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Reflecting on the 2023 assertion by the Global Commission on the Economics of Water that the depletion of blue water by irrigation contributes to the global water crisis, we critique two previous contributions by one of its authors, Johan Rockström. First, to bridge agro-meteorological drought, rainfed (green water) farmers should irrigate. If not regulated, this increases water withdrawals and depletion. Second, the continuum of agricultural water management is a field-scale emphasis on rainfall and/or irrigating to top up soil moisture. This emphasis hinders taking a multi-scale irrigation systems approach to resolve blue water depletion and its inequitable impacts. [ABSTRACT FROM AUTHOR]

Agriculture water use accounts for 70% of the total water withdrawal worldwide. The evapotranspiration during crop growth is one of the important hydrological processes in the agricultural water cycle. This study proposed the concept of artificial irrigation evapotranspiration of irrigated crops to describe that the evapotranspiration caused by irrigation water use. Irrigated crops rely on two kinds of water sources: precipitation and irrigation water. With the construction of irrigation schemes, the artificial irrigation evapotranspiration plays an increasingly important role in the dualistic water cycle system of irrigated cropland. To reveal the amount of artificial irrigation evapotranspiration of 17 categories of irrigated crops in China, this study proposed a new quantitative model system which was established based on traditional evapotranspiration models and soil water balance models. Based on the new model system, we calculated the annual artificial irrigation evapotranspiration of irrigated crops for the period 2013 to 2017 in China. The results showed that the proportion of artificial irrigation evapotranspiration to the total evapotranspiration of irrigated crops was 41.3%, whose value was 228.1 km3 a−1. The artificial irrigation evapotranspiration in different agricultural water management regions were 90.0 km3 a−1 in the northeast region, 86.0 km3 a−1 in the southeast region, and relatively low 52.2 km3a−1 in the west region. The results of this study can provide methods for water management and policy–making in agricultural irrigated areas, and it can also provide a preliminary understanding of the influence of human activities on the dualistic water cycle in cropland. [ABSTRACT FROM AUTHOR]

In this study, the agro-hydrological model Soil and Water Assessment Tool + (SWAT+) is used to simulate runoff in an uncontrolled agricultural catchment with paddy fields irrigated by plots submersion. The objectives are to evaluate the ability of this new, improved version of the SWAT model to reproduce the flows in a complex catchment and to analyse the evolution of these flows over the historical period 1986-2020 (35 years). Sensitivity analysis, calibration and validation were carried out with monthly flow data. The decision tables for irrigation operations and reservoir water release were filled in the SWAT+ Editor to establish the reservoir water balance. The Mann-Kendall trend test with the threshold of the standard normal statistic = 1.96, was applied to the time series of flows to the Nanan Reservoir. The results reveal that SWAT+ is more sensitive to eight parameters, including the new CN3_SWF parameter (-0.04329), which gave the user control of the soil saturation level. Good performances were obtained during calibration and validation, respectively: NSE (0.78; 0.69); R² (0.81; 0.70); PBIAS (-18.58; -23.9) and RSR (0.47; 0.56), with a tendency to slightly overestimate flows. The analysis shows that flows to the Nanan Reservoir are highly variable yearly, with a non-significant upward trend (|Z|=1.3<1.96) from 1986 to 2020. The water balance reveals that the runoff inflow generated will compensate for water withdrawals for irrigation of the Nanan paddy scheme during this period. Furthermore, this study provides a methodological framework for SWAT+ reservoir model calibration in an uncontrolled catchment. [ABSTRACT FROM AUTHOR]

We provide a dataset of irrigation water withdrawals by crop, county, year, and water source within the United States. We employ a framework we previously developed to establish a companion dataset to our original estimates. The main difference is that we now use the U.S. Geological Survey (USGS) variable 'irrigation — total' to partition PCR-GLOBWB 2 hydrology model estimates, instead of 'irrigation — crop' as used in previous estimates. Our findings for Surface Water Withdrawals (SWW), total Groundwater Withdrawals (GWW), and nonrenewable Groundwater Depletion (GWD) are similar to those of prior estimates but now have better spatial coverage, since several states are missing from the USGS 'irrigation — crop' variable that was originally used. Irrigation water use increases in this study, since more states are included and 'irrigation — total' includes more categories of irrigation than 'irrigation — crop'. Notably, irrigation in the Mississippi Embayment Aquifer is now captured for rice and soy. We provide nearly 2.5 million data points with this paper (3,142 counties; 13 years; 3 water sources; and 20 crops). [ABSTRACT FROM AUTHOR]

The consistently low yield turnout of maize on farmers' fields owing to drought and the nutritional challenges attributable to the consumption of white endosperm maize pose a major threat to food and nutritional security in Sub-Saharan Africa (SSA). The objectives of this study were to assess the performance of newly developed extra-early maturing orange hybrids under managed drought and well-watered conditions, compare the outcomes of multiple-trait base index and multi-trait genotype–ideotype distance index selection procedures, and identify drought-tolerant hybrids with stable performance across contrasting environments for commercialization in SSA. One hundred and ninety orange hybrids and six checks were evaluated under managed drought and well-watered conditions at Ikenne for two seasons between 2021 and 2023. A 14 × 14-lattice design was used for the field evaluations under both research conditions. Drought stress was achieved by the complete withdrawal of irrigation water 25 days after planting. Results revealed significant differences among the hybrids under drought and well-watered conditions. Grain yield, ears per plant, and plant aspect under managed drought were correlated to the same traits under well-watered conditions, suggesting that the expression of these traits is governed by common genetic factors. Twenty-nine hybrids were identified as top-performing drought-tolerant hybrids by the multiple-trait base index and the multi-trait genotype–ideotype distance index. Of the selected outstanding 29 hybrids, 34% were derived from crosses involving the tester TZEEIOR 197, demonstrating the outstanding genetic potential of this inbred line. Further analysis of the 29 selected hybrids revealed TZEEIOR 509 × TZEEIOR 197 as the hybrid that combined the most drought-tolerant adaptive traits. However, the hybrids TZEEIOR 526 × TZEEIOR 97, TZEEIOR 384 × TZEEIOR 30, TZEEIOR 515 × TZEEIOR 249, TZEEIOR 510 × TZEEIOR 197, TZEEIOR 479 × TZEEIOR 197, and TZEEIOR 458 × TZEEIOR 197 were identified as the most stable hybrids across drought and well-watered conditions. These hybrids should be extensively tested in multi-location trials for deployment and commercialization in SSA. [ABSTRACT FROM AUTHOR]

Accurate and well-categorized information on water supply, demand, consumption, and withdrawals is necessary for the assessment and management of water resources. In this context, the Water Accounting Plus (WA+) framework is a valuable platform for quantifying water flows. By utilizing remote sensing datasets, WA+ enables it to quantify water flows in a basin and compute hydrological processes while considering the impact of land use. To understand the water inflows, outflows, consumption, withdrawals, and storage variations of water resources, we applied the WA+ framework to a complex river basin, namely the Mahi River basin. Using blue and green water estimation, we segregated the irrigated and rainfed areas and computed the hydrological processes at the pixel level using the WaterPix model. We also calculated performance indicators to illustrate the state of water resources in the basin. Our analysis shows that the Mahi River basin is water-stressed and mainly relies on groundwater (GW) for irrigation. The average exploitable and available water flows from 2012 to 2020 were 34.07 Billion Cubic meter (BCM)/year and 30.38 BCM/year , respectively, and the average outflow was 20.65 BCM/year. The average vertical recharge and withdrawal of GW were 17.47 and 21 BCM/year , respectively, while surface water (SW) withdrawal was very low and concentrated in only a few areas. According to the results of the flow and GW sheets, 95% of the utilized flow came from GW, indicating a high dependency on GW. A 25% depletion of water storage was observed during the study period. These results indicate that overexploitation of GW for irrigation and depletion of water storage are the main problems in the Mahi River basin. Our study can help local and national authorities to identify areas with poor water management practices and develop appropriate water management plans and schemes [ABSTRACT FROM AUTHOR]

