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Irrigation is an important adaptation strategy to cope with climate change which reduces vulnerability to water stress and improves crop productivity to feed millions. There is evidence of crop yield stagnation in many developing countries, and irrigation efficiency is claimed to increase crop productivity. Therefore, this paper uses data envelopment analysis to evaluate the farmer's productivity through technical efficiency (TE), i.e., the relationship between resource inputs and outputs of 513 paddy farmers in Eastern India. The results show that the farms are, on average operating at 14% TE, leaving a considerable scope to improve up to 86% to reach the optimal level. A significant difference is observed between irrigated and rain-fed paddy farmers, such that10% of the irrigated farms achieved efficiency scores over 40% and only 2% of rain-fed farms achieved the same. The tobit and beta fit regression models are estimated to find out the factors that influence the TE. Both surface water and groundwater sources of irrigation are used as predictors, along with other socio-demographic factors. Access to surface water irrigation is identified to be a significant determinant of farm efficiency, however, surface water irrigation, such as canal irrigation, is accessible only to farmers living on plain land. Farmers living on highlands need to explore other sources of irrigation practices, such as drip and sprinkler, that can increase TE and farm productivity. Therefore, this paper calls for government intervention to provide extensive training and facilities for these micro-irrigation practices. • Data Envelopment analysis was estimated to derive the paddy efficiency among the tribal villages of eastern India. • The DEA estimates show that average Technical efficiency in the study region is much below the national average. • Irrigated farmers are more efficient than the rain-fed farmers. Surface irrigation is the dominate factor. • Rain-fed paddy cultivators' farm efficiency would improve by 6.5%, if they had irrigated. • Semi-mountainous regions with little access to surface irrigation must explore micro-irrigation practices such as drips and sprinklers. [ABSTRACT FROM AUTHOR]

Water scarcity threatens food security and leads to various economic, social, and environmental challenges, particularly in arid and semi-arid regions. As the agricultural sector consumes the most significant amount of water, conserving water resources in this sector is particularly important. Cultivation of low-water-demand (LWD) crops with high value-added is one of the effective measures to reduce agricultural water demand and improve farmers' livelihoods. However, changing water-intensive crops to LWD crops (e.g., medicinal plants) is voluntary pro-environmental behavior. Considering the role of psychological theories in understanding and explaining human behaviors, the main purpose of the current paper is to explore the socio-psychological determinants underlying farmers' intention to adopt an LWD cropping pattern using the Health Belief Model (HBM). In this regard, data were collected using face-to-face interviews with 184 farmers living in Zanjan province, Iran to examine their intention to cultivate LWD medicinal plants. Using structural equation modeling for data analysis, the HBM explained 49% of the variance in farmers' behavioral intentions. The structural equation modeling outcomes also revealed that self-efficacy, perceived barriers, cues to action, and perceived benefits are significantly related to farmers' intention to choose medicinal plants. Overall, the findings indicated the effectiveness and applicability of the HBM in illustrating farmers' intention to change their cropping pattern. Applying some strategies such as providing the necessary facilities and training programs for farmers, as well as, advertisements aimed at promoting the cultivation of medicinal plants can significantly contribute to conserving water resources in the study area. • Evaluating farmers' intention to medicinal crops using the Health Belief Model. • The HBM accounted for 49% of the variance of the farmers' behavioral intentions. • Self-efficacy, perceived expectations, and cues to action affect farmers intentions. • Self-efficacy was identified as the main predictor of farmers behavioral intentions. • Cultivating medicinal crops help conserving water resources in the study area. [ABSTRACT FROM AUTHOR]

Climate change has led to extreme weather events and food security issues, which have become urgent global problems. Crop models and hydrological models play important roles in analyzing these issues, but crop models have limitations in large-scale simulations, and hydrological models have shortcomings in depicting underlying surface details. Jointly using the two models to complement each other's shortcomings is becoming an important method, playing an important role in improving the quantitative characterization ability of different facets of agricultural production and is crucial to improving the efficiency of water resources utilization. This paper reviews the development process of crop and hydrological models and summarizes the widely used models at present, providing reference for researchers to select crop and hydrological models; secondly, it summarizes the types, methods, and examples of joint use of models, and analyzes possible problems in model combination; finally, some suggestions are put forward for the joint use of crop and hydrological models, providing a reference for researchers to combine models. • Retrospect on the development process of crop and hydrological models. • Summarized case studies on the combination of crop and hydrological models. • Provide an overview of cases where crop and hydrological models are used in conjunction. • General considerations and suggestions for future development. [ABSTRACT FROM AUTHOR]

Agriculture is the main consumer of freshwater in the world. The paper described the process of virtual water content and flow in crops. Differences in climatic conditions of different regions in China result in large differences in water consumption during crop growth. The virtual water trade in crops connects water flows within and between regions, linking the actual water consumption with the invisible water trade as a whole. The objective of the paper was supplying the agricultural products virtual water trade evaluation system, determining quantitatively the virtual water flow within the region & regional. Using meteorological and agricultural data from 2003 to 2010, a comprehensive analysis of China's domestic & international virtual water trade of agricultural products has been undertaken. The virtual water for the three primary crops and virtual water trade are discussed. The virtual water content of grain crops in northern & southern China was 1293 m 3 /t & 942 m 3 /t, respectively; the national average value was 1117 m 3 /t; and the regional differences in virtual water content for each crop were significant. China's inter-regional agricultural products virtual water trade was not consistent with water resource endowment expectations. The transfer of crops from northern to southern regions would have a significant impact on the sustainable utilization of water resources and would exacerbate water resources shortages in northern regions. China had a trade surplus in global virtual water trade of agricultural products. The exported agricultural products virtual water amounted to 31.5 billion m 3 /yr., and the imported amount was 145 billion m 3 /yr. The net import of virtual water embedded in agricultural products increased from 44 billion m 3 /yr. in 2003 to 178 billion m 3 /yr. in 2010. It is further concluded that the trend for agricultural products total virtual water, green water, and blue water is that China is increasing its imports year on year. A large increase in imports of agricultural products has led to a decline in the rate of self-sufficiency in domestic agricultural production. The paper provided the basis for the comprehensive evaluation of crop planting structure adjustment, grain import & export, and the potential of regional water resources development and utilization. [ABSTRACT FROM AUTHOR]

There was presently a lack of multidimensional investigation on the impact of virtual water flow (VWF) on regional water use and scarcity. A framework for impact analysis of VWF in consideration of blue, green and grey water differentiation, taking the crop-water relationship estimation in 31 provinces of China as case study, was established in current paper. Results showed that, VWF, which mainly from northern to eastern plain and southeast, reduced agricultural water footprints by 8.3 (blue), 322.0 (green) and 52.5 (grey) G m3. National water stress index reduced from 1.20 (severe water stress) to 0.92 (high water stress), comparing crop consumption to production perspectives. VWF alleviated the resource-based water scarcity attributed to green water stress in south of the Yangtze River, and transformed the resource-based to systematic water scarcity in Xinjiang (XJ). Clarifying the influences of VWF on blue, green and grey water is the innovation of the analytical framework proposed in current paper. • Influences of virtual water flow (VWF) on blue, green and grey water footprint scarcity were quantified. • Green and grey VWFs and their effects on water resources were more impressive than blue water. • VWF alleviated water stress and changed water scarcity type in crop production of China. • Crop production improvement and optimization are proposed to increase the benefits of VWF. [ABSTRACT FROM AUTHOR]

• Variations in precipitation and temperature increase have a significant impact on wheat yields in Serbia! • Water scarcity has a significant effect on wheat yield only in the plain regions! • Change in average daily water deficit, within the period 15th November – 15th May, affects the decrease in wheat yields! • Increase in the average daily water scarcity by 0.1 mm, results with up to 250 kg/ha lower yields! In Serbia irrigation is not widely utilized to reduce water scarcity in crop production. Therefore, wheat yields largely depend on weather factors. Over the past two decades, there has been recorded a significant change in weather conditions in Serbia. Such change produces concerns about Serbia's food security and exports since wheat is among the most important agricultural products. In this paper authors analyze and quantify the impact of weather factors on the achieved wheat yields, using a set of panel data on selected Serbian municipalities in fourteen years (2000–2013). The multidimensional regression was conducted as a sort of quasi-experiment, combining data on achieved yields in selected municipalities, with data on weather factors: temperature, precipitation, extraterrestrial radiation, and evapotranspiration. Utilizing the Hargreaves method of determining reference evapotranspiration, average daily water deficit was computed as a single representative indicator of weather conditions. Testing was conducted on four predefined sub-periods within the vegetation season of wheat, and the impact of average daily water deficit on wheat yields was estimated for each of these sub-periods. Results show a robust, statistically significant impact of change in average daily water deficit on decreased wheat yields. Growth of water deficit by 0.1 mm, in the period November 15th to April 1st results with 175 kg/ha lower yields, while in the period April 1st to May 15th results in 45 kg/ha lower yields. Impact shows to be conditional on the altitude, rapidly losing on intensity and significance above 100 m. [ABSTRACT FROM AUTHOR]

