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Water scarcity is a critical threat in arid regions in China due to dry climate and rising human water demand. The sustainability of a recent wetter trend and its impact on future water security remain uncertain. This case study focuses on a hotspot region, the North Slope of the Tianshan Mountains (NSTM), to assess water scarcity in the coming decades (2030–2050) under two climate scenarios. To this end, we developed an integrated agro‐hydrological model to simulate historical and future hydrological processes and crop water dynamics in arid regions. Our results indicate nonsignificant increases in precipitation (around 3%) and evident rising temperatures (0.9–1.5°C) in the NSTM compared to the present‐day (2011–2020) climate. This translates to a projected increase in water availability (5.6%–11.2%) during 2030–2050, with slightly larger increases (6.3%–14%) in glacier runoff. However, the spatial mismatch between precipitation increases and water demand makes this potential gain largely offset by rising irrigation water demand (over 7%) if cropland remains constant from 2020 onwards. As a result, the current annual water deficit (3.3 km3) is likely to increase by 5%–11%, with 32% of NSTM basins facing persistent water scarcity. Most croplands are at high risk of groundwater depletion and 17%–34% of basins will experience intensified water scarcity. These findings highlight the urgent need for comprehensive water management strategies, including improved irrigation efficiency and exploration of alternative water sources, to ensure water security and sustainable development in arid China facing a changing climate. Plain Language Summary: Dry regions in China face a water shortage due to low rainfall and rising water use. Recently, even though more rainfall was observed in some arid regions, scientists aren't sure if this will continue. We focus on the hotspot region, the North Slope of the Tianshan Mountains (NSTM), to see how future climate change might affect water scarcity. We found slightly more rain and warmer temperatures in the coming decades (2030–2050) in the NSTM. This could lead to a small increase in available water. However, the need for irrigation water is expected to offset these gains. The current water deficit is likely to worsen, with some areas facing even greater scarcity and increased risk of groundwater depletion. This highlights the need for better irrigation practices and exploring alternative water sources to ensure water security and sustainable development in these regions under a changing climate. Key Points: Slight increases in precipitation and water availability are projected in the NSTMWater scarcity persists due to the spatial mismatch between increased water availability and high irrigation demandThe water deficit is likely to increase by 5%–11% from the current level of 3.3 km3 per year [ABSTRACT FROM AUTHOR]

Climate change was projected to have negative effects on water availability and consequently a serious constraint to food production in many areas of the world. However, such effects have not been well understood, particularly over rainfed croplands, partly because of the poor representation of green water in associated assessments. In this study, we develop an integrated agricultural water scarcity index (WSIag) that incorporates blue and green water components to examine the agricultural water scarcity in the baseline (1981–2005) and future (2026–2050) periods under the Representative Concentration Pathway (RCP)2.6 and RCP6.0 scenarios. Results show that ∼3.8 million km2 (∼39% of total) croplands experienced water scarcity in the baseline period and it would expand by more than 3% in the future. Under the two scenarios, WSIag projections are similar overall and are higher than that under the baseline in 83%–84% of global total croplands. Differences are found between the scenarios in Amazonia, Southern Africa, and South Asia. The increases in future WSIag are dominated by the decreased water availability in ∼60% of total croplands and ∼24% of which is dominated by the increased crop water requirement. Changes in green water availability have a significant contribution to changes in WSIag in 16% of global croplands, mostly in arid/semiarid regions (e.g., the South edge of the Sahel, Southern Africa, Northeast China, and Central America). This implies the important role of green water management for agriculture in these regions. The integrated assessment can help develop effective strategies for agricultural water management under climate change. Plain Language Summary: Future climate change may intensify water scarcity and adversely affect crop productivity in many regions of the world. Traditionally, water scarcity assessment focused on blue water (from rivers, reservoirs, and lakes) or green water (crop evapotranspiration from soil moisture) alone. In order to examine the impact of climate change on water scarcity in croplands, we develop an integrated agricultural water scarcity index (WSIag) that incorporates blue and green water components and calculate WSIag for both historical and future periods. The assessment suggests that nearly 40% of global croplands have experienced water scarcity in the past and the situation would worsen in the future. WSIag is projected to be higher than in the past in 83%–84% of global total croplands. The increased WSIag is mostly caused by less water availability and larger crop water requirement. It is noted that changes in green water availability could also be a dominant factor in some arid/semiarid regions in the South edge of the Sahel, Southern Africa, India, Northeast China, and Central America. Our study highlights the important role of green water for agriculture water management and is expected to provide useful information for agricultural adaptation to future climate change. Key Points: Agricultural water scarcity will intensify in more than 80% of global croplandsDecreased water availability dominates the aggravation of future water scarcity globallyGreen water have a significant contribution to future changes in water scarcity in 16% of global croplands [ABSTRACT FROM AUTHOR]

Over the past decades, water scarcity has become prevalent in many regions of the world. Previous water scarcity assessments largely considered "blue water" (surface and groundwater) and overlooked "green water" (soil moisture), despite its key role in supporting crop production. Moreover, the long‐term evolution of water scarcity remains unclear. Here, we propose an agricultural water scarcity index (WSIAW) that explicitly combines green and blue water. The WSIAW measures the degree to which both green and blue water availabilities can satisfy the agricultural water requirement. The WSIAW can directly indicate water scarcity in both rainfed and irrigated areas, which cannot be captured by the blue water scarcity index alone. Using the WSIAW, we assessed the evolution of water scarcity across regions of the world during 1971–2010 at a spatial resolution of 0.5 arc degree. We found that 22% of the 228 river basins with a WSIAW of >1 presented a much broader geographical coverage compared with estimates of water scarcity based on blue water only (8% of total basins). The WSIAW also exhibited a clear trend of increasing severity over the study period, particularly in major agricultural regions. Expanding cropland and increasing/competing water withdrawals by other sectors were the main reasons for the intensification of water scarcity, which was pronounced in some Asian and African river basins. The proposed WSIAW can be applied to different regions with various scales and is important for addressing global water scarcity issues. Key Points: We propose a new agricultural water scarcity index (WSIAW) by explicitly incorporating green and blue water for crop productionWSIAW indicated severe water scarcity over a much broader geographical coverage compared with water scarcity based on blue water onlyWSIAW exhibited an increasing trend in many regions, mainly due to expanding cropland and increasing water withdrawals by other sectors [ABSTRACT FROM AUTHOR]

