Water Resource Management Measures Research Articles

Study on the Driving Mechanism of Ecohydrological Regime in the Wandering Section of the Lower Yellow River

Climate change and human activities exert significant impacts on runoff generation and convergence mechanisms. Understanding the evolution mechanisms and driving forces of runoff is crucial for the sustainable development of water resources. This study is based on the runoff data of the Huayuankou (HYK), Jiahetan (JHT), and Gaocun (GC) stations in the lower reaches of the Yellow River from 1951 to 2019. The objectives are to identify and quantify the hydrological pattern and its driving mechanism of the three stations by the Mann–Kendall test, cumulative deviation method, wavelet analysis, the IHA-RVA method, SCRCO method, and the Budyko method. Our study revealed that the runoff disturbance points at all three stations occurred in 1985. During the two periods before and after the disturbance, the trends and periodicities within the year exhibited high consistency, showing an overall downward trend, with runoff increasing in October and decreasing in June and the primary cycles being 5 and 7 years. All three stations experienced high-degree changes in their hydrological situations, with the high-degree change occupying the largest proportion. At the HYK, JHT, and GC stations, human activities accounted for 66.05%, 71.94%, and 74.38% of runoff changes, respectively. Furthermore, we verified the attribution conclusion of runoff at HYK using the Budyko model, confirming that human activities are the primary factor influencing runoff. Finally, we explored the interactive relationships along the spatial trajectory of runoff at the three stations, analyzed 32 hydrological indicators, and detailed the land use changes in the Yellow River Basin. Our research findings complement the understanding of hydrological change mechanisms in the lower reaches of the Yellow River Basin and provide a scientific basis for future water resource management and flood prevention measures.

Coupled natural-social water system in a subwatershed of the Tennessee River Basin

Regional water cycle systems are increasingly characterized by the dual effect of natural and social processes, which have profound impacts on global water security. However, accurately interpreting the changes in the coupled natural-social water system and identifying the driving factors pose significant challenges. Here, we attempted to model a coupled natural-social water system in the East Fork Poplar Creek (EFPC) watershed of the Tennessee River, United States. The study area features two social water cycle components: a local water transfer project and the Oak Ridge Wastewater Treatment Facility (ORWTF). We conducted the Soil and Water Assessment Tool (SWAT) modeling in the open-source light-weight QGIS software, with the synthesis of various climate and land use change scenarios in both historical periods (1980–2016) and future periods (2017–2050). We achieved more accurate and realistic model simulations when considering the social water cycle components, indicating that the social water cycle accounted for 13–18 % of the observed streamflow. Climate variation/change dominates natural runoff changes. Though land use and cover change (LUCC) had minimal effect on natural runoff, it had a profound impact on the process of runoff generation, i.e., surface runoff (RS) and subsurface runoff (RSS). Specifically, LUCC would be responsible for 152 % and 45 % of the changes in RS and RSS, respectively, in future periods. This study highlights the significance of artificial water discharge and withdrawal impacts on the water cycle and emphasizes the need for water resources management measures that fully consider natural-social hydrological processes.

Quantitative assessment of runoff change and its drivers in a multi-scale framework

ABSTRACT Identifying runoff changes and quantifying the impacts of climate change and human activities are important for water resources planning and management in river basins. The impacts of climate change and human activities on runoff can be more accurately assessed through scientific hydrological modeling and data analysis methods. In this study, an integrated assessment framework was established to quantitatively separate the driving mechanisms of runoff at different time scales. The results show that the runoff of Wu River has shown a decreasing trend since 2004, with a change degree of 56%, and the monthly average flow indexes of August and September have changed significantly, both are over 90%. The NSE coefficient of the SWAT simulation effect is above 0.8, we validate the simulation results based on the LSTM model. It was found that climate change was the main factor affecting the runoff of Wu River, with the contribution rates reaching 60 and 57%, respectively. Pearson correlation analysis found that rainfall was the most important factor affecting the runoff. The results of this study are helpful to formulate effective water resources management policies and measures to ensure the sustainable utilization and management of water resources in the Wu River Basin.