Highlights • Function "yield vs. total net water" for 4 commercial cultivars of potato crop was fitted. • Irrigation strategies aiming to increase the irrigation water productivity of potato were proposed. • Crop under real farming conditions and limited volumes of irrigation water. • Optimized regulated deficit irrigation methodology increased the irrigation water productivity in the studied cultivars. Abstract This paper presents the calibration and validation processes of the MOPECO model for the simulation of 4 commercial potato cultivars (Zorba, Mirari, Monalisa and Leire), using the data from a three-year field experiment (years 2010, 2011 and 2012; two per cultivar) under deficit irrigation conditions in the Basque Country region of Spain. The optimized regulated deficit irrigation (ORDI) strategy was used in combination with the typical meteorological year (TMY) methodology to determine irrigation strategies aimed at increasing the irrigation water productivity of potato crop under real farming conditions and limited volumes of irrigation water. The growing degree-days for the whole growth cycle were 1958 °Cd, while the calibrated crop yield response (K y) values for the growth stages proposed by FAO-56 were 0.45 (vegetative period), 0.70 to 0.90 (yield formation), and 0.25 to 0.40 (ripening) depending on the consider e d cultivar. The validation results showed that MOPECO is suitable for simulating the yield versus total water (gross irrigation + effective rainfall) use under the climatic and soil conditions in this study (normalized root mean square error from 7.2 to 8.5% between observed and simulated levels). ORDI maximized the yield of the crop for different volumes of available irrigation water. The irrigation water productivity differed according to the cultivar, increasing for lower volumes of irrigation water (from 23.0 kg m−3 to 58.1 kg m−3 for Monalisa and Mirari cultivars, irrigated with 100% and 40% of the requirements, respectively). [ABSTRACT FROM AUTHOR]

Water is the most essential resource for the production of agricultural goods and services. However, high levels of water stress and increased frequency and intensity of droughts, which are mainly driven by climate change dynamics, have reduced the stock of freshwater resources in arid and semi-arid regions, such as Iran. Despite the major reduction of freshwater resources, the efficiency of irrigation water use has remained very low in the country and performance of water management schemes is far from satisfactory. Using the strengths, weaknesses, opportunities and threats/political, economic, social, technological, legal and environmental (SWOT/PESTLE) analysis, this paper explores 40 internal and external factors that influence irrigation water management in Iran and recognizes legal, social, technological and political dynamics as the major reasons for failure of irrigation water management in the country. A combination of the threats, opportunities, weaknesses and strengths (TOWS) matrix and bottleneck analysis was used to suggest irrigation water management strategies that rehabilitate the failed schemes and enhance water security in the agriculture sector. Rethinking the role of intensified agriculture in development along with raising the awareness and attitude of decision makers towards the risk of shortsighted water resource development plans, in addition to promoting agro-based industries and developing integrated plans to improve water efficiency are the strategies that can contribute to a more effective management of irrigation water in Iran. [ABSTRACT FROM AUTHOR]

In this paper we present PILOTE-N, a crop model devoted to the calculation of crop production from the joint water and nitrogen soil status effects. It is the extension of PILOTE, for contexts in which water might not be the sole limiting factor for crop yield, but the same model structure and credo of parsimonious parameterisation have been kept, assuming simplified descriptions of the physical processes at play. One original aspect of PILOTE-N is the calculation of Leaf Area Index (LAI) and cumulative nitrogen plant demand from similar logistic-type functions. LAI is controlled by specific temperature sums, shape parameters and the occurrence of water and nitrogen stresses, while the time average of LAI values over critical phenological periods also affects the predicted harvest index and crop yield. As specific plant parameters are known from PILOTE, calibration was devoted to nitrogen parameters. Which governing the daily-averaged mineralization rate in a first step, then the two shape parameters of the potential nitrogen plant demand (from the dilution curve) in a second step and, at last, which allowing the link between nitrogen uptake and nitrogen of the soil. Model performance was evaluated using multiple initial soil conditions, irrigation and fertilization strategies for corn, durum wheat and sorghum, over a climatic series of 14 years, at the experimental plot of Lavalette (Montpellier, South-East of France), hence in a Mediterranean context characterized by severe, water stresses during summer, typically exceeding nitrogen stresses. Crop yield as well as the dynamics of nitrogen budget were correctly simulated (R 2  > 0.94 for grain yield, total dry matter and nitrogen in plant). The robustness of such a simple and easy-to-calibrate tool is expected to facilitate its use and implementation in other agro-pedoclimatic contexts, to decipher the effect of abiotic stresses and improve irrigation and fertilization scenarios when included in dedicated tools. [ABSTRACT FROM AUTHOR]

In many arid regions of the world, population growth, groundwater depletion, and uncertain supplies have caused water for agricultural production to become increasingly scarce. Deficit irrigation (DI) provides a potential response to water scarcity, but no consensus exists on its economic viability. In this paper, we develop an agro-economic model that connects plant growth-stage-specific evapotranspiration (ET) targets with farm profitability. We use the model to determine the economic conditions under which ET targets of less than 100% are optimal for profit-maximizing maize farmers in Colorado. With 2015 input costs, as maize grain prices increase beyond $0.19 kg −1 , DI can become optimal during the late vegetative growth stage but requires a water cost greater than U.S. $0.21 m −3 . Under some output price and water cost combinations, DI in the maturation stage also becomes optimal. These results suggest that producers could respond to increasing water scarcity with deficit irrigation, but only in a range of water costs that depends on output price and production costs. [ABSTRACT FROM AUTHOR]

Rice cultivation is globally hampered by several conditions, which urge farmers to maintain adequate production levels while properly managing irrigation water. This has noticeable repercussions on the efficient use of the resource and on water productivity. Nonetheless, more often, this latter topic is addressed by estimating the respective values, without deeply investigating the possible causes behind such discrepancies. The main objective of this paper is to overcome such limitations, by (i) providing a comprehensive and updated overview of Irrigation Water Productivity (IWP) for rice, and (ii) exploring the role of irrigation water in determining IWP value. The analysis of experimental data collected from 51 studies reveals IWP to vary between 0.09 and 8.10 kg m −3 , with mean and median values of 1.36 and 0.85 kg m −3 respectively; moreover, a non-linear relationship between irrigation water amounts and IWP (r 2 = 0.81) is depicted. Further on, data are analyzed using an econometric approach. Specifically, a multivariate linear regression model is used to shed light on the joint contribution of water inputs, regime and irrigation method to productivity. This demonstrates the significant roles of irrigation (β = −1.006) and rainfall (β = 0.062) amounts, while aerobic regime and irrigation method is proved to be a further key driver (β = −0.305). Such results enable identifying the elements to be enforced, if increasing IWP for rice is the prime objective. Finally, some implications are derived for water policy and the connections with weather-climatic and environmental conditions that are globally affecting the availability of water in agriculture. [ABSTRACT FROM AUTHOR]

In intensive breeding farms, maintaining an adequate indoor thermal environment and air quality is crucial in order to establish healthy conditions and increase productivity. In the EU, fossil fuels and electricity are the main energy sources adopted for this purpose, yet introducing renewable energy sources and efficient Heating Ventilating Air Conditioning systems would reduce energy consumption and improve sustainability. Another environmental concern in agricultural production is related to the intensive use of fertilizers, causing nitrate contamination in surface water and groundwater. Therefore, innovative strategies to reduce fertilizers and simultaneously reduce primary energy consumption are worthy of investigation. This paper addresses both issues, studying the application of geothermal heat pumps in the agro-zootechnical sector, where they are rarely applied and thus their potential needs to be verified. The study considers systems based on the closed loop configuration, i.e. Ground Source Heat Pumps (GSHP), and on the open loop configuration, i.e. Groundwater Heat Pumps (GWHP). Firstly, a pilot GSHP system for a piglet stable in Northern Italy is presented. Thanks to the use of both ground source and thermal recovery of air ventilation, the system achieves an appreciable reduction in both primary energy consumption and running costs, compared with a more traditional system typically adopted in this kind of farm. Secondly, the feasibility of an innovative concept of a GWHP combined with the irrigation system is studied through numerical modelling. The area of the piglet stable is represented in a flow and heat transport model; groundwater used by the heat pump is re-injected up-gradient during the cold season, while it is used for irrigation during the warm season. The system would provide energy-efficient climatization to the farm stables and, at the same time, promote the reuse of nitrogen in cultivated fields as a result of groundwater recirculation through irrigation. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of erratic rainfall and related water problems on agricultural productivity. The paper also aims to shed light on the conceptual importance of understanding the incidence and impacts of rainfall shocks for choosing feasible agricultural water risk management strategies both at household and policy levels. To achieve these goals we develop a conceptual framework, use national representative data from Zambia's crop estimates survey for 2017/2018 farming season, employ fixed effects regression approach, and find that dry spells, excessive floods, incidence of water logging are all detrimental to crop productivity. The crop-based equations also reveal the differential impacts of the rainfall shocks on different crops. Since the effect of water factors including dry spells, floods and water logging on agricultural productivity is dependent on the crop types, it is important for the Zambian government as well as other countries to take this into account when planning and implementing strategies for agricultural water risk management. • Water related problems significantly undermine agriculture productivity in Zambia. • The impacts of erratic rainfall on productivity varies depending on the type of crop. • The differential impacts of rainfall shocks calls for crop specific strategies. [ABSTRACT FROM AUTHOR]

