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The arid endorheic basin of northwest China is characterized by rich land resources, water shortage, and a fragile ecological environment. The establishment of a credible coupling model of groundwater and surface water based on multi-source observation data is an effective means to study the change in basin water cycles and the sustainable utilization of water resources in the past and future. Based on the latest understanding of hydrogeological conditions, hydrology and water resource utilization data in the middle reaches of the Heihe River Basin (HRB), this paper constructs an up-to-date coupling model of surface water and groundwater to study the water balance change of the basin. The water resources data series under historical replay and CMIP5 climate model prediction are constructed to predict future changes in water resources. The study shows that, under the joint influence of natural conditions and human activities, the average annual recharge of groundwater in the study area from 1990 to 2020 is 17.98 × 108 m3/a, the average annual discharge is 18.62 × 108 m3/a, and the difference between recharge and discharge is −0.64 × 108 m3/a. The total groundwater storage is −19.99 × 108 m3, of which the groundwater storage from 1990 to 2001 was −17.52 × 108 m3 and from 2002 to 2020 was −2.47 × 108 m3. Abundant water from 2002 to 2020 in the basin significantly improved the loss of groundwater storage. Under the prediction of historical reappearance and the CMIP5 CNRM-CM5 model RCP4.5 and RCP8.5 pathways, the groundwater level of the Heihe River–Liyuanhe River inclined plain falls first because the HRB has just experienced a wet season and then rises according to future climate change. The groundwater level of the inclined plain east of the Heihe River and Yanchi basin decreases continuously because of the change in water cycle caused by human activities. The erosion accumulation plain is located in the groundwater discharge zone, and the water level is basically stable. Under the conditions of water resource development and utilization, the runoff of Zhengyixia hydrological station cannot meet the requirements of the "97 Water Dividing Plan" of the State Council in most years in the future, and the ecological and production water in the lower reaches of HRB cannot be effectively guaranteed. With the implementation of water-saving irrigation under the RCP4.5 and RCP8.5 scenarios, the runoff of Zhengyixia can meet the "97 Water Diversion Plan". It is suggested to further improve the level of agricultural water savings in the middle reaches of the HRB and control the reasonable scale of cultivated land in order to reduce water consumption in the middle reaches of the HRB and implement sustainable utilization of water resources in the HRB. [ABSTRACT FROM AUTHOR]

Irrigated agriculture is indispensable to the Lower Mekong River Basin (LMB), which ensures food security and provides livelihoods for tens of millions of people. Irrigation, agricultural production, hydropower and aquatic ecosystem health are intertwined in LMB, so it is necessary to adopt a holistic approach to analyze irrigation problems. Here, we discuss the challenges and opportunities of LMB irrigation. Bibliometric analysis is carried out to determine the characteristics and patterns of watershed irrigation literature, such as the importance of authors, affiliated institutions, and their distribution in China. Based on bibliometric analysis, research topics are determined for thematic review. Firstly, we investigated the factors that directly affect the demand and supply of irrigation water and associated crop yield impacts. Secondly, we analyzed the influence of water availability, land use and climate change on agricultural irrigation. Thirdly, we analyzed the adverse effects of improper irrigation management on the environment, such as flow pattern change, ecosystem deterioration and land subsidence caused by groundwater overexploitation. Fourthly, the time–space mismatch between water supply and demand has brought serious challenges to the comprehensive water resources management in cross-border river basins. In each specific application area, we sorted out the technologies in which remote sensing technology is used. We hope that this review will contribute to in-depth research and decision analysis of remote sensing technology in agricultural irrigation. [ABSTRACT FROM AUTHOR]

Arid area is very sensitive to global warming and are extremely vulnerable to climate change. Moreover, the water resources system in the arid area is fragile and will undergo tremendous changes with climate change. Therefore, the interaction of climate and hydrology in arid area has an important impact on the formation of regional microclimate and hydrological changes. Daihai Lake is a typical closed inland lake in arid area of China, and a key area for ecological protection in North China. In this paper, WRF-Hydro model is used to simulate the climate hydrological coupling situation of Daihai Basin from 1980 to 2020, and the coupling results are verified and calibrated by meteorological statistics, runoff calculation and remote sensing analysis. Based on the synopsis of climate and hydrology in the past 40 years, the causes and future trends of the hydrological elements in Daihai Basin are analyzed. Through the analysis, it is found that the interannual variation of precipitation in Daihai Basin is sharp, with 401.75 mm as the average from 1980 to 1994; and drastic fluctuations from 1995 to 2011, with a difference of nearly 400 mm between the interannual maximum and minimum; From 2012 to 2020, the fluctuation is small. Although the interannual variation of evaporation fluctuated, it showed an upward trend with a slope of 8.855 mm/year. The annual average temperature showed an obvious upward trend with a slope of 0.040 °C/year. From 1980 to 2020, the inflow of Daihai Lake shows a downward trend; Since 2013, the runoff into the lake has tended to be flat. Climate change and human activities are the decisive factors leading to the change of water quantity in Daihai, among which human activities play a greater role. Cultivated land irrigation and industrial water use are highly correlated with the lake discharge, and these two factors have a great influence on the lake discharge. If the current agricultural and industrial water consumption does not increase, Daihai still has a lifespan of nearly 120 years. If human activities do not change and any protective measures are not taken in time, under the background of global climate change, the flow of the Daihai Lake into the lake will be reduced to zero in 2025, and the Daihai Lake will completely dry up in 2031–2033. The study of climate hydrological coupling of long time series in Daihai Basin can not only make up for the lack of runoff data, but also provide the basis for water resources management, disaster prevention and mitigation. [ABSTRACT FROM AUTHOR]