Sensitivity of Runoff to Climatic Factors and the Attribution of Runoff Variation in the Upper Shule River, North-West China

Climate change and human activities exert significant impact on the mechanism of runoff generation and confluence. Comprehending the reasons of runoff change is crucial for the sustainable development of water resources. Taking the Upper Shule River as the research area, the M-K test and the moving t test were used to diagnose the runoff mutation time. Furthermore, the slope changing ratio of cumulative quantity method (SCRCQ), climate elasticity method, and Budyko equation were utilized to quantitatively evaluate the impacts and contribution rates of climate change and human activities. The following results were obtained: (1) The Upper Shule River experienced a significant increase in runoff from 1972 to 2021, with 1998 marking the year of abrupt change. (2) The runoff sensitivity showed a downward trend from 1972 to 2021. The main factor affecting the decrease in runoff sensitivity was the characteristic parameters of underlying surface (n), followed by precipitation (P), while the influence of potential evapotranspiration (ET0) was the weakest. (3) The response of runoff changes to runoff sensitivity and influencing factors were 90.32% and 9.68%, respectively. (4) The results of three attribution methods indicated that climate change was the primary factor causing the alteration of runoff in the Upper Shule River. The research results supplement the hydrological change mechanisms of the Upper Shule River and provide a scientific basis for future water resources management and flood control measures.

Analyzing the Impact of Dissolved Organic Components on River Water Quality and Its Implications for Human Health: A Case Study from Banjar District

Introduction: Environmental contamination, especially water quality, is a global issue. The association between river water quality and human health is explored in Banjar Regency, rich in natural resources and essential rivers, utilizing dissolved organic components concentration as an indicator. Methods: A mixed-methods study in Banjar District, South Kalimantan, Indonesia, examined the impact of river water quality on human health, using dissolved forganic components as a primary indicator. Water quality assessments, nutrient content measurements, consumption surveys, and water-related disease epidemiology provided data. The statistical studies revealed key correlations and patterns. Results and Discussion: Water quality metrics varied among sampling locations. The dissolved fish feed negatively correlated with dissolved oxygen, while nutrient content weakly correlated with gastrointestinal disorders. High water temperatures increased respiratory illnesses. Drinking water from sources with high dissolved fish feed content caused digestive and respiratory problems. The study confirms previous research linking water quality parameters to health effects. The complex relationship between water quality and health is location-dependent, illustrating how environmental factors, especially water quality, shape illness trends. Conclusion: The study illuminates the complex links between river water quality, human health, and water usage in Banjar District. Dissolved fish feed content affects digestive and respiratory disorders, emphasizing the need of water quality management for regional health. These findings guide Banjar District water resource management and public health measures and help solve worldwide environmental pollution issues.

Spatiotemporal variations of extreme weather events and climate drivers in the Three Gorges Reservoir Area and its surrounding regions from 1960 to 2020