Climate variability and insufficient irrigation are primary constraints to stable and higher agricultural productivity and food security in Nepal. Agriculture is the largest global freshwater user, and integration of surface- and ground-water use is frequently presented as an strategy for increasing efficiency as well as climate change adaptation. However, conjunctive management (CM) planning often ignores demand-side requirements and a broader set of sustainable development considerations, including ecosystem health and economics of different development strategies. While there is generic understanding of conjunctive use, detailed technical knowhow to realize the CM is lacking in Nepal. This article presents a holistic framework through literature reviews, stakeholders consultations and expert interviews for assessing CM and implementation prospects from a systems-level perspective. We demonstrate the framework through a case study in Western Nepal, where climatic variability and a lack of irrigation are key impediments to increased agricultural productivity and sustainable development. Results show that knowledge of water resources availability is good and that of water demand low in the Western Terai. Additional and coordinated investments are required to improve knowledge gaps as well as access to irrigation. There is therefore a need to assess water resources availability, water access, use and productivity, to fill the knowledge gaps in order to pave pathways for CM. This paper also discusses some strategies to translate prospects of conjunctive management into implementation. • Customized framework development for assessing prospects for conjunctive management. • Conjunctive management status in western Nepal assessed by applying the framework. • Knowledge on water availability and demand are moderate and low, respectively. • Additional and coordinated investments required to improve access to irrigation. [ABSTRACT FROM AUTHOR]

Water rights trading is an effective way to promote efficient water allocation. The implementation of agricultural water rights trading can promote water saving, but may reduce the agricultural production scale in irrigation districts. Compensation for crop virtual water export can increase the benefits of agricultural water use, so as to enhance the competitiveness of economic benefit for agricultural production. This paper analyzed the relationship between agricultural water rights trading and virtual water export compensation, then a bi-level programming model was established with multiple objectives. The model was applied in Hetao irrigation district by using enumeration method. The changes of new water use of different users, benefits of irrigation district and water users with different water prices were analyzed and the optimization schemes were selected. Results show that the model through adjusting price variables including both water rights trading price and virtual water compensation price to optimize the allocation of agricultural water quantity saved among different water users, which at the same time makes both the irrigation management administration and water users get more benefit. The optimized scheme can raise the willingness of water saving in irrigation district, and enhance the competitiveness of agricultural water user against non-agricultural water user. This study provides a new method and scientific basis for the water resource management agency in their policy making. [ABSTRACT FROM AUTHOR]

Forty seven percent of the population of Pakistan is food insecure, access to food is uneven and malnutrition is widespread. In addition, food production depends greatly on irrigation, including the use of substantial volumes of water from already stressed aquifers. Our aim in this paper is to examine the implications of continued population growth on the required production of food and the implied water demand. We examine the historical trends of crop production, water use, food availability and population growth in Pakistan, and project them forward to 2050. Food availability has improved over recent decades, mostly as a result of increasing the area and water use of crops and fodder, and partly as a result of importing more pulses and cooking oils. We show that a continuation of current trends leads to nearly a doubling of the (already unsustainable) groundwater use. There is uncertainty in the magnitude of climate change impacts, but climate change may further exacerbate matters. To avoid further increases of groundwater use, some combination would be required of: more dams and other irrigation infrastructure; increasing crop yields (particularly yields per unit volume of water) at a greater rate than in the past; a change in crop mix away from high water use crops like rice and sugarcane, to crops that use less water; and, exporting less and importing more food. The alternatives appear difficult to implement quickly, so it appears likely that in the short to medium term more groundwater will be consumed, with attendant problems of water quality and sustainability. Our analysis provides new perspectives on past trends and future food and water (including groundwater) challenges. [ABSTRACT FROM AUTHOR]

Appropriate plant density is essential for crop production in rainfed areas. However, it is quite difficult to obtain the optimal plant density under plastic film mulch in different hydrological years through field experiments due to its limited treatments, and time and labor costs. Therefore, mathematical models are generally used for searching the optimal alternatives. In this paper, the Agro–Hydrological & chemical and Crop systems simulator (AHC) was adopted to model soil water dynamics, rainfed maize growth, and yield under plastic film mulch and various plant density conditions in Northeast China for different hydrological years. The results showed that the AHC model can simulate rainfed maize water use and growth under plastic film mulch and various plant density conditions, i.e., 60,000 (D1), 67,500 (D2), 75,000 (D3), 82,5000 (D4) and 90,000 plants ha−1 (D5). The average maize yields of all treatments in the severely dry (SD), moderately dry (MD), normal (N), moderately wet (MW), and severely wet (SW) years were 11440.3, 13685.4, 13821.5, 14704.8, and 14014.3 kg ha–1, respectively. Compared with non–mulch, plastic film mulch increased the maize basal crop coefficient by 0.08–0.11 and decreased the soil evaporation coefficient by 0.26–0.32, from SD and SW years, respectively. Thus, plastic film mulch augmented maize transpiration by 46.2–76.8 mm, while reduced evaporation by 163.5–186.8 mm across the simulated years. Ultimately, the maize yield under plastic film mulch was 5.9–17.4% higher than that without mulch. From D1 to D5 treatments, the decrease of soil evaporation coefficient was within 0.02 under plastic film mulch and was over 0.05 without mulch. Under plastic film mulch, the relations between plant density and net profit could be well described by the parabolic curves, and the recommended optimal plant densities of maize in the study area were 91, 101, 101, 105, and 101 thousand plants ha–1 in the SD, MS, N, MW, and SW years, respectively. Our findings provide management implications for maize cultivation in the rainfed areas of Northeast China. • The highest maize yield was observed in the moderately wet year. • Plastic film mulch increased maize optimal plant density. • Higher increase in maize yield was obtained in higher plant density with film mulch. • The highest optimal maize plant density was obtained in moderately wet year. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on both the environmental impact of intensive shrimp farming in the coastal region of Vietnam and the identification of options for cleaner production. We investigated water pollution, sediment contamination and the spread of diseases related to shrimp farming in the Can Gio district of Ho Chi Minh City (Vietnam), an area representative for the impacts of intensive shrimp production in the country. Data on the production process was compiled from site observations, interviews with local farmers and experts, as well as from secondary sources. The results indicate that, while a large number of individual farms may exceed environmental standards, intensive shrimp farming is not always associated with waste streams exceeding water quality standards. This is interesting because it shows currently available technologies can reduce pollution from intensive shrimp farms. The paper concludes by identifying technologically and economically feasible options for reducing water pollution, problems associated with contaminated sediment, and the spread of diseases. [Copyright &y& Elsevier]

The premise of this paper is that the key to effective water resources management is understanding that the water cycle and land management are inextricably linked: that every land use decision is a water use decision. Gains in agricultural water productivity, therefore, will only be obtained alongside improvements in land use management. Expected increases in food demands by 2050 insist that agricultural production – and agricultural water use – must increase. At the same time, competition for water between agricultural and urban sectors will also increase; and the problem is further compounded by land degradation. A global survey suggests that 40% of agricultural land is already degraded to the point that yields are greatly reduced, and a further 9% is degraded to the point that it cannot be reclaimed for productive use by farm level measures. Soil erosion, nutrient depletion and other forms of land degradation reduce water productivity and affect water availability, quality, and storage. Reversing these trends entails tackling the underlying social, economic, political and institutional drivers of unsustainable land use. This paper is based on a review of global experiences, and its recommendations for improving water management by addressing land degradation include focusing on small scale agriculture; investing in rehabilitating degraded land to increase water productivity; and enhancing the multifunctionality of agricultural landscapes. These options can improve water management and water productivity, while also improving the livelihoods of the rural poor. [Copyright &y& Elsevier]

