Search

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office 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.)

In this paper, SWAT model was used to analyze the spatial and temporal distribution characteristics of blue water and green water resources in typical years of Poyang Lake Basin from 1970 to 2018, and the changes of green water coefficient in typical years were analyzed. The results showed that in typical years, the blue and green water resources were the most in the wettest year, the least in the driest year, and the moderate in the normal year. The change trend of blue water was large, and the change of green water was relatively stable. Among them, green water flow was the main part of green water amount, and green water storage only accounted for a very small part. The blue water amount showed a decreasing trend from northeast to southwest, which was basically consistent with the spatial distribution of precipitation. Green water resources were not only related to climatic conditions such as precipitation, but also related to human activities and the nature of underlying surface. The green water coefficient of the basin was not high. The highest green water coefficient in the driest year was 45. 42%, the lowest green water coefficient in the wettest year was 33. 91%, and the normal year was 38. 75%. It showed that blue water resources were the main component of water resources in the Poyang Lake Basin. At the same time, the spatial distribution of the green water coefficient and the spatial distribution pattern of precipitation showed an opposite trend. [ABSTRACT FROM AUTHOR]

Study region: The Mainstream in the Tarim River Basin, Southern Xinjiang, China Study focus: Climate change and human activities have significantly altered the water cycle, and water security evaluation and management are urgent. In arid and semi-arid areas, the assessment of blue and green water is particularly important. In this study, the MIKE SHE model is used to simulate the spatial and temporal changes of blue and green water resources in the mainstream of the Tarim River Basin (TRB) from 1990 to 2050 under land use and climate change conditions. The scarcity and vulnerability of blue-green water are introduced to evaluate the water security of the basin. The impacts of different land uses on blue-green water resources were also calculated according to the model zoning. New hydrological insights for the region: The results indicate that from 1990 to 2050, blue water resources show a spatial pattern of gradual decrease from upstream to downstream. Compared to blue water, green water is dispersed more evenly over space. Future climatic scenarios will impact water security, as will changes in blue and green water security in terms of time and space. By comparing the influence of ecological water transport on the change of blue and green water before and after 2000, it was found that environmental water transport plays a certain role in improving the blue water scarcity in downstream of the TRB. The study is significant in maintaining regional water security and ecosystem stability.

Mountains are important suppliers of freshwater to downstream areas, affecting large populations in particular in High Mountain Asia (HMA). Yet, the propagation of water from HMA headwaters to downstream areas is not fully understood, as interactions in the mountain water cycle between the cryo-, hydro- and biosphere remain elusive. We review the definition of blue and green water fluxes as liquid water that contributes to runoff at the outlet of the selected domain (blue) and water lost to the atmosphere through vapor fluxes, that is evaporation from water, ground, and interception plus transpiration (green) and propose to add the term white water to account for the (often neglected) evaporation and sublimation from snow and ice. We provide an assessment of models that can simulate the cryo-hydro-biosphere continuum and the interactions between spheres in high mountain catchments, going beyond disciplinary separations. Land surface models are uniquely able to account for such complexity, since they solve the coupled fluxes of water, energy, and carbon between the land surface and atmosphere. Due to the mechanistic nature of such models, specific variables can be compared systematically to independent remote sensing observations – providing vital insights into model accuracy and enabling the understanding of the complex watersheds of HMA. We discuss recent developments in spaceborne earth observation products that have the potential to support catchment modeling in high mountain regions. We then present a pilot study application of the mechanistic land surface model Tethys & Chloris to a glacierized watershed in the Nepalese Himalayas and discuss the use of high-resolution earth observation data to constrain the meteorological forcing uncertainty and validate model results. We use these insights to highlight the remaining challenges and future opportunities that remote sensing data presents for land surface modeling in HMA. [ABSTRACT FROM AUTHOR]