We estimate the effects of the federal crop insurance premium subsidy on freshwater withdrawals for irrigation among U.S. counties to the west of the 100th meridian. Our results indicate that a 1% increase in premium subsidy leads to a 0.446% (about 475,901 acre-feet/year) and 0.673% (about 474,026 acre-feet/year) increase in total freshwater withdrawals for irrigation and fresh surface water withdrawals for irrigation, respectively. The elasticity of total freshwater withdrawals for irrigation and fresh surface water withdrawals for irrigation with respect to revenue insurance premium subsidy is more than twice as large as those with respect to yield insurance premium subsidy. Groundwater withdrawals for irrigation are not found to be responsive to crop insurance premium subsidy. Because the elasticities are all non-negative, moral hazard should not be a dominant factor in the relationship between crop insurance subsidies and freshwater withdrawals for irrigation. Thus, exploring the causal relationship between crop insurance premium subsidy and agricultural input uses, this study underscores the unintended effect of the federal crop insurance programme on water resource sustainability in the U.S. [ABSTRACT FROM AUTHOR]

Hydrological conditions are key factors in the evaluation of water resources and ecosystems. The Yongding River Basin has many irrigated areas, and excessive agricultural water consumption has led to serious water shortages and ecosystem damage. To investigate the evolution of ecohydrological conditions and their driving factors in the Yongding River basin in a changing environment, this study combines indicators of hydrologic alteration with the range of variability approach (IHA-RVA) to identify the most ecologically relevant hydrological indicators (ERHIs) and to determine the periods of hydrological variability in the basin, using the Xiangshuipu section on the Yang River as the study area. By calculating the degree of hydrological alteration, the evolutionary pattern of ecohydrological conditions in the basin was analyzed, and the WetSpa model was used to quantitatively identify the contributions of climate change, reservoir storage, and irrigation water withdrawal to the alteration of hydrological conditions. The results showed that the rise and fall rate; maximum and minimum 1 day flows; dates of maximum flow; and July flows were the most ecologically relevant hydrological indicators for the Xiangshuipu section. Variability of this section occurred between 1982 and 1988; except for the annual maximum 1 day flows and fall rate, which underwent moderate changes; all other indicators exhibited small changes and the overall hydrological alteration of the Xiangshuipu section was low. The most influential change in the hydrological conditions was irrigation water withdrawal (from specific irrigation); followed by climate change and reservoir storage. The results of this study provide an important basis for water resources utilization and ecological management in the Yongding River basin. [ABSTRACT FROM AUTHOR]

Global climatic change intensifies the water crisis, particularly in arid and semi-arid regions. In this regard, the provision of enough water for irrigation is a serious dilemma because the agricultural sector consumes the largest amount of water (70% withdrawal and 90% consumption). In this review, we have summarized recent innovations that have emerged as unconventional techniques to supply adequate water for irrigation purposes. We present the principles and basics of seven approaches: the Sahara Forest Project (SFP), water extraction from the air (WEA), aquifer recharge, the treatment of marginal water using a magnetic field, desalination and wastewater treatment (DWT), electro-agric technology (E-AT), and the Toshka Project. The SFP is currently being utilized in Aqaba, Jordan, and DWT is considered a common practice worldwide, whereas some of these innovations are still under investigation to ensure their feasibility for large-scale applications, such as E-AT. The Toshka Project is considered a wonderful idea that utilizes the water stored behind the High Dam in Lake Nasser, Egypt. Several approaches have been adopted to reduce the amount of water being used for irrigation, as the current amount of freshwater is insufficient for the requirements of increased agricultural consumption, particularly in hot, arid, and semi-arid regions. [ABSTRACT FROM AUTHOR]

Water withdrawals for irrigation at an unsustainable rate resulted in a decline in the groundwater levels in the Mississippi River Valley Alluvial Aquifer (MRVAA) in the central southern USA. This drawdown of groundwater threatens agricultural production in the Mississippi Delta, an important agricultural region in the state of Mississippi, USA. Effective and efficient use of available resources is important to sustain and enhance agricultural productivity in this area. This study assessed the opinions of farmers on water conservation management practices and technologies that improve irrigation management and save water in the Mississippi Delta region based on data collected in an irrigation survey conducted in 2012. Most landowners believed that water conservation practices were effective in reducing irrigation water use without reducing maximum crop yields and have a positive return on investment. Land forming, tailwater recovery system, on‐farm storage, instream weirs to pond surface water, computerized hole selection for furrow irrigation, short irrigation runs, and irrigation scheduling were considered efficient water conservation technologies by landowners. Perceptions about use of different practices also depend upon the crops produced by the respondents. About 20 to 24% and 14.9 to 86% of survey respondents thought that on‐farm storage and center pivot, respectively, were inefficient water conservation practices for irrigating crops in the Mississippi Delta. The adoption of these practices may be increased if the landowners know the economic returns of implementing them. [ABSTRACT FROM AUTHOR]

Irrigation activities are important for sustaining food production, and account for 70 % of total global water withdrawals. In addition, due to increased evapotranspiration (ET) and changes on leaf area index (LAI), these activities have an impact on hydrology and climate. In this paper we present a new irrigation scheme within the land surface model ORCHIDEE. It restrains actual irrigation according to available freshwater by including a simple environmental limit and using allocation rules depending on local infrastructure. We perform a simple sensitivity analysis and parameter tuning to set the parameter values and match the observed irrigation amounts against reported values, assuming uniform parameter values over land. Our scheme matches irrigation withdrawals amounts at global scale, but we identify some areas in India, China and the US (some of the most intensively irrigated regions worldwide) where irrigation is underestimated. In all irrigated areas, the scheme reduces the negative bias of ET. It also exacerbates the positive bias of the leaf area index (LAI) except for the very intensively irrigated areas, where irrigation reduces a negative LAI bias. The increase of ET decreases river discharge values, in some cases significantly, although this does not necessarily lead to a better representation of discharge dynamics. Irrigation, however, does not have a large impact on the simulated total water storage anomalies (TWSA) and its trends. This may be partly explained by the absence of non-renewable groundwater use, and its inclusion could increase irrigation estimates in arid and semiarid regions by increasing the supply. Correlation of irrigation biases with landscape descriptors suggests that inclusion of irrigated rice and dam management could improve the irrigation estimates as well. Regardless of this complexity, our results show that the new irrigation scheme helps simulating acceptable land surface conditions and fluxes in irrigated areas, which is important to explore the joint evolution of climate, water resources and irrigation activities. [ABSTRACT FROM AUTHOR]

As a sensitive climate change indicator, global multi‐depth soil moisture (SM) has undergone great variation due to warming trends during the past decades. Here, we investigate the evolutionary pattern of SM and then carry out an attribution analysis from climate and human perspectives. The results reveal an unbalanced surface and rootzone variation trend during 1980–2020. The surface soil had approximately equal proportions of drying and wetting. Nonetheless, the percentage of the wetting region is significantly higher than that of the drying region for rootzone soil. The significantly drying region is mainly distributed in habitable areas, while the remarkably wetting region is usually located in the harsh climate and tropical humid zones. According to the attribution analysis using the Feature Importance Index of the Random Forest model, Pearson correlation coefficient, Maximum information coefficient, Spearman rank correlation coefficient, and Granger causality with 99% statistical significance, both climatic and human factors presented significant impacts on SM. Specifically, air temperature and evaporation are thought to be the primary climatic factors affecting the seasonal and long‐term variability of SM, respectively. Irrigation water withdrawal is regarded as the dominant driving force of SM variation among six human water withdrawals, and domestic and electricity water withdrawals play indispensable roles in SM fluctuation. Additionally, SM also provides profound feedbacks on climatic factors and human water withdrawals. The global spatial‐temporal SM variation along with warming temperatures could seriously risk food security and sustainable development, which needs to be addressed. Key Points: Drying regions are distributed in habitable areas, while wetting regions are located in the harsh climate and tropical humid zonesAir temperature and evaporation are thought to be the primary climatic factors affecting the seasonal and long‐term variability of soil moisture (SM)Irrigation water withdrawal is regarded as the dominant driving force of SM variation among the six human water withdrawals [ABSTRACT FROM AUTHOR]