Arid area is very sensitive to global warming and are extremely vulnerable to climate change. Moreover, the water resources system in the arid area is fragile and will undergo tremendous changes with climate change. Therefore, the interaction of climate and hydrology in arid area has an important impact on the formation of regional microclimate and hydrological changes. Daihai Lake is a typical closed inland lake in arid area of China, and a key area for ecological protection in North China. In this paper, WRF-Hydro model is used to simulate the climate hydrological coupling situation of Daihai Basin from 1980 to 2020, and the coupling results are verified and calibrated by meteorological statistics, runoff calculation and remote sensing analysis. Based on the synopsis of climate and hydrology in the past 40 years, the causes and future trends of the hydrological elements in Daihai Basin are analyzed. Through the analysis, it is found that the interannual variation of precipitation in Daihai Basin is sharp, with 401.75 mm as the average from 1980 to 1994; and drastic fluctuations from 1995 to 2011, with a difference of nearly 400 mm between the interannual maximum and minimum; From 2012 to 2020, the fluctuation is small. Although the interannual variation of evaporation fluctuated, it showed an upward trend with a slope of 8.855 mm/year. The annual average temperature showed an obvious upward trend with a slope of 0.040 °C/year. From 1980 to 2020, the inflow of Daihai Lake shows a downward trend; Since 2013, the runoff into the lake has tended to be flat. Climate change and human activities are the decisive factors leading to the change of water quantity in Daihai, among which human activities play a greater role. Cultivated land irrigation and industrial water use are highly correlated with the lake discharge, and these two factors have a great influence on the lake discharge. If the current agricultural and industrial water consumption does not increase, Daihai still has a lifespan of nearly 120 years. If human activities do not change and any protective measures are not taken in time, under the background of global climate change, the flow of the Daihai Lake into the lake will be reduced to zero in 2025, and the Daihai Lake will completely dry up in 2031–2033. The study of climate hydrological coupling of long time series in Daihai Basin can not only make up for the lack of runoff data, but also provide the basis for water resources management, disaster prevention and mitigation. [ABSTRACT FROM AUTHOR]

Drought is a major natural hazard that can have devastating impacts on regional agriculture, water supply, ecological environment and social economy. Extreme events, including droughts, are expected to be severer and more frequent because of climate warming. This paper presents an analysis of observed changes and future projections of meteorological drought in the Daqing River Basin (DRB), North China, based on the modified Standardized Precipitation Index (SPImod). Observed changes of meteorological drought are analyzed based on the precipitation series of 26 meteorological stations from 1971 to 2011, and future projections are made under two representative concentration pathways (RCPs 4.5 and 8.5) from 2021 to 2050. The result shows a change from wet to dry detected in most areas of the DRB in summer, winter and annual series. The drought risk is higher under the condition of "OR" and "AND" return period during the observation period, and the high-risk regions cover a large area. The drought risk from 2021 to 2050 will increase across the basin under RCP 4.5 and RCP 8.5, compared with which in the base period from 1971 to 2000. Most regions will be at a higher drought risk under the condition of "OR" return period, and the area with high-risk under RCP 4.5 is slightly larger than that under RCP 8.5. Under the condition of "AND" return period, the high-risk regions will cover the area from the northwest to the northeast, while the area of high-risk regions under RCP 8.5 will be larger than that under RCP 4.5. The result of this paper will be helpful for performing an efficient water resource management in the DRB under the impacts of global warming and climate change. [ABSTRACT FROM AUTHOR]

The Heihe River basin in northwest China depends heavily on both anthropogenic and natural storage (e.g., surface reservoirs, rivers and groundwater) to support economic and environmental functions. The Qilian Mountain cryosphere in the upper basin is integral to recharging these storage supplies. It is well established that climate warming is driving major shifts in high-elevation water storage through loss of glaciers and permafrost. However, the impacts on groundwater–surface-water interactions and water supply in corresponding lower reaches are less clear. We built an integrated hydrologic model of the middle basin, where most water usage occurs, in order to explore the hydrologic response to the changing cryosphere. We simulate the watershed response to loss of glaciers (glacier scenario), advanced permafrost degradation (permafrost scenario), both of these changes simultaneously (combined scenario) and projected temperature increases in the middle basin (warming scenario) by altering streamflow inputs to the model to represent cryosphere-melting processes, as well as by increasing the temperature of the climate forcing data. Net losses to groundwater storage in the glacier scenario and net gains in the permafrost and combined scenarios show the potential of groundwater exchanges to mediate streamflow shifts. The result of the combined scenario also shows that permafrost degradation has more of an impact on the system than glacial loss. Seasonal differences in groundwater–surface-water partitioning are also evident. The glacier scenario has the highest fraction of groundwater in terms of streamflow in early spring. The permafrost and combined scenarios meanwhile have the highest fraction of streamflow infiltration in late spring and summer. The warming scenario raises the temperature of the combined scenario by 2 ∘ C. This results in net groundwater storage loss, a reversal from the combined scenario. Large seasonal changes in evapotranspiration and stream network connectivity relative to the combined scenario show the potential for warming to overpower changes resulting from streamflow. Our results demonstrate the importance of understanding the entire system of groundwater–surface-water exchanges to assess water resources under changing climatic conditions. Ultimately, this analysis can be used to examine the cascading impact of climate change in the cryosphere on the resilience of water resources in arid basins downstream of mountain ranges globally. [ABSTRACT FROM AUTHOR]

Water resources are essential for human beings. It is of significance to project future water resources carrying capacity for water resources planning and management. In this study, the Huang-Huai-Hai River Basin (HHHRB), where the contradiction between humans and water is prominent in China, is selected as the study area. The fuzzy comprehensive evaluation model of regional water resources carrying capacity is constructed, the variation characteristics of water resources affected by climate change are analyzed based on the Budyko-Fu model, and considering the influence of transit water resources and water diversion projects, the future water resources carrying capacity in HHHRB under four future climate scenarios in CMIP6 is projected. The results indicate that: (1) On the whole, the carrying capacity of water resources in HHHRB is weak, and the spatial difference is great. (2) Under the background of climate change in the future, precipitation, temperature, and water resources in HHHRB all show increasing trends with changes of 0.90–12.59%, 1.22–1.80 °C, and 13.12–34.29%. (3) Under the background of global change, the water resources carrying capacity of most prefecture-level cities in HHHRB will be greatly improved in the future, and the spatial distributions of change rates among different climate scenarios are relatively consistent. (4) The construction of water diversion projects such as the South-to-North Water Diversion Project has played an obvious role in improving the carrying capacity of water resources. The research results can provide important scientific and technological support for the rational allocation of water resources in the basin under the background of global change. [ABSTRACT FROM AUTHOR]

