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• Introducing the DPSIRM model to establish an evaluation indicator system. • Utilize the Extension Cloud Model to assess the health status of the water cycle. • Introduced the Degree of Obstacle Model to analyze the main obstacle factors in 11 provinces and cities. • Utilized the ARIMA model to forecast the future health of water circulation. • Put forward relevant suggestions according to the evaluation results. The regional water cycle reflects the dual processes of nature and society. A healthy and benign water cycle is a fundamental guarantee for achieving regional sustainable development.The Yangtze River Economic Belt, as a densely populated urban cluster with abundant water resources in China, plays a crucial role in promoting the sustainable development of Chinese urban clusters. It is of significant importance to optimize the water cycle health of the Yangtze River Economic Belt and explore its primary obstacles.This study integrates the natural-social attributes of the water cycle and selects 25 evaluation indicators from six dimensions: Drivers (D), Pressures (P), States (S), Impacts (I), Responses (R), and Management (M), to construct the water cycle evaluation system for the Yangtze River Economic Belt.Combining Analytic Hierarchy Process (AHP), Decision-Making Trial and Evaluation Laboratory (DEMATEL), and the Criteria Importance Through Intercriteria Correlation (CRITIC) method, the comprehensive weights of subjective and objective factors are obtained based on the principle of minimum relative entropy.Based on this, an Extended Cloud Model is constructed to evaluate the water cycle health status of the region from 2012 to 2022.Furthermore, the Obstacle Degree Model is introduced to identify the primary obstacles affecting the water cycle health in the region. Finally, the ARIMA model is applied to forecast the water cycle health status in the region from 2023 to 2030.The results indicate that the comprehensive water cycle health level in the region improved gradually from initially sub-pathological to sub-healthy status from 2012 to 2022.Per capita GDP, industrial water consumption per ten thousand yuan of industrial value added, per capita water consumption, forest coverage rate, sediment transport module, proportion of environmental protection investment to GDP, and proportion of water resources management investment to GDP are the primary obstacles affecting the improvement of health in this region.The forecast indicates that the overall water cycle health status in the region will remain at a sub-healthy level from 2023 to 2030.The research results can provide a scientific reference for further promoting the high-quality development of the Yangtze River Economic Belt, better supporting and serving China's modernization, and providing scientific reference basis. [ABSTRACT FROM AUTHOR]

• Vegetation greening is the major driver of ET and water resource risks. • Temperature mainly indirectly affected ET and water resource risks. • Water resource risks are concentrated in the middle and upper reaches of the YRB. • Water-saving should be prioritized in ecological restoration strategies. Quantifying the impacts of climate change, vegetation greening and human activities (CVH) on evapotranspiration (ET), surface drought intensity (ET divided by precipitation, SDI), and vegetation available water (precipitation minus ET, VAW) would improve our understanding of water cycle processes. The Yellow River Basin (YRB) is a significant climate-sensitive region in China, resulting in an obvious spatiotemporal heterogeneity of ET, SDI, and VAW in response to driving variables. In this study, we analysed the spatiotemporal variation characteristics of ET, SDI, and VAW in the YRB from 1984 to 2018. We also quantified the direct and indirect contributions of the CVH to the changes in ET, SDI, and VAW, and revealed the influence mechanism of each link. Finally, water resource risks were assessed from a probabilistic perspective. The results indicated that vegetation greening was the primary driver of ET with an increase rate of 1.60 mm/a, which was also the most important influencing factor of SDI increase and VAW decrease. Leaf area index (LAI) and relative humidity (RH) jointly dominated the ET changes in 66 % of the YRB, temperature (Temp) dominated the SDI changes in nearly half of the basin, precipitation (Pre) and LAI jointly dominated the VAW changes in 66 % of the YRB. Temp indirectly influenced ET primarily through LAI, whereas LAI primarily influenced ET directly. Temp had a significant direct impact on SDI, while LAI mainly influenced SDI through RH and wind speed (WS). Temp exhibited the most substantial negative influence on VAW. LAI was identified as the primary factor contributing to water resource risks, with a probability reaching 0.8, while the probabilities associated with other factors inducing such risks were similar at the basin level, but disparities existed among different land use types. The findings of the study significantly enhanced our understanding of the role that the CVH played in hydrological processes, serving as a crucial foundation for achieving a balance between ecological restoration and socio-economic development in the YRB. [ABSTRACT FROM AUTHOR]

• Assessing terrestrial ecosystems' CUE and WUE responses to climate is crucial. • Carbon and water use efficiencies in most Huai River Basin exhibit synergies. • LAI, within a threshold, significantly promotes CUE and WUE synergistic change. Carbon Use Efficiency (CUE) and Water Use Efficiency (WUE) are pivotal ecological indicators. Clarifying whether they change synergistically can aid in understanding how terrestrial ecosystems adapt to climate and environmental changes. Utilizing meteorological and remote sensing data, our study assessed the spatial and temporal patterns of CUE and WUE in terrestrial ecosystems within the Huai River Basin from 2001 to 2020. Our findings revealed multi-year annual averages of 0.43 and 0.82 gC kg−1H 2 O for CUE and WUE, respectively. While CUE showed a significant increasing trend (P < 0.01), the increase in WUE was not significant (P > 0.05). The primary drivers behind temporal variations in these efficiencies included leaf area index (LAI), temperature, and soil moisture. In 77.96 % of the basin area, CUE and WUE exhibit synergistic changes. LAI was the predominant factor affecting both CUE and WUE, and dual-factor interactions amplify their influence. These insights enhance our understanding of regional carbon and water cycles and offer valuable guidance for the refinement of ecological conservation strategies. [ABSTRACT FROM AUTHOR]