Mountains are important suppliers of freshwater to downstream areas, affecting large populations in particular in High Mountain Asia (HMA). Yet, the propagation of water from HMA headwaters to downstream areas is not fully understood, as interactions in the mountain water cycle between the cryo-, hydro- and biosphere remain elusive. We review the definition of blue and green water fluxes as liquid water that contributes to runoff at the outlet of the selected domain (blue) and water lost to the atmosphere through vapor fluxes, that is evaporation from water, ground, and interception plus transpiration (green) and propose to add the term white water to account for the (often neglected) evaporation and sublimation from snow and ice. We provide an assessment of models that can simulate the cryo-hydro-biosphere continuum and the interactions between spheres in high mountain catchments, going beyond disciplinary separations. Land surface models are uniquely able to account for such complexity, since they solve the coupled fluxes of water, energy, and carbon between the land surface and atmosphere. Due to the mechanistic nature of such models, specific variables can be compared systematically to independent remote sensing observations – providing vital insights into model accuracy and enabling the understanding of the complex watersheds of HMA. We discuss recent developments in spaceborne earth observation products that have the potential to support catchment modeling in high mountain regions. We then present a pilot study application of the mechanistic land surface model Tethys & Chloris to a glacierized watershed in the Nepalese Himalayas and discuss the use of high-resolution earth observation data to constrain the meteorological forcing uncertainty and validate model results. We use these insights to highlight the remaining challenges and future opportunities that remote sensing data presents for land surface modeling in HMA.

Exploring the spatiotemporal impacts of climate change and human activities on freshwater resources through the concepts of blue and green water can effectively improve the sustainability of basin water resource management. However, previous relevant studies have not considered the specific impacts of different climate models and land use changes on the future simultaneously. To mitigate this issue, this study proposes a hydrological modeling framework by integrating geographic detectors, Future Land Use Simulation (FLUS) models, and the Soil and Water Assessment Tool (SWAT) model. This framework was capable of identifying the major driving factors of land use changes, predicting future land use patterns, and assessing the spatiotemporal characteristics of water resources under different future climate scenarios and land use distributions. Applying the framework to the Wei River Basin (WRB) in northwest China, it identified the primary drivers of land use change in the WRB and quantitatively analyzed the spatiotemporal changes of blue and green water resources in the WRB under four scenarios. The results show that: 1) FLUS model and SWAT model can effectively simulate land use change and runoff process with high simulation accuracy; 2) Precipitation, temperature and GDP are the main drivers of land use change; 3) The amount of blue and green water in the middle and lower reaches of the basin is significantly higher than that in the tributaries and upper reaches. Blue water and green water flow are more affected by climate than land use, while green water storage is more sensitive to land use change. This study can provide effective information for basin land planning and rational allocation of water resources.

Study region: The study area was Nanjing, Jiangsu Province, eastern China. Study focus: Blue-green water utility assessment in crop cultivation is profound to better sustainability of regional resources, agriculture and ecosystems. The aim of current study is to establish a blue-green water differentiation and efficiency evaluation methods for paddy fields, based on daily water migration observation under four irrigation-drainage protocols. The blue-green water use performance under different irrigation-drainage protocols and precipitation patterns in paddy fields and the advantage of the water resources analysis model proposed in the current study were analyzed and discussed. New hydrological insights for the region: The green and blue water efficiency indices (GWE and BWE) were significantly affected by precipitation. GWE (0.495) was 35.1% higher in dry years than in wet years, and BWE was mainly affected by precipitation distribution during the crop growth season. The green and blue water productivity indices (GWP and BWP) showed pronounced differences among various irrigation-drainage measures, and the controlled irrigation (COI) performs the best. BWE and GWP obtained by previous method were 48.9% and 38.9% greater than those reported here, showing that the neglect of interactive blue-green water migration process would overestimate the field irrigation efficiency. The methods employed and results obtained in the present study suggest that it is important to assess the water footprint and blue-green performance for crop cultivation systems.

Study region: Kaidu River Basin, an arid region of China Study focus: Water resources are scarce and unstable. Adverse changes in blue-green water resources can disrupt water balance and availability in arid regions. Therefore, it is crucial to effectively assess and predict future blue-green water resources in arid areas. This study utilizes the Soil and Water Assessment Tool (SWAT), Patch-generating Land Use Simulation (PLUS), and Global Circulation Models (GCMs) to analyze the interactive impacts of climate and land use/cover changes (LUCC) on blue-green water in arid basin from 1990 to 2050. New hydrological insights for the region: This work identified key factors influencing blue-green water changes, including forests, grasslands, and snowmelt. In the historical scenarios, the Kaidu River basin exhibited significant interannual variations in blue water and precipitation. In the future scenarios, blue water increases (+3.6%), and green water decreases (−1.8%) under SSP245 (medium emissions). Under SSP585 (high emissions), blue water decreases (−2.4%), and green water increases (+1.8%). Under SSP126 (low emissions), both blue water (+8.5%) and green water (+0.73%) show an increasing trend. The change in snowmelt is the main reason for the first peak of blue water in April May. Under historical and future snowmelt conditions, blue water shows a significant upward or downward trend with the amount of snowmelt. The findings provided practical hints for the enhancement of the management and allocation of precious water resources.

