Search

Improving irrigation water management is a key concern for the agricultural sector, and it requires extensive and comprehensive tools that provide a complete knowledge of crop water use and requirements. This study presents a novel methodology to explicitly estimate daily gross and net crop water requirements, actual crop water use, and irrigation efficiency of center pivot irrigation systems, by mainly utilizing the Sentinel-2 MultiSpectral Instrument (MSI) imagery at the farm scale. ETMonitor model is adapted to estimate actual water use (as the sum of canopy transpiration and evaporation of water intercepted by canopy and evaporation from soil) at daily/10-m resolution, benefiting from the high-resolution Sentinel-2 data and thus to assess the irrigation efficiency at the farm scale. The gross irrigation water requirement is estimated from the net crop water requirement and the water loss, including the water droplet evaporation directly into the air during application before droplets fall on the canopy and canopy interception loss. The method was applied to a pilot farmland with two major crops (wheat and potato) in the Inner Mongolia Autonomous Region of China, where modern equipment and appropriate irrigation methods are deployed for efficient water use. The estimated actual crop water use showed good agreement with the ground observations, e.g. the determination coefficients range from 0.67 to 0.81 and root mean square errors range from 0.56 mm/day to 1.24 mm/day for wheat and potato when comparing the estimated evapotranspiration with the measurement by the eddy covariance system. It also showed that the losses of total irrigated volume were 25.4% for wheat and 23.7% for potato, respectively, and found that the water allocation was insufficient to meet the water requirement in this irrigated area. This suggests that the amount of water applied was insufficient to meet the crop water requirement and the inherent water losses in the center pivot irrigation system, which imply the necessity to improve the irrigation practice to use the water more efficiently.

Crop evapotranspiration (ETC) water demands are critical decision support information for the sustainable use of water resources for optimum crop productivity. When measurements of ETC at all locations are not feasible, the prediction of ETC and crop growth from weather and soil–water–crop management data using state-of-the-science cropping system simulations is a viable alternative. This study compared soybean (Glycine max (L.) Merr.) ETC quantified using the eddy covariance (EC) method against simulations from two models, (i) the CSM-CROPGRO-soybean module within the Decision Support System for Agroecology Transfer (DSSAT) and (ii) CSM-CROPGRO-soybean module within the Root Zone Water Quality Model v2.0 (RZWQM) for a grower's field in the Mississippi Delta, USA, during 2017, 2018, and 2019 growing seasons. The measured soybean grain yields during the three seasons, respectively, were 4979 kg ha−1, 5157 kg ha−1, and 5665 kg ha−1. The DSSAT and RZWQM simulated yields deviated from the measured yields by −10.8% and 15.4% in 2017, −24.0% and 1.56% in 2018, and −6.22%, and 9.98% in 2019. Simulated daily ETC values were less than EC estimates by 0.33 mm, 0.29 mm, and 0.23 mm for DSSAT and 0.05 mm, 0.42 mm, and 0.24 mm for RZWQM, respectively, for the three seasons. EC-quantified seasonal values of ETC were 584 mm, 532 mm, and 566 mm, respectively, for three seasons. Similarly, simulated seasonal ETC values were less than EC estimates by 40 mm, 31 mm, and 16 mm by DSSAT, and 7 mm, 46 mm, and 29 mm by RZWQM. The results obtained demonstrated that accuracy in the prediction of ETC varied among models and growing seasons. When the magnitude of errors in daily ETC simulations does not deter its applications in tactical irrigation water management decisions, a higher degree of agreement between measured and simulated ETC values at a seasonal scale is more promising for strategical irrigation water management planning decision support. Further improvement of the models for more accurate simulations of daily ETC can help in more confident applications of these models for tactical crop-water management applications. [ABSTRACT FROM AUTHOR]

Information on actual consumptive water use and water productivity of wine grape vineyards grown with high-wire cordon (HWC) and vertical shoot position (VSP) trellis systems is limited, but it is critical to inform the selection of resource-efficient grapevine training systems and irrigation water management practices. This article describes an applied-research study conducted in the Central Valley of Chile to determine the actual evapotranspiration (ETa), actual crop coefficients (Ka), water productivity (WP), and water footprint (WFP) of microirrigated wine grape vineyards operated for commercial production with HWC and VSP trellis systems. ETa and Ka were determined using the residual of the energy balance (REB) method from micrometeorological measurements collected at the study vineyards with a combination of surface renewal and eddy covariance equipment. Field measurements of other biophysical parameters were also collected at each study site to characterize the soil water status in multiple locations across the vineyards at various soil depths using moisture tension–monitoring units, vine water status using midday stem water potential (ΨSTEM) , and fraction of photosynthetically active radiation (fPAR) intercepted by the vine canopy at different times during the growing season. Finally, the fruit yield was determined from grape samples collected at the HWC and VSP vineyard blocks during commercial harvest operations. The study was conducted over the course of two consecutive growing seasons (2019–2020 and 2020–2021). A reduction of 37% in the available water supply occurred during the 2019–2020 season with respect to the average water supply. Findings from the research study showed that when the water supply was less limited, the HWC trellis had 12% higher seasonal cumulative ETa than the VSP trellis, whereas the HWC system appeared more affected by water stress than the VSP trellis during the water-limited season. The analysis of the data sets also showed that the HWC enabled wine grape growers to achieve significantly higher fruit yield and water productivity, and lower water footprint per unit of wine grapes produced during the water-limited season. [ABSTRACT FROM AUTHOR]