Irrigation water use represents the primary source of freshwater consumption by humans. The amount of water withdrawals for agricultural purposes is expected to further increase in the upcoming years to face the rising world population and higher living standards. Hence, effective plans for enacting a rational management of agricultural water use are urgent, but they are limited by knowledge gaps about irrigation. Detailed information on irrigation dynamics (i.e., extents, timing, and amounts) is generally lacking worldwide, but satellite observations can be used to fill this gap. This paper describes the first regional-scale and high-resolution (1 and 6 km) irrigation water data sets obtained from satellite observations. The products are developed over three major river basins characterized by varying irrigation extents and methodologies, as well as by different climatic conditions. The data sets are an outcome of the European Space Agency (ESA) Irrigation+ project. The irrigation amounts have been estimated through the SM-based (soil-moisture-based) inversion approach over the Ebro river basin (northeastern Spain), the Po valley (northern Italy), and the Murray–Darling basin (southeastern Australia). The satellite-derived irrigation products referring to the case studies in Europe have a spatial resolution of 1 km, and they are retrieved by exploiting Sentinel-1 soil moisture data obtained through the RT1 (first-order Radiative Transfer) model. A spatial sampling of 6 km is instead used for the Australian pilot area, since in this case the soil moisture information comes from CYGNSS (Cyclone Global Navigation Satellite System) observations. All the irrigation products are delivered with a weekly temporal aggregation. The 1 km data sets over the two European regions cover a period ranging from January 2016 to July 2020, while the irrigation estimates over the Murray–Darling basin are available for the time span April 2017–July 2020. The retrieved irrigation amounts have been compared with benchmark rates collected over selected agricultural districts. Results highlight satisfactory performances over the major part of the pilot sites falling within the two regions characterized by a semiarid climate, namely, the Ebro and the Murray–Darling basins, quantified by median values of RMSE, Pearson correlation r , and bias equal to 12.4 mm/14 d, 0.66, and - 4.62 mm/14 d, respectively, for the Ebro basin and to 10.54 mm/month, 0.77, and - 3.07 mm/month, respectively, for the Murray–Darling basin. The assessment of the performances over the Po valley is affected by the limited availability of in situ reference data for irrigation. The developed products are made available to the scientific community for use and further validation at 10.5281/zenodo.7341284 (Dari et al., 2022a). [ABSTRACT FROM AUTHOR]

Agriculture is the largest user of water in the United States. Yet, we do not understand the spatially resolved sources of irrigation water use (IWU) by crop. The goal of this study is to estimate crop‐specific IWU from surface water withdrawals (SWW), total groundwater withdrawals (GWW), and nonrenewable groundwater depletion (GWD). To do this, we employ the PCR‐GLOBWB 2 global hydrology model to partition irrigation information from the U.S. Geological Survey Water Use Database to specific crops across the Continental United States (CONUS). We incorporate high‐resolution input data on agricultural production and climate within the CONUS to obtain crop‐specific irrigation estimates for SWW, GWW, and GWD for 20 crops and crop groups from 2008 to 2020 at county spatial resolution. Over the study period, SWW decreased by 20%, while both GWW and GWD increased by 3%. On average, animal feed (alfalfa/hay) uses the most irrigation water across all water sources: 33 from SWW, 13 from GWW, and 10 km3/yr from GWD. Produce used less SWW (43%), but more GWW (57%), and GWD (27%) over the study time‐period. The largest changes in IWU for each water source between the years 2008 and 2020 are: rice (SWW decreased by 71%), sugar beets (GWW increased by 232%), and rapeseed (GWD increased by 405%). These results present the first national‐scale assessment of irrigation by crop, water source, and year. In total, we contribute nearly 2.5 million data points to the literature (3,142 counties; 13 years; 3 water sources; and 20 crops). Key Points: A national database of crop‐specific irrigation water use by source is developedAnimal feed uses the most irrigation water compared to other crops across all water sourcesRice decreased surface water use by 71%, sugar beets increased groundwater use by 232%, and rapeseed increased groundwater depletion by 405% from 2008 to 2020 [ABSTRACT FROM AUTHOR]

This paper describes the University of New Hampshire Water Balance Model, WBM, a process-based gridded global hydrologic model that simulates the land surface components of the global water cycle and includes water extraction for use in agriculture and domestic sectors. The WBM was first published in 1989; here, we describe the first fully open-source WBM version (v.1.0.0). Earlier descriptions of WBM methods provide the foundation for the most recent model version that is detailed here. We present an overview of the model functionality, utility, and evaluation of simulated global river discharge and irrigation water use. This new version adds a novel suite of water source tracking modules that enable the analysis of flow-path histories on water supply. A key feature of WBM v.1.0.0 is the ability to identify the partitioning of sources for each stock or flux within the model. Three different categories of tracking are available: (1) primary inputs of water to the surface of the terrestrial hydrologic cycle (liquid precipitation, snowmelt, glacier melt, and unsustainable groundwater); (2) water that has been extracted for human use and returned to the terrestrial hydrologic system; and (3) runoff originating from user-defined spatial land units. Such component tracking provides a more fully transparent model in that users can identify the underlying mechanisms generating the simulated behavior. We find that WBM v.1.0.0 simulates global river discharge and irrigation water withdrawals well, even with default parameter settings, and for the first time, we are able to show how the simulation arrives at these fluxes by using the novel tracking functions. [ABSTRACT FROM AUTHOR]

Irrigation water use represents the primary source of freshwater consumption by humans. The amount of water withdrawals for agricultural purposes is expected to further increase in the upcoming years to face the rising world population and higher living standards. Hence, effective plans for enacting a rational management of agricultural water use are urgent, but they are limited by knowledge gaps about irrigation. Detailed information on irrigation dynamics (i.e., extents, timing, and amounts) is generally lacking worldwide, but satellite observations can be used to fill this gap. This paper describes the first regional-scale and high-resolution (1 and 6 km) irrigation water data sets obtained from satellite observations. The products are developed over three major river basins characterized by varying irrigation extents and methodologies, as well as by different climatic conditions. The data sets are an outcome of the European Space Agency (ESA) Irrigation+ project. The irrigation amounts have been estimated through the SM-based (Soil-Moisture-based) inversion approach over the Ebro river basin (North-eastern Spain), the Po valley (Northern Italy), and the Murray-Darling basin (South-eastern Australia). The satellite-derived irrigation products referring to the case studies in Europe have a spatial resolution of 1 km, and they are retrieved by exploiting Sentinel-1 soil moisture data obtained through the RT1 (first-order Radiative Transfer) model. A spatial sampling of 6 km is instead used for the Australian pilot area, since in this case the soil moisture information comes from CYGNSS (Cyclone Global Navigation Satellite System) observations. All the irrigation products are delivered with a weekly temporal aggregation. The 1 km data sets over the two European regions cover a period ranging from January 2016 to July 2020, while the irrigation estimates over the Murray-Darling basin are available for the time span April 2017 – July 2020. The retrieved irrigation amounts have been compared with benchmark rates collected over selected agricultural districts. Results highlight satisfactory performances over the major part of the pilot sites falling within the two regions characterized by a semi-arid climate, namely the Ebro and the Murray-Darling basins, quantified by median values of RMSE Pearson correlation, r and BIAS equal to 12.4 mm/14-day, 0.66, and -4.62 mm/14-day, respectively, for the Ebro basin and to 10.54 mm/month, 0.77, and -3.07 mm/month, respectively, for the Murray-Darling basin. The assessment of the performances over the Po valley is affected by the limited availability of in situ reference data for irrigation [ABSTRACT FROM AUTHOR]

Several previous studies have highlighted the irrigation‐induced impacts on the global and regional water cycle, energy budget, and near‐surface climate. While land models are widely used to address this question, the implementations of irrigation in these models vary in complexity. Here, we expand the representation of irrigation in Community Land Model to enable six different irrigation methods. We find that using a combination of irrigation methods, including default, sprinkler, flood and paddy techniques performs best as determined by evaluating the simulated irrigation water withdrawals against observations, and therefore select this combination as the new irrigation scheme. Then, the impact of the new irrigation scheme on surface fluxes is evaluated and detected using single‐point simulations. Finally, the global and regional irrigation‐induced impacts on surface energy and water fluxes are compared using both the original and the new irrigation scheme. The new irrigation scheme substantially reduces the bias and root‐mean‐square error of simulated irrigation water withdrawal in the USA and other countries, but considerably overestimates withdrawals in Central China. Results of single‐point experiments show that different irrigation methods have different effects on surface fluxes, while the magnitudes are small. At the global scale, the new scheme enlarges the irrigation‐induced impacts on water and energy variables relative to the original scheme, with varying magnitudes across regions. Overall, our results suggest that this newly developed scheme is a better tool for simulating irrigation‐induced impacts on climate, and highlight the added value of incorporating human water management in Earth system models. Plain Language Summary: Knowing the effects of irrigation on the water and energy cycle is important, as it helps us to understand better how irrigation may affect the near‐surface climate such as dampening heat extremes and increasing local air humidity. Land models are widely used for this purpose. However, in most of these models, different irrigation techniques are currently not considered. In this study, we develop a new irrigation scheme for the Community Land Model, and evaluate it by comparing modeled and observed irrigation water withdrawals and surface energy and water fluxes. Results show that this new scheme performs better in simulating irrigation water withdrawals in most countries. Results of one‐dimensional simulations show that different irrigation methods have small but varying impacts on surface fluxes. At the global and regional scale, incorporating more realistic irrigation methods enlarges the effects of irrigation on water and energy variables. We therefore conclude that improving the realism of irrigation in models can help us to improve our understanding of how irrigation affects climate through altered water and energy fluxes. Key Points: A newly‐developed irrigation module considering different irrigation methods is implemented in Community Land ModelThe new irrigation scheme shows a better performance of simulating irrigation water withdrawal against the original moduleDifferent irrigation methods have different effects on water cycle and energy budgets, changing regional irrigation‐induced impacts [ABSTRACT FROM AUTHOR]