The process of blue water used in crop cultivation has both natural and economic properties due to the intervention of irrigation facilities. This study revealed crop water use (CWU) from 1999 to 2018 in each province of China based on water footprint theory, and then established the blue water dependence index (BDI) to evaluate the dependence of agricultural cultivation on irrigation water from the perspective of water withdraw, and conducted a spatial and temporal pattern analysis.The influencing factors and structural pathways of BDI were explored using least squares structural equation modeling (PLS-SEM) at national and regional scales. Results indicated that the annual amount of water used for crop production in China exceeded 900.0 Gm³. The growth in CWU from 1999 to 2018 for cash crops and grain crops was 145.4 Gm³ and 74.4 Gm³, respectively.BDI of all crops was 0.281 over the study period in China, with grain crops being 2.6 times more dependent on blue water resources than cash crops. Xinjiang, with annual average BDI of 0.716, 0.805, and 0.620 for all, grain and cash crops, respectively, has the highest irrigation demand. The PLS-SEM results showed a significant causal relationship between the economy and BDI, with obvious regional differences in structural path analysis. Based on the analysis of agricultural water use, the regions can adjust the structure of crop cultivation, optimize the allocation of water and soil resources, expand the cultivation of fodder grains and promote steady economic growth, to achieve a ''win-win'' situation of ensuring food security and sustainable use of agricultural water resources.

Different canopy characteristics of industrial eucalyptus may lead to differences in water evaporation and availability to plants. This study aims to understand rainfall partitioning in a young clonal plantation (age of 2–4.5 years) of three eucalyptus species by relating tree parameters: diameter at breast height, total height, and leaf area index. We measured rainfall, throughfall, stemflow and litter interception, along with the tree parameters. The eucalyptus trees had rainfall interception varying between 22 mm (for 178 mm of rainfall) and 42 mm (for 87 mm of te rainfall), throughfall between 106 mm (for 186 mm of rainfall) and 44 mm (for 74 mm of rainfall), and stemflow between 0.5 mm (for 92 mm of rainfall) and 1.4 mm (for 24 mm of rainfall). For the three species, rainfall interception varied between 12 and 48%, throughfall between 57 and 90%, and stemflow between 0.3 and 5.4%. The coefficient of determination between interception and rainfall was 0.76, indicating interception depends on other variables, possibly including antecedent rainfall, rainfall intensity, and seasonality. Interception decreased with a reduction in leaf area index caused by eucalyptus defoliation. The E. benthamii had 0.75 mm of throughfall per 1 mm of rainfall, whereas in E. dunnii and E. saligna, these ratios were 0.71 and 0.68, respectively. Stemflow in E. benthamii and E. dunii had a higher positive relationship with the diameter at breast height of the trees, whereas in E. saligna the highest relationship was with the rainfall. These results contribute to establishing management strategies, such as choosing suitable eucalyptus species to local climate, and to improve the synchronization of crop-demand versus soil-water-supply while maintaining streamflow to fulfill ecological and production needs.