Background: The system output of groundnut based intercropping system depends on the selected companion crop as well as the frequency with which irrigation is supplied. This initiates a requisite to evaluate the performance of present traditional intercropping systems and thereby optimize the level of irrigation for both the crops under the system. Methods: A two-year field experiment was conducted during the rabi season 2017-2019 at Oilseeds Research Station, Tamil Nadu Agricultural University, Tindivanam, Tamil Nadu, India The experiment was laid out in split plot design with three replications. Main plot comprised of five treatments with four intercrops viz., castor (TMV 5), blackgram (VBN 8), sesame (TMV 7), pearl millet (CO 10) and sole groundnut (TMV 13). The sub plot was assigned with three irrigation regimes based on IW/CPE ratio of 0.50, 0.75 and 1.0. Result: Groundnut + blackgram combination recorded higher pod yield (6.31 g plant-1), equivalent pod yield (1986 kg ha-1) with increased water use efficiency (5.49 kg ha-1 mm-1) and economic water productivity (' 309 ha-1 mm-1) over sole groundnut while other intercropping combinations failed to express. Soil moisture extraction pattern was higher at top layers and decreased with soil depth. More frequent irrigations (IW/CPE 1.0) mismatched with the crop water requirement and resulted in higher consumptive water use (500.8 mm) with moisture extraction pattern from initial layers favouring evaporation losses. At peak growth stage (60 days after sowing) higher light interception was observed in groundnut + pearl millet (41.4%) followed by castor (38.2%) combinations which was the prime reason for decreased yields as groundnut is susceptible to shading. Therefore, groundnut + blackgram combination under rabi season when supplied with six irrigations at twenty days interval (based on IW/CPE 0.50) could significantly increase the productivity and monetary returns from the system. [ABSTRACT FROM AUTHOR]

Reducing methane emissions and water use is critical for combating climate change and declining aquifers on food production. Reductions in irrigation water use and methane emissions are known benefits of practicing alternate wetting and drying (AWD) over continuous flooding (CF) water management in lowland rice (Oryza sativa L.) production systems. In a two-year (2020 and 2021) study, methane emissions from large farm-scale (∼50 ha) rice fields managed under CF and AWD in soils dominated by Sharkey clay (Sharkey clay, clay over loamy, montmorillonitic non-acid, thermic Vertic halauepet) were monitored using the eddy covariance method (EC). In the EC system, an open-path laser gas analyzer was used to monitor air methane gas density in the constant flux layer of the atmosphere over the rice-crop canopies. Total water pumped into the field for floodwater management was higher in CF compared to AWD by 24 and 14% in 2020 and 2021, respectively. Considerable variations between seasons in the amount of methane emitted from the CF and AWD treatments were observed: CF emitted 29 and 75 kg ha−1 and AWD emitted 14 and 34 kg ha−1 methane in 2020 and 2021, respectively. Notwithstanding, the extent of reduction in methane emissions due to AWD over CF was similar for each crop season (52% in 2020 and 55% in 2021). Rice grain yield harvested differed by only ±2% between AWD and CF. This investigation of large-scale system-level evaluation, using the EC method, confirmed that by practicing AWD floodwater management in rice, water pumped from aquifers could be reduced by about a quarter and methane emissions from rice fields could be cut down by about half without affecting grain yields, thereby promoting sustainable water management and greenhouse gas emission reduction during rice production in the Lower Mississippi Delta.

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The general perception of canal irrigation systems in India is one of built infrastructure with low service performance. This paper presents an analytical framework, applied to the Sina medium irrigation system in Maharashtra state of India, to study the performance of an expanded water influence zone (WIZ) including a buffer zone outside the canal command area (CCA) influenced by the irrigation system's water resources. The framework used satellite-based estimates of land-use and cropping patterns. The results indicate that there is hardly any gap between the irrigation potential created (IPC) and the irrigation potential utilized (IPU) in the CCA. The fraction of consumptive water use (CWU) of irrigation is low in the CCA, but almost one in the WIZ, due to the reuse of return flows in the WIZ. Future investments should focus on increasing economic water productivity ($/m3) in order to enhance the resilience of the farming community in the WIZ, which is frequently affected by water scarcity. Highlights An expanded water influence zone shows a holistic approach to performance assessment of canal irrigation systems.; The satellite-based estimate shows the underestimation of the cropped area.; The consumptive fraction of water is high in the WIZ.; The assessment of an irrigated area and water-use efficiency requires a new direction.; Increasing economic water productivity is the way forward for water-scarce canal command systems.;

Water crises have risen over the past decade. In the Brazilian context, extreme events have intensified over the country, undermining water systems in regions that already face water shortages. Although previous studies have focussed on individual regions of Brazil, an overview of the entire country will contribute to developing a national action plan for mitigating water inequalities. Therefore, we reviewed and analysed water security in Brazil, presenting a diagnosis focussed on the peculiarities of each geographic region and hydrographic area. One of the biggest threats is the slow pace towards a robust policy for strengthening national water security. As shown here, water security depends on several variables such as availability, quality, and external factors such as climate forcing and anthropogenic pressure. Therefore, water governance needs to integrate human needs with ecosystem functioning, considering climate uncertainties to move towards better water resources planning. [ABSTRACT FROM AUTHOR]

A field experiment was conducted at Oilseeds Research Station, Tindivanam during 2017–18 to evaluate the production potential of groundnut (Arachis hypogaea L.) based intercropping under different levels of irrigation. Groundnut when grown in intercropping systems can provide scope for improving the productivity and monetary return per unit area per unit time. As different crops have different water requirement which could be a main hurdle in intercropping system, the present study was conducted to identify the consumptive water use, water use efficiency and water productivity under intercropping system. Study revealed that, groundnut intercropped with blackgram was superior in number of nodules/plant, root depth and root volume and registered yield of 10.5% over sole crop of groundnut. Irrigation scheduling at 0.50 IW/CPE ratio recorded higher root depth and root volume but, yielded 26.5 and 18.4% lesser over IW/CPE ratio of 0.75 and 1.0, respectively. Higher net return and B: C ratio was recorded in groundnut + blackgram intercropping system with 0.75 IW/CPE ratio. The soil moisture extraction pattern varied under different intercropping systems and the frequency of irrigation. Groundnut + blackgram intercropping system utilised lesser consumptive water compared to the sole crop. Thus, from the study it may be inferred that, groundnut + blackgram intercropping system with irrigation scheduling at 0.75 IW/CPE ratio enhances the productivity with better water use efficiency and water productivity.