Many irrigation districts along the Yellow River have been suffering shallow groundwater depression and agriculture-use water shortage. For comprehending response relationships of shallow groundwater level and various factors under different conditions of groundwater buried depth, the hydro-meteorological time series and the agricultural production data in Puyang area of Henan Province, China during 2006–2018 were collected for performing wavelet analysis of the relationship between the groundwater level and the four different factors, such as precipitation, air temperature, water stage of the Yellow River, and well irrigation water amount. It is shown that when the burial depth of groundwater varied from 0–10 m to over 10 m, the groundwater level was related with both the precipitation and air temperature from moderately to weakly and the delayed response times of the groundwater level to them extended from 2–4 months to more than 5 months. The groundwater level maintained a medium correlation with the well irrigation water amount as the burial depth increased, but the lag response time of groundwater level to well irrigation dramatically decreased when the burial depth exceeded 10 m. The dynamic response relationship between the groundwater and the water stage of the Yellow River was mainly affected by the distance away from the Yellow River rather than the burial depth and the influence of the river stage on the groundwater level was limited within the distance approximate to 20 km away from the Yellow River. The findings are expected to provide the reference for groundwater level prediction and groundwater resources protection. [ABSTRACT FROM AUTHOR]

The agriculture of the Texas High Plains (THP) region is primarily dependent on groundwater irrigation. Changing weather patterns along with competing demands for water resources and other anthropogenic effects have dramatically increased withdrawals from the Ogallala aquifer. In addition to on-farm changes, policy tools based on off-farm mechanisms are equally indispensable in addressing sustainable groundwater use in the THP. One such policy tool is water pricing using estimates of price elasticity of irrigation water demand. This paper estimates the elasticity of irrigation water demand in the THP and assesses the influence of water price on major inputs used in dominant irrigated crops such as corn and cotton. Using the translog profit function on an annual county-level dataset of THP crop production, spanning 23 years (1998–2020), we find that irrigation water demand is price elastic for cotton (η = – 1.58) but inelastic for corn (η = – 0.81). Our findings suggest that a non-uniform pricing policy could be a useful tool to promote the efficient use of groundwater for irrigation. [ABSTRACT FROM AUTHOR]

Irrigated agriculture is the dominant user of water globally, but most water withdrawals are not monitored or reported. As a result, it is largely unknown when, where, and how much water is used for irrigation. Here, we evaluated the ability of remotely sensed evapotranspiration (ET) data, integrated with other datasets, to calculate irrigation water withdrawals and applications in an intensively irrigated portion of the United States. We compared irrigation calculations based on an ensemble of satellite-driven ET models from OpenET with reported groundwater withdrawals from hundreds of farmer irrigation application records and a statewide flowmeter database at three spatial scales (field, water right group, and management area). At the field scale, we found that ET-based calculations of irrigation agreed best with reported irrigation when the OpenET ensemble mean was aggregated to the growing season timescale (bias = 1.6–4.9 %, R2 = 0.53–0.74), and agreement between calculated and reported irrigation was better for multi-year averages than for individual years. At the water right group scale, linking pumping wells to specific irrigated fields was the primary source of uncertainty. At the management area scale, calculated irrigation exhibited similar temporal patterns as flowmeter data but tended to be positively biased with more interannual variability. Disagreement between calculated and reported irrigation was strongly correlated with annual precipitation, and calculated and reported irrigation agreed more closely after statistically adjusting for annual precipitation. The selection of an ET model was also an important consideration, as variability across ET models was larger than the potential impacts of conservation measures employed in the region. From these results, we suggest key practices for working with ET-based irrigation data that include accurately accounting for changes in soil moisture, deep percolation, and runoff; careful verification of irrigated area and well-field linkages; and conducting application-specific evaluations of uncertainty. [Display omitted] • Compared ET-based irrigation volumes to reported water use data at multiple scales. • ET-based irrigation volumes and reports agreed best at field scale. • Uncertainties include water balance closure and linking irrigated area to wells. • Variation among ET models is substantial relative to irrigation management actions. • ET-based irrigation tracking is promising but application-relevant uncertainties exist. [ABSTRACT FROM AUTHOR]

The pressure on freshwater resources is leading to diminishing flows in some of the critical river systems across the globe. India is no exception, and this is mainly because of water withdrawal for irrigation, which is often to the tune of 70% to 80% of the lean season flows, with some proportion for domestic and industrial use. While graduating from the concept of environmental flows and its assessment methodologies in India, the water-managers, the researchers and the conservationists are now moving towards answering the next question, if the rivers are to be revived, where will the water come from, especially in the case of over-allocated rivers, including the River Ganga. While the logical way is to look at the biggest user of water, i.e., irrigation, it remains to be seen whether the irrigation water savings will actually lead to enhancing flows in a river, complementing the efforts towards maintaining e-flows in rivers, or whether it will lead to more area under agriculture, bring changes in cropping patterns towards more water-intensive crops or result in something else. This is a growing debate across the globe, where India is no exception, and there has been a wide range of opinions in this regard. This paper discusses the process, findings and lessons from a joint initiative involving farmers, the Uttar Pradesh state Irrigation and Water Resources Department, Bijnor District Administration and a conservation organisation, WWF, to enhance flows in a sub-tributary, called the Karula River, which is part of the Ganga River system. Another objective of this paper is to look at the scalability and replicability of similar approaches in other irrigation command areas to benefit nearby river systems in general. Under this initiative, the team attempted to enhance flows in the river Karula by routing the saved water from irrigation supplies in a canal commanded area. This saving of water is being achieved due to supply-side and demand-side measures that are being adopted in the project area. With the objective of ensuring the sustainability of the initiative, efforts are made to form an institutional arrangement, through which this initiative can be sustained beyond the project support. [ABSTRACT FROM AUTHOR]

Irrigation is the dominant section of human water use, exerting essential impacts on hydrological processes and water resources. To more realistically simulate irrigation processes in water‐rich regions, an irrigation scheme is incorporated into a land surface‐hydrological model. It calculates the irrigation water requirement according to meteorological conditions, cropping area and growing stage, and root‐zone soil moisture, and determines the irrigation water withdrawal based on the available water resources as well as describing water extraction and irrigation processes in the model. The coupled model is applied to the Yangtze River Basin (YRB) in China, and verified using the observed daily river discharge from 1987 to 1990, evapotranspiration and irrigation amounts from 1999 to 2003. The results first show that the model can well reproduce hydrological processes within the basin, and the simulated irrigation largely agrees with the observation, in terms of annual irrigation and its spatial pattern. Second, inclusion of irrigation processes allows the model to better estimate evapotranspiration, with relative biases decreased from about −10% to −3%. It is also found that in comparison to arid/semi‐arid areas, although presenting a less effect on river discharge and groundwater, the irrigation in the YRB significantly alters hydrological processes through water redistribution. The irrigation‐induced evapotranspiration increment and runoff decrease indicate a shift in the surface water and energy balance, implying a potential effect on the atmosphere. Therefore, representing irrigation processes properly is important, particularly for understanding the coupling effect of the nature‐human system and improving the hydrological prediction accuracy. Plain Language Summary: As the human population has dramatically increased, the agricultural irrigation has grown rapidly over the past 200 years. The critical implications of irrigation on water resources exert through impact on hydrological processes and further influence on weather and climate via the surface energy balance. Representing irrigation processes in the hydrological models or in the climate models is meaningful for improving accuracy of hydrological predictions. Therefore, we described irrigation processes in a land surface‐hydrological model, and the coupled model was used for the YRB in China and verified. It has confirmed that the model appropriately reproduces the hydrological processes impacted by climate variability and human activities. In the future, we intend to use the model to study the coupling effect of the nature‐human systems, which is expected to contribute to sustainable water resources management. Key Points: We developed a land surface‐hydrological model that describes irrigation processes by incorporating an irrigation schemeWe used the Global Crop Water Model method to more realistically estimate irrigation and described water extraction and irrigation processesWe conducted verification in terms of river discharge, evapotranspiration, and irrigation water amount to evaluate model performance [ABSTRACT FROM AUTHOR]