Determining the contributions of climate change and human activities to runoff variation is important for water resource management. An improved double mass curve method (IDMC), which can distinguish the individual impact of each climatic factor (precipitation and potential evapotranspiration), is proposed in this study to attribute runoff variation to climate change and human activities. The runoff variation characteristics of four subregions of the Jinsha River Basin (JRB) were detected using statistical methods, and the contributions of climate change and human activities to runoff variation were comprehensively assessed using IDMC, Budyko-based elasticity method, and slope change ratio of cumulative quantity analysis. Results show that annual runoff had an increasing trend in the upstream, midstream, and downstream of JRB and a decreasing trend in Yalong River Basin (YRB) of JRB during 1966–2016. Changed points in 2004, 1986, 1996, and 2005 were detected for the upstream, midstream, and downstream of JRB and YRB, respectively; the study period was, therefore, partitioned into the base period and impacted period for each subregion. Suggested attribution methods gave consistent conclusions that climate change dominated the runoff variation in the upstream of JRB with an average contribution rate of 86.5%, whereas human activities were the major force for the runoff variation in the midstream and downstream of JRB and YRB with average contribution rates of 73.0%, 113.6% and 75.8%, respectively. Furthermore, precipitation caused the increase of runoff in the upstream and midstream of JRB and the reduction of runoff in the downstream of JRB and YRB. Potential evapotranspiration caused the reduction of runoff in the subregions of JRB except for the midstream of JRB. The findings of this study are meaningful for water resources management in the JRB. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of how future climate change may affect water availability in a typical arid endorheic river basin, the Heihe River basin (HRB), in northwest China. The analysis is based on the improved Soil Water Assessment Tool (SWAT), which is calibrated and validated with historical streamflow data from the upper HRB and is used to predict future hydrological responses. Six general circulation models (GCMs), under two emission scenarios (RCP4.5 and RCP8.5), are downscaled to construct future climate change scenarios. The results suggest that the climate of the upper HRB will likely become warmer and wetter in the near future (2021-50), with the largest increase in precipitation occurring in the summer. Correspondingly, the basinwide evapotranspiration, snowmelt, and runoff are projected to increase over the same period. The mean temperature in the near future is projected to rise, relative to the recent 30 years (1981-2010), by 1.2°-1.7°C under scenario RCP4.5 and by 1.4°-2.1°C under scenario RCP8.5. The mean precipitation is projected to increase by 10.0%-16.6% under scenario RCP4.5, and by 10.5%-22.0% under scenario RCP8.5. The mean values of evapotranspiration, snowmelt, and runoff are expected to increase by 14.2%, 4.3%, and 11.4%, respectively, under scenario RCP4.5 and to increase by 18.7%, 5.8%, and 12.8%, respectively, under scenario RCP8.5. Though the model simulations forecast an increase in streamflows in the headwater region of the HRB, future water availability varies significantly over space and time. The findings of this study will help to frame more effective water management strategies for the HRB under changing climatic conditions. [ABSTRACT FROM AUTHOR]

Reference crop evapotranspiration (ET0) is of great importance in assessing the potential impacts of climate changes on hydrological cycles and the global energy balance. The spatiotemporal change of ET0 and the drought response over Poyang Lake watershed of China from 2011 to 2100 are the main concern in this work. Based on the meteorological data and the output of the general circulation model (GCM) from the Coupled Model Intercomparison Project Phase 5 (CMIP5), we used the Penman–Monteith formula and downscaling model to calculate the history and future ET0 in Poyang Lake watershed, respectively. Major results are drawn as follows. First, the annual average ET0 decreased during 1961–2014 and the average ET0 of the basin is high in the north and south, but low in the middle. The ET0 was most dominated by sunshine duration in the spring, summer, and fall and by relative humidity in the winter. Second, the downscaling model has a good simulation effect, and the GCM data-downscaling simulation results are significantly improved after the deviation correction. Third, under the representative concentration pathway (RCP) 4.5 and RCP 8.5 scenarios, ET0 in the Poyang Lake watershed will increase over the next three periods, with the middle future (2041–2070) as the largest increase period. The spatial distribution of ET0 is generally high in the east and low in the west. Fourth, under the RCP 8.5 scenario, the drought index (DI) of the watershed showed an increasing trend, the seasonal distribution of DI is fall>summer>spring>winter , and the Ganjiang River subbasin will be the key prevention area for future drought risks. The results can provide basic data support for the optimal management of water resources and scientific response to the impact of climate change on agricultural production in the watershed for associated policymakers and stakeholders. [ABSTRACT FROM AUTHOR]

As an extremely important region for the socioeconomic development of China, the Yangtze River Basin (YRB) is vulnerable to climate change and natural disasters. In recent decades, hydrological droughts have jeopardized regional water supply, local ecosystem services, and economic development in this region. This study simulates the characteristics of hydrological droughts in the YRB using the PCR-GLOBWB v2.0 model and the variable threshold method. High-spatial-resolution (about 10 km) PCR-GLOBWB v2.0 simulations considering the effects of human activities closely match the observed hydrological data for the YRB. Thus, the results indicate that human activities directly influence the tempo-spatial characteristics of hydrological droughts in the YRB. Reservoir operation decreases the multi-year monthly discharge but increases low flow in the severe drought years in the middle and lower subbasins of the YRB. These findings highlight the uneven effects of human activities on hydrological droughts in the YRB. In conclusion, anthropogenic activities must be considered when developing future mitigation and adaptation strategies for the YRB. [ABSTRACT FROM AUTHOR]

The Keriya River Basin was chosen as the study site in this paper in order to investigate the suitable scales of natural and artificial oases with a certain water resource quantity. A calculation model was constructed and the suitable scales of natural and artificial oases were analyzed using remote sensing images, water resources, weather and socioeconomic data. The results showed that (1) high- and low-flow variations were apparent for the Keriya River. The mean values for the high-flow period, normal flow period and low-flow period were 9.23 × 10 m, 7.177 × 10 m and 5.741 × 10 m, respectively. (2) The ecological water demand of natural oasis in the lower reaches of the Keriya River Basin was 2.561 × 10 m. (3) In the Tarim Basin, the proportion of natural and artificial oases was 6:4. (4) In the middle reaches, after guaranteeing the unchangeable scale of artificial oases, the most suitable size of a natural oasis was 798-1,157 km. Under the reasonable proportion (i.e. proportion of 6:4 for the natural and artificial oases), the respective suitable scales of natural and artificial oases in the middle reaches were 831-1,003 km and 554-669 km. This study constructed a model for calculating the suitable scale of an oasis, verified the suitable proportions of natural and artificial oases and discussed the reasonable scales of oases in order to provide a new theoretical basis for determining reasonable development planning in similar river basins located in extremely arid regions. [ABSTRACT FROM AUTHOR]

To manage water resources effectively, a multiscale assessment of the vulnerability of water resources on the basis of political boundaries and watersheds is necessary. This study addressed issues on the vulnerability of water resources and provided a multiscale comparison of spatial heterogeneity under a climate change background. Using improved quantitative evaluation methods of vulnerability, the Theil index and the Shannon-Weaver index, we evaluated the vulnerability of water resources and its spatial heterogeneity in the Haihe River Basin in four scales, namely, second-class water resource regions (Class II WRRs), third-class water resource regions (Class III WRRs), Province-Class II WRRs, and Province-Class III WRRs. Results show that vulnerability enhances from the north to south in the different scales, and shows obvious spatial heterogeneity instead of moving toward convergence in multiscale assessment results. Among the Class II WRRs, the Tuhai-Majia River is the most vulnerable area, and the vulnerability of the Luanhe River is lower than that of the north of the Haihe River Basin, which in turn is lower than that of the south of the Haihe River Basin. In the scales of Class III WRRs and Province-Class III WRRs, the vulnerability shows obvious spatial heterogeneity and diversity measured by the Theil index and the Shannon-Weaver index. Multiscale vulnerability assessment results based on political boundaries and the watersheds of the Haihe River Basin innovatively provided in this paper are important and useful to characterize the real spatial pattern of the vulnerability of water resources and improve water resource management. [ABSTRACT FROM AUTHOR]

