based on the water balance. The soil water deficit (depth of water required to bring the soil to field capacity) is calculated using ET and rainfall data, and rules are defined for calculating the dates and depths of irrigation. The rules are based on the critical SWD, the amount of water that the crop can extract in the rooting depth before water stress occurs. The critical SWD is the product of root depth, soil available water and allowable depletion. The later depends on evaporative demand when we want to prevent reductions in expansive growth. Otherwise most crops can use around 70 % of stored soil water before stomatal closure occurs. In arid areas we can calculate mean irrigation calendars for planning purposes. Irrigation scheduling of high frequency irrigation systems is very simple as it focuses only on irrigating with an amount equal to actual crop ET since the last irrigation, while ignoring water storage in the soil.