• An integrated model framework was established using blue water and green water concepts to better understand the spatio-temporal evolution of water resources. • The CMIP6 and FLUS models are coupled by SWAT model. • Land use change alters local hydrological cycle processes. • Blue water and green water flow are affected by climate, and green water storage is more sensitive to land use change. Exploring the spatiotemporal impacts of climate change and human activities on freshwater resources through the concepts of blue and green water can effectively improve the sustainability of basin water resource management. However, previous relevant studies have not considered the specific impacts of different climate models and land use changes on the future simultaneously. To mitigate this issue, this study proposes a hydrological modeling framework by integrating geographic detectors, Future Land Use Simulation (FLUS) models, and the Soil and Water Assessment Tool (SWAT) model. This framework was capable of identifying the major driving factors of land use changes, predicting future land use patterns, and assessing the spatiotemporal characteristics of water resources under different future climate scenarios and land use distributions. Applying the framework to the Wei River Basin (WRB) in northwest China, it identified the primary drivers of land use change in the WRB and quantitatively analyzed the spatiotemporal changes of blue and green water resources in the WRB under four scenarios. The results show that: 1) FLUS model and SWAT model can effectively simulate land use change and runoff process with high simulation accuracy; 2) Precipitation, temperature and GDP are the main drivers of land use change; 3) The amount of blue and green water in the middle and lower reaches of the basin is significantly higher than that in the tributaries and upper reaches. Blue water and green water flow are more affected by climate than land use, while green water storage is more sensitive to land use change. This study can provide effective information for basin land planning and rational allocation of water resources. [ABSTRACT FROM AUTHOR]

• A water cycle intensity evaluation model based on the landscape index is developed. • The evolution relationship between the water cycle and landscape pattern is explored. • Three water cycle statuses: natural circulation, moderately developed & overdeveloped. • The model can be used to predict the WCS in ungauged basins or landcover scenarios. • The model is a positively promoting RS technologies for water resources management. Landscape patterns and water cycle processes have changed significantly in recent decades as a result of intensive interference from human activities. Although the intensification of the global water cycle is well illustrated from a climate change perspective, using landscape index to characterize the evolution of water cycle have been less explored. This study aimed to investigate the water cycle status and its evolution from the perspective of landscape patterns. A water cycle intensity (WCI) evaluation model based on the landscape index was developed. Defined as the ratio of the water resource circulation to the natural circulation, the WCI was used to analyze the water cycle evolution trend in each region of the Haihe River Basin. Through correlation and dynamic change trend analyses, the patch density (PD) of the urban areas and runoff landscape index (RLI) were identified as synchronizing with the WCI changes. The mathematical relationships between the landscape indicators (PD and RLI) and WCI were explored. Thereafter, according to the WCI development and its impact on the ecological environment, three categories of water cycle statuses (WCSs) were proposed: the natural circulation status (NCS), moderately developed status (MDS), and overdeveloped status (ODS). The WCS evolution trend in the Haihe River Basin was evaluated and the results showed all regions have evolved into a state of ODS with WCIs above 35% in 2010 and five of the plain regions greater than 80%. The proposed approach can be effectively applied to evaluating and predicting WCS in ungauged basins or future landcover scenarios, thereby providing a new perspective and effective tools for water resource management. [ABSTRACT FROM AUTHOR]

• GPP/T increase and T/ET decrease respectively dominates WUE increase and decrease. • Below 1000 m, the increase in LAI dominates the increase in GPP/T. • Between 1000 and 2700 m, the decrease in VPD dominates the increase in GPP/T. • Above 2700 m, the increase in SM dominates the increase in GPP/T. • The decrease in LAI dominates the decrease in T/ET at varying altitudes. Water use efficiency (WUE) is commonly expressed as the ratio of gross primary productivity (GPP) to evapotranspiration (ET) and reflects the integrated impacts of water, energy, and carbon cycles on ecosystem processes. Understanding the spatiotemporal variations of WUE in the Qinling–Daba Mountains and its influencing factors will contribute to identifying the characteristics of the carbon and water cycles in Qinling–Daba Mountains within the context of climate change. This study analyzed spatiotemporal variations of WUE, GPP to transpiration ratio (GPP/T), transpiration to ET ratio (T/ET), soil moisture (SM), leaf area index (LAI), and vapor pressure deficit (VPD) in the Qinling–Daba Mountains and explored the dominant factors influencing changes in WUE. The study produced several interesting results: (1) The Distance between Indices of Simulation and Observation for the PML-GPP, PML-ET, SMCI, and MOD15A2H datasets are 0.89, 0.87, 1.22, and 1.02, respectively. Hence, they most accurately represent the conditions of GPP, ET, SM, and LAI in the Qinling-Daba Mountains, respectively. (2) GPP/T and WUE show similar spatiotemporal trends, unlike T/ET, which differs significantly. (3) At the regional scale, the contribution rate of the increase in GPP/T and the decrease in T/ET to the increase and decrease in WUE are 74.5 % and 106.83 %, respectively. At both regional and pixel scales, the increase in GPP/T and the decrease in T/ET respectively dominate the increase and decrease in WUE. (4) The increase in LAI, decrease in VPD, and increase in SM indirectly dominate the increase in WUE by controlling the increase in GPP/T at altitudes below 1000 m, between 1000 and 2700 m, and above 2700 m, respectively. The decrease in LAI indirectly dominates the decrease in WUE by controlling the decrease in T/ET at different altitude ranges. The interactions between meteorological and vegetation factors constrain WUE variations in the Qinling-Daba Mountains. [ABSTRACT FROM AUTHOR]