It is of great significance to study the hydrological effect of no-tillage of rice for the popularization of no-tillage technology and the sustainable development of agriculture.However,previous studies were mainly conducted at station scale,and the effect of no-tillage of rice on blue-green water at basin scale is still unclear.Taking the Xiangjiang River Basin as the test area,based on the land use data,digital elevation data,soil data,agricultural management data in 2000 and meteorological data-driven SWAT model,this paper simulates the effect of no-tillage of rice on blue water (water yield+deep groundwater recharge) and green water (actual evapotranspiration+soil moisture content) in the basin.The results show that:Compared with traditional tillage,no-tillage of rice had a greater influence on recharge of deep groundwater,resulting in a decrease of 5.62%,which was 5.35% higher than that of water yield.However,the change of blue water was mainly attributed to the change of water yield,whose contribution was 72.46%.The green water flow (actual evapotranspiration) decreased by 8.460×107 m3 due to no-tillage of rice,but the increase of green water reservoir (soil moisture content) offset these and eventually resulted in the increase of green water.Therefore,the change of blue-green water distribution under no-tillage of rice was mainly achieved by changing water yield and soil moisture content.The water yield mainly caused the change of blue water,while the soil moisture content mainly resulted in the change of green water.Due to the mutual offset of hydrological factors,there was no significant final effect of no-tillage rice on the blue-green water of the whole basin,but large spatial differences within the basin.No-tillage of rice increased the proportion of green water in the total water resources,and increased the ecological water available in the farmland ecosystem,so it played a positive role.

Water scarcity mitigation in regional agricultural systems contributes to water use efficiency improvement. Blue (WSIblue), green (WSIgreen) and grey (WSIgrey) water scarcity indices were proposed to describe various water stresses in detail and further determine the type of regional water scarcity. WSIblue and WSIgreen reveal resource-based water scarcities, and WSIgrey characterizes environment-based water shortages. Provincial water scarcity indices of China from 2000–2014 were calculated and analyzed in the current paper. The results indicated that the national WSI, WSIgrey, WSIblue and WSIgreen values are 0.84, 0.16, 0.39 and 0.89, respectively. China is facing a high water stress, manifested as a resource-based water shortage. Northwest and Northeast China experience a severe water quantity scarcity with high WSIblue and WSIgreen values, and the central and eastern regions exhibit a high WSIgrey value. Eastern China faces both serious resource-based and environmental water shortages. The constructed blue, green and grey water scarcity indices compensate for the inability of the existing index to determine the type of water shortage and indicate the reason for water scarcity. They also provide a targeted guiding significance for the formulation of effective measures to improve agricultural water resource management and alleviate regional water scarcity. [ABSTRACT FROM AUTHOR]

BACKGROUND: Water productivity improvement is fundamental to agricultural water use control, and the water footprint provides a new and comprehensive method for identifying the crop‐water relationship. This study is intended to explore the spatiotemporal pattern and driving forces underlying the rice water footprint productivity (WFP) in China during the years 1996–2015 based on calculations of the provincial blue, green, gray, and white water footprints. RESULTS: The national water footprint in paddy rice cultivation was 240.97 Gm3, and green water accounted for 43.9% of the total. The WFP was 0.795 kg m−3 and increased over time in all 30 provinces for which it was calculated. The growth rate in the northern provinces was greater than that in the southern part of the country. The WFP clustered geographically in all years observed. High‐value provinces were concentrated to the south of the Yangtze River, whereas most of the provinces that showed a low WFP were distributed in the north China and northwest subregions. Precipitation and sunshine hours were the most obvious driving factors of rice WFP. The effects of agricultural input, e.g., agricultural machinery power, pesticides, and irrigation efficiency, on WFP also could not be ignored. CONCLUSION: The WFP is a comprehensive and useful index of the crop‐water relationship and water‐use efficiency. Improving agricultural input and irrigation technology are reliable approaches for WFP promotion. Areas in northeast China showed the most urgent need for improving the rice WFP, and the inclusion of the main grain producing areas in the Yangtze River Basin will further reduce ineffective water occupancy to improve water‐use efficiency. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Water footprint scarcity (WFS) was quantified based on blue-green water availability and appropriation. • WFS increased in drought agriculture-based region and dropped in economic developed area. • WFS increased in drought agriculture-based region and dropped in economic developed area. • Controlling the development of irrigation can reduce WFS and alleviate regional water scarcity. Abstract The mitigation of water stress in crop production is important for relieving the growing global water shortage. The water footprint scarcity (WFS) for regional water stress evaluation integrating blue and green water resources and the water footprint of the crop production industry were developed in this paper. Three subregions in China, industry-based southern Jiangsu (SJS), agriculture-based northern Jiangsu (NJS) and middle-type central Jiangsu (CJS), were selected to study the spatiotemporal pattern and driving mechanism of WFS. The results show that green water accounts for 56.6% and 71.8% of agricultural water resources available (AWA) and crop water footprint (CWF) of Jiangsu Province. The WFS of Jiangsu was calculated to be 2.26, and almost all prefectures for every year from 1996 to 2015 faced very high water stress (WFS > 1.20). The WFS value increased in NJS and CJS and decreased in SJS over time; meteorological and social factors affected the WFS at the same time. Land irrigation was the main factor to explain the growing water stress in the agriculture-based NJS. The WFS revealed the water shortage more clearly, especially in the water-poor agriculture-based areas, than the results of the conventional water stress index. The strategies for environmental change adaptation suggested by this study are to use WFS for agricultural water suitability evaluation and water resource management policy formulation; to reduce WFS through irrigation efficiency and crop variety promotion worldwide; and to implement compensation measures for agricultural products and virtual water trade to help underdeveloped agricultural production areas improve their agricultural production technology and control irrigation expansion. [ABSTRACT FROM AUTHOR]