Water crises are becoming severe in recent times, further fueled by population increase and climate change. They result in complex and unsustainable water management. Spatial estimation of consumptive water use is vital for performance assessment of the irrigation system using Remote Sensing (RS). For this study, its estimation is done using the Soil Energy Balance Algorithm for Land (SEBAL) approach. Performance indicators including equity, adequacy, and reliability were worked out at various spatiotemporal scales. Moreover, optimization and sustainable use of water resources are not possible without knowing the factors mainly influencing consumptive water use of major crops. For that purpose, random forest regression modelling was employed using various sets of factors for site-specific, proximity, and cropping system. The results show that the system is underperforming both for Kharif (i.e., summer) and Rabi (i.e., winter) seasons. Performance indicators highlight poor water distribution in the system, a shortage of water supply, and unreliability. The results are relatively good for Rabi as compared to Kharif, with an overall poor situation for both seasons. Factors importance varies for different crops. Overall, distance from canal, road density, canal density, and farm approachability are the most important factors for explaining consumptive water use. Auditing of consumptive water use shows the potential for resource optimization through on-farm water management by the targeted approach. The results are based on the present situation without considering future changes in canal water supply and consumptive water use under climate change. [ABSTRACT FROM AUTHOR]

Soil and water conservation (SWC) practices like that of erosion control and soil fertility measures were commonly practiced in the semiarid region of southern Mali since the 1980s. The SWC practices were mainly meant to increase water availability in the subsurface, reduce farm water runoff and gully formation and improve nutrient content of the soil, thereby increasing crop yield. Despite such efforts to promote at scale SWC practices, the landscape of southern Mali is still affected by high rates of runoff and soil erosion and low crop yield in farmers' fields. Data are lacking on previous beneficial SWC practices that could be adapted for wider application. In this paper, a watershed approach to managing rainfed agriculture is presented to show potential benefits of SWC practices at field and watershed scales. The approach included (1) community participation in establishing and monitoring new sets of hydro-meteorological monitoring stations and field experiments; (2) studying the dynamics and consumptive water uses of different land uses over time; and (3) evaluating the biophysical and economic advantages of SWC practices implemented in the watershed. Results showed that over a period of 34 years (1980–2014) cropping area and consumptive water uses of crops (sorghum and cotton) increased at the expenses of natural vegetation. However, the yield of these crops remained low, indicating that soil fertility management and soil moisture were insufficient. In such cases, implementation of more SWC practices can help provide the additional soil moisture required. [ABSTRACT FROM AUTHOR]

Recent prolonged droughts in California have emphasized the urgent need to implement more efficient water management practices for high value tree crops. Accurate estimation of evapotranspiration (ET), a main component of consumptive water use, is critical for improving management of micro-irrigated pistachio orchards grown in the San Joaquin Valley of California. We estimated ET of three mature commercial pistachio orchards on non-saline and increasingly saline soils in 2015 and 2016, using the Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC) method and Landsat 8 satellite observations. Based on a comparison with field observations at 8 sites, we modified the parameterizations of the momentum roughness length and net radiation for pistachio tree crops and reduced the uncertainty of daily ET estimates. When compared with field data, the recalibrated METRIC ET estimates had an R 2 of 0.59, a mean absolute error of 1.1 mm/day, and a RMSE of 1.4 mm/day during Landsat overpass dates (n = 72). The METRIC ET map captured the temporal dynamics and spatial heterogeneity both within and among the orchards. The mean annual crop season estimated ET (mid-March to mid-October in 2016) with remote sensing decreased by 32% from 1064 ± 99 mm in the non-salt affected control orchard to 725 ± 82 mm in the orchard with the highest level of soil-water salinity. The ET reduction was consistent with canopy volume differences among the study orchards, as shown by summer Normalized Difference Vegetation Index (NDVI) from Landsat observations, e.g., 0.72 ± 0.06 in the control vs. 0.52 ± 0.06 in the most saline orchard. The available energy was controlled mostly by canopy features and explained 64% of daily ET variation among all Landsat pixels and satellite overpass days. The normalized differenced water index (NDWI) could be considered as an important parameter to capture the partitioning of available energy for ET (R 2  = 0.38), suggesting that the lower soil osmotic potential in saline orchards further reduced crop ET. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ethanol has been promoted as alternative fuel for vehicles in Thailand. The impact of water use on producing the feedstock for ethanol is important. Nipa palm ( Nypa fruticans ) is a potential alternative feedstock to bioethanol production. This work aimed at determining the consumptive water use and water deprivation caused by nipa sap based ethanol production in the potential growing areas of southern Thailand. These potential nipa growing areas could produce nipa sap ethanol at the rate 2.64 × 10 6 L/day (L/d). The consumptive water use by nipa sap ethanol was determined as from 893 to 1573 L water/L ethanol, and over 90% of it originated at the nipa plantations. The yield of nipa sap significantly affects the consumptive water use. The water deprivation, an indicator of the water scarcity footprint of nipa sap ethanol, was found to be between 10.7 and 184 L H 2 Oeq/L ethanol. The large range of water deprivation values was mainly due to differences in the water stress index between watersheds. Peninsula-West coast and Thale sap Songkhla watersheds were considered, based on the water deprivation values, as areas with high potential to produce nipa sap ethanol, while Pattani, Tapi, and Peninsula-East coast watersheds have moderate potential. To support the targets in the alternative energy development plan of Thailand (2015–2036), the expansion of nipa plantations should focus on areas with high or moderate potential. To establish the nipa sap ethanol on a commercial scale, further studies are necessary. The yield and chemical composition of nipa sap may depend on plant variety, maturity, and type of plantation. Good management practices need to be established for nipa plantations, and pilot scale ethanol conversion needs to be demonstrated and assessed. [ABSTRACT FROM AUTHOR]