• Introduce an evaluation approach for the Ecological Service Value of Water (ESV-W). • Improve the assessment of Ecosystem Services Value (ESV) by introducing the Agricultural Price Index (API) into the Equivalence Factor (EF). • Improve the Water Allocation and Simulation Model (WAS) to simulate and quantify the 'natural-artificial' soil water cycle. • Analysis of the ESV and ESV-W in the Yangtze River Basin from 2005 to 2020. This paper introduces an evaluation approach for the Ecological Service Value of Water (ESV-W) by coupling the assessment of Ecosystem Services Value (ESV) with the Water Allocation and Simulation Model (WAS). The proposed method is applied to evaluate ESV and ESV-W in the Yangtze River Basin from 2005 to 2020. Firstly, an improved Equivalence Factor (EF) method is employed to estimate ESV by considering different land use types and service categories. Then, the enhanced WAS model is used to quantify and identify the role of the 'natural-artificial' soil water cycle in supporting the ecological service functions. Finally, by integrating the ESV evaluation system with the WAS model, the evaluation method for ESV-W is established. The results indicated that from 2005 to 2020, the total ESV increased from 4.0 to 5.6 trillion US Dollars, with forests being the primary contributor among land use types (about 52%), and regulating services are dominating among service categories (about 70%). The spatial distribution of the ESV showed a decreasing trend from southeast to northwest in the Yangtze River Basin, while the ESV-W exhibited high values concentrated along the main stream of the upper reaches of the Yangtze River and lower in the middle. The ESV-W of the 'natural' soil water cycle still dominates (over 96%), but the ESV-W of the 'artificial' soil water cycle has been rapidly increasing in recent years. In 2020, the ESV-W per unit water of precipitation, irrigation, and ecological water were 4.0 Dollars/ m 3 , 0.7 Dollars/ m 3 , and 32.4 Dollars/ m 3 , respectively. This study aims to provide references for the protection of water ecosystems and the sustainable utilization of water resources. It also serves as a reference for improving the evaluation system of ESV. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new concept model is proposed the first time. • Water cycle health can be described by the model and 28 indicators. • WCHI is used to conduct assessment on water cycle health. • The Central Plains Urban Agglomeration 's water cycle health showed a clear trend of change. • The research findings can provide theoretical basis for water resource evaluation in densely populated urban clusters worldwide. The health status of the water cycle has a significant impact on the sustainable development of a region. As a densely populated urban cluster, the Central Plains Urban Agglomeration plays an important role in promoting the sustainable development of China urban agglomerations. It is of great significance to optimize the water cycle health of the Central Plains Urban Agglomeration and explore its main barriers. In this article, we propose a conceptual model called DS WU N WU S WS N WS A ("Driving force—Social development uses water—Natural development uses water—Situation of social water resources—Situation of natural water resources—Ameliorate") and establish an assessment system for the water cycle health of the Central Plains Urban Agglomeration. By combining the FAHP and ICV, we use linear programming to obtain comprehensive weight values that combine subjective and objective factors. Based on this, in order to quantify the degree of WCH, we introduce the Water Cycle Health Index (WCHI) and evaluate the water cycle health of the Central Plains Urban Agglomeration from 2002 to 2022, taking into account the randomness and fuzziness of water cycle health. By introducing an obstacle degree model, we identify the main barriers to water cycle health in the Central Plains Urban Agglomeration in 2022. The results show that the proposed method for evaluating the WCH based on DS WU N WU S WS N WS A — WCHI is feasible. According to the evaluation results, the WCH of most cities in the Central Plains Urban Agglomeration is trending towards "Very healthy," with a gradual increase in WCHI , and the gap between cities is gradually narrowing. The analysis of barrier factors shows the eight main influencing factors affecting the water cycle health of the Central Plains Urban Agglomeration. The research findings of this article can provide theoretical basis for water resource evaluation, indicator construction, and policy guidance in densely populated urban clusters worldwide. [ABSTRACT FROM AUTHOR]

[Display omitted] • Between 1980 and 2018, greenspaces decreased, yet the river system still developed. • The greenspaces exhibit a trend towards fragmentation and complexity. • Changes in surface runoff and groundwater flow varied greatly in space. • Water yield is affected by both relief ratio and forest land morphology. • The Geographically Weighted Regression has high accuracy in water yield simulation. The rapid shifts in landuse and the frequency of flooding events brought by urbanization significantly impact the urban basins, which means that optimizing landscape patterns is crucial for improving urban hydrology. Therefore, the Liuxi River Basin (LRB), an important river in the Pearl River Delta region, was utilized as an example in the study to examine how the landscape configuration of greenspaces and water bodies influences the hydrological components. However, there are few studies on landscape hydrology in the Pearl River Delta (PRD) and the spatial linkages between landscape metrics and hydrological components are not clear. Based on this, this paper aims to explore the mathematical and spatial associations between landscape configuration and hydrological variables in the PRD region. The SWAT model was constructed to simulate hydrological components based on landuse changes from 1980 to 2018, and regressions were established for landscape pattern indices, water morphology parameters, and hydrological components using stepwise multiple linear regression and geographically weighted regression (GWR). According to the results, the LRB continued to develop, although the greenspaces spread out and changed shape considerably. The influence of water bodies on the hydrological component is mainly in evapotranspiration, and some three-dimensional parameters such as relief ratio favor surface runoff. In the case of greenspace, the runoff is less in connected and wide farmland areas. Irregular forest land will promote water yield but suppress evapotranspiration, and the effect of forest's shape on hydrological components is more obvious in upstream areas because the regression coefficients in this range are higher, such as 90.27. Methodologically, we found that for water yield, the accuracy of GWR was significantly higher (R2 = 0.814) than that of multiple linear regression (R2 = 0.243). In addition, understanding land use changes before conducting landscape hydrology studies can help make the results more interpretable. We supplemented the relevant research gaps in the PRD region and revealed the spatial correlation between landscape metrics and the hydrological cycle. These findings can aid urban planners in improving their comprehension of hydrological processes and landscape design, leading to more sustainable management of the urban basins. [ABSTRACT FROM AUTHOR]