The Three Gorges Reservoir Area and its Surrounding Region (TGRASR) play a crucial role in the Yangtze River Basin. Over the past years, there has been growing concern about the effects of extreme weather events in this area, mainly attributed to climate change. To effectively address the implications of climate change, a thorough understanding of the temporal and spatial variability of these events is necessary. However, some of the previous studies have been limited to analyzing trend changes in events and have not sufficiently considered the connection with atmospheric circulation indices. In this study, we analyzed the spatio-temporal variations of extreme weather events using the Mann-Kendall and Sen's slope trend methods. Then, the correlation between extreme weather events and climate factors is explored using the Mantel test, Geo-Detector method (GDM), and Partial wavelet coherency (PWC) in terms of linear, hierarchical heterogeneity, and nonlinear, respectively. Finally, we investigated the potential climate factors that affect the temporal and spatial variability of extreme weather occurrences. The results showed that(1) among the 12 extreme indices analyzed in the TGRASR region from 1960 to 2020, there was a decreasing trend observed in Consecutive dry days (CDD), Consecutive wet days (CWD), and Annual count of days when precipitation is ≥10 mm (R10), while the remaining indices exhibited an increasing trend. Subsequent analysis employing the M-K mutation revealed that the mutation point for CWD occurred around 1975, resulting in a significant decrease in its trend. Additionally, the Simple daily intensity index (SDII), Annual count of days when the daily maximum temperature (TX) is >25 °C (SU25), and R10 displayed a decreasing trend. Mutations in the trends SU25, Annual count of days when the daily minimum temperature (TN) is >20 °C (TR20), and Annual count of days with at least 6 consecutive days when TX > 90th percentile (WSDI) were observed in 1997, 1999, 2003, and 2005, respectively. Following these mutations, all four indices displayed a substantial increase. (2) CDD, CWD, and R10 exhibit a decreasing trend across most stations, whereas the remaining indices demonstrate an increasing trend. Regarding spatial distribution, indices characterizing precipitation frequency and intensity exhibit higher mean values in the southeastern part of the TGRASR. (3) Mantel test: North Pacific pattern (NP), North Tropical Atlantic (NTA), and Global Mean Land/Ocean Temperature (GMLOT) have significant linear correlations with extreme precipitation and extreme temperature events; GDM: GMLOT and NTA are the main contributors to extreme precipitation and extreme temperature; PWC: 12 extreme indices have some nonlinear associations with all five climate factors. The study's findings can assist decision-makers in formulating sustainable water resource management strategies and measures for mitigating drought and flood risks. Additionally, the study contributes to uncovering climatic factors that influence changes in extreme weather events.

A new factorial sensitivity model for analyzing the impacts of climatic factors on crop water footprint

The impact of climate change on the crop water footprint (WF) is highly uncertain, hindering effective agricultural water use in response to climate change. This study proposes a factor sensitivity analysis method, which can screen out statistically significant climatic factors and interactions on crop WF under various uncertainties and determine water resource management measures to mitigate drought for different crops. A special case study was conducted in Heilongjiang Province, China. The results showed that (1) the annual change in crop WF showed a downward trend from 1988 to 2018. The crop WF was dominated by green water footprint (WFgreen), and the average occupancy rate of WFgreen in crops was 58.7%–74.1 %; the spatial distribution of WF has latitude zonality. (2) Drought has different effects on WF of different crops, and WF of soybean is susceptible to drought. Wind speed, sunshine hours, and humidity have a greater impact on crop WF in most growth stages. (3) The effect of climatic factors on crop WF varies in different months. The rice WF is mainly affected by the climate in May, and there is an interaction between May humidity and May rain. The WF of maize and soybeans are affected primarily by the climate in July, especially sunshine hours. The proposed approach attempts to analyze that crop WF is affected by not only an individual climatic factor but also their interactions. Crop water management practices should be adjusted based on the results to mitigate the adverse impact of climatic conditions on crop WF during different growing months.

THE HARVESTED RAINWATER AS A SOURCE OF NON-DRINKING WATER SUPPLY IN TYPICAL RESIDENTIAL MICRODISTRICTS OF UKRAINIAN CITIES

Ukraine, facing water resource scarcity, finds it increasingly challenging to provide high-quality drinking water for both its population and industries, particularly in times of war. Harvested rainwater, among these sources, aligns well with water resource protection and management measures to counteract drinking water shortages. A literature review indicates that domestic needs in cities (flushing toilets, cleaning, and laundry) account for over 50% of drinking water demand, which could be supplemented by harvested rainwater. The estimated volume of harvested rainwater for a residential building in Odesa and Uzhgorod showed a drinking water saving to 15% and 36.5%, respectively. Similar calculations were carried out for residential microdistricts with high-rise buildings in these cities, showing a saving of drinking water due to the use of rainwater to 9% and 19%, respectively.