The present study aim to explore temporal–spatial patterns of water use (WU) efficiency and its influencing factors of maize production in China during 1998–2010. WU and productivity (WP) were quantified by taking irrigation loss into account and the links between WP and nine selected indicators were revealed by the partial least squares regression (PLSR) model. Results showed that national WU and WP in maize production were 138.56 cubic gigametres (Gm3; 0.755 green and 0.245 blue) and 1.079 kg/m3, respectively. WP was enhanced in the present study due to an increase in irrigated crop yield. Provinces located in the middle–lower part of the Yellow River had high proportions of green water and WP , while high proportions of irrigation water and low WP were found in Northwest China. The dosage of pesticides per unit area, relative humidity, average temperature and precipitation were the dominant factors that affected WP. However, the relationships between WP and solar radiation, fertilizer, agricultural machinery power, irrigation proportion and irrigated efficiency were not significant. Findings of the present research may also provide a reference for regional agricultural water management. [ABSTRACT FROM AUTHOR]

In order to meet the demand for food from a growing global population, aquaculture production must be increased as capture fisheries have stagnated. Rapid population growth with competition for land and water could affect aquaculture production. Although aquaculture uses non-consumptive water, there are significant water footprints for aquaculture due to water lost and water required for fish-feed production. Moreover, climate change affects water availability and demand for aquaculture, and poses a further threat to global fish production. Nevertheless, the efficient use of blue water (surface and groundwater) and green water (rain) in inland, coastal, and marine aquaculture could make a significant contribution to global fish production and climate change adaptation. Sustainable intensification of freshwater aquaculture, mangrove restoration with brackish water fish production, and the expansion of mariculture could increase global fish production with adaptation to climate change. Institutional support with technical and financial assistance is needed to implement the proposed adaptation strategies. [ABSTRACT FROM AUTHOR]

Efficient utilization of water resources contributes to regional food, water and ecological security. An indicator, generalized efficiency (GE), was established based on a blue-green water framework for evaluating regional effective use of water resources. GE is defined as the ratio of total water consumption (TWC) to total water inflow (TWI) into an agricultural production system over a single year. Then, the spatial pattern of GE in the irrigated, rain-fed and total cropland of China in 2010 was analysed based on the quantification of provincial TWI and TWC, taking grain production as a case study. The results show that TWI in China was approximately 978.6 Gm 3 , of which rain water was close to 70.0%; national TWC was approximately 577.5 Gm 3 in the study year, including 72.0% green and 28.0% blue water; and rain-fed cropland made up approximately 33.0% of the TWI and TWC. The spatial distributions of TWI and TWC per unit arable land differs greatly; national GE in irrigated, rain-fed and total cropland were 0.584, 0.603 and 0.590, respectively; and regional rain-fed GE was larger than that in irrigated farmland due to the uneven distribution of precipitation. This work expanded the applicability of evaluation of effective use rate of water resources from blue water and irrigated cropland, to generalized water resources and any designated region. GE cannot be replaced by other exciting indicators in either scientific connotation or spatial distribution. Hence, the establishment of GE is a more advanced agricultural water use efficiency evaluation indicator system. [ABSTRACT FROM AUTHOR]