In this study, we examine the spatial and temporal characteristics of water stress in China for the historical (1971–2010) and the future (2021–2050) periods using a multimodel simulation approach. Three water stress indices (WSIs), that is, the ratios of water withdrawals to locally generated runoff (WSIR), to natural streamflow (WSIQ), and to natural streamflow minus upstream consumptive water withdrawals (WSIC), are used for the assessment. At the basin level, WSIR estimates generally match the reported data and indicate severe water stress in most northern basins. At the grid cell level, the WSIs show distinct spatial patterns of water stress wherein WSIR (WSIQ) estimates higher (lower) water stress compared to WSIC. Based on the WSIC estimates, 368 million people (nearly one third of the total population) are affected by severe water stress annually during the historical period, while WSIR and WSIQ suggest 595 and 340 million, respectively. Future projections of WSIC indicate that more than 600 million people (43% of the total) might be affected by severe water stress, and half of China's land area would be exposed to stress. The found aggravating water stress conditions could be partly attributed to the elevated future water withdrawals. This study emphasizes the necessity of considering explicit upstream and downstream relations with respect to both water availability and water use in water stress assessment and calls for more attention to increasing levels of water stress in China in the coming decades. Plain Language Summary: Severe water stress in China has been widely reported, but its time evolution and spatial patterns are rarely assessed. We examine the spatial and temporal change patterns of water stress in China by using multimodel simulations and three different water stress indices (WSIs). Results suggest that different WSIs imply distinct spatial patterns of water stress over China. The WSIs indicate that water stress conditions in northern China are quite distinct from that in southern China. During the past decades (1971–2010), severe water stress is found in northern areas while little is found in southern areas. In the future (2021–2050), however, water‐stressed areas might expand in southern China and water stress levels might aggravate in urban areas, putting considerably more people exposed to severe water stress. This assessment provides useful information for regional water planning/management within the context of future climate change and socioeconomic development in China. Key Points: Water stress estimates can be much different with the consideration of upstream water withdrawal and consumptionSevere water stress conditions are found in northern China in the pastWater‐stressed areas significantly expand over southern China in the future [ABSTRACT FROM AUTHOR]

• Effects of water withdrawal and water availability to water scarcity were separated. • Increased water withdrawal intensified water scarcity for 57.5% of global population. • Decreased water withdrawal mitigated water scarcity for several developed countries. • Water availability dominated water scarcity change for 4.8% of global population. Water scarcity has become a major issue to sustainable development. It can be estimated by available fresh water resources and human water withdrawal, which are affected by both climate change and human activities. However, the key drivers for the changes in water scarcity at global scale remain unclear due to large uncertainties in the estimations of the contributions from changes in water withdrawal and water availability. By using a newly reconstructed water withdrawal dataset and multi-model simulations of water availability, this study assessed global water scarcity evolution during 1971–2010 at half degree resolution and monthly time scale by applying the water stress index (WSI). Results showed that WSI increased in areas with 61.1% of global population during 1971–2010, and the increase in water withdrawal (especially agricultural sector) was the key driving factor for areas with 57.5% of global population. Specifically, growing water withdrawal led to increased water scarcity for areas with 21% of global population in spite of rising water availability resulted from climate change, such as in southeastern China, Southeast Asia, southern India, and Central Africa. In contrast, water scarcity mitigated over some developed areas including parts of USA, Europe and Japan with 8.8% of global population, which resulted from decreased human water withdrawal (especially industrial sector) and increased water availability. This study reveals the synergistic or contrary effects of changes in water withdrawal and water availability on the changes in water scarcity over the globe, and provides useful information for regional water planning and management. [ABSTRACT FROM AUTHOR]

• This study addresses if inter-basin water transfer transmit or buffer water scarcity. • This is a first national analysis of inter-basin water transfer and supply chain nexus. • Water transfer infrastructure increasingly supports supply chains of China. • Water transfer overall reduced virtual scarce water embedded in supply chains of China. • Changing water scarcity exposure due to water transfer showed spatial heterogeneity. Inter-basin water transfer (IBWT) infrastructure has been expanding to deliver water across China to meet water demands in populated and industrial areas. Water scarcity may threaten the ability to produce and distribute goods through supply chains. Yet, it is not clear if IBWTs transmit or buffer water scarcity throughout supply chains. Here we combine a national database of IBWT projects and multi-region input-output analysis to trace water transferred by IBWT and virtual scarce water (scarcity weighted water use) from IBWT sourcing basins to production sites then to end consumers. The results indicate that production and final consumption of sectoral products have been increasingly supported by IBWT infrastructure, with physically transferred water volumes doubling between 2007 and 2017. Virtual scarce water is about half of the virtual water supporting the supply chain of the nation. IBWT effectively reduced virtual scarce water supporting the supply chains of most provinces, with the exposure to water scarcity reduced by a maximum of 56.7% and 15.0% for production and final consumption, respectively. IBWT Infrastructure development can thus buffer water scarcity risk to the supply chain and should be considered in water management and sustainable development policy decisions. [Display omitted] [ABSTRACT FROM AUTHOR]