Hydroclimatic trends, breakpoints and future projection analysis of the Ogun River Basin in West Africa

Abstract Trend analysis is important to understand the performance and features of hydrological variables over a long-time scale. This study analyses the hydroclimatic trends in precipitation, temperature (minimum and maximum) data from seven synoptic stations and river discharge from three outlets that were investigated between 1984–2019 and projected between 2020–2060 over the Ogun River Basin. The results of the trend analysis showed a non-significant positive trend in precipitation and a significant positive trend (p,0.05 and p,0.01 significant trends) in maximum and minimum temperatures. The discharge reveals a non-significant positive trend on the annual scale while a significant decreasing trend in the dry season. The annual rainfall projection is expected to increase by 1.3% under RCP 2.6 and 1.4% under RCP 8.5 by 2060. The mean annual temperature is expected to increase between 1.5-2.5 °C under RCP 2.6 and 2-3.5 °C under RCP 8.5 by 2060, respectively. The variations in discharge without significant changes in rainfall suggested other variables were influencing the discharge. These could be changes in river basin physical elements such as alterations in the dynamics of land use land cover changes. The findings of this study can be used for strategizing adaptation and mitigation measures for water resources management.

A comprehensive overview of groundwater salinization and recharge processes in a semi-arid coastal aquifer (Essaouira, Morocco)

Study regionThe downstream part of the Essaouira basin, Morocco, Northwestern Africa. Study focusThis study combines multivariate statistical analyses, stable isotopes, hydrogeochemical, hydrogeological, geological and remotely sensed data to gain a better understanding of the hydrological and groundwater salinization processes in a coastal aquifer. Hydrogeochemical data from 223 samples as well as stable isotope data collected during 10 sampling campaigns between 1990 and 2020 were compiled and subjected to a comprehensive analysis. Groundwater recharge obtained from the stable isotope approach was checked using a water balance method based on remote sensing data of actual evapotranspiration. New hydrological insights for the regionSeawater intrusion was detected only for the period of 2009–2020, nearby the ocean, whereas hyper-salinity due to evaporite dissolution occurred throughout the entire period (1990–2020) primarily in the southern part of the aquifer. Additionally, the isotopic mass balance model shows that aquifer recharge from the Ksob river area is mainly located in the northeastern region. Furthermore, based on average values of stable isotopes of rainfall and groundwater, preliminary results show that only months of November, December and January with rainfall higher than 54 mm contribute to groundwater recharge. The water balance approach confirmed these results, but also revealed a lower recharge in February, with a monthly average precipitation of 46 mm. The outcomes of this research enabled the construction of a comprehensive conceptual 3D model of the Essaouira coastal aquifer. The insights from this research are important to guide measures for sustainable water resources management.

To calculate the maximum annual level according to the water rating curve (on example the small River Zlaya)

The rating curve of water in the river is an important characteristic of the water regime. In this article, the series of maximum annual levels and discharges of the Zlaya River (hydrological post Priozerye, Kaliningrad region) are indicated; rating curves of Zlaya River for different years were constructed. It has been established that the number of maximum annual discharges of the Zlaya River after 1991 tends to decrease, while the linear trend of the maximum annual levels shows an increase. The largest positive drawdown of the rating curve of Zlaya River was recorded from the early 60s to the mid-70s of the 20th century, which, presumably, was affected by the commissioning of a large array of drained lands during this period. The results of the study can be used in conducting hydrological surveys, developing measures for water resources management.

Climate change rather than vegetation greening dominates runoff change in China

China leads the world in vegetation greening and accounts for one-fourth of the global net increase in leaf area over the past two decades. However, it remains elusive on the relative importance of vegetation greening and climate change on China’s hydrological cycle due to the lack of observational-based constraints on notorious model uncertainties. Here, we developed a process-based distributed hydrological model that couples a nonlinear runoff generation mechanism with a remotely-sensed evapotranspiration (ET) module. This model could well capture the spatiotemporal patterns of the main hydrological components (runoff, ET, and soil moisture) at grid scale and streamflow at watershed scale during 1982–2012 over the mainland China. We show that the changes in climatic factors (precipitation and potential ET) dominated hydrologic change at the national scale, with climate induced runoff decrease by 7.6 mm year−1 compared to 0.6 mm year−1 caused by vegetation change. Vegetation effect was primarily notable in water-limited regions as a higher correlation between vegetation contribution to runoff change and absolute leaf area index (LAI) trend in water-limited regions (r = 0.52, p < 0.01) than energy-limited regions (r = 0.19, p < 0.01). Our results highlight the significance of region-dependent differential measures for sustainable water resources management and climate change adaptation under a changing climate.