• Diatom assemblages were analyzed from 45 lakes from the Tibetan Plateau (TP) region. • Diatom diversity and richness was often highest in lower salinity lakes. • Salinity and maximum lake depth best explained differences amongst assemblages. • A diatom-based salinity inference model was developed. • These data can be used to potentially reconstruct past lakewater salinity in TP lakes. The Tibetan Plateau (TP) is often referred to as the "Asian Water Tower", as it plays a crucial role in supplying water for ∼1.9 billion people. Lakes in this arid mountain region have a wide salinity gradient and are sensitive to the complex interactions between climate and the water cycle, affecting aquatic ecosystems and species distributions. Here, we analyzed relationships between measured environmental variables and the spatial distribution of surface sediment diatom assemblages from 45 lakes located throughout the TP with the intention of developing a diatom-inference model for salinity. Diatom assemblage composition and diversity differed among lakes from the western (W), southern (S), northern (N), and southeastern (E) regions of the TP. The most common taxa observed in the lake set, Pantocsekiella ocellata , Nitzschia palea , and Staurosira venter , tended to have widespread distributions across the TP. In general, diatom diversity and richness tended to be highest in lakes with salinity concentrations between 0.1 and 10 g/L and were lowest in high salinity lakes (>20 g/L) of the N region. Canonical correspondence analysis (CCA) identified lake water salinity and maximum lake depth as explaining a statistically significant portion of diatom assemblage variation. Weighted-averaging (WA) was used to develop a diatom-based salinity inference model (R2 jack = 0.71, RMSEP jack = 0.28) based on diatom optima from freshwater to meso -hyposaline lakes of the TP. Diatom-salinity reconstructions and changes in diatom community composition can potentially be used to track long-term patterns in climate and environmental conditions across the highly complex mountain landscape of the TP. [ABSTRACT FROM AUTHOR]

• The study used multisource observation data to analyze ET on Loess Plateau in China. • Actual ET from eddy covariance and simulated by HYDRUS-1D showed similar patterns. • The crop coefficient was determined around 0.8 for the actual evaporation. • Net radiation is the main factor affecting ET at daily and half-hourly time scale. • The asymmetric complementary relationship of evaporation was validated. Evapotranspiration is an important process in the hydrologic cycle. In this study, different types of daily evapotranspiration were accurately estimated and comparatively analyzed for 2020–2021 in the gully area of Loess Plateau, China with multisource observation data. The daily actual evapotranspiration was directly observed by the eddy covariance system and then compared with the daily evapotranspiration simulated by HYDRUS-1D, and they showed reasonable agreement and similar variability characteristics it with a correlation coefficient of 0.71. The FAO-56 Penman-Monteith equation was used to calculate the reference evapotranspiration and compared with the pan evaporation in the study area. The reference evapotranspiration has a single-peak pattern and seasonal variation, similar to the actual evapotranspiration process during the annual period. The crop coefficient had seasonal-variation characteristics and remained 0.8 in the mid-growth period. The correlation analysis between evapotranspiration and environmental factors at different time scales suggested that energy was the dominant factor affecting evapotranspiration in the study area. The validation results of the complementary relationship of evaporation indicated a significant asymmetric complementary relationship in the study area. Both generalized nonlinear complementary relationship functions have good applicability, but the performance of the sigmoid function was slightly better than that of the polynomial function. The results provided a reference for local water resource management and agricultural production. [ABSTRACT FROM AUTHOR]

[Display omitted] • The leaf area index of Japanese cedar significantly reduced after expansion. • The expansion of moso bamboo significantly reduced the root biomass of Japanese cedar. • Moso bamboo expansion into Japanese cader had contrasting effects on the transpiration of Japanese cedar. • The expansion reduces the root biomass by decreasing the leaf area index and directly affects the transpiration of Japanese cader. Moso bamboo (Phyllostachys edulis) expansion into adjacent forests has been reported to alter the local water cycle. Transpiration is the most important component of the water budget. However, the changes in transpiration within Japanese cedar forests following moso bamboo expansion, as well as the primary factors driving these changes, remain unclear. In this study, we conducted an investigation in a mixed plantation of Japanese cedar and moso bamboo, a pure Japanese cedar forest, and a Japanese cedar forest after the removal of moso bamboo, from July 2017 to June 2018. We measured leaf area index (LAI), root biomass (Root), and sap flow density (J s). The annual transpiration of Japanese cedar significantly decreased from 521.48 mm in the pure Japanese cedar forest to 293.34 mm in the mixed plantation of Japanese cedar and moso bamboo. Likewise, the leaf area index decreased from 5.26 to 3.96, and the root biomass decreased from 252.78 g/m2 to 160.24 g/m2. In Japanese cedar forest, the transpiration in summer (189.47 mm) is greater than the sum of transpiration in autumn and winter (143.36 mm). The partial least squares path modeling (PLS-PM) analysis demonstrated that the decrease in root biomass was the direct cause of the reduced transpiration, while the decrease in leaf area index primarily led to the decline in root biomass. The results imply that the expansion of moso bamboo changed the above-ground canopy structure of Japanese cedar through the competition of above-ground mechanical damage, which reduced the leaf area and photosynthetic capacity of Japanese cedar, and then affected the below-ground root biomass, finally leading to the reduction of transpiration and the variation of ecohydrological process. [ABSTRACT FROM AUTHOR]