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Agriculture is the economic activity which uses water the most in Brazil, particularly in São Francisco River Basin, where water withdrawals for irrigation granted by water authorities amount to 22.3 billion m3 per year, a number which is close to 81% of the total withdrawal. On the other hand, bulk water in Brazil is underpriced. Water charges for agricultural users neither reflect the economic value of water nor induce a rational and efficient use of water resources, two key concepts of the Brazilian water law. Even so, it is common for irrigators to complain about the water prices charged for their use of bulk water. To throw some light on the real impact of charging water in the agriculture sector, this article evaluates the economic value of irrigation water in the São Francisco River basin through the shadow price approach, calculated by using the Residual Value Method. The analysis was performed for the top ten major São Francisco River basin crops in water use terms, namely corn, soybean, mango, beans, coffee bean, banana, cotton, sugar cane, papaya and rice. Results for the 2019 harvests show that except for sugar cane, all water shadow prices were positive, notably mango, beans and papaya. This paper also evaluated water shadow prices interannual variation from 2014 to 2019 for six crops. Except for sugarcane, the other crops have been profitable most of the time in the last 6 years. A wide fluctuation in the shadow price of water was observed over these years due to variations in sales prices and costs of production. [ABSTRACT FROM AUTHOR]

Dashte Abbas is one of the fertile plains of the Ilam Province situated in the southwest of Iran, where water resources are scarce, and often the quality of water is not suitable for agricultural uses. To solve the problem of water scarcity, the Karkheh-Dashte Abbas inter-basin water transfer project started operation in 2008. The objective of this study was to investigate the effects of different agricultural water management scenarios on the environmental and economic conditions in the Dashte Abbas using the System Dynamics (SD) approach. The conceptual model was considered based on five sub-models, including water demand, water supply, environmental stresses, environment, and water economics. The evaluated water transfer scenarios were allocation of 160, 170, 180, 200 Million Cubic Meters (MCM) water transferred from the Karkheh Dam and 90, 80, 70, and 60 MCM annual groundwater withdrawal from the aquifer, respectively. The results showed that in all scenarios, water transfer increased groundwater level, decreased groundwater quality, reduced soil aeration and drainage, increased salinity of root zone and, consequently, reduced agricultural production in the plain. The results of the SD model demonstrate that the need for drainage is reduced with increasing groundwater consumption. The alternative cropping systems with higher water requirements, including forage crops and sugar beet, may be helpful to reduce drainage problems and to prevent construction of an underground drainage system. The results also confirmed that with the implementation of the first water allocation scenario (allocation of annual 160 MCM surface water transfer and annual 90 MCM of groundwater withdrawal) and cultivation of higher water requirement crops can reduce the rise in groundwater level and drainage problems. In these conditions, the water table remains almost constant at a depth of 10 meters. [ABSTRACT FROM AUTHOR]

• A SWAT model with good performance is established for the watershed with irrigation interference. • Evapotranspiration of winter wheat was precisely considered. • The optimized SWAT accurately estimates agricultural evaporation. Evapotranspiration (ET) is the true water consumption of the watershed and is key to achieving water conservation. The accurate estimation of ET by distributed hydrological model can provide an important basis for watershed water resources management. At present, the traditional approach calibrating distributed hydrological model parameters by runoff has low accuracy in watersheds under human interference. The reason is that the measured runoff is no longer natural due to various human activities such as river water withdrawals, reservoir regulation and inter-basin water transfer. While using ET for model calibration can effectively overcome this interference, making it a more accurate approach for watersheds under human interference. Therefore, we calibrated the Soil and Water Assessment Tool (SWAT) model using PMLV_2 ET in Ziya River under frequent human activities. The results indicated that calibrating the model with remote sensing ET could improve the model's simulation performance, increasing the NS from 0.65 to 0.83. However, the annual ET calculated by the model was 21.7% lower than PMLV_2 ET. The largest underestimation was for the annual ET of cropland (agricultural ET), which was underestimated by 24.4%. This is partly because the model did not account for irrigation evaporation from cropland. Therefore we used Landsat 8 data to extract the planting areas of winter wheat, which consumes the highest irrigation water in the Ziya River Basin, from 2013 to 2018. The planting areas and irrigation regimes of winter wheat were incorporated into the SWAT model to calculate the agricultural ET. The results indicate that the agricultural ET calculated by the SWAT model that considers irrigation evaporation is 6.9% lower than that of PMLV_2 ET. The simulation accuracy of ET is significantly improved. This study provides a reference for accurate estimation of agricultural ET and a basis for ET management. [ABSTRACT FROM AUTHOR]

Quantification of the global irrigation water use (IWU) is crucial to understanding the anthropogenic disturbance of the natural hydrological cycle and optimal agricultural water management. However, it is challenging to obtain time series data with the conventional survey‐based approach, while the current satellite‐based IWU estimations are subject to data gaps and the model structure. In this paper, we propose a comprehensive framework to couple the different processes associated with irrigation and integrate multiple satellite observations to estimate the global IWU. The ensemble IWU estimate demonstrates an improved performance when compared to the IWU obtained from individual satellite observations. The results show reasonable correlation with the survey‐based irrigation water withdrawal in states of the US (bias = −0.42 km3), provinces of China (bias = −3.10 km3), and country statistics from the Food and Agriculture Organization (bias = −10.84 km3). Large amounts of IWU are apparent in India, China, the US, Europe, and Pakistan, making up >70% of the global IWU. A general underestimation of IWU is found both in this work and previous studies, due to the coarse resolution and asynchronism of the various satellite products, the changes in irrigated areas, and the deficiency in detecting irrigation events under the case of saturated soil moisture. Nevertheless, we demonstrate advantages in integrating multiple satellite observations to reduce the uncertainty in estimating global IWU. However, additional efforts are needed to produce high‐quality and finer spatiotemporal resolution satellite‐based products, to further improve the accuracy of the global IWU estimation. Key Points: An integrated framework is proposed to estimate global irrigation water use (IWU) from multiple satellite‐based productsThe IWU estimation scheme can capture the trends of irrigation dynamics well during the study periodThe underestimation in global IWU can be mainly attributed to the coarse resolution of the satellite‐based products [ABSTRACT FROM AUTHOR]

When water scarcity restricts agricultural production, expanding water resources is only one option to increase or maintain output; investments in research to raise productivity can also release constraints on growth. In this paper, we construct a model of optimal resource allocation with both public and private inputs in production—the public sector invests in research and irrigation infrastructure to supply technology and water, respectively, whereas the private sector supplies other inputs. The model is used to derive shadow values for water that suggest "crop per drop" valuations are likely to significantly overstate the marginal value of water in agriculture. We apply our model to analyze sources of growth in Egyptian agriculture, which is almost entirely dependent on publicly supplied irrigation water, over 1961–2016. We construct two indexes of total productivity: total factor productivity treats resources from a producer perspective, where water is free and resource rents accrue to land. Total resource productivity takes a social perspective, where government subsidies for irrigation are included as a cost of production, and resource rents are assigned to water withdrawals for agriculture. Our results find that technological innovations and efficiency gains contributed significantly more to agricultural growth in Egypt than expansion of irrigated area or water use. Productivity growth accelerated in the 1980s following the transition from a socialist to a market‐oriented economy. Including social costs of irrigation provision reduces the implied rate of total productivity growth only marginally. Nonetheless, the rise in total resource productivity significantly increased the value of natural resource rents in Egyptian agriculture. [ABSTRACT FROM AUTHOR]

A sustainable management of global freshwater resources requires reliable estimates of the water demanded by irrigated agriculture. This has been attempted by the Food and Agriculture Organization (FAO) through country surveys and censuses, or through Global Models, which compute irrigation water withdrawals with sub-models on crop types and calendars, evapotranspiration, irrigation efficiencies, weather data and irrigated areas, among others. Here we demonstrate that these strategies err on the side of excess complexity, as the values reported by FAO and outputted by Global Models are largely conditioned by irrigated areas and their uncertainty. Modelling irrigation water withdrawals as a function of irrigated areas yields almost the same results in a much parsimonious way, while permitting the exploration of all model uncertainties. Our work offers a robust and more transparent approach to estimate one of the most important indicators guiding our policies on water security worldwide. The global water demands of irrigated agriculture are estimated through country surveys or through hydrological models, but both approaches are taxing. Here, the authors show that they can simply be estimated as a function of irrigated areas. [ABSTRACT FROM AUTHOR]