Hydrological models are widely applied for simulating complex watershed processes and directly linking meteorological, topographical, land-use, and geological conditions. In this study, the Soil and Water Assessment Tool (SWAT) was calibrated at two monitoring stations, which improved model performance and increased the reliability of flow predictions in the Upper Xijiang River Basin. This study evaluated the potential impacts of climate change on the streamflow and water yield of the Upper Xijiang River Basin using Arc-SWAT. The model was calibrated (1991–1997) and validated (1998–2001) using the Sequential Uncertainty Fitting Algorithm (SUFI-2). Model calibration and validation suggest a good match between the measured and simulated monthly streamflow, indicating the applicability of the model for future daily streamflow predictions. Large negative changes of low flows are projected under future climate scenarios, exhibiting a 10% and 30% decrease in water yield over the watershed on a monthly scale. Overall, findings generally indicated that winter flows are expected to be affected the most, with a maximum impact during the January–April period, followed by the wet monsoon season in the May–September period. Water balance components of the Upper Xijiang River Basin are expected to change significantly due to the projected climate change that, in turn, will seriously affect the water resources and streamflow patterns in the future. Thus, critical problems, such as ground water shortages, drops in agricultural crop yield, and increases in domestic water demand are expected at the Xijiang River Basin. [ABSTRACT FROM AUTHOR]

Previous studies attempting to quantify the contributions of climate change and human activities to runoff variations in a changing environment have widely focused on an annual scale, while seasonal scales are rarely involved. China is the largest socialist country in the world, and its economic development is affected by its Five-year Plan policy. To this end, the upper Han River Basin, the largest tributary of the Yangtze River Basin, was selected as a case study. A seasonal-scale Budyko framework was extended based on the monthly abcd model in this study for quantifying the effects of climate and human activities changes on seasonal runoff variations, especially exploring the effect of China's Five-year Plan policy. Results disclose that: (1) the change point in the annual runoff series is 1990, and the monthly abcd model achieves good performance in the prechange and postchange period; (2) the relative contribution of climate change to runoff variations is 62.99%, 70.20%, 87.54%, and 90.30% in spring, summer, autumn, and winter, respectively, indicating that climate change is the dominant factor controlling runoff variations in every season; (3) the contributions of climate change and human activities show obvious dynamic and seasonal characteristics, which are strongly impacted by the implementation of the Five-year Plan policy. Generally, the findings of this study provide valuable references for local reasonable water resource planning and management to make timely and appropriate use of the water supply. [ABSTRACT FROM AUTHOR]

Accurate estimation of groundwater recharge is critical for evaluating the available freshwater resources in the Heihe River basin. Based on the statistical downscaling method coupled with the soil and water assessment tool, this study predicted the variations in precipitation, surface runoff, lateral flow, evapotranspiration, and groundwater recharge in the Heihe River basin under the A1B scenarios in the future 45 years (2019–2063). It was found that relative errors (Re), coefficient of determination (R2), and coefficient of Nash–Sutcliffe efficiency (Ens) at calibration and validation period were 19%, 0.90, 0.82 and 12%, 0.83, 0.75, respectively. These results indicated that the new SWAT models can be properly applied for predictions in the Heihe River basin. The next 45 years were divided into four stages, and precipitation change will follow the order stage III > stage I > stage IV > stage II. In addition, temperatures will gradually increase with time. Precipitation and evapotranspiration will be the major input and output of water resources, respectively. The surface runoff value with large precipitation stage will be nearly six times that of lateral flow. The daily highest temperature affects evapotranspiration, and the temporal variation rate of evapotranspiration is low because of extensive distribution of forests and grasslands. The groundwater recharge will reach a maximum in 2037–2046, which will be nearly two times that in 2019–2029. Groundwater recharge will be small in both 2047–2063 and 2030–2036. Precipitation is a major influence factor on groundwater recharge, but temperature slightly affects groundwater recharge. Underlying surface conditions such as land use, soil type, and properties also affect groundwater recharge. The precipitation after 2047 will not be very large, and temperatures will be high, and large evapotranspiration will lead to a rapid decrease in groundwater recharge. [ABSTRACT FROM AUTHOR]

Climate change, over abstraction, pollution and questionable engineering-based paradigms are contributing to a state of crisis in water governance. This paper reports on preliminary research in Lake Baiyangdian catchment, China, which has the potential to realise more systemic and adaptive forms of water governance through development and use of a method that reframes water catchment management in the form of social learning. A cross-disciplinary research group worked together with multiple-department managers and stakeholder representatives within a purposefully designed ‘learning system’ to create an insipient social learning platform. The results demonstrate the potential to reframe water catchment management in Lake Baiyangdian so as to better address the questions: who should manage the water catchment and what in the catchment should be the focus of managing? [ABSTRACT FROM AUTHOR]

Understanding the dominant causes of streamflow alteration and effects of the current water diversion scheme is beneficial for sustainable management of water resources in an arid area. This study presents a quantitative attribution of the run‐off changes between headstreams and mainstream from 1960 to 2015 using the Choudhury–Yang equation and evaluates the effects of 18 times of ecological water conveyance in the lower reaches of the Tarim River Basin (TRB). Our results suggest that climate change was the primary determinant of increase of the streamflow in the headstreams from 2000 to 2015. While in the mainstream, human activities played a dominant role in deduction in the streamflow with the contribution of 54.8–355.6%. Eighteen episodes of ecological water conveyance have a positive effect on rising groundwater level and are highly related to seed falling time of Shrub and Perennial herbaceous and Annual herbaceous except for Arbor. It indicates that restoring the long‐term drying of the lower reaches through continuous water conveyance is feasible, although the existing programme has not restored the entire riparian system. Our study suggests that it is necessary to adopt an integrated approach for water resources allocation rather than relying on a single tributary contribution in the TRB. [ABSTRACT FROM AUTHOR]