Human activities use more than half of accessible freshwater, above all for agriculture. Most approaches for reconciling water conservation with feeding a growing population focus on the cropping sector. However, livestock production is pivotal to agricultural resource use, due to its low resource-use efficiency upstream in the food supply chain. Using a global modelling approach, we quantify the current and future contribution of livestock production, under different demand- and supply-side scenarios, to the consumption of “green” precipitation water infiltrated into the soil and “blue” freshwater withdrawn from rivers, lakes and reservoirs. Currently, cropland feed production accounts for 38% of crop water consumption and grazing involves 29% of total agricultural water consumption (9990 km 3 yr −1 ). Our analysis shows that changes in diets and livestock productivity have substantial implications for future consumption of agricultural blue water (19–36% increase compared to current levels) and green water (26–69% increase), but they can, at best, slow down trends of rising water requirements for decades to come. However, moderate productivity reductions in highly intensive livestock systems are possible without aggravating water scarcity. Productivity gains in developing regions decrease total agricultural water consumption, but lead to expansion of irrigated agriculture, due to the shift from grassland/green water to cropland/blue water resources. While the magnitude of the livestock water footprint gives cause for concern, neither dietary choices nor changes in livestock productivity will solve the water challenge of future food supply, unless accompanied by dedicated water protection policies. [ABSTRACT FROM AUTHOR]

California growers face challenges with water shortages and there is a strong need to use the least amount of water while optimizing yield. Timely information on evapotranspiration (ET), a dominant component of crop consumptive water use, is critical for growers to tailor irrigation management based on in-field spatial variability and in-season variations. We evaluated the performance of a remote sensing-based approach, Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC), in mapping ET over an almond orchard in California, driven by Landsat satellite observations. Reference ET from a network of weather stations over well-watered grass (ETo) was used for the internal calibration and for deriving ET at daily and extended time period, instead of alfalfa based reference evapotranspiration (ETr). Our study showed that METRIC daily ET estimates during Landsat overpass dates agreed well with the field measurements. During 2009–2012, a root mean square error (RMSE) of 0.53 mm/day and a coefficient of determination (R2) of 0.87 were found between METRIC versus observed daily ET. Monthly ET estimates had a higher accuracy, with a RMSE of 12.08 mm/month, a R2 of 0.90, and a relatively small relative mean difference (RMD) of 9.68% during 2009–2012 growing seasons. Net radiation and Normalized Difference Vegetation Index (NDVI) from remote sensing observations were highly correlated with spatial and temporal ET estimates. An empirical model was developed to estimate daily ET using NDVI, net radiation (Rn), and vapor pressure deficit (VPD). The validation showed that the accuracy of this easy-to-use empirical method was slightly lower than that of METRIC but still reasonable, with a RMSE of 0.71 mm/day when compared to ground measurements. The remote sensing based ET estimate will support a variety of State and local interests in water use and irrigation management, for both planning and regulatory/compliance purposes, and it provides the farmers observation-based guidance for site-specific and time-sensitive irrigation management [ABSTRACT FROM AUTHOR]

This study was carried out in farmers' fields to quantify the total and consumptive water use (CWU) in carp polyculture under different water management protocols. Treatment-wise estimated total crop water requirement ha-1 (culture duration-180d) was 3.69, 4.62 and 3.9 ha-m, while the computed consumptive water use index (m3 kg-1 biomass) was 6.62, 9.31 and 7.08, in T1 (no water exchange), T2(10% water exchange on monthly basis) and T3 (10% water exchange depending on the water quality variables), respectively. Water use in ponds usually varies with the intensity of production, frequency and amount of water exchange employed. Higher the amount of water exchange, higher is the total water use (TWU) as in case of T2. Various hydro-biological parameters prevailing in the different treatments were within the optimum ranges and did not fluctuate drastically. This was probably due to the similar levels of inputs in all the treatments in the form of organic manure, inorganic fertilizer and periodic liming. The regulated water exchange in T3, showed improved water quality and crop performance (P<0.05) over the zero water exchange, T1. Evaporation loss contributed significantly to CWU (2.9-3.1 m3 water kg-1 production) followed by seepage losses. Regulated water exchange and low apparent feed conversion ratio, helped in lowering the sedimentation rate (54.6-62.8 m3 t-1 biomass). Higher net total water productivity (Rs. 4.4 m-3), net consumptive water productivity (Rs. 8.5 m-3) and ratio of the output value to the cost of cultivation (OV: CC, 2.15) also inferred that T3 had a distinct edge over T1 and T2. In general, total water use varied greatly in aquaculture depending mainly upon the culture method used. [ABSTRACT FROM AUTHOR]

For sustainable irrigated crop production, enhancing the productivity of pumped water from aquifers, which are fast declining, is critical. In this investigation, the yield and water use efficiency (WUE) of corn planted in a single-row (SR) on a raised-bed ridge-furrow system was compared with corn planted in a twin-row (TR) pattern. The crop's consumptive water use (evapotranspiration, ET) was quantified using the eddy covariance (EC) technology. The crops for the investigation were raised on large-scale farmer's fields (above 100 ha). In the EC system, CO 2 and water vapor fluxes over corn plant canopies were monitored using an infrared gas analyzer, and wind turbulence was quantified using an omnidirectional 3D sonic anemometer. The LAI, grain yield, ET, net ecosystem exchange of CO 2 (NEE), and gross primary productivity (GPP) measured under TR were higher than SR by 18%, 19%, 22%, 90%, and 41%, respectively. Also, WUE in NEE (WUE NE , ratio of NEE to ET) was higher under TR than SR by 40%, rendering TR the best choice for corn planting in the region. WUE for grain yield (WUE GY , ratio of grain yield to ET) and net ecosystem respiration did not differ appreciably across TR and SR systems. The measured ET in TR was 518 mm, while SR was 426 mm during the crop season (emergence to physiological maturity). The study conducted in large-scale farm fields gives better confidence than results obtained based on conventional small-plot studies recommending the TR over SR planting in the region for grain yield and WUE NE in corn production systems. • Water use efficiency (WUE) of single-row (SR) and double-row (TR) planted corn were quantified and compared. • Corn consumptive water use (ET) and net ecosystem exchange (NEE) were quantified using eddy covariance method. • Leaf are index, ET, NEE and gross primary productivity under TR were higher than SR. • Water use efficiency for NEE was higher under TR than SR. • Water use efficiency for grain yield and net ecosystem respiration did not differ between TR and SR systems. [ABSTRACT FROM AUTHOR]