Freshwater salinisation is a growing problem, yet cross-regional assessments of freshwater salinity status and the impact of agricultural and other sectoral uses are lacking. Here, we assess inland freshwater salinity patterns and evaluate its interactions with irrigation water use, across seven regional river basins (401 river sub-basins) around the world, using long-term (1980–2010) salinity observations. While a limited number of sub-basins show persistent salinity problems, many sub-basins temporarily exceeded safe irrigation water-use thresholds and 57% experience increasing salinisation trends. We further investigate the role of agricultural activities as drivers of salinisation and find common contributions of irrigation-specific activities (irrigation water withdrawals, return flows and irrigated area) in sub-basins of high salinity levels and increasing salinisation trends, compared to regions without salinity issues. Our results stress the need for considering these irrigation-specific drivers when developing management strategies and as a key human component in water quality modelling and assessment. Freshwater salinisation is a growing water quality problem, but impacts and drivers across regional to global scales have been lacking. A new assessment of inter-regional freshwater salinisation demonstrates the importance of irrigation as a driver of salinisation. [ABSTRACT FROM AUTHOR]

The reuse of purified wastewater can supplement water availability for irrigation and limit withdrawals from groundwater which contribute to deteriorating its quality in many Italian coastal agricultural areas. The regulatory framework defined by EC Reg. 741/2020 specifies the legal and technical conditions, which from 2023 allow this use to be promoted in Italy. However, Italian agriculture is also differentiated in the ways in which farms obtain water for irrigation, and it is advisable to direct the treated wastewater towards the types that will then effectively reduce the use of groundwater. Our study seeks to identify these typologies by examining irrigation conditions in an important agricultural area of Southern Italy. Some districts of this territory are reached by collective irrigation networks of a Consortium that supply all the irrigation water; other areas are connected to those networks, but its supplies are lacking, and the farms also draw on underground aquifers; other areas are not reached by the collective network and groundwater is the only irrigation resource available. An econometric estimate of the irrigation demand in these areas defines whether the relationship between irrigation demand for groundwater and consortium is complementary or substitutive. This outlines the possible responses to the increase in consortium supplies with the introduction of treated wastewater, identifying the farm types to which those additional water resources can be allocated to reduce withdrawals from aquifers. A Seemingly Unrelated Regression Equations system of two irrigation water demand functions, from Consortium and from farm wells, is estimated with data from the National Information System for the Management of Water Resources in Agriculture (SIGRIAN) and the Farm Accountancy Data Network (FADN). The unitary costs of using each of these two sources are amongst the technical and economic regressors. The results indicate that in the farm type that uses both water sources, consortium and groundwater, there is a substitution relationship between these two sources. Also, the irrigation of these farms is the most responsive to current trends in the profitability of the various groups of crops, with the possibility of a further growth in the groundwater use. Supporting irrigation with treated wastewater on these farms would not induce rebound effects that increase the groundwater use: a greater irrigation supply of purified and conventional water at lower costs would instead reduce the use this water source. • EU Reg. 2020/741 defines the reuse of wastewater in irrigation to limit water withdrawals from aquifers. • Irrigation in the South often integrates the availability of surface water by using aquifers which, however, it overexploits. • A SURE econometric model estimates whether irrigation from collective waters and farm wells is complementary or substitutive. • Providing treated wastewater to farms will not increase withdrawals from aquifers as their use replaces collective water. [ABSTRACT FROM AUTHOR]

Many scenarios of future climate evolution and its anthropogenic drivers include considerable amounts of bioenergy as a fuel source, as a negative emission technology, and for providing electricity. The associated freshwater abstractions for irrigation of dedicated biomass plantations might be substantial and therefore potentially increase water limitation and stress in affected regions; however, assumptions and quantities of water use provided in the literature vary strongly. This paper reviews existing global assessments of freshwater abstractions for bioenergy production and puts these estimates into the context of scenarios of other water-use sectors. We scanned the available literature and (out of 430 initial hits) found 16 publications (some of which include several bioenergy-water-use scenarios) with reported values on global irrigation water abstractions for biomass plantations, suggesting water withdrawals in the range of 128.4 to 9000 km3yr-1 , which would come on top of (or compete with) agricultural, industrial, and domestic water withdrawals. To provide an understanding of the origins of this large range, we present the diverse underlying assumptions, discuss major study differences, and calculate an inverse water-use efficiency (iwue), which facilitates comparison of the required freshwater amounts per produced biomass harvest. We conclude that due to the potentially high water demands and the tradeoffs that might go along with them, bioenergy should be an integral part of global assessments of freshwater demand and use. For interpreting and comparing reported estimates of possible future bioenergy water abstractions, full disclosure of parameters and assumptions is crucial. A minimum set should include the complete water balances of bioenergy production systems (including partitioning of blue and green water), bioenergy crop species and associated water-use efficiencies, rainfed and irrigated bioenergy plantation locations (including total area and meteorological conditions), and total biomass harvest amounts. In the future, a model intercomparison project with standardized parameters and scenarios would be helpful. [ABSTRACT FROM AUTHOR]

Climate variability is an important driver of irrigation water use in many regions. Efforts to anticipate climate change impacts on future water availability can benefit from understanding how irrigation water demand has responded to these drivers to date. Here we apply satellite‐derived data, meteorological reanalysis, an advanced land surface model, and available state‐level reports to quantify irrigation demand sensitivities to temperature and precipitation across the Contiguous United States, for the period of 2002–2017. As expected, strong negative correlations are found between precipitation and irrigation withdrawals, both simulated and reported. Temperature sensitivities, however, vary by region and season, as do the interactive effects of temperature and precipitation on irrigation. Climate‐induced irrigation variability is largest in transitional climate zones. These transitional zones are generally separate from the regions where rates of irrigation withdrawals are greatest, such that climate‐induced variability in irrigation demand represents a water resource consideration that is distinct from chronic overpumping. Key Points: Widespread sensitivity of irrigation water use to precipitation is found in both model and available reportsTemperature and interactions of temperature—precipitation sensitivity vary by region and season and might be underestimated by the modelGeographical disconnects exist between aquifers that are stressed by pumping and the basins that exhibit strong climate sensitivities [ABSTRACT FROM AUTHOR]

Accurately measuring water use by the economy is essential for developing reliable models of water resource availability. Indeed, these models rely on retrospective analyses that provide insights into shifting human population demands and adaptions to water shortages. However, accurate, methodologically consistent, empirically authentic, and spatiotemporally comprehensive historical datasets for water withdrawals are scarce. Herein, we present a reanalysis of annual resolution (1950–2016) historical data set on irrigation, electric power, and public supply water withdrawal within the conterminous United States (US) at the county‐level, and, for power plants, at the site‐level. To estimate electric power water use, we synthesized a historically comprehensive list of generators and historic patterns in generation across fuels, prime movers, and cooling technologies. Irrigation water use estimation required building a crop‐demand model that utilized historical information on irrigated acreage for crops and golf courses, stage‐specific crop water demand, and climate information. To estimate public water supply use, we developed a random forest model constructed from information on population, infrastructure, climate, and land cover. These estimates generally agree with total county and state water use information provided by the US Geological Survey (USGS) water use circular and estimates generated from independent studies for specific years. However, we also observed discrepancies between our estimates and USGS data that appear to be caused by inconsistencies in the methods used by the USGS's primary data sources at the state level over decades of data collection, highlighting the importance of reanalysis to yield spatiotemporally consistent and intercomparable estimates of water use. Key Points: Spatiotemporally comprehensive water use data are needed to characterize water resource availability and model long‐term hydrologic changesWe present an annual (1950–2016) data set on US agriculture, electric power, and public supply water use at the county levelThe data set provides new spatiotemporally rich information compiled using consistent reanalysis methods to inform multi‐sectoral research [ABSTRACT FROM AUTHOR]

