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Quantitatively evaluation of satellite precipitation and potential evapotranspiration products with the high resolution, wide coverage and dynamic continuity is an important foundation for drought monitoring over mainland China. This paper examined the accuracy of products and the utility of drought monitoring using the newly released long-term (more than 30 years) satellite precipitation products (climate hazards group infrared precipitation with station, CHIRPS) data version 2.0 and potential evapotranspiration products (global land-surface evaporation: the Amsterdam methodology, GLEAM) dataset. We selected standardized precipitation evapotranspiration index (SPEI) and six statistical and classification measures indexes to evaluate accuracy and the utility of CHIRPS and GLEAM-Ep (potential evapotranspiration derived from GLEAM), with China Gauge-based Precipitation Daily Analysis dataset (CGDPA) and potential evapotranspiration calculated by Penman-Monteith (PM-Ep) as evaluation reference data sets. The results showed that CHIRPS and GLEAM-Ep performed well in eastern and southwest of China. However, their performance in western China was uncertain due to the sparsity of meteorological stations. SPEIs (SPEI value calculated by the CHIRPS and GLEAM-Ep) had a good performance on drought monitoring in eastern and southwestern China. Values of correlation coefficient (CC) between SPEIs and SPEIm (SPEI value calculated by the CGDPA and PM-Ep) were more than 0.6 in southeastern China, southwestern China, the middle and lower reaches of the Yangtze River region and northern China, especially in relatively humid areas, which the correlation coefficient values were more than 0.7 and the root mean-squared error (RMSE) values were less than 0.8. In order to further evaluate the performance of SPEIs in drought monitoring at spatial and temporal scales, the SPEIs3 (SPEIs at three-month scale) and SPEIm3 (SPEIm at three-month scale) in southeastern China, southwestern China, the middle and lower reaches of the Yangtze River region and northern China were compared. SPEIs3 had a better simulation effect on the evolution process of the ratio of drought area in those regions during1981-2016. And the success ratio of simulating drought duration was about 0.93, 0.57, 0.71 and 0.81, respectively. Moreover, SPEIs3 displayed a high accuracy over the four regions in capturing drought, which was the spatial distribution of typical drought events on specific month. In conclusion, SPEI based on long-term CHIRPS and GLEAM-Ep could be applied to monitor and evaluate drought in eastern and southwestern China. This paper can provide reliable reference for monitoring and warning of drought events and water resources management in those regions. [ABSTRACT FROM AUTHOR]

Global climate change is considered one of the greatest environmental threats in the world. It is expected to significantly change the global hydrological cycle. The two main water cycle components, potential evapotranspiration (PET) and precipitation (P), are closely related to vegetation dynamics. In this study, the partial correlation analysis method was used to analyzed the relationship between Normalized Difference Vegetation Index (NDVI) and climate factors (PET and P) based on grid cells. PET was calculated by FAO-56 Penman-Monteith method. Moreover, we also investigated the NDVI and climate factors in different vegetation cover types. The results showed that grassland, forest and cropland in China were positively correlated with PET and P. The time scales of the maximum partial correlation coefficients between NDVI and PET of grassland vegetation were mostly longer than 5-6 months. These time scales were longer than the time scales related to P. The partial correlation coefficients between NDVI and PET, P of forest vegetation were higher in northern China, whereas the spatial distribution of related time scales was the opposite. The partial correlation coefficients between NDVI and PET, P of forest vegetation were higher in northern China. However, the spatial distribution of related time scales was the opposite. The correlations between NDVI and PET, P of cropland vegetation and the time scales related to PET had clear spatial heterogeneity. The time scale of the correlation between NDVI and P for cropland in the northern China was about 2 months. P had a strong influence on the growth of various types of vegetation in the study area, and grassland vegetation was affected by P over the shortest time scale. We compare and analyze the results of this study with other related studies. These results provide a reference for exploring the dynamic changes in different vegetation types and factors impacting them. [ABSTRACT FROM AUTHOR]