In this paper, a model for fuzzy risk of low yield of a crop is developed to study the implications of a reservoir operating policy model. When an optimal operating policy is derived based on a known objective, the policy itself does not, in general, indicate a measure of the system performance unless a criterion to this effect is embedded in the objective function. While a systems analyst is interested in the nature of the objective function used in arriving at a policy, the irrigation decision maker would look for the implications of using the policy through answers to the questions such as, how often the system will fail and how quickly it will recover from a failure. It is, therefore, important that the implications of reservoir operation with a given policy be studied keeping in view the interests of the decision makers. Some earlier studies on reservoir operation models for irrigation have considered reliability, resiliency and productivity index, as the performance indicators of the operating policy. In this paper, fuzzy risk of low yield of a crop is considered as another performance indicator to address uncertainties due to both randomness and fuzziness. Uncertainty due to randomness arises primarily because of the random variations of hydrologic variables such as reservoir inflows and rainfall in the command area. Uncertainty due to imprecision or fuzziness arises because of uncertain crop yield response to various factors (such as farm practices and climatic variables) other than to the applied water. Two important concepts are introduced in this paper with respect to irrigation reservoir system. The first one is related to viewing the low yield of a crop, as a fuzzy event. The second concept is related to the definition of fuzzy risk of low yield of a crop. The fuzzy risk of low yield is derived using the concept of probability of a fuzzy event. Application of the methodology is demonstrated with a case study in India. [Copyright &y& Elsevier]

Agricultural subsurface drainage is necessary for crop production in humid, poorly drained regions with frequent rainfall. Flooding and waterlogging have become more widespread and frequent in recent years, and effective measures should be adopted to increase the subsurface drainage capacity and alleviate flooding and waterlogging disasters after short-term heavy rainfall. However, subsurface drainage focused on the layout parameters (drain depth, drain spacing, etc.) in previous studies, and these measures were limited and cumbersome in the improvement of the flow rate of subsurface drainage. Thus, we aimed to alleviate the flooding and waterlogging threats to farmland and innovatively proposed a new method to increase the flow rate of subsurface drainage, namely siphon-type subsurface drainage. The paper evaluated the performance of the siphon-type subsurface drainage by the indoor sand tank test and the HYDRUS-2D model. Three factors were considered during the experiments: conventional and improved subsurface drainage; shallow, medium, and deep drain depth; and the outlet elevation, including the outlet elevation of the drain pipe under the non-siphon drainage and the outlet elevation of the siphon pipe under the siphon drainage. The results indicated that the siphon-type subsurface drainage performed better under the conditions of steady-state ponding and ponding subsided. The flow rate of the siphon-type subsurface drainage was 27.1–45.7%, 41.8–89.8%, and 39.3–50.5% higher than that of conventional, thin-improved, and thick-improved subsurface drainage with non-siphon drainage under steady-state ponding, respectively. It also had a significant advantage when the outlet elevation was the same. The siphon-type subsurface drainage could increase the flow rate during ponding subsided and reduce the flow rate attenuation degree before the ponding disappears. The flooding removal effect of the siphon-type subsurface drainage was significantly better than that of non-siphon subsurface drainage. The water head and flow rate were used to calibrate and validate the HYDRUS-2D model. The results indicated that the simulated values of flow rate matched well with the measured ones and the relative errors were less than 10%. The influence range and absolute values of the negative water head increased with the decrease of outlet elevation, and the increase effect of flow rate increased with the decrease of the water head. The siphon-type subsurface drainage has more control distance than the non-siphon. The advantages of siphon-type subsurface drainage are not only prominent in quart sand but also applicable to field soil. The results of this study could provide technical support for the application of flooding and waterlogging removal in areas where waterlogging is prone to occur and could improve the ability of agricultural production to address waterlogging disasters. • A siphon-type subsurface drainage to improve the subsurface drainage capacity is proposed. • The drainage rule of the siphon-type subsurface drainage is studied. • Effect of flooding and waterlogging removal of siphon-type subsurface drainage is revealed. • The flow rate attenuation degree of a siphon is assessed. • The performance of siphon-type subsurface drainage is validated by HYDRUS-2D model. [ABSTRACT FROM AUTHOR]

Does the implementation of agricultural water conservation policy necessarily bring about a reduction in agricultural water extraction? Taking China's National Agricultural Water Conservation Outline proposed in 2012 as an example, this paper uses the data of 31 provinces from 2000 to 2019, and employs an empirical strategy of Difference-in-Differences (DID) to estimate the impact of the agricultural water conservation policy on agricultural water extraction. The results show that the agricultural water conservation policy does not achieve the decline of agricultural water extraction, but increases agricultural water extraction. When addressing contemporaneous water-related policies or estimating in subsample, these results are robust. The possible reason for this phenomenon is that the agricultural water conservation policy promotes agricultural production, especially by increasing the sown area and irrigated area, and the expansion of irrigated area is the main reason for the increase in agricultural water extraction. Moreover, land potentiality for crop production may affect the water-saving effect of the agricultural water conservation policy, in which provinces with higher land potentiality will have less increase in agricultural water extraction caused by the agricultural water conservation policy. Therefore, with the empirical evidence from China, agricultural water conservation policy may not necessarily reduce agricultural water extraction, and this phenomenon is always regarded as rebound effects. In order to avoid the adverse impacts of the rebound effect, agricultural water-saving technologies can be strengthened in areas with high land potentiality for agricultural production, and market-oriented policies, such as water rights reform, can be employed to avoid excessive use of water resources in areas with severe over-extraction. • Water-saving effect of agricultural water conservation policy is estimated. • Agricultural water conservation policy increases water extraction. • Possible reason for increase in agricultural water extraction is clarified. • Increase in agricultural water extraction is interpreted as rebound effects. [ABSTRACT FROM AUTHOR]

Agricultural water use in heavily irrigated regions can reduce surface water flow. The most remarkable hydrological change in recent times in Central Asia is the rapid dry-up of the Aral Sea. In this paper, the evolution of agricultural development was traced back to the 1910s, Land-Water-Food (LWF) nexus in Central Asia was evaluated, and the relationship between agricultural development and Aral Sea dry-up was built. It was noted that for the 1910–2010s, the harvested land area in the region expanded nearly two folds — from 7.2 to 21.6 million ha. Production of cereal crops increased over eight folds — from 4.0 to 37.6 million tonnes. Cotton production reached 5.5 million tonnes, a seven-fold increase. The high increase in productivity was driven by increasing agricultural irrigation since the 1950s. Irrigation water requirement for the five main crops (wheat, cotton, maize, barley and rice) increased by about 50%; from 64.3 km3 in the 1950s to 95.9 km3 in the 2010s. Cotton and wheat were the top two crops, with respective total irrigation water use of 66.9% and 16.4%. For the study area, LWF nexus was quantified in terms of production efficiency using the data envelopment analysis method, and it was shown that excess water and land resources made agricultural production inefficient. Analysis of the irrigated area and the Aral Sea water surface area suggested that for every 1.0 km2 increase in irrigated land area, water surface area in the Aral Sea declined by 1.2 km2. The analysis of LWF tradeoff was key not only for sustainable land, water and ecological management, but also for food production in degraded arid lands around the globe. • A nexus analysis showed the tradeoff among land, food, water and the Aral Sea. • There was production increase of 7–8 folds and cultivated area increase of 2 folds since the 1910s. • Irrigation water requirement increased by 50% since the 1950s. • For 1.0 km2 increase in irrigated land, the Aral Sea water area shrank by 1.2 km2. [ABSTRACT FROM AUTHOR]

The use of recycled water as a valued resource is becoming well established worldwide as a means to support agricultural irrigation. This paper describes a case study of agricultural use of recycled water and associated mixed land-use needs in a peri-urban setting of northwest Sydney. The Hawkesbury campus of Western Sydney University has an established water recycling scheme to support both agricultural productivity and landscape amenity, along with increasing linkages to infrastructure protection from bush fire risk. Risk management strategies are described for a range of land use needs across the campus, and discussed in terms of supporting local resilience, activities of the range of communities of practice involved, and ecosystem services from the local peri-urban landscape. Conclusions are drawn in terms of risk management of agricultural water recycling as an integrative process for managing associated land use needs. [ABSTRACT FROM AUTHOR]

Addressing irrigation water efficiency continues to emerge as one of the potential solutions to minimize irrigation water use, improve water quality, and enhance soil health. Despite the clear importance of financial information in decision‐making regarding adoption of irrigation tools, little information is available regarding the profitability outlook of such adoption. Lack of assessment of costs and returns could lead to producers resisting adoption citing profit reductions. Hence, a cost-assessment using the financial information is necessary to evaluate the tools’ economic outlook. By using long-term projections of input prices, crop yield, and crop prices, this paper develops a financial analysis of irrigation using surge valves by calculating annual cash flows and net present value. The analysis is based on demonstration plot results and anecdotal estimates related to water savings and yield improvements in corn and soybeans in Louisiana and Mississippi. The positive estimates for net present value indicate that an investment in irrigation efficiency improvement is an economically sound choice. These estimates can enhance the adoption of irrigation‐efficiency improvement practices by providing an initial understanding of the overall profitability independent of short-term management decisions. [ABSTRACT FROM AUTHOR]