Climate change and hydrologic process response in the Tarim River Basin over the past 50 years are the tocus of more and more researchers' attention. In this paper, both temperature and precipitation time series were found to present a monotonic increasing trend using nonparametric tests. Noticeably, a significant step change in both temperature and precipitation time series occurred in 1986. By contrasting the trends of natural water process in headstream and mainstream, we found that it was anthropogenic activities not climate change that caused the river dried up and vegetation degenerated in the lower reaches of Tarim River. The results of gray correlation analysis show that the runoff of higher latitude distributing river is more closely associated with winter snow stocking, while that of lower latitude is more closely related to summer temperature. Runoff in the headstream is more sensitive to precipitation, while that in the mainstream is more sensitive to evaporation. The strong evaporation caused by increasing temperature weakened runoff to some extent in spite of the fact that precipitation increased over the past 50 years. [ABSTRACT FROM AUTHOR]

In ecologically fragile areas with arid climate, such as the Heihe River Basin in northwestern China, sustainable social and economic development depends largely on the availability and sustainable uses of water resource. However, there is more and more serious water resource shortage and decrease of water productivity in Heihe River Basin under the influence of climate change and human activities. This paper attempts to identify the severe water scarcity under climate change and presents possible solutions for sustainable development in Heihe River Basin. Three problems that intervened land use changes, water resource, the relevant policies and institutions in Heihe River basin were identified, including (1) water scarcity along with serious contradiction between water supply and demand, (2) irrational water consumption structure along with low efficiency, and (3) deficient systems and institutions of water resource management along with unreasonable water allocation scheme. In this sense, we focused on reviewing the state of knowledge, institutions, and successful practices to cope with water scarcity at a regional extent. Possible solutions for dealing with water scarcity are explored and presented from three perspectives: (1) scientific researches needed by scientists, (2) management and institution formulation needed by governments, and (3) water resource optimal allocation by the manager at all administrative levels. [ABSTRACT FROM AUTHOR]

Climate change and its potential threats on water security call for reliable predictions of evapotranspiration (ET) and runoff Q at different time scales, but current knowledge of the differences in their predictability between humid and nonhumid regions is limited.Based on spatially distributed catchments inChina, the authors characterized their predictability and provided plausible explanations. Using the Budyko framework, it was confirmed that annualET is predictable in nonhumid regions but less predictable in humid regions, and annualQ is predictable in humid regions but less reliable in nonhumid regions. Themain cause of the varied predictability lies in the variation of water storage change DS in the water balance equation. It affects both the estimation and the variability ofQin nonhumid catchmentsmore than that in humid catchments, which increases the challenge of predicting annual Q in nonhumid regions, while the opposite effect occurs in annual ET prediction between humid and nonhumid catchments.Moreover, the differences between the controlling factors of ET variability in different regions add more differences in their predictability. The dominant control of precipitation makes it easy to predict annual ET in nonhumid regions. By contrast, precipitation, potential evaporation, and their covariance take considerable effort to determine annualETvariations,which leads to less reliableETestimation and predictability in humid catchments. Therefore, one can accurately predict annual ET in nonhumid catchments andQ in humid catchments based on commonly used hydrological models.With proper consideration of ΔS, the predictability of annual ET and Q in both humid and nonhumid catchments can be improved. [ABSTRACT FROM AUTHOR]

The assessment of water resource responses to climate change is required in water resource planning and management, protecting environmental quality, and managing watersheds. This study modeled surface runoff and baseflow responses to variations in precipitation (0%, ±10%, and ±20%) and temperature (0 °C, ±1 °C, and ±2 °C) in 25 types of scenarios in the LanheWatershed (1140 km2), which possesses the typical hydrological and meteorological characteristics of the Loess Plateau in China. The study is based on the Soil and Water Assessment Tool (SWAT), which was calibrated and validated using the coefficient of determination (R2), Nash-Suttcliffe (Ens), and Percent bias (PBIAS), using the observed streamflow of Shangjingyou Station, a unique gauging station in the study area. The model was calibrated with daily streamflow, from 1967 to 1996, and then validated from 1997 to 2011. R2, Ens, and PBIAS were 0.95 and 0.84, 0.78 and 0.72, and 0.6% and -9.1% in annual and monthly calibration periods, 0.90 and 0.78, 0.74 and 0.67, and 22.1% and 18.8% in annual and monthly validation periods, and the overall performance ratings was ?satisfactory?. The assessment indicates that surface runoff is likely to be more affected than baseflow when altering temperatures and precipitation, and the noticeable changes of surface and baseflow are from June to September and October to November, respectively. Results also indicate that surface runoff and baseflow are very sensitive to the projected reduction in temperature, rather than to an increase of temperature, while precipitation is a constant. In turn, when the temperature is a constant, the surface runoff is sensitive to the projected increase in precipitation and the baseflow is sensitive to the decrease in precipitation. [ABSTRACT FROM AUTHOR]

Glacier runoff in mountain areas of the Shiyang River Basin (SRB), Qilian Mountain, western China is important for the river and water supply downstream. Small glaciers with area of less than 1 km are dominant (87%) in the SRB. A modified monthly degree-day model was applied to quantify the glacier mass balance, area, and changes in glacier runoff in the SRB during 1961-2050. The comparison between the simulated and observed snow line altitude, annual glacier runoff, and mass balance from 1961 to 2008 suggests that the degree-day model may be used to analyze the long-term change of glacier mass balance and runoff in the SRB. The glacier accumulation shows a significant (p<0.01) decreasing trend of −0.830 mm a. The mass balance also shows a significant (p<0.01) decreasing trend of −5.521 mm a. The glacier total runoff has significantly (p<0.05) increased by 0.079 × 10 m from 1961 to 2008. The monthly precipitation and air temperature are projected to significant (p<0.005) increase during 2015 to 2050 under three different scenarios. The ablation is projected to significant (p<0.001) increase, while the accumulation has no significant (p=0.05) trend. The mass balance is projected to decrease, the glacier area is projected to decrease, and the glacier runoff depth is projected to increase. However, the glacier total runoff is projected to decrease. These results indicate that the glacier total runoff over glacier areas observed in 1970 reached its peak in the 2000s. This will exacerbate the contradiction between water supply and downstream water demands in the SRB. [ABSTRACT FROM AUTHOR]

Restored annual streamflow ( Qr) and measured daily streamflow of the Chaohe watershed located in northern China and associated long-term climate and land use/cover data were used to explore the effects of land use/cover change and climate variability on the streamflow during 1961-2009. There were no significant changes in annual precipitation ( P) and potential evapotranspiration, whereas Qr decreased significantly by 0.81 mm/yr ( p < 0.001) over the study period with a change point in 1999. We used 1961-1998 as the baseline period ( BP) and 1999-2009 the change period ( CP). The mean Qr during the CP decreased by 39.4 mm compared with that in the BP. From 1979 to 2009, the grassland area declined by 69.6%, and the forest and shrublands increased by 105.4 and 73.1%, respectively. The land use/cover change and climate variability contributed for 58.4 and 41.6% reduction in mean annual Qr, respectively. Compared with the BP, median and high flows in the CP decreased by 38.8 and up to 75.5%, respectively. The study concludes that large-scale ecological restoration and watershed management in northern China has greatly decreased water yield and reduced high flows due to the improved land cover by afforestation leading to higher water loss through evapotranspiration. At a large watershed scale, land use/cover change could play as much of an important role as climate variability on water resources. [ABSTRACT FROM AUTHOR]