An indicator, agricultural water stress index (AWSI), was established based blue-green water resources and water footprint framework for regional water scarcity in agricultural production industry evaluation. AWSI is defined as the ratio of the total agricultural water footprint (AWF) to water resources availability (AWR) in a single year. Then, the temporal and spatial patterns of AWSI in China during 1999–2014 were analyzed based on the provincial AWR and AWF quantification. The results show that the annual AWR in China has been maintained at approximately 2540 Gm 3 , of which blue water accounted for > 70%. The national annual AWF was approximately 1040 Gm 3 during the study period and comprised 65.6% green, 12.7% blue and 21.7% grey WFs The space difference in both the AWF for per unit arable land (AWFI) and its composition was significant. National AWSI was calculated as 0.413 and showed an increasing trend in the observed period. This index increased from 0.320 (mid-water stress level) in 2000 to 0.490 (high water stress level) in the present due to the expansion of the agricultural production scale. The Northern provinces, autonomous regions and municipalities (PAMs) have been facing high water stress, particularly the Huang-Huai-Hai Plain, which was at a very high water stress level (AWSI > 0.800). Humid South China faces increasingly severe water scarcity, and most of the PAMs in the region have converted from low water stress level (AWSI = 0.100–0.200) to mid water stress level (AWSI = 0.200–0.400). The AWSI is more appropriate for reflecting the regional water scarcity than the existing water stress index (WSI) or the blue water scarcity (BWS) indicator, particularly for the arid agricultural production regions due to the revealed environmental impacts of agricultural production. China should guarantee the sustainable use of agricultural water resources by reducing its crop water footprint. [ABSTRACT FROM AUTHOR]

Background Land use change and climate variability influence water resources availability and separation of these influences are important for water resources management. Methods SWAT model and the Mann–Kendall method were used in this study which investigated the spatiotemporal variations of blue and green water resources under different land use change, agricultural irrigation expansion and climate variability scenarios during the 1980s–2000s for the Weihe River Basin. Results Farmland area decreased by 1.4% and woodland, grassland, and construction land area increased by 0.6%, 0.2%, and 0.6%, respectively. The combined impact of land use change, agricultural irrigation expansion and climate variation decreased the blue water flow, green water flow, and green water storage by 21.62 mm year − 1 , 35.01 mm year − 1 and 28.07 mm year − 1 , respectively. Climate variability decreased the blue/green water flow and green water storage, land use change decreased the blue water and green water flow while it increased the green water storage, irrigation expansion decreased the blue water flow while it increased the green water flow/storage. The spatial distribution showed an uneven change in the Weihe River Basin. Together, we suggested that the variability of water resources availability in the Weihe River Basin was mainly attributed to climate variability, while land use change plays a key role in the sub-basins which experienced dramatic changes in land use. [ABSTRACT FROM AUTHOR]

Hydrology-oriented silviculture might adapt Mediterranean forests to climatic changes, although its implementation demands a better understanding and quantification on the water fluxes. The influence of thinning intensity (high, medium, low and a control) and its effect on the mid-term (thinned plots in 1998 and 2008) on the water cycle (transpiration, soil water and interception) and growth [basal area increment (BAI)] were investigated in 55-year-old Aleppo pine trees. Thinning enhanced a lower dependence of growth on climate fluctuations. The high-intensity treatment showed significant increases in the mean annual BAI (from 4.1 to 17.3 cm) that was maintained in the mid-term. Thinning intensity progressively increased the sap flow velocity ( v) in all cases with respect to the control. In the mid-term, an increased functionality of the inner sapwood was also observed. Mean daily tree water use ranged from 5 (control) to 18 (high intensity) l tree. However, when expressed on an area basis, daily transpiration ranged from 0.18 (medium) to 0.30 mm (control), meaning that in spite of the higher transpiration rates in the remaining trees, stand transpiration was reduced with thinning. Deep infiltration of water was also enhanced with thinning (about 30 % of rainfall) and did not compete with transpiration, as both presented opposite seasonal patterns. The changes in the stand water relationships after 10 years were well explained by the forest cover metric. The blue to green water ratio changed from 0.15 in the control to 0.72 in the high-intensity treatment, with the remaining treatments in the 0.34-0.48 range. [ABSTRACT FROM AUTHOR]