Irrigation is an essential component of crop production to meet retailer demands for premium quality when rainfall is insufficient. Under drought conditions, irrigation can be constrained by water resources availability, with consequent impacts on yield, quality and revenue. Whilst most agriculture in Europe is rainfed, greater dependence on supplemental irrigation could become more important in humid environments due to a changing climate with greater rainfall uncertainty and higher frequency of droughts. By combining industry and farm level economic data, with geospatial information on agricultural land use, agroclimate, soils and irrigation practices within a GIS, this paper estimates the total financial benefit of outdoor irrigated production in England and Wales assuming no constraints in resource availability and optimal irrigation practices. The analysis suggests that the total net benefits of irrigation in a ‘design’ dry year are around £665 million, with an average irrigation water productivity in excess of £3.3 per m 3 (close to £1.1 per m 3 excluding soft fruit). Map outputs highlight significant regional differences in water productivity reflecting the composition of land use and the importance of crop mix in determining economic value. A sensitivity analysis to changes in agroclimate, market conditions (crop prices) and water supply (costs) illustrates how the benefits might change under contrasting scenario. The study highlights the importance of supplemental irrigation, even in a humid climate, and the risks that future droughts and/or constraints in water resource availability might have on agricultural systems, livelihoods and the rural economy. The implications for water resources and drought management are discussed. [ABSTRACT FROM AUTHOR]

Water scarcity has become a worldwide phenomenon as a result of climate change. For that reason most countries are adopting various measures to reduce the impact of water scarcity on their agricultural sector and Ghana is no exception. Ghana's agricultural sector is the backbone of the rural economy in the country. The agricultural sector employs about 90 percent of the rural population and contributes extensively to the GDP of the country. But, low productivity and inefficient water use have resulted in a significant threat to the livelihoods of the rural population. The paper used a programing model named MATA (Multi-Analysis Tool for the Agricultural Sector) to achieve the stated objectives. The main objective of the study was to find out the impact of water-pricing policy on the demand for water resources by the farmers in relation to their cropping activities and income. The results of the study indicated that water-pricing policy has a negative impact on the demand for water resources in Ghana. But this impact happens only when water prices are increased significantly. However, if water prices are high it has a negative impact on cropping activities, farmers’ income, employment and crop varieties. Hence the study recommends that in order to at least reduce water wastage in the sector, it be proposed that a price (around 2 cedi/m 3 ) might be of significance in order to make farmers conscious of the scarcity of water resources, and to persuade them to adopt water saving technologies without affecting crop distribution. The study also recommends that water-pricing policy should not be used as a policy tool on its own but should be used together with other water saving policies in order to achieve the best results. [ABSTRACT FROM AUTHOR]

The 2011 and 2012 droughts considerably affected the Ogallala Aquifer supplying irrigation water for agricultural production in the US High Plains (HP). Shrinking water resources and growing demand for water create a challenging tradeoff situation. This also poses a question about the value of water and efficient water allocation. Currently, water rates for irrigating crops paid by farmers do not reflect the actual value of water that can be expressed solely as a shadow price. Also studies are missing that would comprehensively compare different states and different crops in one methodological framework. This paper helps to fill this gap. Farm-budget residual valuation is applied to estimate the shadow price of water for irrigation in three High Plains states: Texas, Kansas and Nebraska, for five prevailing crops: corn, cotton, sorghum, soybean, and wheat. Among the analyzed High Plains states the highest shadow price of water was found for wheat production in the Texas Northern High Plains ($865.99/af = $0.70/m 3 ), while the lowest shadow price was found for corn in the Texas Southern High Plains ($5.13/af = $0.004/m 3 ). The study can be helpful to stakeholders and policy makers to evaluate scenarios and tradeoffs between profitable crop production and conservation of water resources. [ABSTRACT FROM AUTHOR]

There is a knowledge gap and limited tools to readily identify trade-off relationships between competing economic and environmental goals, and between the upstream and downstream areas, of river basins. In this paper we aim to construct the trade-off relationship between midstream agricultural development and downstream ecosystem sustainability at the basin scale, using the Heihe River basin as an example. An improved top–down method was developed to understand the impacts of land use change on catchment hydrology. Based on this, trade-off relationships between cereal production in the midstream area and the runoff flowing downstream, and between cereal production in the midstream area and ecosystem service values in the downstream area, were constructed. The results showed that from 1960 to 2000 every 1000 t of increased cereal production in the midstream area (Zhangye catchment) was at the expense of 0.52 million m 3 of runoff flowing to downstream and $0.052 million of ecosystem service values in the downstream area (Ejina oasis). The analysis also showed that water productivity increased six-fold in the recent study period which greatly offset the trade-off impacts on downstream ecosystem sustainability. Linking conventional trade-off analysis involving competing economic and environmental goals to a simplified hydrological model and remote sensing image analysis to determine land use is a useful tool for integrated river basin management and will enable more transparent, informed, and inclusive water governance. [ABSTRACT FROM AUTHOR]

Nitrogen is essential to improving agricultural production systems, explaining why the contamination of groundwater by this nutrient is widespread. The aim of this paper was to describe data collected over 9 years on estimated leaching levels using a simple computation procedure and measurements of soil water content and water balance, nitrate concentrations in drainage water and meteorological data, and to assess the impacts of the duration of the grassland phase and the level of nitrogen fertilization on grassland on the drainage water quality. The study was carried out at a site of the Long-term Environmental Research Observation and Experimentation facility (SOERE) for Environmental Research- Agro-ecosystems, Biogeochemical Cycles and Biodiversity, run by the INRA experimental unit of Lusignan. The experimental treatments were sequences of maize, wheat and barley with different grassland rotational periods (a pure arable crop rotation; three or six years of grassland receiving high-level nitrogen applications; six years of grassland with a low N application rate and long-term grassland with nitrogen application). The study covered the period from April 2005 to June 2013, during which most drainage occurred in the autumn and early winter. Treatments with the longest duration of grassland exhibited less drainage than those containing a higher proportion of arable crops. The average nitrate concentration was 52.7 ± 38.63 mg NO 3 L −1 under a pure crop rotation, compared to 14.9 ± 14.76 mg NO 3 L −1 under a permanent grassland treatment. There were significant differences ( P < 0.0001) in cumulative nitrogen leaching between the different cropping systems, ranging from 9 to 37 kg N ha −1 year −1 . The introduction of mowed grassland sequences into this arable crop rotation caused a marked reduction in the nitrate levels in groundwater, and the greater the proportion of grassland within the rotation the more markedly was the NO 3 − concentration reduced, whatever the level of N fertilization during the grassland sequence. [ABSTRACT FROM AUTHOR]

Crops For the Future Research Centre (CFFRC) is currently developing CropBASE—a cross-cutting web-based platform for decision support and knowledge sharing on underutilised crops and their end uses. It provides a quantitative basis to compare underutilised crop productivity and resource-use-efficiency with that of major crops and cropping systems under current and future climate scenarios, and will include interactive tools to integrate underutilised crop data with geo-referenced information in existing and new databases. Specific crop application models form the analysis engine of CropBASE, including crop-climate, crop-quality, crop-economic models to assess agroecological suitability, nutritional value, livelihood or food security potential of underutilised crops and products at field, farm and regional scales. A geospatial information system framework will link currently available climate databases as input data for crop models. CFFRC, already using major models for a range of crops around the world under the AgMIP program, will spearhead the inclusion of specific underutilised crops into recognised crop models. After briefly introducing CropBASE, this paper presents use cases as examples comparing yield and water productivity predictions for bambara groundnut (an underutilised African legume) and pearl millet (an alternative major cereal) under current and future climate scenarios in contrasting sub-Saharan African locations. [ABSTRACT FROM AUTHOR]

There is growing scientific interest in the potential role that precision irrigation (PI) can make towards improving crop productivity, and increasing water and energy efficiency in irrigated agriculture. Most progress has been made in arid and semi-arid climates for use in high value crop production where irrigation costs coupled with concerns regarding water scarcity have stimulated PI innovation and development. In temperate and humid climates where irrigation is supplemental to rainfall, PI is less developed but nevertheless offers scope to make more effective use of rainfall, help reduce the non-beneficial losses associated with irrigation (deep drainage, nitrate leaching) and provide farmers with evidence to demonstrate environmentally sustainable practices to processors and retailers. This paper reports on recent experiences in developing precision irrigation in UK field-scale agriculture, drawing on evidence from field research and modelling studies. By combining data from these sources, a critical evaluation focusing on selected technical, agronomic and engineering challenges that need to be overcome are described, including issues regarding PI scheduling, and the delineation of irrigation management zones to ensure compatibility with existing methods of overhead irrigation. The findings have relevance to other countries where irrigation is supplemental and where precision agriculture is gaining popularity. [ABSTRACT FROM AUTHOR]