Large quantities of water are consumed by irrigated crops and riparian vegetation in western U.S. irrigation districts. Remote sensing methods for estimating evaporative water losses by soil and vegetation (evapotranspiration, ET) over wide river stretches are needed to allocate water for agricultural and environmental needs. We used the Enhanced Vegetation Index (EVI) from MODIS sensors on the Terra satellite to scale ET over agricultural and riparian areas along the Lower Colorado River in the southwestern U.S., using a linear regression equation between ET of riparian plants and alfalfa measured on the ground, and meteorological and remote sensing data, with an error or uncertainty of about 20%. The algorithm was applied to irrigation districts and riparian areas from Lake Mead to the U.S./Mexico border. The results for agricultural crops were similar to results produced by crop coefficients developed for the irrigation districts along the river. However, riparian ET was only half as great as crop coefficient estimates set by expert opinion, equal to about 40% of reference crop evapotranspiration. Based on reported acreages in 2007, agricultural crops (146,473 ha) consumed 2.2 × 109 m3 yr−1 of water. All riparian shrubs and trees (47,014 ha) consumed 3.8 × 108 m3 yr−1, of which saltcedar, the dominant riparian shrub (25,044 ha), consumed 1.8 × 108 m3 yr−1, about 1% of the annual flow of the river. This method could supplement existing protocols for estimating ET by providing an estimate based on the actual state of the canopy as determined by frequent-return satellite data.

The water scarcity footprints (WSF) of ribbed smoked sheet (RSS) from 14 cooperative rubber sheet factories (CRSF) in nine provinces in southern Thailand were evaluated. The WSF of ribbed smoked sheet bales (RSSB) was determined in two large rubber sheet factories (LRSF) in two provinces. Average values of consumptive water use (CWU) for RSS and RSSB were 549 and 592 m 3 /tonne, respectively. The CWU for both CRSF and LRSF was found to be very small in comparison to that for producing inputs from the rubber plantation. The CWU used for producing RSS arose from acquisition of fresh latex. Acquisition of unsmoked sheet and RSS had a major contribution for the RSSB production. WSFs of RSS and RSSB in terms of water deprivation ranged from 0.12 to 72.8 and 5.12 to 52.4 m 3 water-equivalent/tonne, respectively. The major difference of CWU in the rubber plantations caused the difference of WSF for RSS and RSSB. The results of this study revealed that the policy makers should focus on the rubber plantation as the first priority. CWU and WSF values should be included as indicators for determining suitable areas of rubber plantation and for getting government support. In the factories, technologies or processes that used less water must be employed in the washing process to reduce CWU. [ABSTRACT FROM AUTHOR]

The surface energy balance algorithm for land (SEBAL) estimates land surface evapotranspiration (ET) from radiometric surface temperature (TR), but requires manual selection of calibration pixels, which can be impractical for mapping seasonal ET. Here pixel selection is automated and SEBAL implemented using global climate grids and satellite imagery. SEBAL is compared with the MOD16 algorithm, which uses remotely sensed data on vegetation condition to constrain reference ET from the Penman-Monteith equation. The difference between the evaporative fraction (Λ, range 0-1) from SEBAL and six eddy flux correlation towers was less than 0.10 for three of six towers, and less than 0.24 for all towers. SEBAL ET was moderately sensitive to surface roughness length and implementation over regions smaller than ∼10,000 km2 provided lower error than larger regions. Pixel selection based on TR had similar errors as those based on a vegetation index. For maize, MOD16 had lower error in mean seasonal evaporative fraction (−0.02) compared to SEBAL Λ (0.23), but MOD16 significantly underestimated the evaporative fraction from rice (−0.52) and cotton fields (−0.67) compared with SEBAL (−0.09 rice, −0.09 cotton). MOD16 had the largest error over short crops in the early growing season when vegetation cover was low but land surface was wet. Temperature-based methods like SEBAL can be automated and likely outperform vegetation-based methods in irrigated areas, especially under conditions of low vegetation cover and high soil evaporation. [ABSTRACT FROM AUTHOR]

In the semi-arid tropics (SAT) farmers practice calendar-based irrigation scheduling, which generally results in over irrigation and poor water use efficiency. The lack of a simple decision tool to decide timing and quantity of water to be applied is a bottleneck. An Excel-based decision support system termed Water Impact Calculator (WIC) is developed using data collected at the ICRISAT, which were validated at three pilot sites on farmers' fields in Rajasthan, Gujarat and Telangana. Field studies were conducted under two land-form treatments (broad bed and furrow (BBF) and flat fields); and irrigation water was applied following two different methods (drip and flood). The data collected at micro-watershed at the ICRISAT and three other sites showed that WIC could be used under wide range of soil and rainfall conditions. WIC simulated soil moisture was comparable with the observed moisture data, which forms the basis of irrigation scheduling. The WIC-based water balance at these experimental sites showed that number and amount of irrigation could be reduced by 30-40% using WIC-based irrigation scheduling without compromising the crop yield. The WIC could be a potential tool for water resources planning and efficient management at the field and watershed scale in the SAT. [ABSTRACT FROM AUTHOR]

The indiscriminate use of wastewater for irrigation as a result of freshwater shortage could impair soil functions and cause environmental pollution. The objective of this study was to evaluate soil physico-chemical properties, growth parameters and water use pattern of two indigenous vegetables irrigated with three kinds of wastewater in southwest Nigeria. The study was a 2 × 4 factorial (wastewater versus vegetable) pot experiment, laid out in randomized complete block design (RBCD) with three replications in a screen house. The tested vegetables were SM — Eggplant ( Solanum macrocarpon ) and CA — Spinach ( Celosia angentea ) while the wastewater treatments were abattoir wastewater (AW), bathroom, laundry wastewater (BW) cassava effluent (CE) and rainwater (RW) as control. The wastewaters were analyzed for physical, chemical and biological properties while the soil samples collected from the field at 0–20 cm soil layer and pots at 0–10 and 10–20 cm layer were analyzed for physico-chemical properties before and after the experiment, respectively. Soil hydrophobicity was determined using the water-droplet penetration time (WDPT) method, plant growth parameters were monitored every 5 days while leaf area was determined shortly before harvest. Consumptive water use was determined using the soil water balance technique. The wastewaters had moderate to very high degree of restriction for use in relation to salinity and sodicity. Except for CE treatment, wastewater irrigation increased the soil pH, Mg, K, Ca, TOC, TN and CEC at harvest. SAR surpassed the threshold value of 6 in the surface layer of CA soil irrigated with BW wastewater. Wastewater irrigation caused the occurrence of soil hydrophobicity, with the highest hydrophobic degree from CE treatment. The plant growth indices showed that the SM vegetable performed better under AW treatment while the CA vegetable performed better under BW treatment compared with RW treatment. The vegetables differed in relation to water use and there was no discernible trend among the different wastewater treatments as regards the temporal distribution of the consumptive water use. The CE wastewater had the most negative impact on both soil function and plant growth. The study showed that wastewater resources are valuable because of improvement of soil fertility and enhanced crop growth compared with rainwater, however they need to be managed with caution, preferably treatment, before reused in relation to soil functions and crop quality. [ABSTRACT FROM AUTHOR]