Variability of the climate in the headwater drainage basins of the Yangtze River and Yellow River during 1961-2010 was investigated by examining four typical climatic variables: daily minimum, mean, and maximum temperatures and daily precipitation. The results indicate that the temporal trends vary among the climatic variables and the time periods examined. The increase in daily minimum temperature began later than the daily mean and maximum temperatures, but the increase rate of the former was relatively greater after 1985. The abrupt increases in precipitation that occurred near 1978 were much clearer than the three temperature variables. Four dominant periodicities (3, 7, 11, and 18-20 yr) of temperature and precipitation were identified, and these variation patterns directly determined the periodic discharge variations in the two rivers. Under climate change impacts, periodic variations in temperature and precipitation at long temporal scales were intensified after the 1980s. Comparatively, climate change more severely impacts the minimum temperature and precipitation than the maximum and mean temperatures in the study area, and the variability of daily precipitation is more complex than the three temperature variables. Overall, the headwater drainage basin of the Yellow River is more susceptible to climate change compared with the other basin. After 2008, the increase rate of temperature (especially the daily mean and minimum temperatures) became greater, and precipitation showed a downward trend in the study areas. These trends are unfavorable for the safety of water resources and for eco-environmental safety in the two basins. [ABSTRACT FROM AUTHOR]

Ji, Yuhe, Liding Chen, and Ranhao Sun, 2012. Temporal and Spatial Variability of Water Supply Stress in the Haihe River Basin, Northern China. Journal of the American Water Resources Association (JAWRA) 48(5): 999-1007. DOI: 10.1111/j.1752-1688.2012.00671.x Abstract: Water resources are becoming increasingly stressed under the influence of climate change and population growth in the Haihe River Basin, Northern China. Assessing the temporal and spatial variability of water supply stress is urgently needed to mitigate water crisis caused by water resource reallocation. Water supply and use data were compiled for the time period of 1998-2003 in this synthesis study. The Water Supply Stress Index (WSSI) as defined as Water Demand/Water Supply was used to quantitate whether water supply could meet the demand of human activities across the study region. We found a large spatial gradient of water supply stress in the study region, being much higher in the eastern subbasins (ranging from 2.56 to 4.31) than the west subbasins (ranging from 0.56 to 1.92). The eastern plain region not only suffered more serious water supply stress but also had a much higher interannual variability than the western hilly region. The uneven spatial distribution of water supply stress might result from the distribution of land use, population, and climate. Future climate change and rapid economic development are likely to aggravate the existing water crisis in the study region. [ABSTRACT FROM AUTHOR]

Quantitative evaluations of the impacts of climate change on water resources are primarily constrained by uncertainty in climate projections from GCMs. In this study we assess uncertainty in the impacts of climate change on river discharge in two catchments of the Yangtze and Yellow River Basins that feature contrasting climate regimes (humid and semi-arid). Specifically we quantify uncertainty associated with GCM structure from a subset of CMIP3 AR4 GCMs (HadCM3, HadGEM1, CCSM3.0, IPSL, ECHAM5, CSIRO, CGCM3.1), SRES emissions scenarios (A1B, A2, B1, B2) and prescribed increases in global mean air temperature (1 °C to 6 °C). Climate projections, applied to semi-distributed hydrological models (SWAT 2005) in both catchments, indicate trends toward warmer and wetter conditions. For prescribed warming scenarios of 1 C to 6 C, linear increases in mean annual river discharge, relative to baseline (1961-1990), for the River Xiangxi and River Huangfuchuan are +9% and 11% per +1 C respectively. Intra-annual changes include increases in flood (Q05) discharges for both rivers as well as a shift in the timing of flood discharges from summer to autumn and a rise (24 to 93%) in dry season (Q95) discharge for the River Xiangxi. Differences in projections of mean annual river discharge between SRES emission scenarios using HadCM3 are comparatively minor for the River Xiangxi (13 to 17% rise from baseline) but substantial (73 to 121%) for the River Huangfuchuan. With one minor exception of a slight (-2%) decrease in river discharge projected using HadGEM1 for the River Xiangxi, mean annual river discharge is projected to increase in both catchments under both the SRES A1B emission scenario and 2 rise in global mean air temperature using all AR4 GCMs on the CMIP3 subset. For the River Xiangxi, there is substantial uncertainty associated with GCM structure in the magnitude of the rise in flood (Q05) discharges (-1 to 41% under SRES A1B and -3 to 41% under 2 global warming) and dry season (Q95) discharges (2 to 55% under SRES A1B and 2 to 39% under 2° global warming). For the River Huangfuchuan, all GCMs project a rise in the Q05 flow but there is substantial uncertainty in the magnitude of this rise (7 to 70% under SRES A1B and 2 to 57% under 2 global warming). Differences in the projected hydrological changes are associated with GCM structure in both catchments exceed uncertainty in emission scenarios. Critically, estimated uncertainty in projections of mean annual flows is less than that calculated for extreme (Q05, Q95) flows. The common approach of reporting of climate change impacts on river in terms of mean annual flows masks the magnitude of uncertainty in flows that are of most importance to water management. [ABSTRACT FROM AUTHOR]

The Yarlung Zangbo River is the largest river on the Tibetan Plateau and a major international river in South Asia. Changes in the blue and green water resources in its basin are of great importance to the surrounding local and Asian regions in the context of global warming. This research used the Soil and Water Assessment Tool model to estimate blue and green flows (BWF and GWF) and analyze the spatial-temporal distribution characteristics under different hypothetical climate change scenarios. The results show that (1) the multi-year average BWF in the middle and upper reaches of the Yarlung Zangbo River Basin is 176.2 mm, the GWF is 213.1 mm, and the difference between precipitation and total water resources is only 5.4 mm; (2) both BWF and GWF in this basin showed a slightly increasing trend from 1980 to 2010, but the distribution of subbasins from upstream to downstream is decreasing; and (3) GWF has a positive correlation with both precipitation and temperature, but BWF only increases with precipitation and decreases with increasing temperature. Moreover, the change in blue and green water resources is more sensitive to the changes in precipitation than to changes in the temperature. [ABSTRACT FROM AUTHOR]