Properly terminating furrow irrigation in mid-southern United States (U.S.) crops could reduce irrigation costs, the likelihood of adverse harvest conditions, and agricultural withdrawal from the Mississippi River Valley Alluvial Aquifer (MRVAA). This research was conducted to determine an optimum termination window for furrow-irrigated cotton (Gossypium hirsutum L.) in the mid-southern U.S. The effects of irrigation termination timing on cotton lint yield, net returns, and irrigation water use efficiency (IWUE) were evaluated on a Leeper silty clay loam (fine, smectitic, nonacid, thermic Vertic Epiaquepts) and on a Dundee silty clay (fine-silty, mixed, active, Typic Endoaqualfs). Neither terminating nor continuing to irrigate cotton from cutout (NAWF = 5) up to three weeks past first cracked boll had an effect on lint yield or fiber quality (p ≥ 0.6107). Irrigation water use efficiency declined when water was applied past cutout (p < 0.0001). Results indicate that irrigation in cotton can be terminated at cutout without adversely effecting lint yield and fiber quality if soil water potential does not exceed -130 kPa prior to first cracked boll. Terminating irrigation in cotton at cutout could reduce late season irrigation cost and reduce water withdrawal from the MRVAA thus improving it sustainability. [ABSTRACT FROM AUTHOR]

The remote sensing (RS) technique is less cost- and labour- intensive than ground-based surveys for diverse applications in agriculture. Machine learning (ML), a branch of artificial intelligence (AI), provides an effective approach to construct a model for regression and classification of a multivariate and non-linear system. Without being explicitly programmed, machine learning models learn from training data, i.e., past experience. Machine learning, when applied to remotely sensed data, has the potential to evolve a real-time farm-specific management system to reinforce farmers' ability to make appropriate decisions. Recently, the use of machine learning techniques combined with RS data has reshaped precision agriculture in many ways, such as crop identification, yield prediction and crop water stress assessment, with better accuracy than conventional RS methods. As agriculture accounts for approximately 70% of the worldwide water withdrawals, it must be used in the most efficient way to obtain maximum yields and food production. The use of water management and irrigation based on plant water stress have been demonstrated to not only save water but also increase yield. To date, RS and ML-based results have encouraged farmers and decision-makers to adopt this technology to meet global food demands. This phenomenon has led to the much-needed interest of researchers in using ML to improve agriculture outcomes. However, the use of ML for the potential evaluation of water stress continues to be unexplored and the existing methods can still be greatly improved. This study aims to present an overall review of the widely used methods for crop water stress monitoring using remote sensing and machine learning and focuses on future directions for researchers. [ABSTRACT FROM AUTHOR]

Irrigation supports agricultural production, but widespread use of irrigation can perturb the regional and global water cycle. The one‐way coupled irrigation scheme used in some land surface models and Earth system models assumes that surface water demand is always met and ignores the surface water constraints, leading to overestimation of surface water usage, underestimation of groundwater pumping, and unrealistic simulation of their seasonal variability. To better represent the irrigation processes, a two‐way coupled irrigation scheme is developed within the Energy Exascale Earth System Model (E3SM). The new irrigation scheme simulates irrigation water demand and applies irrigation water in E3SM Land Model (ELM), which is coupled to a river routing model and a water management model (MOSART‐WM) that simulate streamflow, reservoir operations, and irrigation water supply. With two‐way coupling, surface water irrigation is constrained by the available runoff, streamflow, and reservoir storage. Simulations were performed for 1979–2008 at 0.5° spatial resolution to estimate irrigation surface water and groundwater use and their seasonality in global and large river basin scales. Compared to one‐way coupling, the two‐way coupling scheme (1) estimates less surface water withdrawal and less return flow due to the surface water constraint; (2) better represents groundwater recharge and groundwater level decline at global scale; and (3) is able to capture the seasonal dynamics of irrigation water allocations which reflect the local water conditions. The new development is an important step to more realistically account for the interactions between human water use and the terrestrial water cycle in an Earth system model. Plain Language Summary: A novel method is developed in the Energy Exascale Earth System Model (E3SM) to better represent the irrigation processes. The old method applies the irrigation water by assuming there is no limitation on the water availability. This will lead to overestimation of irrigation withdrawal in dry conditions. The new development, however, constrains the irrigation withdrawal by evaluating river water availability every computational time step. It is an important step to more realistically represent the interactions between water management and natural hydrologic processes. Compared to the old method, the new method (1) estimates less surface water withdrawal and less return flow due to the surface water constraint; (2) better represents groundwater recharge and groundwater level decline at global scale; and (3) is able to capture the seasonal dynamics of irrigation water allocations which reflect the local water conditions. The new development is an important step to more realistically account for the interactions between human water use and the terrestrial water cycle in an Earth system model. Key Points: A two‐way coupled irrigation scheme is developed in E3SM to dynamically constrain surface water withdrawal based on water availabilityWith two‐way coupling, the models estimate less surface water withdrawal and less return flow compared to one‐way coupled simulationsWith surface water constraint, groundwater recharge, groundwater decline, and the seasonal dynamics of water allocation are better captured [ABSTRACT FROM AUTHOR]

Groundwater is a valuable natural resource which is directly related to food production, human and ecosystem health. In the US, 48% of irrigated agriculture relies on groundwater, but there is no systematic national program responsible for groundwater management. For this paper, each US state was classified based on its most prevalent groundwater doctrine: Absolute Ownership, Prior Appropriation, Reasonable Use, and Correlative Rights. The Köppen climate zone of each state, USGS runoff data and USGS county-level water use data from 1985 to 2015 were used to analyze how groundwater use varies with climate and groundwater doctrine. Semi-arid states, which all follow Prior Appropriation doctrine, have the highest average irrigation rate, while states following Reasonable Use doctrine have the lowest average rate, but the largest variability. Analysis of Covariance shows that in Prior Appropriation states, irrigation volume and area do not increase during warm, dry periods but in Absolute Ownership states irrigation volume does increase. Water use trend analysis shows that irrigated area and groundwater withdrawals have increased over the last 30 years in humid and temperate regions, while irrigated area has decreased in semi-arid regions. At the same time, irrigation rate and the fraction of irrigation coming from groundwater has increased everywhere, suggesting a potential shift in the preferred water source for irrigation. This data analysis will provide insights for future work on how water policy should respond to water scarcity in US. [ABSTRACT FROM AUTHOR]

In the Southeast US, El Niño Southern Oscillation (ENSO), climate variability phenomena affect the quantity of water that is available for irrigation. The goals of this study were to determine the effect of upstream surface water withdrawals for irrigation on the quantity of water available for irrigation in downstream areas as a function of the ENSO phase and quantify the watershed area that can be irrigated using water withdrawn from streams in an ecologically sustainable manner. The study was conducted in the Swan Creek watershed (97 km2) located in Limestone County, Alabama, USA. The soil and water assessment tool (SWAT) model was used to simulate stream flows and develop water withdrawal prescriptions. Results indicated that when simultaneous water withdrawals were made at the outlet of each subwatershed throughout the year, on average water withdrawals were sufficient to irrigate 4-16% of the area upstream of withdrawal point depending on stream order. On making sustainable withdrawals at the outlets of all subwatersheds and at the watershed outlet throughout the year, approximately 40% of the watershed area could be irrigated. [ABSTRACT FROM AUTHOR]

Increase in population, agricultural development, and the reduction of surface water resources have resulted in an untapped harvest of ground water. On the other hand, the lack of attention to the balance between the exploitation and recharge of aquifers has led to a drop in water level in the aquifer. To understand the behavior of the ground water system and the status of resources and uses in the basin, as well as the situation of water exchange in these two parts, it is possible to connect reliable groundwater and surface water models The purpose of this study was to simulate Gorganroud aquifer flow by using using the groundwater model to understand the behavior of the aquifer system in different hydrological conditions and to provide a management solution to improve the supply and demand conditions. First, the status of the aquifer under study was simulated by using the information available in the area by Modflow; then the groundwater model results were transferred to the Water Evaluation and Planning model (WEAP) by the LINK KITCHEN Software. Then different management scenarios including increased irrigation efficiency in agriculture, the use of refinery effluents and the reduction of river flow due to climate changes were considered as two combinations of the above scenarios to alleviate water demand under this scenario; so, projections for a period of 20 years water resources of the basin were studied. The results of modflow calibration showed that there was a good agreement between observation and simulated water table, such that the RMSE for Steady and Transient condition was 0/972 and 0/97, respectively. The results also showed that simultaneously applying multiple water management strategies seems to be better than any of its individual states, thereby reducing water withdrawal on various resources. [ABSTRACT FROM AUTHOR]

This paper aims to analyze the variation pattern of irrigation water use in the Huang- Huai- Hai Plain and its relationship with drought. Based on the irrigation water consumption and withdrawal data, GRACE data and scPDSI data, the relationship between irrigation water use and drought in the Huang-Huai-Hai Plain was analyzed in this paper. The results showed that (1) irrigation water consumption accounts for about one-third of the water withdrawal. The irrigation water use in the southern part of Hebei province, Henan and Shandong province is higher than that of other regions. Irrigation water withdrawal in the Huang- Huai- Hai Plain increased from 2003 to 2014, with a rate of about 37 mm/month. (2) The meteorological condition tended to be arid, and there was a significant nonlinear correlation between scPDSI and the number of cells with positive irrigation water withdrawal anomaly (R2=0.60), especially from August to December. (3) The obvious decrease of precipitation led to occurrence of drought events. Therefore, irrigation water withdrawal was increased to ensure grain production. This indicates that drought is a major cause for increased irrigation water use in the Huang-Huai-Hai Plain and exacerbates the terrestrial water storage deficit. [ABSTRACT FROM AUTHOR]

The article discusses a study global agricultural economic water scarcity. It mentions that to meet the increasing food demand without expanding cultivated areas, agriculture will likely need to introduce irrigation in croplands that are currently rain-fed but where enough water would be available for irrigation. It also mentions that the author's develop a monthly agrohydrological analysis to map agricultural regions affected by agricultural economic water scarcity.