Reducing methane emissions and water use is critical for combating climate change and declining aquifers on food production. Reductions in irrigation water use and methane emissions are known benefits of practicing alternate wetting and drying (AWD) over continuous flooding (CF) water management in lowland rice ( Oryza sativa L.) production systems. In a two-year (2020 and 2021) study, methane emissions from large farm-scale (∼50 ha) rice fields managed under CF and AWD in soils dominated by Sharkey clay (Sharkey clay, clay over loamy, montmorillonitic non-acid, thermic Vertic halauepet) were monitored using the eddy covariance method (EC). In the EC system, an open-path laser gas analyzer was used to monitor air methane gas density in the constant flux layer of the atmosphere over the rice-crop canopies. Total water pumped into the field for floodwater management was higher in CF compared to AWD by 24 and 14% in 2020 and 2021, respectively. Considerable variations between seasons in the amount of methane emitted from the CF and AWD treatments were observed: CF emitted 29 and 75 kg ha -1 and AWD emitted 14 and 34 kg ha -1 methane in 2020 and 2021, respectively. Notwithstanding, the extent of reduction in methane emissions due to AWD over CF was similar for each crop season (52% in 2020 and 55% in 2021). Rice grain yield harvested differed by only ±2% between AWD and CF. This investigation of large-scale system-level evaluation, using the EC method, confirmed that by practicing AWD floodwater management in rice, water pumped from aquifers could be reduced by about a quarter and methane emissions from rice fields could be cut down by about half without affecting grain yields, thereby promoting sustainable water management and greenhouse gas emission reduction during rice production in the Lower Mississippi Delta., Competing Interests: The authors declare no competing interests.

This study was carried out in farmers' fields to quantify the total water and consumptive water use in grow-out culture of Penaeus monodon under recommended package of practice with two different water management protocols: T1, with no water exchange and T2, with regulated water exchange. Treatment-wise estimated total water use, was 2.09 and 2.43 ha-m 122 day−1, while the computed consumptive water use index (m3 kg−1 biomass) was 5.35 and 6.02 in T1 and T2 respectively. Lower rates of water exchange (T2) showed significantly improved ( P < 0.05) crop performance in terms of performance index (19.75 ± 0.75), production-size index (74.1 ± 3.4), survival rate (80.13 ± 1.7%) and productivity (2.44 ± 0.08 t) over the zero water exchange. The shrimp pond water quality suitability index ( WQSI) infers that regulated water exchange (T2) improved the overall suitability of water quality for shrimp culture. WQSI up to 90 days of culture ranged between 7.5-9.0 in T2, needs little management while in the last month of rearing, it was good with moderate management requirements. Treatment-wise sediment load ranged between 50.4-56.3 m3 t−1 shrimp biomass. High intensity of water exchange and low apparent feed conversion ratio influenced in lowering the sedimentation rate. Regulated water exchange protocol (T2) performed well (higher net total water productivity and net consumptive water productivity) against no water exchange (T1). A higher OV: CC ratio (ratio of the output value to the cost of cultivation) indicated that T2 had a distinct edge over the T1 protocol. [ABSTRACT FROM AUTHOR]

Inefficient use of irrigation water threatens coffee production in Vietnam, the second largest producer worldwide after Brazil. This paper examines the irrigation issues that constrain sustainable coffee production in Vietnam. The period from January to April is a crucial time in the growth of the coffee crop. It requires irrigation, because rainfall only provides 25% of the potential crop evapotranspiration demand. According to crop phenology, this period also requires induced water stress, because it coincides with breaking the dormancy of flower buds and initiation of cherry development, which is crucial for achieving high yield. This paper proposes an irrigation supply of 120 or 150 mm between January and April in a year preceded by good or average rainfall respectively, in November and December. This is equivalent to 364 or 456 liters/plant/round in 3 rounds/year, which is only 70% of the locally recommended level by the Ministry of Agriculture and Rural Development. Synchronizing this irrigation supply with the management of other inputs could increase average yield up to 4000 kg/ha, from the present level of 2400 kg/ha making coffee production both sustainable and economically viable. In order to achieve this, building capacity of farmers to follow the irrigation and input application schedules is crucial. [ABSTRACT FROM AUTHOR]

Summary Reallocation of water resources in any irrigation scheme is only possible by detailed assessment of current irrigation performance. The performance of the Lower Chenab Canal (LCC) irrigation system in Pakistan was evaluated at large spatial and temporal scales. Evaporative Fraction (EF) representing the key element to assess the three very important performance indicators of equity, adequacy and reliability, was determined by the Surface Energy Balance Algorithm (SEBAL) using Moderate Resolution Imaging Spectroradiometer (MODIS) images. Spatially based estimations were performed at irrigation subdivisions, lower and upper LCC and, whole LCC scales, while temporal scales covered months, seasons and years for the study period from 2005 to 2012. Differences in consumptive water use between upper and lower LCC were estimated for different crops and possible water saving options were explored. The assessment of equitable water distribution indicates smaller coefficients of variation and hence less inequity within each subdivision except Sagar (0.08) and Bhagat (0.10). Both adequacy and reliability of water resources are found lower during kharif as compared to rabi with variation from head to tail reaches. Reliability is quite low from July to September and in February/March. This is mainly attributed to seasonal rainfalls. Average consumptive water use estimations indicate almost doubled water use (546 mm) in kharif as compared to (274 mm) in rabi with significant variability for different cropping years. Crop specific consumptive water use reveals rice and sugarcane as major water consumers with average values of 593 mm and 580 mm, respectively, for upper and lower LCC, followed by cotton and kharif fodder. The water uses for cotton are 555 mm and 528 mm. For kharif fodder, corresponding values are 525 mm and 494 mm for both regions. Based on the differences in consumptive water use, different land use land cover change scenarios were evaluated with regard to savings of crop water. It is found that such analyses need to be complemented at more fine spatial resolutions (i.e. irrigation subdivisions). [ABSTRACT FROM AUTHOR]