Shallow water-tables strongly influence agro-ecosystems and pose difficult management challenges to farmers trying to minimize their negative effects on crops and maximize their benefits. In this paper, we evaluated how the water-table depth interacts with rainfall and sowing date to shape maize performance in the Western Pampas of Argentina. For this purpose, we analyzed the influence of water-table depth on the yields of 44 maize plots sown in early and late dates along eight growing seasons (2004–2012) that we rated as dry or wet. In addition, we characterized the influence of the water-table depth on intercepted radiation and crop water status by analyzing MODIS and Landsat images, respectively. The four conditions we evaluated (early sown-dry growing season, early-wet, late-dry, late-wet) showed similar yield response curves to water-table depth, with an optimum depth range (1.5–2.5 m) where yields were highest and stable (∼11.6 Mg ha −1 on average). With water-table above this range, yields declined in all conditions at similar rates ( p > 0.1), as well as the crop water status, as suggested by the Crop Water Stress Index, evidencing the negative effects of waterlogging. Water-tables deeper than the optimum range also caused declines of yield, intercepted radiation and crop water status, being these declines remarkably higher in early maize during dry seasons, evidencing a greater reliance of this condition on groundwater supply. Yield in areas with deep water-tables (>4 m) was significantly reduced to between a quarter and a half of yields observed in areas with optimum water-tables. Rainfall occurred around flowering had a strong impact on maize yield in areas with deep water-tables, but not in areas with optimum depth, where yields showed high temporal stability and independence from rainfall in that period. Our study confirmed the strong influence of water-table on rainfed maize and provides several guidelines to help farmers to take better decisions oriented to minimize hydrological risks and maximize the benefits of shallow water-tables. [ABSTRACT FROM AUTHOR]

Irrigation is essential for agricultural production in semi-arid areas, but it is also an important consumer and contaminator of water. Therefore, it is necessary to improve the efficiency of water and nitrogen use. This paper analyzes the relation between nitrogen fertilization practices, irrigation and the nitrate concentration in the drainage waters of the sprinkler-irrigated LASESA district (LD) in Northeast Spain. The methodology is based on developing water and nitrogen balances in the seven main basins that drain LD (9980ha) from November 2008 to October 2010, covering the agricultural campaigns of 2009 and 2010. The results show that the hydrological properties of each basin determine the evolution of the flow of and nitrate concentration in drainage waters. In basins with soils located on Quaternary terraces, the drainage fraction (DF) and the concentration of nitrate are 22% and 120mgL-1, respectively, and the annual mass of nitrogen exported is 64kgha-1. In those with soils located on Tertiary marls and sandstones, the lower DF and nitrate concentrations (9% and 90mgL-1) lead to an annual mass of exported nitrogen which is five times lower (12kgha-1). The excess of irrigation and fertilizer use in corn make this crop the main source of nitrogen pollution. In recent years, corn fertilization has been reduced. Nevertheless, 26% of the nitrogen applied as mineral or organic fertilizer is still lost in the drainage water. [ABSTRACT FROM AUTHOR]

• We introduce a hydro-economic model for agricultural groundwater management. • MOD$$AT integrates economic, hydrologic and agronomic model components. • Application of MOD$$AT shows how a pumping tax impacts groundwater levels and profits over time. • The benefits of a pumping tax are spatially heterogeneous. In this paper, we introduce a hydro-economic modeling framework for the management of groundwater resources that are used for irrigated agricultural production. The model, MOD$$AT, can be used to study the costs of aquifer depletion and the net benefits of specific aquifer management policies. MOD$$AT is composed of three components, namely, an economic component, a hydrologic component and an agronomic component. A main goal of this paper is to introduce the hydro-economic model and describe how it can be transferable to different contexts. With this objective in mind, we describe model components step-by-step so that the process of integration can be replicated easily. We then apply the model to study the efficacy of a pumping tax in Finney County, Kansas, USA, which overlies the High Plains Aquifer. The results show that a pumping tax results in an increase in average well capacities in the county over time relative to the status quo, which increases the average profitability of agricultural production. However, the increase in profitability is not uniform across producers and some producers gain more than others under the tax. [ABSTRACT FROM AUTHOR]

Flood-based Agricultural Systems (FAS), which rely on temporary floods, provide livelihoods for nearly 50 million smallholder farmers across water-stressed African basins. This paper analyses the impact of externally driven agricultural production and productivity improvement interventions in FAS, taking the Ethiopian Fogera floodplain as a case study. Ostroms' Governing the Commons Principles were used as analytical framework. Field data was gathered through focus group discussions and interviews with 266 farmers and pastoralists, and 10 local administration staff, while the AquaCrop model was used to simulate maize yield under varied floodwater management and farming practices. The interventions in the Fogera floodplain replaced vital maize and teff food crops with high-return upstream rice cultivation. It has characteristics similar to other interventions across Africa: 1) inadequate integration of local agricultural water management practices; 2) narrow focus on short-term economic gains and insufficient attention to long-term sustainability of livelihoods and environmental issues; and 3) lack of detailed ex-ante analysis of basin-wide consequences – it failed to prioritize the needs of downstream vegetable producers and pastoralists using shallow wells. The intervention missed several low-cost opportunities, including the establishment of rules to protect downstream water rights; the construction of gabion-strengthened on-farm structures to efficiently distribute floods or raised brick-walls to reinforce shallow wells; and the implementation of measures for improved soil fertility and weed management. The study establishes that these missed opportunities could have enhanced livelihoods by doubling rice yield to 6 tons/ha; increased teff and maize harvests by one-third, to 3 and 5 tons/ha respectively; and mitigated 25% vegetable yield loss and 40% reduction in grazing land. These opportunities could have also produced environmental benefits, including reduced soil moisture and fertility depletion. Lessons from the Fogera floodplain on making interventions cost-effective and considering basin-wide livelihood impacts are relevant to FAS globally. • Analysed external improvement interventions in Flood-based Agricultural Systems. • Farmer-led systems have fair floodwater sharing, but low agricultural productivity. • Implemented interventions have not improved floodwater management and productivity. • Many low-cost improvement opportunities missed due to lack of basin-wide approach. • Identified affordable and up-scalable basin-wide livelihood improving interventions. [ABSTRACT FROM AUTHOR]

Abstract: Rice farming in the Lower Colorado River basin of Texas, US, is a major economic engine and a major water consumer. The Lower Colorado River Authority (LCRA) and the San Antonio Water System (SAWS) sponsored a joint project from 2004 through 2009 to study the feasibility of developing and conserving water to provide sufficient water to farmers in the Lower Colorado River basin, while allowing transfer of water to the city of San Antonio. A major focus of the project was the development of a web-based rice water conservation analyzer (RiceWCA) to evaluate field- and regional-level costs, water savings, and yield benefit associated with implementing on-farm conservation measures, including precision leveling, multiple inlets, conservation tillage, lateral improvement, tailwater recovery, and a production system based on growing high-yielding water efficient cultivars. This paper describes the development and evaluation of the crop development and water balance components of RiceWCA. RiceWCA uses a phenology model to time water management events, including flushing and flush drainage for the main crop, and permanent flood, flood maintenance, and drainage before harvest for the main and ratoon crops. RiceWCA simulates daily water balance for each rice field within the Lower Colorado River basin, as affected by the degree of implementing different conservation measures. The water balance model includes site-specific estimation of soil saturation deficit, evapotranspiration, percolation, seepage, rainfall, irrigation, and tailwater. The water balance model was calibrated and verified using 2000 and 2002 weekly irrigation records for the Lakeside and Gulf Coast irrigation districts, and validated using 2001, 2003, and 2004 weekly irrigation records. Tailwater recovery offers the largest water saving, followed by adoption of high-yielding cultivars, multiple inlet systems, precision leveling, and conservation tillage. Water saving from lateral improvement varies depending on the extent of existing laterals. [Copyright &y& Elsevier]