Glaciers in the Tuotuo River basin, western China, have been monitored in recent decades by applying topographical maps and high-resolution satellite images. Results indicate that most of glaciers in the Tuotuo River basin have retreated in the period from 1968/1971 to 2001/2002, and their shrinkage area is 3.2% of the total area in the late 1960s. To assess the influence of glacier runoff on river runoff, a modified degree–day model including potential clear-sky direct solar radiation has been applied to the glaciated regions of the river basin over the period 1961–2004. It was found that glacier runoff has increased in the last 44 years, especially in the 1990s when a two-thirds increase in river runoff was derived from the increase in glacier runoff caused by loss of ice mass in the entire Tuotuo River basin. [ABSTRACT FROM AUTHOR]

The plausible association between climate change and the variability of water resources in the Tarim River basin, west China is investigated in this study. The long-term trend of the hydrological time series including temperature, precipitation, and streamflow are detected by using both parametric and nonparametric techniques. The possible association between the El Niño/Southern Oscillation (ENSO) and these three kinds of time series are tested. This study enhances the knowledge of the climate change impact on water resources in the Tarim River basin. The conclusion obtained in this investigation shows that the temperature experienced a significant monotonic increase at the 5% level of significance during the past 50 yr, and precipitation also exhibited an upward tendency during the past several decades. A significant jump is also detected for both time series around 1986. This may be resulted from the possible impact of climate change, although the interior climate mechanism needs further investigation. Although precipitation and the streamflow from the headwater of the Tarim River exhibited significant increase, decreasing trend has been detected in the streamflow along the mainstream of the river. It implies that anthropogenic activities instead of the climate change dominated the streamflow cessation and the drying-up of the river. Results also showed that no significant association exists between the ENSO and the temperature, precipitation and streamflow in the study area. This conclusion shows that the water curtailment, river desiccation, and ecosystem deterioration in the Tarim River basin may be mainly resulted from the impact of human activities. [ABSTRACT FROM AUTHOR]

Estimating Terrestrial Water Storage (TWS) not only helps to provide a comprehensive insight into water resource variability and the hydrological cycle but also for better water resource management. In the current research, Gravity Recovery And Climate Experiment (GRACE) data are combined with the available hydrological data to reconstruct a longer record of Terrestrial Water Storage Anomalies (TWSA) prior to 2003 of the Tarim River Basin (TRB), based on a Long Short-Term Memory (LSTM) model. We found that the TWSA generated by LSTM using soil moisture, evapotranspiration, precipitation, and temperature best matches the GRACE-derived TWSA, with a high correlation coefficient (r) of 0.922 and a Normalized Root Mean Square Error (NRMSE) of 0.107 during the period 2003–2012. These results show that the LSTM model is an available and feasible method to generate TWSA. Further, the TWSA reveals a significant fluctuating downward trend (p < 0.001), with an average decline rate of 0.03 mm/month during the period 1982–2016 in the TRB. Moreover, the TWSA amount in the north of the TRB was less than that in the south of the basin. Overall, our findings unveiled that the LSTM model and GRACE data can be combined effectively to analyze the long-term TWSA in large-scale basins with limited hydrological data. [ABSTRACT FROM AUTHOR]

Understanding and quantifying changes in hydrological systems due to human interference are critical for the implementation of adaptive management of global water resources in the changing environment. To explore the implications of hydrological variations for water resources management, the Wuding River Basin (WRB) in the Loess Plateau, China, was selected as a case study. Based on the Budyko-type equation with a time-varying parameter n, a human-induced water–energy balance (HWEB) model was proposed to investigate the hydrological variability in the WRB. The investigation showed that runoff continuously reduced by 0.424 mm/a during 1975–2010, with weakly reducing precipitation and increasing groundwater exploitation causing a decrease in groundwater storage at a rate of 1.07 mm/a, and actual evapotranspiration accounting for more than 90% of precipitation having an insignificantly decreasing trend with a rate of 0.53 mm/a under climate change (decrease) and human impact (increase). Attribution analysis indicated that human-induced underlying surface condition change played a dominant role in runoff reduction by driving an increase in actual evapotranspiration, and that mainly impacted the overall decrease in runoff compounded by climate change during the entire period. It is suggested that reducing the watershed evapotranspiration and controlling groundwater exploitation should receive greater attention in future basin management. [ABSTRACT FROM AUTHOR]

Water is the most critical factor that restricts the economic and social development of arid regions. It is urgent to understand the impact on cryospheric changes of water resources in arid regions in western China under the background of global warming. A cryospheric basin hydrological model (CBHM) was used to simulate the runoff, especially for glaciers and snowmelt water supply, in the Shiyang River Basin (SRB). A cryosphere water resources service function model was proposed to evaluate the value of cryosphere water resources. The annual average temperature increased significantly (p > 0.05) from 1961 to 2016. The runoff of glacier and snowmelt water in the SRB decreased significantly. This reduction undoubtedly greatly weakens the runoff regulation function. The calculation and value evaluation of the amount of water resources in the cryosphere of Shiyang River Basin is helpful to the government for adjusting water structure to realize sustainable development. [ABSTRACT FROM AUTHOR]

Quantitatively figuring out the effects of climate and land-use change on water resources and their components is essential for water resource management. This study investigates the effects of climate and land-use change on blue and green water and their components in the upper Ganjiang River basin from the 1980s to the 2010s by comparing the simulated changes in blue and green water resources by using a Soil and Water Assessment Tool (SWAT) model forced by five climate and land-use scenarios. The results suggest that the blue water flow (BWF) decreased by 86.03 mm year−1, while green water flow (GWF) and green water storage (GWS) increased by 8.61 mm year−1 and 12.51 mm year−1, respectively. The spatial distribution of blue and green water was impacted by climate, wind direction, topography, and elevation. Climate change was the main factor affecting blue and green water resources in the basin; land-use change had strong effects only locally. Precipitation changes significantly amplified the BWF changes. The proportion of surface runoff in BWF was positively correlated with precipitation changes; lateral flow showed the opposite tendency. Higher temperatures resulted in increased GWF and decreased BWF, both of which were most sensitive to temperature increases up to 1 °C. All agricultural land and forestland conversion scenarios resulted in decreased BWF and increased GWF in the watershed. GWS was less affected by climate and land-use change than GWF and BWF, and the trends in GWS were not significant. The study provides a reference for blue and green water resource management in humid areas. [ABSTRACT FROM AUTHOR]