Trend analysis of hydro-climate variables in the Jemma sub-basin of Upper Blue Nile (Abbay) Basin, Ethiopia

The change in climate elements such as rainfall and temperature are determinant factors of hydrological components (e.g., streamflow, water yield, evapotranspiration). Thus, understanding the trends of hydro-climate variables are imperative for planning water resources management measures. This study examines the trends of precipitation and temperature (1980–2014) as well as streamflow (1990–2008) changes in the Jemma sub-basin of the Upper Blue Nile (Abbay) Basin. A homogeneity test was performed for pre-processing data to inspect the statistical nature of data homogeneity viz., Pettitt’s, SNHT, Buishand range test, and Von Neumann test (VNT). The Mann–Kendall (MK) test, Modified Mann–Kendall (MMK) test, Sen’s slope estimator, and Innovative trend analysis (ITA) were applied to compute the existence of trend and the magnitude of change at an annual timescale. In a nutshell, the study portrays a change in the trends of hydro-climate variables when using different statistical tests. The result showed that the mean annual temperature in many stations depicted upward trends. There is a significant increasing trend (p < 0.05) by 0.029 °C per year in the mean annual temperature of all climatic stations. Based on Sen’s slope estimator, the annual precipitation and streamflow were increased by 1.781 mm/year and 0.085 m3/s, respectively. But no significant trends were detected in precipitation and streamflow when using Sen’s slope estimator test. The results of this study are worthwhile for evaluating the trends of hydro-climatic variables in other areas of Ethiopia in particular and elsewhere in the world in general, which are fundamental for planning water resource management measures.

A comprehensive assessment of runoff dynamics in response to climate change and human activities in a typical karst watershed, southwest China

The Chengbi River Basin is a typical karst watershed in Southwest China. Understanding the effects of climate change (CC) and human activities (HAs) on hydrological process is important for regional water resources management and water security. However, a comprehensive assessment of the effects of CC and HAs on runoff dynamics at different time scales in the Chengbi River Basin is still lacking. To address these needs, we used Budyko Mezentsev-Choudhurdy-Yang and Slope change ratio of accumulative quantity methods to assess the contribution of the changing environment to annual and intra-annual runoff changes in the Chengbi River Basin. The results indicated that annual runoff time series was divided into the base phase Ta (1980–1996) and the change phase Tb (1997–2019). Compared to the natural status in Ta, the relative contributions of CC and HAs to the runoff increase in Tb were 154.86% and −54.86%. In addition, the shift in intra-annual runoff occurred in 2007 and was mainly caused by HAs, with a contribution rate of 76.22%. The increase in annual runoff in Tb could be attributed to the positive contribution of rainfall. Changes in rainfall and reservoir construction altered the original state of intra-annual runoff. Furthermore, the high degree of heterogeneity in the surface karst zone increased the runoff coefficient. The spatial unsaturation of the subsurface water-bearing media and rainfall patterns caused a significant lag effect in the response of surface runoff to rainfall. This study can help researchers and policy makers to better understand the response of karst runoff to changing environment and provide insights for future water resources management and flood control measures.