[Display omitted] • This is the first study to estimate the impacts of wildfires on snow melt in the San Joaquin watershed. • Spatiotemporal visual variations in SWE were mapped in the San Joaquin watershed. • Random forest and deep analytics were performed to examine the SWE in the San Joaquin watershed. • Wildfires have increased the speed of snowmelt and shortened the timing of water availability. • The correlation between fire severity and SWE values was determined to be strongly positive. Farmers and ranchers living in snow mountainous regions heavily rely on melting snow for agricultural irrigation. However, major natural disturbances, such as wildfires, have markedly reduced melt durations, disrupting the local hydrological cycle. In this study, we estimate the impacts of wildfires on snow accumulation and retention in the San Joaquin watershed of Sierra Nevada around California during the 2000 to 2016 water year through spatiotemporal visual variations in the snow water equivalent (SWE). To better explore the relationship between SWE and wildfire, machine learning methods, including regression analysis and deep analytics, were performed to examine the original remote sensing dataset of SWE in the San Joaquin watershed. The results suggested that wildfires have greatly increased the speed of snowmelt and shortened the timing of water availability, which may result in water resource shortages. We also comparatively analyzed the peak SWE values in each year, in which two water year groups (group (1): 2000–2003, group (2): 2013–2016) were selected and compared based on the frequency of major wildfires. Interestingly, higher fluctuations in SWE curves were observed from 2010 to 2016 than from 2000 to 2003, which suggested that the frequency of wildfires was much higher in recent years than in the past twenty years. Ultimately, the correlation between fire severity and SWE values was determined to be strongly positive (p < 0.05). Overall, our study provides visual-mathematical perspectives for local ecology management authorities to understand the most related factors behind the shortened melt duration. [ABSTRACT FROM AUTHOR]

• California has shown a wide range of ombroxeric levels (OXI). • Upper strong dry level was found in the north of the State. • Lower weak arid level was found in both the Sonora and Mojave deserts. • Annual trend results have shown an increase in bioclimatic drought throughout California. • June, July and August are the months that show the highest levels of bioclimatic drought. Drought occurs naturally all over the world. Global warming has led an increase in the areas affected by this phenomenon. The study of drought involves the analysis of indicators and indices used to assess changes in the hydrological cycle of a region. A large number of indices developed for drought monitoring are based on meteorological and hydrological variables. This research has applied the Ombroxeric Index for the first time in California. It is based on the concept of ombroxericity: a condition of the territory characterised from an ombrothermic point of view, which can develop in relatively humid areas/zones, depending on the time scale of the study (i.e. monthly, seasonal or annual basis). Temperatures and precipitation from 180 meteorological stations have been considered for a period of observation from 1980 to 2016. In order to know the evolution of this index, a modified trend analysis based on the Mann-Kendall test and a modified Sen slope analysis were used. Empirical Bayesian Kriging was applied as an interpolation technique. Results are presented in both surface and contour maps. California showed a wide range of ombroxeric levels that went from upper strong dry in northern zones, to lower weak arid. Trend results showed an increase in bioclimatic drought throughout the whole State. In addition, summer showed the highest levels on the Ombroxeric Index. An increase in drought trends was observed at the seasonal level, being more pronounced in summer and spring. In both cases are increases in the central (+5 and +3.6 units year−1 respectively) and the southern (+4 and +4.5 units year−1 respectively) areas of the State. Increasing frequency and severity of droughts could have implications for the management of water resources and the survival of Californian vegetation types, such as conifers. [ABSTRACT FROM AUTHOR]