This study sets out to measure CWU (litre/kg ECM, energy-corrected milk) of typical milk production systems in 60 dairy regions from 49 countries representing 85% of the world׳s milk production. The extended version of TIPI-CAL 5.2 including water model was used for data analysis. The results have shown the CWU/kg ECM ranged between 739 L on the Danish farm to 5622 l on the Ugandan farm with a global average of 1833 L. When looking at averages per region, the CWU was lowest in Europe (913 L) and highest in Africa (3384 L) with large intra- and inter-regional differences. Compared with grazing and intensive production system, low yielding cows on small-scale farms have the highest CWU/kg ECM. The key driver for variation in CWU/kg ECM is feed, accounting for 94–99% of the total CWU. Increasing milk productivity might be one of the promising ways to reduce CWU/kg ECM. However, this might also lead to the negative impact into water supply systems if this increase is dependent on land irrigation in water scarce areas. The findings of this study showed the need to address the location of the farm, the feed quality, feeding system and milk production intensity simultaneously when aiming at efficient water resource management which would help to contribute food production and livelihood security of dairy farmers worldwide. [ABSTRACT FROM AUTHOR]

Water productivity (WP) and water footprint (WFP) are popular concepts in research and discourses on water management. Yet there are concerns about their theoretical validity and practical value. This paper shows that the water production function, the concept with a sound theoretical foundation, is the basis for WP. Total WFP is the reciprocal of WP. The practical value of WP and WFP depends on the context of water use and stress. Maximizing WP, not a panacea to all water problems, mainly suits arid rainfed areas. In other regions, economic and marginal WP for increasing overall production should take precedence in water management and policy decisions. [ABSTRACT FROM AUTHOR]

The bulk of the water productivity (WP) literature has focused on static cross-sectional analysis with inadequate attention given to long-term, time series analysis, either at the country level or at a lower level of aggregation (e.g., district). The present study fills this gap by analyzing WP in Bangladesh using panel data of 21 districts over 37 years (1968-2004) divided into three phases. It estimated levels of, and trends in, WPs of one irrigated rice (rabi) crop, and two mainly rain-fed (kharif) rice crops, with occasional supplementary irrigation. Also examined were WPs for rice crops in irrigated and rain-fed ecosystems. The findings indicated that WP levels in Bangladesh were significantly lower than that by global standards. Overall, WP growth rates varied significantly among districts and between phases with no consistent pattern emerging. On the whole, WPs trended upwards while differing widely among districts and between phases, seasons, ecosystems and areas differentiated by physiographic characteristics. The 1980s represented a period of stagnation. Drought-prone areas grew faster while salinity-prone areas grew slower vis-à-vis non-drought and non-saline areas. In the Ganges-dependent area, WP grew faster than that in the non-Ganges-dependent area. Rice production in Bangladesh represented a highly groundwater-dependent and fossil fuel-using process with significant environmental implications suggesting that WP growth may be unsustainable. Sustaining WP growth required a range of market and non-market-based policy options. [ABSTRACT FROM AUTHOR]

Purpose: This study quantifies freshwater consumption throughout the life cycle of Brazilian exported yellow melons and assesses the resulting impact on freshwater availability. Results are used to identify improvement options. Moreover, the study explores the further impact of variations in irrigation volume, yield, and production location. Methods: The product system boundary encompasses production of seeds, seedlings, and melon plants; melon packing; disposal of solid farm waste; and farm input and melon transportation to European ports. The primary data in the study were collected from farmers in order to quantify freshwater consumption related to packing and to production of seeds, seedlings, and melons. Open-field melon irrigation was also estimated, considering the region's climate and soil characteristics. Estimated and current water consumptions were compared in order to identify impact reduction opportunities. Sensitivity analysis was used to evaluate variations in the impact because of changes in melon field irrigation, yield, and farm location. Results and discussion: This study shows that the average impact on freshwater availability of 1 kg of exported Brazilian yellow melons is 135 l HO-e, with a range from 17 to 224 l HO-e depending on the growing season's production period. Irrigation during plant production accounts for 98 % of this impact. Current melon field water consumption in the Low Jaguaribe and Açu region is at least 39 % higher than necessary, which affects the quality of fruits and yield. The impact of melon production in other world regions on freshwater availability may range from 0.3 l HO-e/kg in Costa Rica to 466 l HO-e/kg in the USA. Conclusions: The impact of temporary crops, such as melons, on water availability should be presented in ranges, instead of as an average, since regional consumptive water and water stress variations occur in different growing season periods. Current and estimated water consumption for irrigation may also be compared in order to identify opportunities to achieve optimization and reduce water availability impact. [ABSTRACT FROM AUTHOR]

This paper assesses the potential loss of irrigation benefits in reallocating water from irrigation to meet requirements for environmental flows (e-flows) in the Upper Ganga Basin (UGB) in northern India. The minimum requirement for e-flows in the UGB is 32 billion cubic meters (BCM), or 42 % of the mean annual runoff. The current runoff during the low-flow months falls below the minimum requirement for e-flows by 5.1 BCM. Depending on irrigation efficiency, reallocation of 41-51 % of the water from canal irrigation withdrawals can meet this deficit in minimum e-flows. The marginal productivity of canal irrigation consumptive water use (CWU), estimated from a panel regression with data from 32 districts from 1991 to 2004, assesses the potential loss of benefits in diverting water away from crop production. In the UGB, canal irrigation contributes to only 8 % of the total CWU of 56 BCM, and the marginal productivity of canal irrigation CWU across districts is also very low, with a median of 0.03 USD/m. Therefore, at present, the loss of benefits is only 1.2-1.6 % of the gross value of crop production. This loss of benefits can be overcome with an increase in irrigation efficiency or marginal productivity. [ABSTRACT FROM AUTHOR]