Effect of freeze–thaw process on heat transfer and water migration between soil water and groundwater

Understanding the mechanisms of water migration and heat transfer in frozen soil is essential for the selection of water resource management measures and determination of irrigation schemes for winters. However, the dynamics of the groundwater level and temperature caused by freezing and thawing and their impact on soil water redistribution remain unclear. In this field study, the mechanisms of water migration and heat transfer in the soil during the freeze–thaw period under the combined action of the surface temperature change (upper boundary) and groundwater level fluctuation (lower boundary) were comprehensively considered with the theory and method of heat transfer, freeze–thaw characteristic curves of soil, and water balance model. The results showed that: (1) The soil temperature distribution and groundwater temperature dynamics can be interpreted intuitively by the soil temperature gradient and accumulated heat storage. (2) The freeze–thaw characteristic curves of soil indicated that the soil temperature dynamics caused a phase transition of the soil water. This further changed the soil water potential and permeability by 1–2 magnitudes and 1–5 magnitudes, respectively, which affected the direction and quantity of water migration. (3) The water balance quantitatively revealed the controlling effect of groundwater level changes caused by freezing and thawing on soil moisture dynamics. About 20% of the ice in the frozen layer was formed by the upward recharge of the groundwater during the freezing period. In the thawing period, most of this water returned to the groundwater (84%), while the rest (16%) increased the soil water content. These results systematically explain the mechanisms of heat transfer and water migration between the soil water and the groundwater during the freeze–thaw period, providing a theoretical reference for agricultural water management in seasonally frozen regions.

Evaluation and prediction of water resources carrying capacity using a multiple linear regression model in Taizhou City, China

To identify the status of the water resources carrying capacity in Taizhou City in China, this article selected 17 evaluation indicators and used principal component analysis to analyze the factors influencing that capacity. Then, an evaluation model was established to assess the water resources carrying capacity in Taizhou City from 2011 to 2020, and a multiple linear regression model was established to predict the total water consumption from 2021 to 2026. The results showed that as Taizhou has constructed a water-saving society, its water resources carrying capacity has gradually increased. As a result, the total water consumption is predicted to show a downward trend from 2021 to 2026. Based on the evaluation and prediction results of water resources carrying capacity, some water resources management and control measures for Taizhou were proposed, such as strengthening strict water resources management, upgrading to the water consumption structure and securing the ecological flow of downstream rivers. This research can provide scientific support for the rational development and utilization of water resources in the Taizhou City and can also set an example to similar studies over the world.

Hydrological Impact Assessment of Future Climate Change on a Complex River Basin of Western Ghats, India

Climate change (CC) affects millions of people directly or indirectly. Especially, the effect of CC on the hydrological regime is extensive. Hence, understanding its impact is highly essential. In this study, the Bharathapuzha river basin (BRB) lying in the Western Ghats region of southern India is considered for CC impact assessment, as it is a highly complex and challenging watershed, due to its varying topographical features, such as soil texture, land use/land cover types, slope, and climatology, including rainfall and temperature patterns. To understand the CC impact on the hydrological variables at BRB in the future, five downscaled global circulation models (GCMs) were used, namely BNU-ESM, Can-ESM, CNRM, MPI-ESM MR, and MPI-ESM LR. These GCMs were obtained for two representative concentration pathway (RCP) scenarios: 4.5 representing normal condition and 8.5 representing the worst condition of projected carbon and greenhouse gases concentration on the lower atmosphere. To obtain the continuous simulation of hydrological variables, the SWAT hydrological model was adopted in this study. Results showed that rainfall pattern, evapotranspiration, and soil moisture will increase at moderate to significant levels in the future. This is especially seen during the far future period (i.e., 2071 to 2100). Similar results were obtained for surface runoff. For instance, surface runoff will increase up to 19.2% (RCP 4.5) and 36% (RCP 8.5) during 2100, as compared to the average historical condition (1981–2010). The results from this study will be useful for various water resources management and adaptation measures in the future, and the methodology can be adopted for similar regions.

Comprehensive analysis of water resources from the perspective of water footprint and water ecological footprint: a case study from Anyang City, China.