The increasing shortage of water resources and the growing demand for crops make water use efficiency a decisive factor for the sustainable and healthy development of the agricultural system. In order to evaluate agricultural water use efficiency from the water footprint perspective, the current study constructed the comprehensive water efficiency (CWE) index based on eight single agricultural water use efficiency performance parameters. The water resources utilization and efficiency in the wheat production system of China from 2006 to 2015 were analyzed and the sensitivity of single indices for CWE was identified. The results show that the national crop water footprint (CWF) for wheat production was estimated to be, including 46.3% blue, 36.6% green and 17.0% blue components, respectively. The spatial distribution patterns of water use efficiency performance indices were different. CWE of the country was 0.387, showing an upward trend over time and decreased from the southeast to the northwest geographically. Crop water productivity (CWP), productive water ratio (PWR) and rainwater consumption ratio (RCR) turned out to be the first three sensitive parameters for CWE in China. The improvement of China's overall CWE relied on reducing inefficient blue-green water use and increasing the output capacity for per unit water. Advanced agricultural water-saving technologies were in high need for goal achievement, especially for the Huang-Huai-Hai plain, which held more than 70% of Chinese wheat production and CWF. The results provide support for efficient utilization and sustainable development of water resources in the agricultural system. [ABSTRACT FROM AUTHOR]

• Virtual water trade has a bright future in agricultural water management due to its water saving effect. • Essential features of arable land, irrigation, and green water are ignored in existing water saving evaluation frameworks. • Unexpected results were obtained when the role of irrigation was considered. • Research on virtual water should be carried out in combination with the agricultural water utilization process. Water saving by agricultural virtual water trade (VWT) is regarded as a new way to address water shortage, and many studies have considered it at local and global scales. However, the existing calculation methods do not consider how agricultural products should be produced in export and import areas without crop trade. We believe that three facts related to irrigation should be considered in water saving in agricultural VWT evaluation: 1) arable land is highly restricted, 2) irrigation increases crop yield significantly, and 3) green water does not require cost. The role of irrigation, which is important for both the export and import region, is very important for determining how to cultivate crops without virtual water trade. In the case of grain VWT between Heilongjiang and Guangdong, China, the national blue water saving in 2010 with this consideration was −2562.1 Mm³ (water loss), whereas the figure was 975 Mm³ under the existing calculation framework. Therefore, there is a possibility that VWT can be used in agricultural development and water management decision-making while considering the role of irrigation. [ABSTRACT FROM AUTHOR]

• Hybrid framework for agricultural water utilization and efficiency evaluation was constructed. • WRU, WRE and WRP are water appropriation amount, effective rate and production ability measurement. • Water use efficiency in China promoted over time while varied among both regions and crops. • Indices in hybrid framework were novelty and unique on scientific nature and spatial performance. Efficient agricultural water use is required for food safety and water alleviation on a global scale. Combining the water footprint and agricultural water use paradigms and enveloping water resource movement and its impact on the environment in the agricultural production process, a hybrid framework for agricultural water utilization and efficiency evaluation was constructed in the current paper. The indicators water resources use (WRU), efficiency (WRE) and productivity (WRP) are used in this framework for the total water exploitation, the effective utilization rate and the production capacity measurement, respectively. An empirical study on the framework was conducted with major cereals (wheat, maize and rice) in 31 provinces, autonomous regions and municipalities (PAMs) of China. The national WRU, WRE and WRP values of integrated cereal were calculated to be 669.0 G m³, 0.633 and 0.679 kg/m³, respectively, from 1996 to 2015. The PAMs with high WRE values were located in southwestern, northeastern and northern China, while the ones with low values were clustered in northwestern and southeastern China. The spatial distribution pattern of WRP is consistent with precipitation. The water use efficiency (WRE and WRP) of the three specific crops in this framework increased over time. The WRE of maize was significantly higher than that of rice and wheat, while the WRP of wheat was the lowest. WRU measures the total water resource appropriation during crop growth in both quantity and quality; WRP was able to show where water use efficiency needs to be improved; and the function of WRE to indicate water saving potential could not be replaced by notable indices, such as irrigation efficiency or generalized efficiency. Therefore, further research is warranted to evaluate agricultural water use efficiency at different scales using this hybrid framework. [ABSTRACT FROM AUTHOR]