Purpose: The assessment of water footprints of a wide range of products has increased awareness on preserving freshwater as a resource. The water footprint of a product was originally defined by Hoekstra and Hung () as the sum of the volumetric water use in terms of green, blue and grey water along the entire life cycle of a product and, as such, does not determine the environmental impact associated with freshwater use. Recently, several papers were published that describe building blocks that enable assessment of the site-specific environmental impact associated with freshwater use along the life cycle of a global food chain, such as the impact on human health (HH), ecosystem quality (EQ) or resource depletion (RD). We integrated this knowledge to enable an assessment of the environmental impact associated with freshwater use along the life cycle of milk production, as a case for a global food chain. Material and methods: Our approach innovatively combined knowledge about the main impact pathways of freshwater use in life cycle assessment (LCA), knowledge about site-specific freshwater impacts and knowledge about modelling of irrigation requirements of global feed crops to assess freshwater impacts along the life cycle of milk production. We evaluated a Dutch model farm situated on loamy sand in the province of Noord-Brabant, where grass and maize land is commonly irrigated. Results and discussion: Production of 1 kg of fat-and-protein corrected milk (FPCM) on the model farm in Noord-Brabant required 66 L of consumptive water. About 76 % of this water was used for irrigation during roughage cultivation, 15 % for production of concentrates and 8 % for drinking and cleaning services. Consumptive water use related to production of purchased diesel, gas, electricity and fertiliser was negligible (i.e. total 1 %). Production of 1 kg of FPCM resulted in an impact on HH of 0.8 × 10 disability adjusted life years, on EQ of 12.9 × 10 m × year and on RD of 6.7 kJ. The impact of producing this kilogram of FPCM on RD, for example, was caused mainly by cultivation of concentrate ingredients, and appeared lower than the average impact on RD of production of 1 kg of broccoli in Spain. Conclusions: Integration of existing knowledge from diverse science fields enabled an assessment of freshwater impacts along the life cycle of a global food chain, such as Dutch milk production, and appeared useful to determine its environmental hotspots. Results from this case study support earlier findings that LCA needs to go beyond simple water volume accounting when the focus is on freshwater scarcity. The approach used, however, required high-resolution inventory global data (i.e. especially regarding crop yield, soil type and root depth), and demonstrated a trade-off between scientific quality of results and applicability of the assessment method. [ABSTRACT FROM AUTHOR]

This paper presents and discusses the possibility of using the life cycle assessment (LCA) methodology as a support instrument in water resources management. Traditionally, water is considered in LCA studies as a transport media for other impact generators and not as an impact category itself (i.e. damaged environmental component). In this context, this study introduces and discusses the possibility of implementing two new impact categories in the life cycle impact assessment phase (LCIA) of LCA to account for the impacts of water consumption and discharge of wastewater flows to subsequent or downstream water uses. These two new indicators, named consumptive water use and degradative water use are implemented into the widely used Eco-Indicator 99 (EI99) LCIA methodology in the resources impact class and are tested in a LCA case study from a wine making industry. This research approaches the wine life cycle, since its production contributes to a variety of environmental impacts due to the high demand of water and energy. The LCIA was performed using the classic Eco-Indicator 99 methodology and the updated methodology using the two new impact categories. The results have shown that the production phase in the wine life cycle generated the highest impacts, although the impact profiles are different for the two methodologies. Also, by using the classic EI99 methodology it is difficult to identify, quantify and analyze the water related impacts, while the proposed new methodology allows for an in-depth analysis of water related impacts, in terms of water consumption and wastewater discharges. [ABSTRACT FROM AUTHOR]

This paper examines the nexus between milk production and water use in India. The nexus is examined in the context of extended consumptive water use (CWU) of milk production beyond drinking water. It includes the real CWU (evapotranspiration (ETa) that occurs during the production of green fodder and feed grains) and the virtual CWU (ETa embedded in by-products for animal feed). The real CWU appears as large as that of sugarcane, and the real and virtual CWU combined is as large as that of rice. However, milk production generates more value than the outputs of rice and sugarcane combined. Sustainable water use and agricultural growth in major milk-producing areas require a drastic reduction in groundwater CWU, which, at present, exceeds natural recharge. It is suggested that diversifying to a mix of milk and high-value (but low water consuming) crops can reduce groundwater CWU while ensuring higher total output. [ABSTRACT FROM PUBLISHER]

Improvements in water productivity (WP) are often suggested as one of the alternative strategies for overcoming growing water scarcity in India. This paper explores the potential improvements in WP of food grains at district level, which currently varies between 0.11 and 1.01 kilogram per cubic metre (kg/m3), in the 403 districts that account for 98% of the total production of food grains. The paper first finds the maximum yield function conditional on consumptive water use (CWU) and then explores the potential improvements in WP by: (a) bridging the gap between actual and maximum yield while keeping CWU constant; and (b) changing the maximum yield by adjusting the CWU using supplementary or deficit irrigation. Deficit irrigation in some areas may decrease yield but can increase production if land availability is not a constraint. A large potential exists for bridging the yield gap in irrigated areas with CWU between 300 and 475 mm. Of the 222 districts that fall under this category, a 50% reduction in yield gap alone could increase production by 100 million tonnes (Mt) without increasing CWU. Supplementary irrigation can increase yield and WP in rain-fed and irrigated areas of 266 and 16 districts with CWU is below 300 mm. Deficit irrigation in irrigated areas of 185 districts with CWU above 475 mm could increase yield, WP and production. Decreasing CWU in irrigated areas with CWU between 425 and 475 mm reduces yield slightly, but if availability of land is not a constraint then the benefits due to water saving and production increases could exceed the cost. [ABSTRACT FROM AUTHOR]