Agriculture is the largest freshwater consumer, accounting for ~ 70% of global freshwater consumption. The agricultural water footprint (WF) and water resources ecological footprint (EFw) are used to describe the ecological environment and socioeconomic functions of water resources. Anyang in the North China Plain is a typical area with freshwater shortage and was selected as a study area to estimate water consumption by agriculture. We estimated the spatiotemporal variation of green, blue, and grey WF of five crops in Anyang during 1990-2018 based on the WF theory, EFw, and water resources carrying capacity (ECw) methods. To analyze the EFw of specific crops, we developed the framework between agricultural WF and EFw, and quantified the EFw of specific crops. The results show that the WFgreen, WFblue, and WFgrey of Anyang increased from 1188, 1560, and 511 million m3 in 1990 to 1440, 1736, and 1010 million m3 in 2018, respectively, mainly owing to the increase of cultivated area and amount of agricultural nitrogen. Winter wheat and maize were the two leading crops in both green and blue water consumption, taking 31.35 and 55.25% of the total WFgreen, and 71.32 and 22.52% of the total WFblue, respectively. The average unit mass WFgreen and WFblue of crops showed a reducing trend during 1990-2018 because of the urbanization of farmland and the increase of crop yields. Both ECw and water ecological deficit per capital in Anyang decreased. Anyang has been in a state of water ecological deficit since 2000. The results imply that Anyang has been importing a large amount of water from other areas for its consumption since 2000. This study is expected to contribute to agricultural water management by providing suitable information to policy-makers. Furthermore, the results of this study indicate that it is urgent to make strict water resource management and water pollution prevention measures to improve the water use efficiency in Anyang and to ease the pressure on water scarcity.

Dynamic change of inter-regional virtual water transfers in China: Driving factors and economic benefits

Whether rapid urbanization promote inter-regional virtual water transfers, and whether economic benefits produced by virtual water trade differ across regions, which have become the two significant issues concerned by relevant stakeholders. To this end, on the basis of investigating dynamic change of inter-regional virtual water transfers in Chinese 30 provinces from 2002 to 2015, this paper constructed the Logarithmic Mean Divisia Index models to analyze the factors driving such change, particularly the impacts from the urbanization, and evaluated quantitatively regional economic benefits resulted from virtual water transfers, so as to develop relevant policies that potentially facilitate optimal allocation of water resources. Results indicated that compared to that from 2002 to 2007, the total volume of inter-regional virtual water transfers in China were smaller during 2010 and 2015. The rapid development of urbanization within China continued to improve the increase in the trend of virtual water flowing out of water-scarce regions. Moreover, regarding provincial economic benefits resulted from inter-regional virtual water trade, the ratio of income to loss for most provinces in the eastern region was greater than one, while the ratio was less than one for the rest of China. Furthermore, this paper articulated more targeted water resources management measures from the perspective of the economically benefited regions and the economically damaged regions. • Rapid urbanization facilitated inter-regional virtual water transfers. • Water shortages in northern China had become more severe owing to rapid urbanization. • The ratio of income to loss for eastern regions was greater than one.

The timing of unprecedented hydrological drought under climate change

Droughts that exceed the magnitudes of historical variation ranges could occur increasingly frequently under future climate conditions. However, the time of the emergence of unprecedented drought conditions under climate change has rarely been examined. Here, using multimodel hydrological simulations, we investigate the changes in the frequency of hydrological drought (defined as abnormally low river discharge) under high and low greenhouse gas concentration scenarios and existing water resource management measures and estimate the time of the first emergence of unprecedented regional drought conditions centered on the low-flow season. The times are detected for several subcontinental-scale regions, and three regions, namely, Southwestern South America, Mediterranean Europe, and Northern Africa, exhibit particularly robust results under the high-emission scenario. These three regions are expected to confront unprecedented conditions within the next 30 years with a high likelihood regardless of the emission scenarios. In addition, the results obtained herein demonstrate the benefits of the lower-emission pathway in reducing the likelihood of emergence. The Paris Agreement goals are shown to be effective in reducing the likelihood to the unlikely level in most regions. However, appropriate and prior adaptation measures are considered indispensable when facing unprecedented drought conditions. The results of this study underscore the importance of improving drought preparedness within the considered time horizons.