[Display omitted] • We constructed ecological network combining with semi-natural habitat planning. • Construct resistance surface was modified with 'Cultivated Land Use Intensity' • Ecosystem services assessment were used to explore optimal ecological network design. • Optimizing vegetation configuration is critical to improve the benefits of ecological networks. • Forest network accounting 10% area of the region is optimal balancing ecosystem services with yield. In modern agricultural landscapes, constructing 'ecological networks' is regarded as an efficient way to conserve biodiversity and maintain ecosystem services. Here we aimed to develop an approach to design ecological corridor by employing the ecological source - resistance surface - ecological corridor framework in combination with semi-natural habitat planning and ecosystem service trade-off assessment. 'Ecological source patches' were identified based on a 'Remote Sensing Ecological Index' (RSEI) to objectively classify ecological and environmental conditions. Our resulting spatial resistance surface was further modified used based on the 'Cultivated Land Use Intensity' index, to derive a high accuracy and rationality of ecological corridor extraction in agriculture landscape. While planning the ecological network, key nodes and resulting semi-natural habitat (SNH) distribution were identified using Linkage Mapper tools and circuit theory. We constructed ecological network scenarios with different amounts of semi-natural habitats and calculated resulting regional ecosystem service values (ESV) using an equivalence factor method to explore optimal spatial layouts. The results showed, while regional ecosystem service values generally increased in line with semi-natural habitat area contained within the ecological network, ecological networks with forests covering 10% of the total area were predicted as an optimal scenario balancing ecosystem services with agricultural yield in the study region. Networks with mixed forest and grassland cover totaling 20% of the area represented an alternative choice that strongly enhanced regional ecosystem services while may still allowing for high agricultural productivity. In constructing corridors, identifying, restoring and protecting key ecological nodes using targeted management and habitat restoration, while protecting existing wetlands and other water bodies that support regional water cycle and supply services, should be prioritized. Regional policy measures furthermore need to promote targeted ecological network planning to help improve the overall sustainability of agricultural production. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual type extraction algorithm for ecosystem conversion processes is proposed. • The area of barren converted to grassland increases at the fastest rate in 2001–2020. • In the Dwa climate zone, the reforestation project is beneficial to improve WUE. Ecosystem conversion processes in different regions of China have different impacts on carbon and water cycle changes. Water use efficiency (WUE) is a key factor in coupling ecosystem carbon and water cycles, and it is important to quantify the effects of ecosystem conversional processes on the WUE in different regions of China to improve our understanding of the effects of ecological restoration projects and ecosystem conversional processes on carbon and water cycles in different regions. In this study, we proposed a dual–type extraction algorithm for ecosystem conversion processes (DTEA–ECP) to study the impact of ecosystem conversion processes on the WUE in different regions of China from 2001 to 2020. Our results showed that in the 2001–2020 period, the area of barren ecosystem conversion to grassland ecosystem increased at the fastest rate (4.29*103 km2 y-1). In the snow climate zone with dry winters and warm summers, projects returning cropland to forest were beneficial for improving WUE. In the northwestern part of the semiarid climate zone, returning cropland to grassland was beneficial for increasing the WUE of the ecosystem, while in northeastern China, the change in WUE after the conversion of grassland ecosystem to cropland ecosystem was not significant. WUE decreased after the conversion of forest ecosystems to grassland ecosystems, while WUE increased after the conversion of grassland ecosystems to forest ecosystems. This study identified where it was most suitable to plant each vegetation type and can help with the implementation of ecological projects such as afforestation, returning farmland to forest and grass, grassland protection and wind and sand management. The results provide information support for the in-depth development of national greening and low-carbon land restoration, improve vegetation carbon sink capacity, enhance carbon emission reduction and carbon sequestration, and help to achieve the goal of peak carbon and carbon neutrality. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adding ' management (M) ' factor to DPSIR model to construct DPSIRM model. • TOPSIS model was constructed to evaluate water cycle health. • The obstacle factors of nine provinces were analyzed. • Put forward relevant suggestions according to the evaluation results. The regional water cycle reflects both natural and social processes. The health of the regional water cycle is of great significance to the sustainable development of human beings. Focusing on the nine provinces and regions in the Yellow River Basin, this study utilized the DPSIRM model, including 21 basic indicators. In this paper, according to the principle of minimum information entropy, the three-scale AHP and EFAST algorithms were combined and weighted, and water cycle health status in the nine provinces and regions was evaluated based on the hook trapezoidal fuzzy TOPSIS model. Moreover, the traditional TOPSIS model was compared with the FCE method so as to evaluate the objectivity of the results. The obstacle degree model was introduced to obtain the main obstacle factors affecting the improvement of water circulation health in the nine provinces and regions. The results show that the water circulation health status in the nine provinces and regions is tending towards health, coordination, and balance. Water consumption in the ecological environment, water consumption per CNY 10,000 of GDP and forest coverage rate are the key factors that influence the improvement of water circulation health in the nine provinces and regions. The research results herein provide a scientific reference for the nine provinces and regions to achieve a healthy urban water cycle and regional sustainable development. [ABSTRACT FROM AUTHOR]

[Display omitted] Water availability profoundly and simultaneously affects the water cycle and disturbs terrestrial carbon cycle. However, there is currently a lack of knowledge about how carbon–water coupling occurs in response to soil moisture availability, and the underlying mechanisms. Here, using two kinds of observational datasets (i.e., leaf gas exchange and ecosystem eddy-covariance), we evaluated a normalized water-use efficiency (WUE) measure (g 1 , the "stomatal conductance slope"), and explored its dynamic behavior in response to soil moisture availability. It was found that patterns of seasonal variations in WUE were not consistent between the two datasets. A contrasting response of G 1 (the capital letter denotes g 1 at the ecosystem level) to volumetric water content (VWC) during different stages of the growing season was confirmed, which was attributed to the different sensitivities of biological processes (i.e., photosynthesis and transpiration) to soil moisture availability. WUE variability during the main growing seasons was primarily controlled by transpiration, whereas WUE variability during the early and late growing seasons was mostly controlled by photosynthesis. Our findings suggest that phenology plays a significant role in regulating carbon–water coupling processes, and then exerts biotic control. The insights gained from this study will facilitate an in-depth understanding of the responses of plant biological processes to global change. [ABSTRACT FROM AUTHOR]

• WRECC indicators were selected from dualistic water cycle analysis and represented a reciprocal relationship between humans and nature. • Insufficient natural river base flow and wastewater collection rate were key water environmental issues. • Strategies for increasing recycled water use and sewage treatment efficiency were proposed to promote WRECC. Maintaining water quantity and quality are two problems that occur during water resource development. Considering the reciprocal relationship, the threshold of water resource development urgently needs to be evaluated to guarantee environmental water function. In this study, the water resources and environmental carrying capacity (WRECC) evaluation method was proposed based on dualistic water cycle analysis. Nine indicators from 4 aspects, including the water resource utilization proportion, water use efficiency, pollutant treatment efficiency, river flow, and mutual coupling in the dualistic water cycle processes, were selected to represent the comprehensive WRECC. The first-order tributary of the Yangtze River, the Tuo River Basin, was chosen to validate the method. During the year 2009 to 2018, the water environment quality was improving in the study area, and WRECC evaluation results were in accordance with the change in the water system, which showed a decreasing trend during the study periods. WRECC revealed that the upstream area had severer water pressure than the middle area, mainly coming from insufficient freshwater to support social development and provide dilution capacity. The study proposed a human water cycle intervention scenario by increasing the recycled water use rate and wastewater treatment rate to improve the WRECC, and the improvement effects can reach 30%. The WRECC method provides a useful tool for water environment management and water resource planning. [ABSTRACT FROM AUTHOR]