Abstract: Large-scale irrigation schemes have not yielded the expected outcomes in Sub-Saharan Africa. In Mauritania, average land productivity of rice schemes lies between 3 and 3.5tha−1 and irrigated land has progressively being abandoned. At the same time, there is new international attention towards interventions in large-scale irrigation in the Sahel. Spatial and temporal variability of production are main causes of low productivity of large-scale irrigation schemes in Mauritania and threats to their sustainability. The present paper focuses on the performance of three representative large-scale schemes located along the River Senegal by analysing intra-scheme variability with respect to yield and irrigation intensity using field observations and satellite images. A sample of tertiary canals was selected in each irrigation scheme for weekly surveys of irrigation processes and maintenance. Yield measurement, irrigation (II) and harvest intensity (HI), indicators of irrigation adequacy (IIA) and drainage adequacy (IDA) constituted the basis of this analysis. Semi-structured interviews with the different actors at the various management levels (farmers; cooperatives; union of cooperatives; state irrigation agency; and the private service provider managing the water delivery in one of the schemes) were held in order to gain information on irrigation and drainage infrastructure, organisation and management of the schemes, financial aspects and irrigated surface. Within each irrigation scheme, a great variability was detected with respect to irrigation intensity and yield. Irrigation intensity could vary as much as from 0 to 1 whilst yield could range from 0.4 to 7tha−1 in a single scheme. The analysis of water distribution patterns at scheme level indicated that variability in irrigation supplies and drainage were main sources of variability of yields and irrigation intensity. Physical, technical, and organisational factors underlie non-uniform water distribution patterns. The understanding of the origins of patterns of variability is a first step towards a more realistic assessment of schemes’ sustainability and contribution to food security. [Copyright &y& Elsevier]

Abstract: Irrigated agriculture is facing rising competition worldwide for access to reliable, low cost, high quality water. In England, farmers are under regulatory pressure to improve irrigation efficiency; indeed, demonstrating efficient water use is now a prerequisite for renewing an irrigation abstraction licence (permit). However, there are differences between the concepts of efficient water use as viewed by scientists, regulators and farmers, further confused by the overlap of similar terminology with both precise technical and wider less specific meanings. Most farmers’ concepts of water efficiency are linked to maximising the farms’ economic productivity rather than saving water per se, except perhaps when their own allocated resources may be inadequate. Using a financial criteria for water efficiency rather than an engineering one appears a sensible approach when assessing irrigation performance at the farm level, since any managerial (e.g. scheduling) and operational (e.g. equipment) inefficiencies associated with irrigation are implicitly included in the assessment. It also allows comparison between individual irrigators (benchmarking) and between different water sectors (e.g. agriculture, leisure, industry). However, estimating the direct financial benefits (value) of water to the farm is only part of the equation; assessing indirect economic benefits, such as the importance of irrigated production to the sustainability of rural communities is equally important, but much harder to achieve. Demonstrating efficient or ‘best’ use of water is not straightforward, but farmers and the water regulator need a rational approach that reflects the needs of the farming community whilst providing a policy framework for protecting the environment. This paper reviews the concept of irrigation efficiency in a temperate climate, considers the farmer perspectives, and supports using the ‘pathway to efficiency’ as a means to assist farmers and the water regulator in achieving better irrigation management and abstraction control. [Copyright &y& Elsevier]

Abstract: Pasture productivity depends on soil hydro-physical properties, which in turn are deeply affected by livestock grazing. However, the comparative response of different soil types, and particularly gypseous soil types, to grazing has hardly been studied before. This paper compares the effect of grazing on the soil hydro-physical properties of silty gypseous (Gy) and non-gypseous (NGy) soils located in a semi-arid region (Middle Ebro Valley, NE, Spain). Two different soil managements were selected: ungrazed natural shrubland (N) and grazed shrubland (GR) soils. The gypsum, CaCO3 and organic matter content (OM), soil texture, soil bulk density (ρ b ), penetration resistance (PR), saturated sorptivity (S), hydraulic conductivity (K), and the water retention curve (WRC) for undisturbed soil samples from 1 to 10cm depth soil layer were measured. The ρ b and PR in NGy soils were significantly higher than those observed in the Gy ones. Soil compaction due to grazing treatment tended to increase ρ b and decrease the K and S values. While no differences in PR were observed in the Gy soils between grazing treatments, the PR measured in the NGy soils under GR was significantly higher than the corresponding values observed under N. Differences in K and S between GR and N treatments were only significant (p <0.05) in NGy soils, where K and S values under the N treatment were almost four times greater than the corresponding values measured under GR. Overall, no differences in the WRCs were observed between soil types and grazing treatments. While the WRCs of NGy soils were not significantly affected by the grazing treatment, Gy soils under N treatment present a significantly higher level of soil macropores than under GR treatment. The hydro-physical features of Gy soils tended to be less affected by grazing than those of the NGy soils. These results suggest that livestock grazing, in both Gy and NGy soils, has a negative effect on the physical soil properties, which should be taken into account by land managers of these semi-arid regions where silty gypseous and non-gypseous areas coexist. [Copyright &y& Elsevier]

Abstract: Phreatic groundwater pumping is affecting water availability for crops in areas with a shallow water table. This can reduce crop growth and so affect farm income. There is a need for a generic and transparent method to assess the agricultural damage caused by water table drawdown. This paper proposes such a method that consists of ‘damage tables’ relating agricultural production losses to the groundwater regime for different soil/crop combinations found in Northern Belgium. The damage tables are constructed based on numerous simulations with the agrohydrological model SWAP, in which the bottom boundary conditions are gradually changed to reflect different groundwater regimes. The credibility of the resulting metamodel is assessed in three ways: using (1) field data, (2) an existing local expert system for land suitability assessment and (3) literature applying to a wider region. Field data of actual transpiration for two grasslands do not systematically deviate from the model predictions. This provides some credibility to the claim that the model captures the processes determining evapotranspiration and agricultural production. The local expert system allows us to evaluate the range of groundwater regimes where optimal growth is expected for maize and grassland across different soil types. Diverging predictions of the optimal groundwater regime between the metamodel and the local expert system can be explained in terms of differences in assumptions underlying both models. One notable limitation of the damage tables is that only direct physiological stress is reckoned while indirect effects of wet conditions (decreased accessibility of the terrain, soil structural damage) may also limit growth on soils with a water table near the surface. Further comparison with literature data focused on two issues: the contribution of groundwater to evapotranspiration and the extinction depth, i.e., the depth at which groundwater no longer contributes to evapotranspiration. This comparison revealed that damage tables developed for our area of interest are only valid under similar climatic conditions for the following two reasons: they assume a relatively small groundwater contribution to evapotranspiration, which is typical for humid climates, and they take into account temporal variations in plant characteristics such as root depth, which is also climate dependent. [Copyright &y& Elsevier]

Abstract: Water productivity in agriculture needs to be improved significantly in the coming decades to secure food supply to a growing world population. To assess on a global scale where water productivity can be improved and what the causes are for not reaching its potential, the current levels must be understood. This paper describes the development and validation of a WATer PROductivity (WATPRO) model for wheat that is based on remote sensing-derived input data sets, and that can be applied at local to global scales. The model is a combination of Monteith''s theoretical framework for dry matter production in plants and an energy balance model to assess actual evapotranspiration. It is shown that by combining both approaches, the evaporative fraction and the atmospheric transmissivity, two parameters which are usually difficult to estimate spatially, can be omitted. Water productivity can then be assessed from four spatial variables: broadband surface albedo, the vegetation index NDVI, the extraterrestrial radiation and air temperature. A sensitivity analysis revealed that WATPRO is most sensitive to changes in NDVI and least sensitive to changes in air temperature. The WATPRO model was applied at 39 locations where water productivity was measured under experimental conditions. The correlation between measured and modelled water productivity was low, and this can be mainly attributed to differences in scales and in the experimental and modelling periods. A comparison with measurements from farmer''s fields in areas surrounded by other wheat fields located in Sirsa District, NW India, showed an improved correlation. Although not a validation, a comparison with SEBAL-derived water productivity in the same region in India proved that WATPRO can spatially predict water productivity with the same spatial variation. [Copyright &y& Elsevier]

Abstract: Although the ways in which farmers access irrigation services in areas that rely on groundwater have changed over the past decade, little empirical work has measured the impact of these changes. This is surprising given the potential effects—both positive and negative. In this paper we explore the impacts of the emergence of the markets for irrigation services from groundwater on agricultural production – including crop water use and crop yields – and farmer income in northern China. From a survey of 35 randomly sampled villages and 338 households in two provinces (Hebei and Henan Provinces) in 2001 and 2004, we show that when farmers access water from markets for irrigation services, they significantly reduce water use, compared with farmers who have their own tubewells. However, there is no significant difference between the volume of water used by farmers who access irrigation services provided by the village, and the volume used by farmers who access water from markets for irrigation services. Importantly, although water use decreases, we find little effect on either agricultural productivity (yields) or income. [Copyright &y& Elsevier]

Abstract: In this paper the residual method is used to determine the disaggregated economic value of irrigation water used in agriculture across crops, zones and seasons. This method relies on the belief that the value of a good (its price by its quantity) is equal to the summation of the quantity of each input multiplied by its average value. By applying this method to the Musi sub-basin; a subdivision of the Krishna basin in India, it was found that the value of irrigation water use is not equated across the crops, zones and seasons. The reasons why there is no sinlge value of irrigation water use are suggested. As farmers do not have perfect knowledge, do not all possess the same resource base, plant different crops for a variety of reasons (some for a financial return on land instead of water and others for sustenance), possess different crop rotation practices and are possibly riks adverse, they all value water differently. However, the results need to be interpreted with care as the crop with the lowest return to water is probably not the one to be sacrificed if water is restricted, since farmers plant crops for a variety of reasons (and sometimes not for the highest return to water that they can achieve). [Copyright &y& Elsevier]