Characterized by increasing surface air temperature, global warming has altered the hydrological cycle at global and regional scales. In order to adapt water resources management under the context of global warming, attribution analysis on regional differentiation of water resources in the Yangtze River basin (YRB) was conducted in this study. Meteoro-hydrological variations across the basin were examined for the period 1960–2013, and then a statistic-based method was applied in quantifying the contributions of climate variability and human activities on annual runoff variations in different tributary sub-basins in the YRB. Our observation indicates that both the annual increasing rate and the inter-annual fluctuations of temperature in China and in the YRB were higher than that of the global average since the turn of the century. Climate change analysis indicates that the YRB experienced a hot-wet period during 1994–2002 and a hot-dry period during 2003–2013, since the step change of temperature in 1993. Contributions of climate change and human activities on runoff variations varied spatially in the basin. With reference to the baseline period of 1960–1993, the contribution of climate change played a dominant role in most regions of the basin, especially in those upstream sub-basins. The effect of human activities in the basin was quite complicated, not only its regional differentiation, but also its contribution were opposite during the hot-wet period and the hot-dry period in some sub-basins. The result of this study is helpful in understanding the impacts of climate change and human activities on water resources variation in both temporal and spatial scales. [ABSTRACT FROM AUTHOR]

Conducting water resource assessment and forecasting at a basin scale requires effective and accurate simulation of the hydrological process. However, intensive, complex human activities and environmental changes are constraining and challenging the hydrological modeling development and application by complicating the hydrological cycle within its local contexts. Six sub-catchments of the Yellow River basin, the second-largest river in China, situated in a semi-arid climate zone, have been selected for this study, considering hydrological processes under a natural period (before 1970) and under intensive human disturbance (2000–2013). The study aims to assess the capacity and performance of the hydrological models in simulating the discharge under a changing environment. Four well-documented and applied hydrological models, i.e., the Xin'anjiang (XAJ) model, GR4J model, SIMHYD model, and RCCC-WBM (Water Balance Model developed by Research Center for Climate Change) model, were selected for this assessment. The results show that (1) the annual areal temperature of all sub-catchments presented a significant rising trend, and annual precipitation exhibited insignificant decline trend; (2) as a result of climate change and intensive human activities, the annual runoff series showed a declining trend with abrupt changes mostly occurring in the 1980s with the exception of the Tangnaihai station; (3) the four hydrological models generally performed well for runoff simulation for all sub-catchments under the natural period. In terms of Nash–Sutcliffe efficiency coefficient, the XAJ model worked better in comparison to other hydrological models due to its detailed representations and complicated mechanism in runoff generation and flow-routing scheme; (4) environmental changes have impacted the performance of the four hydrological models under all sub-catchments, in particularly the Pianguan River catchment, which is could be attributed to the various human activities that in turn represent more complexity for the regional hydrological cycle to some extent, and reduce the ability to predict the runoff series; (5) the RCCC-WBM model, well known for its simple structure and principles, is considered to be acceptable for runoff simulation for both natural and human disturbance periods, and is recommended for water resource assessment under changing environments for semi-arid regions. [ABSTRACT FROM AUTHOR]

The serious soil erosion problems and decreased runoff of the Loess Plateau may aggravate the shortage of its local water resources. Understanding the spatiotemporal influences on runoff changes is important for water resource management. Here, we study this in the largest tributary of the Yellow River, the Weihe River Basin. Data from four hydrological stations (Lin Jia Cun (LJC), Xian Yang (XY), Lin Tong (LT), and Hua Xian (HX)) and 10 meteorological stations from 1961–2014 were used to analyze changes in annual runoff. The Mann–Kendall test and Pettitt abrupt change point test diagnosed variations in runoff in the Weihe River basin; the time periods before and after abrupt change points are the base period (period I) and change period (period II), respectively. Within the Budyko framework, the catchment properties (ω in Fu's equation) represent land surface changes; climate variability comprises precipitation (P) and potential evapotranspiration (ET0). All the stations showed a reduction in annual runoff during the recording period, of which 22.66% to 50.42% was accounted for by land surface change and 1.97% to 53.32% by climate variability. In the Weihe River basin, land surface changes drive runoff variation in LT and climate variability drives it in LJC, XY, and HX. The contribution of land surface changes to runoff reduction in period I was less than that in period II, indicating that changes in human activity further decreased runoff. Therefore, this study offers a scientific basis for understanding runoff trends and driving forces, providing an important reference for social development, ecological construction, and water resource management. [ABSTRACT FROM AUTHOR]

Juma River, located in the Midwest of the Haihe River basin, is an important source of water supply to Beijing and Hebei. Over the past decades, the region has been seriously threatened by water shortages owing to complex climate conditions and intensive human activities. This study investigated the runoff characteristics of the Juma River by employing the Soil and Water Assessment Tool (SWAT) and stochastic methods for the period of 1961–2013. Accordingly, the runoff changes attributed to the climate variation and different types of anthropogenic activities (land use change and direct human intervention) were estimated, respectively, in conjunction with the improved quantitative response analysis. The results indicated that the annual runoff of both Zijingguan station and Zhangfang station has decreased significantly at the 0.001 significance level, and reduction rates were −0.054 billion m3 and −0.10 billion m3, respectively. Moreover, the persistency of this trend has been shown for decades (Hurst coefficient > 0.50). The SWAT model was calibrated and validated during the baseline period of 1961–1978. Significant rising temperatures and declining precipitation were the main reasons for runoff reduction, especially during the two periods of 1998–2002 and 2003–2008. Additionally, water withdrawal of Wuyi canal aggravated the runoff reduction and water scarcity conditions in the region. After 2009, the effects of direct human intervention exceeded those of climate change. However, the impact of land use change can be seen as negligible during the study period. Climate change had a greater effect on runoff reduction in winter, while the impact of human activities was more dramatic in summer. [ABSTRACT FROM AUTHOR]

The present study developed a novel approach to study the climate change impact on the water resources and generation of hydropower optimally using forecasted stream flows for the Xin'anjiang water shed in China. Future flows were projected using six large-scale Global circulation models (GCMs) with RCP4.5 and RCP8.5 scenarios. A newly developed mathematical modeling using particle swarm optimization was incorporated to work out the projected optimal electricity generation from the Xin'anjiang hydropower station. The results reveal that watershed will be warmer by the end of the 21st century with a maximum increase of up to 4.9 °C for mean maximum, and 4.8 °C for mean minimum temperature. Six GCMs under Representative Concentration pathways (RCPs) showed that future precipitation is complex to predict with certainty and significant differences were observed among the different GCMs. The overall mean monthly and seasonal precipitation increase for most scenarios with the maximum increase during the 2020s and 2080s, whereas 2050s exhibited the lesser increase. Resultantly, there would be an increase in the stream flows during these periods, which was used for electricity production up to 31.41 × 108 kW·h. [ABSTRACT FROM AUTHOR]