• WUE in the TP exhibited spatial heterogeneity, reduced under dry and cool conditions. • Grassland in most areas of the TP is resistant to hydroclimatic fluctuations. • Grassland in areas with lower temperature or higher precipitation has greater drought resistance. An increasing trend of hydroclimatic disturbances, such as droughts, which are projected to become more frequent and intense with global warming and climate change. Droughts adversely affect the structure and function of terrestrial ecosystems, damage vegetation growth, and even increase mortality. In this study, we assess the drought resistance (R d) of ecosystems in the Tibetan Plateau. Ecosystem water use efficiency (WUE) was used as an indicator of change in carbon and water cycles, and then ecosystem resistance in terms of change in WUE in drought years was analyzed. Our results suggested that the WUE in the Tibetan Plateau exhibited significant spatial heterogeneity and drastically reduced under dry and cool conditions. The evaluation of ecosystem drought resistance indicated that the grassland in most areas of the Tibetan Plateau is resistant to hydroclimatic fluctuations. In particular, the grassland ecosystem in areas with lower temperatures or higher precipitation exhibited greater drought resistance. Our results facilitate the identification of drought-vulnerable areas in the Tibetan Plateau to inform grassland ecosystem management and climate policy-making and sustain ecosystem stability under future climate conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Climate factors have synergistic effects on driving ET 0. • The annual ET 0 with insignificant increase is most sensitive to relative humidity in the LP. • Average temperatures rise dominated in the increased amount of annual ET 0 in the LP. Potential evapotranspiration (ET 0) is an important part of regional hydrological cycle and energy cycle. In the context of global climate change, it is of great significance to reveal the spatiotemporal variation of ET 0 and its response to climate change for further understanding the evolution mechanism of water cycle in changing environment. In this study, the Penman-monteith formula was utilized to calculate ET 0 in 6 sub-basins of the Loess Plateau (LP) during 1974–2019 using the daily observed data from 84 meteorological stations. The Mann-Kendall trend test and Kriging interpolation were applied to analyze the temporal and spatial characteristics of ET 0 on annual and seasonal scales. In addition, the multivariate adaptive regression splines model, sensitivity analysis and contribution rate were used to identify the driving factors of ET 0 variations by considering the synergistic effect of multiple factors. Results showed that (1) The ET 0 of LP showed an insignificant increase at a rate of 5.448 mm/10a on the annual scale. At the seasonal scale, ET 0 increased in spring and winter, but decreased in summer and autumn. Spatially, the annual average, spring, summer and autumn ET 0 showed a trend of higher north–south and lower east–west; (2) The annual ET 0 of LP is most sensitive to relative humidity (RH). At the seasonal scale, ET 0 was most sensitive to sunshine hours(S) in spring and autumn, average temperature (T) in summer and RH in winter; (3) RH is the main influencing factor of ET 0 change in the LP. At the seasonal scale, wind speed (WS) and T dominated the ET 0 variation in spring and winter, respectively. S dominated the ET 0 variation in summer and autumn; (4) The variation trend and driving factors of ET 0 in each sub-catchment were different from those in the LP, and there were significant differences among the sub-catchments. This study provides a reference for the sustainable development of vegetation restoration and the management of agricultural water resources in the LP. [ABSTRACT FROM AUTHOR]

• Detailed processes of energy and material flows are defined. • All input and output materials in the water cycle links are described. • Multiple benefits between agricultural water cycle links are quantified. • A comprehensive eco-economic evaluation in agricultural system iscarried out. • The losses to human, plants and animals caused by pollution are assessed. The current assessment of the positive and negative benefits of agricultural water use lacks a depiction of the overall internal energy flow, which lead to the identification and analysis of agricultural water use benefits are not comprehensive enough. Based on the "water supply - water use and consumption - drainage - pollutant carrying" link in the ecological economic system of agricultural water resources, the energy conversion relationship of each link were analyzed, and the main connotation and composition of the positive and negative benefits of agricultural water use were raised, then a set of emergy quantitative method system of the positive and negative benefits of agricultural water use was built. Taking Zhengzhou city as an example, the positive and negative benefits of agricultural water use in 2017 were calculated. The research results show that the negative benefits of agricultural water resources eco-economic system production account for 37.93% of the positive benefits. The main reason for the negative benefits is non-point source pollution caused by TN, TP and COD.Consequently, developing production and social policies to limit the amount of non-point source pollution caused by pollutants in agricultural production is an effective way to increase the efficiency of agricultural water production while reducing the negative benefits generated. [ABSTRACT FROM AUTHOR]

• Lagged and cumulative effects of drought on global grassland GPP are assessed. • 74.85% of the grassland shows lagged response to drought, mainly with a time scale of 1 month. • 59.06% of the grassland is affected by drought cumulatively, mainly within 2–4 months. • The cumulative effect is stronger in relatively arid area than in relatively humid area. • Globally, the cumulative effect exceeds the lagged effect for grassland productivity. Drought has large impacts on the vegetation growth of global terrestrial ecosystems, particularly grasslands. Extensive in-situ studies have shown that the impact of drought on vegetation growth has lagged and cumulative effects, but it is not well known how grassland productivity (gross primary production or GPP) responds to drought over time at large scales. Here, we investigated the spatiotemporal patterns of lagged and cumulative effects of drought on global grassland GPP using an OCO-2 solar-induced chlorophyll fluorescence (SIF) based GPP product (GOSIF GPP) and the Standardized Precipitation Evapotranspiration Index (SPEI). The results showed that globally, 88.37% of the grassland had a lagged response to drought, with a lagged time scale of mainly 1 month. With the increase in soil water availability, the magnitude of the lagged effect gradually weakened. Grasslands in semiarid and semi humid conditions that were adaptable to periodic drought responded fastest to drought. Globally, more than three quarters (78.55%) of the grassland was affected by the cumulative effect of drought. The accumulated months occurred at longer time scales (8 ∼ 10 months) for the region at 40°N–55°N, which is relatively arid. The cumulative effect in relatively arid areas was stronger than that in relatively humid areas, indicating that grasslands in more arid areas had stronger tolerance to drought. More importantly, we found that the cumulative effect of drought on grassland GPP was stronger than the lagged effect. This study highlights the great importance of considering the legacy effect, especially the cumulative effect, of drought on grassland productivity, which would advance our understanding of the impact of climate change on the carbon and water cycles of terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