Abstract: Irrigated agriculture experienced a water supply shock during a drought in southern India in 2002–2003. In this paper, hotspots of agricultural change were mapped and put in the context of hydrology and water management. Time series of MODIS imagery taken every eight days before (2001–2002) and during (2002–2003) the supply shock were combined with agricultural census data to document changes in cropping patterns in four large irrigation projects in the downstream sections of the Krishna and Godavari River basins (total command area 18,287km2). The area cropped in rice in the four irrigated command areas decreased by 32% during the drought year, and rice production in the two districts that experienced the largest flow reductions fell below production levels of 1980. The irrigation project that showed the largest change in double cropped area (−90%) was upstream of the Krishna Delta. In the Krishna Delta, large areas changed from rice–rice to rice–gram double cropping. Historical water management contributed to the vulnerability of rice production to drought: the main reservoir in the system was drained to dead storage levels by the end of each growing season over 1968–2000, with little carryover storage. The land cover change maps suggested that the lower Krishna Basin has experienced a “hard landing” during basin closure, and revised management strategies that account for the new flow regime will be required to maintain agricultural production during droughts. [Copyright &y& Elsevier]

Abstract: During the last quarter of the 20th century, many irrigation schemes were constructed along the bank of the Senegal River in Mauritania. About 40,000ha were developed but less than 23,000ha remain irrigated today. A program for rehabilitation is now in place to counteract deterioration and abandonment of these schemes. This paper presents an evaluation of the rehabilitation of a small, representative irrigation scheme governed by a farmers’ cooperative in the village of Bélinabé. Before rehabilitation, the scheme covered 37.7ha comprising 107 plots each of 0.33ha, essentially all devoted to production of rice. Water for irrigation was pumped directly from the river into two head basins and distributed through open canals. After rehabilitation, the scheme was extended to 115ha with new plots averaging 0.36ha. Water is now supplied by a single cluster of pumps and conveyed through pipes and open canals. Evaluation of performance consisted in analysis of: capacity; distribution losses; flexibility, adequacy and reliability of the system; maintenance status; farmer''s perception of system performance. Field data were collected during irrigation campaigns before rehabilitation in 2004 and during 2006 and 2007 afterwards. A model of network distribution and field water balance was developed to assist evaluation. It was established that before rehabilitation the scheme could operate satisfactorily if proper maintenance were practiced. After rehabilitation, more families have access to irrigation but reliability and flexibility of water distribution have been reduced. Furthermore, pumping capacity is now insufficient to cover crop water requirements. Recommendations are provided for future rehabilitation work and maintenance of schemes generally. [Copyright &y& Elsevier]

Abstract: As water resources are limited and the demand for agricultural products increases, it becomes increasingly important to use irrigation water optimally. At a farm scale, farmer''s have a particularly strong incentive to optimize their irrigation water use when the volume of water available over a season is production limiting. In this situation, a farmer''s goal is to maximize farm profit, by adjusting when and where irrigation water is used. However, making the very best decisions about when and where to irrigate is not easy, since these daily decisions require consideration of the entire remaining irrigation season. Future rainfall uncertainty further complicates decisions on when and which crops should be subjected to water stress. This paper presents an innovative on-farm irrigation scheduling decision support method called the Canterbury irrigation scheduler (CIS) that is suitable when seasonal water availability is limited. Previous optimal scheduling methods generally use stochastic dynamic programming, which requires over-simplistic plant models, limiting their practical usefulness. The CIS method improves on previous methods because it accommodates realistic plant models. Future farm profit (the objective function) is calculated using a time-series simulation model of the farm. Different irrigation management strategies are tested using the farm simulation model. The irrigation strategies are defined by a set of decision variables, and the decision variables are optimized using simulated annealing. The result of this optimization is an irrigation strategy that maximizes the expected future farm profit. This process is repeated several times during the irrigation season using the CIS method, and the optimal irrigation strategy is modified and improved using updated climate and soil moisture information. The ability of the CIS method to produce near optimal decisions was demonstrated by a comparison to previous stochastic dynamic programming schedulers. A second case study shows the CIS method can incorporate more realistic farm models than is possible when using stochastic dynamic programming. This case study used the FarmWi$e/APSIM model developed by CSIRO, Australia. Results show that when seasonal water limit is the primary constraint on water availability, the CIS could increase pasture yield revenue in Canterbury (New Zealand) in the order of 10%, compared with scheduling irrigation using current state of the art scheduling practice. [Copyright &y& Elsevier]

Abstract: This study reports an analysis of the economics of options for strategic land-use change to attain future catchment level target combinations of salt load and water yield. Farm level survey information on land use, productivity, prices and costs of production were integrated with spatially specific soil, rainfall, topography, hydrology and salinity results of the simulation model CAT (Catchment Analysis Tool). This information was used to populate a two stage economic optimization model in which subcatchment economic results were combined for catchment level analyses. This study is the first to exploit CAT results in an economic framework and the first in which economic results are mapped using CAT. The 64,000ha Bet Bet Catchment in Victoria, Australia, once deemed among the highest priority areas in the Murray Darling Basin for dryland salinity reduction, is the focus of this study. The calculated current net present value (NPV) of agricultural production in the catchment is AU$ 78 million 3 [3] AU$ 1=US$ 0.9 December 2009. while providing 42 GL of water yield 4 [4] 1 GL=1 gigalitre=106 m3 =109 L. annually for use downstream with a salt load of 22,600t. Results show that salt loads may be reduced to 18,600t (reduction of 4000t) through expansion of tree plantations and lucerne production, reducing water yield to 31 GL (11 GL reduction) and NPV to AU$ 63 million (AU$ 15 million reduction). Water yields could be increased from current levels by 2 GL while maintaining current salt loads. Alternatively, catchment NPV could be increased by approximately AU$ 7 million with little or no reduction in water yield; but there may be reasons (small farm size) why this is unlikely. For this catchment, the maximum reduction in salt load appears insufficient to justify public investment in tree planting and perennial pasture establishment, particularly when the reduced NPV and reduced water yields are taken into account. The results for this catchment do not support regulation of land use for the sake of lowering river salinity. However, the capacity of tree plantations to reduce water yields may support a regulation requiring purchase of water entitlements from downstream entitlement holders for new plantations. Despite millions of dollars of past public investment, it is now clear that Bet Bet Catchment was never one where land-use changes could benefit downstream water users. The approach described in this paper enables catchment management authorities to weigh costs of land-use change against downstream benefits and natural resource management (NRM) options elsewhere. [Copyright &y& Elsevier]

Abstract: This article gives a brief review of the development and current situation in global irrigation, and looks at the drivers affecting irrigation performance, development and modernization. The article concludes that the options for new developments are limited, and that future investment will need to be more precisely targeted to specific niches in different agroecological and economic contexts. The paper notes the powerful implications of global climatic change on irrigation through changes in hydrology and water supply that, in conjunction with (1) continued demand for cheap food to satisfy continuously growing populations and changing dietary preferences (projected to 2050) and (2) increasing competition for high reliability water from higher value economic sectors, indicate irrigation performance and the productivity of agricultural water use must further improve, and are also likely to become more targeted at higher value enterprises. Improving management, through better institutions and better technology will require constant adaptation and finessing, with no silver bullets currently on the horizon. [Copyright &y& Elsevier]

Abstract: The authors of the recently completed Comprehensive Assessment of Water Management in Agriculture (CA) concluded that there are sufficient water resources to produce food for a growing population but that trends in consumption, production and environmental patterns, if continued, will lead to water crises in many parts of the world. Only if we act to improve water use will we meet the acute fresh water challenge. Recent spikes in food prices, partially caused by the increasing demand for agricultural products in non-food uses, underline the urgent need to invest in agricultural production, of which water management is a crucial part. The world experienced similar pressure on per capita food supplies and food prices in the 1960s and 1970s, but the challenges now are different than those we experienced 50 years ago. The world''s population is substantially larger, there are many more people living in poverty, and the costs of many agricultural inputs are much higher. The current situation and the long-term outlook require a fresh look at approaches that combine different elements such as the importance of access to water for the poor, providing multiple ecosystem services, rainwater management, adapting irrigation to new needs, enhancing water productivity, and promoting the use of low-quality water in agriculture. This special issue highlights the analysis behind a number of policy options identified by the CA, a five-year multi-disciplinary research program involving 700 scientists. This introductory article sets the background and context of this special issue, introduces the key recommendations from the CA and summarizes the papers in this issue. [Copyright &y& Elsevier]