In China, irrigation is widespread in 40.7% cropland to sustain crop yields. By its action on water cycle, irrigation affects water resources and local climate. In this study, a new irrigation module, including flood and paddy irrigation technologies, was developed in the ORCHIDEE‐CROP land surface model which describes crop phenology and growth in order to estimate irrigation demands over China from 1982 to 2014. Three simulations were performed including NI (no irrigation), IR (with irrigation limited by local water resources), and FI (with irrigation demand fulfilled). Observations and census data were used to validate the simulations. Results showed that the estimated irrigation water withdrawal (W) based on IR and FI scenarios bracket statistical W with fair spatial agreements (r=0.68±0.07; p<0.01). Improving irrigation efficiency was found to be the dominant factor leading to the observed W decrease. By comparing simulated total water storage (TWS) with GRACE observations, we found that simulated TWS with irrigation well explained the TWS variation over China. However, our simulation overestimated the seasonality of TWS in the Yangtze River Basin due to ignoring regulation of artificial reservoirs. The observed TWS decrease in the Yellow River Basin caused by groundwater depletion was not totally captured in our simulation, but it can be inferred by combining simulated TWS with census data. Moreover, we demonstrated that land use change tended to drive W locally but had little effect on total W over China due to water resources limitation. Key Points: A new irrigation module is developed in ORCHIDEE including drip, flood, and paddy irrigationSimulations can explain broad scale patterns and the trends of irrigation amount from census dataIrrigation efficiency and land use change are key factors affecting the trend of irrigation [ABSTRACT FROM AUTHOR]

Intensively cultivated rice-wheat cropping sequence of Punjab, India responsible for many sustainability issues viz. declining underground water, declining soil health, arising micronutrient deficiencies etc. Around 1.3 M ha-m additional withdrawal of water from the ground is being taken place annually in Punjab and mainly it is used for the rice crop which is not a traditional crop of the region. Puddling, seepage and percolation losses are the main sources of water loss from the rice based cropping systems in the Indo-Gangetic plains (IGPs) and many Resource Conservation Technologies (RCTs) have been recommended for water saving. The real water saving techniques are those which hinder the water from going into those sinks from where it cannot be reused (Evaporation, E) and diverted greater fraction of water of ET toward transpiration (T) which is desired as greater transpiration, greater the inflow of water and nutrients andwhich ultimately increase the grain yield with the lesser consumption of irrigation water as interval in between two irrigation increases, which further increase the water productivity. Among different RCTs, short duration crop varieties and delaying transplanting time are the real water saving techniques for the regions where water table is already declining down, however other RCTs may be suitable for the regions facing water logging problems as these cut down the drainage losses and these energy saving rather than water saving techniques. [ABSTRACT FROM AUTHOR]

Typical single-factor productivity measures are easy to grasp and to develop but are misleading because they ignore other inputs used in the production process. This study develops a single-factor productivity approach that accounts for conventional inputs as well as observed and unobserved characteristics of the production environment. We then apply this approach to evaluate irrigation productivity in U.S. agriculture using U.S. Department of Agriculture input-output data alongside state-level estimates of volumetric measures of irrigation water withdrawals obtained from the U.S. Geological Survey. An irrigation productivity index is constructed and subsequently decomposed in order to capture irrigation productivity growth due to technological progress, input (factor) deepening, output-oriented scale-and-mix efficiency, output-oriented technical efficiency, and environmental effects. In addition, we evaluate spatial patterns of irrigation productivity across the United States. Our findings indicate that, on average, irrigation productivity has risen modestly in most states, and this growth has primarily been driven by technological progress and input (factor) deepening. [ABSTRACT FROM AUTHOR]

Highlights • Maize has the highest water productivity and tomato has the least. • To keep groundwater level steady, crop area should reduce to 96%. • In sub-basins with negative values, groundwater recharging occurs during winter cultivation. Abstract Unsustainable groundwater withdrawal is a major challenge facing semi-arid and arid regions of the world, where groundwater is the primary source of irrigation water. Conversion of some agricultural land to fallow land is one of the possible solutions to reduce the groundwater withdrawal to bring it to safe yield. Such a solution has a negative economic impact. In this study, we have developed an optimization approach that can use used to identify the size (and type) of the agricultural area to be fallowed to ensure sustainable groundwater use for irrigation with as little economic impact as possible. This approach is based on the concept of profit productivity, which relies on Landsat imageries to calculate crop yield and irrigation water withdrawal, and available in-situ data to calculate energy cost. We have applied this approach to the Neyshabour basin in Iran that has been experiencing unsustainable groundwater withdrawal for the last 30 years. Our sample results indicate that in order to ensure sustainable groundwater withdrawal with minimum economic impact, 4% of the agricultural land needs to be converted to fallow land by fallowing most of the agricultural land used for growing tomatoes. [ABSTRACT FROM AUTHOR]

Under current global warming and accelerated population growth scenarios, cropland irrigation water consumption has become a central issue limiting the sustainability of coupled human‐natural systems. This study proposes a new estimate of recent global cropland water consumption constrained by observations and provides attributions for its recent trend. By incorporating observations, including extracted cropland leaf area index and irrigation threshold data, this study provides improved estimates of recent global cropland evapotranspiration and transpiration as well as irrigation water consumption and withdrawal. The global annual consumption and withdrawal of irrigation water are estimated to be approximately 874 and 1,867 km3 (in 2005), respectively. From 2000 to 2014, a rapid increase in cropland irrigation was detected, especially in water‐deficient areas (i.e., hyperarid, arid, and semiarid regions). Climate change, which mainly consists of rising temperature and reduced moisture conditions, is usually distinguished as the major driving factor. Human‐induced increases in crop canopy cover have also contributed to more irrigation in hyperarid and arid regions. This study also provides suggestions for water‐savings‐targeted cropland management in water‐deficient areas based on the transpiration ratio (i.e., ratio of transpiration to evapotranspiration). Key Points: This study provides a new estimate of global cropland irrigation water consumption and withdrawal constrained by observationsFrom 2000 to 2014, climate change and increased crop coverage lead to more irrigation water use, especially in water‐deficient areasIntensive farming and cropping schedule rearrangement are recommended in water‐deficient areas to reduce water loss by evaporation [ABSTRACT FROM AUTHOR]

Water and energy are highly interdependent. On one hand, water is used for extracting, refining and producing fuels, cooling power plants and producing hydropower, on the other hand, energy is also used to catch, convey and treat drinking and irrigation water. In addition, an important quantity of energy is also used for the collection, treatment and disposal of wastewater. At the level of Oum Er-Rbia basin, the use of water for energy production is mainly in hydroelectric power. The area has indeed a hydraulic generating park comprising of 13 hydroelectric plants with an installed capacity of 662.1 MW that represents 70% of national hydropower production. This energy is mainly consumed in the operations of pumping stations for wastewater and drinking water treatment and supply that use an average of 0.17 kWh/m3. Whereas irrigation consumes higher energy rate with an estimated average of 0.82 kWh/m3. This work focuses on the central sub-basin of Oum Er-Rbia to make a detailed analysis of energy uses in the water sector and vice versa. We used the collected and treated data to create a Sankey diagram that describes the interdependence of the two resources on a local scale. Additionally, this paper reviews some of the water and energy challenges such as climate change and growing demand, and shows how the nexus can resolve these problems through an integrative management of both resources at the regional level. [ABSTRACT FROM AUTHOR]