• A revised method is used to estimate the economic value of green water. • Case study illustrates how economic value could further the virtual green-water trade. • Economic value can inform horizontal expansion and intensification of rainfed agriculture. • Environmental economics needs to recognise larger spatial units and the whole hydrological cycle. Green water – precipitation that is stored in the soil as moisture and consumed in the production of biomass – provides the main source of water for crop cultivation, pasturelands, forestry, and terrestrial ecosystems. At a local level, green water is land-bound and cannot be easily allocated between uses. However, at the global level, agricultural commodities and their embodied virtual water are traded between countries. This trade typically sees the cultivation of crops in water abundant rainfed locations exported to regions that would otherwise have employed local irrigation resources. The result is a global saving of irrigation water and the negative environmental externalities associated with irrigation. In addition, scarce blue water resources are freed up for other (often higher valued) uses. Here we assess whether there is an economic rationale for the virtual green-water trade and the increased and intentional allocation of crop cultivation to water abundant rainfed locations. We model a realistic case study of maize cultivation on representative farms in 16 major maize producing regions (across four continents) and provide the first spatially variable estimates of the economic value of the green water employed. These economic values are contrasted with the economic value of blue water used for irrigation. We find that the volume of green water employed in the cultivation of maize varies between 409 m3/tonne and 1547 m3/tonne; the estimated economic value of green water varies between $ −0.04 m3 and $0.12 m3. We demonstrate how these economic value estimates can inform crop allocation decisions in favour of green water-based cultivation and inform decisions regarding the intensification and horizontal expansion of rainfed agriculture. In so doing, we aim to provide a further rationale for the green water-based measures that have been identified in the literature as the principal means of providing the additional fresh water needed to address pressing global challenges beyond the case study. [ABSTRACT FROM AUTHOR]

[Display omitted] • The response of ecosystem WUE to soil moisture drought was quantitatively examined. • WUE increased significantly in most vegetated areas of the world during 1982–2018. • Drought had approximately 4-month lagged effect on WUE. • Drought-resilient ecosystems were concentrated in the Northern Hemisphere. Water use efficiency (WUE) is an ecological indicator reflecting the link between carbon and water cycles in terrestrial ecosystems, which is often affected by drought disturbance. However, knowledge about the influences of soil moisture drought on WUE is still lacking. Therefore, this paper aims to quantify the lagged effect and impact of soil moisture drought on terrestrial ecosystem WUE from 1982 to 2018 using ERA5 and Global Land Surface Satellite (GLASS) datasets. Drought conditions are described by the soil moisture anomaly percentage index (SMAPI). The lagged effect of drought on WUE is measured by the month with the maximum significant correlation between SMAPI and WUE. The impact of drought on WUE is estimated through the relative change of WUE during drought and non-drought periods. The results showed that: (1) Drought had an approximately 4-month lagged effect on WUE, which was observed in 70.87% of the global vegetated areas. The lagged effect of drought on WUE was a short period (1–4 months) for shrubland and sparse vegetation, middle and long periods (5–12 months) for forest. (2) When drought occurred, WUE decreased by 36.95% in the Tibetan Plateau and 24.93% in West Africa, while WUE in North Europe, Alaska/N.W. Canada, and West Asia increased by 14.64%, 8.83%, and 8.53%, respectively. The negative and positive impacts of drought on WUE in each vegetation type were commensurate. Our results provide useful information for understanding the response of ecosystem carbon and water cycles to drought.. [ABSTRACT FROM AUTHOR]

[Display omitted] • Global warming accelerates the water cycle, which is mainly manifested in the switching between dry and wet. • Dry-wet switching leads to the area of warm-dry, warm-wet, cold-dry and cold-wet becoming equal. • The convergence of hydrothermal pattern is conducive to the improvement of global vegetation productivity. Changes in terrestrial net primary productivity (NPP) with climate were thought to arise from the direct effects of temperature and precipitation on plant metabolism. However, the change of NPP may be due to the indirect effect of global hydrothermal pattern changes caused by climate change on vegetation distribution. To prove this hypothesis, this study uses land outside Antarctica as the study area, combines temperature and precipitation into standard scores, classifies the globe into four hydrothermal types: warm-wet, warm-dry, cold-wet and cold-dry, analyses changes in hydrothermal patterns since 2000, relates them to changes in NPP, to explains the relationship between changes in global hydrothermal patterns and NPP of vegetation. We found that climate warming reduced the area difference of the four hydrothermal types, which led to the increase of vegetation NPP. The mechanism is mainly manifested in a convergence model of hydrothermal pattern of dry wet transformation (i.e. dry to wet, wet to dry). This shows that the global water and heat distribution has a balanced trend, which is shown as a better resource allocation scheme. This perspective provides a new explanation for the increase in global NPP in terms of global hydrothermal resource allocation, which could enhance the understanding of the impact of global warming on terrestrial vegetation productivity and improve the predictions of global carbon cycle models. [ABSTRACT FROM AUTHOR]