• Significantly changes of LAI and GPP mostly occurred in eastern and southern China. • Divergence between LAI and GPP were found in regions with dense vegetation coverage. • The importance of VPD, SM, and PT to vegetation indices increased as latitude decreases. Climate change notably boosts terrestrial hydraulic redistribution pattern, which could directly affect the spatiotemporal evolution characteristics of vegetation productivity. However, the spatiotemporal evolution pattern of long-term hydrometeorological controls of vegetation productivity is still not fully understood. This paper comprehensively explored the impacts of hydrometeorological controls on leaf area index (LAI) and gross primary productivity (GPP) in China during 1982–2015 using both satellite observations and reanalysis. Vapor pressure deficit (VPD), evapotranspiration (ET), precipitation (PT), and soil moisture (SM) were used as representative indicators during investigation. The dynamics of LAI and GPP displayed increasing trends on the whole. And significantly changes mostly occurred in eastern and southern China, accompanied by moderate to dense vegetation coverage. An accelerated increasing trend for LAI could be observed since September 2003 (+0.175 per decade), while the growth rate of GPP (+16.76 g C/m2 per decade) basically maintained stable. In terms of hydrometeorological controls, VPD and ET showed consistently increasing trend and SM presented falling trend in the context of warming climate. Through analysis of feature importance index established by Random Forest, the importance of VPD, SM, and PT obviously increased as latitude decreases, which implied the high sensitivity of vegetation in semi-humid\humid regions to water availability. Additionally, divergence between LAI and GPP can be found in southern Tibet Plateau region and coastal regions, which provides compelling evidence that in the case of high LAI, increasing LAI could weaken the improvement effect on GPP. Findings of this study is expected to promote the understanding of long-term vegetation responses to hydrometeorological variations. [ABSTRACT FROM AUTHOR]

Summary: In this paper, the trends of the annual streamflow and precipitation and cross correlations between them were analyzed in nine large river basins of China during 1956–2005. The results indicate that: (1) the annual mean streamflow decreases in arid and semi-arid regions of north China; however, increasing trends occur in south and Southwest China; (2) the annual streamflow and precipitation exhibit reasonable correlation in nine large river basins except those located in inland areas. The annual streamflow over most areas of China is fed by precipitation; however, the decline in streamflow is faster than the decreases of precipitation since 1970s in the arid and semi-arid regions of north China. The relationship between the annual precipitation and streamflow presents a non-stationary state in north China. This non-stationary relationship is strongly influenced by both human activities and precipitation changes; (3) a significant increase of water use might be the major factor responsible for the steeper decline in streamflow than in precipitation in Haihe River, Yellow River and Songliao River basins in north China. In inland river areas, increase of water use and actual evapotranspiration might result in decline in streamflow although precipitation has an increase tendency. This paper sheds light on the non-stationary relationship between annual precipitation and streamflow and possible underlying causes, which will be helpful for a better understanding of the changes of precipitation and streamflow in China at large scale and in other regions of the world. [Copyright &y& Elsevier]

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Loess Plateau has great uncertainty on drought occurrence due to climate change. This paper analyzes the evolution of precipitation, potential evapotranspiration and standardized precipitation evapotranspiration index (SPEI) based on the Coupled Model Inter-comparison Project Phase 5 (CMIP5) data and regional downscaling model (RegCM4.0). Results indicate that, under RCP2.6 Scenario, the precipitation will increase significantly (5% confidence level) at the rate of 16.40 mm/10 a. However, the potential evapotranspiration is showing non-significant decreasing trend at the rate of 2.16 mm/10 a. Moreover, the SPEI will decrease in the south and northernmost area and increase in the central northern area of Loess Plateau. Under RCP8.5 Scenario, the precipitation will increase significantly (5% confidence level) at the rate of 19.12 mm/10 a. The potential evapotranspiration will non-significantly decrease at the rate of 2.16 mm/10 a and the SPEI is showing increasing trend almost in the whole Loess Plateau. Generally, Loess Plateau is becoming wetter in the central part under RCP2.6 Scenario and the wet area will be enlarged to almost the whole plateau under RCP8.5 Scenario. Based on the results, the water resources will increase under global warming, which may alleviate the water scarcity issue in the Loess Plateau. [ABSTRACT FROM AUTHOR]

Quantifying the impacts of future climate change on the ecosystem and hydrology is very important to ecohydrology research. In this paper, the vegetation model BIOME BioGeochemicalCycles (BIOME-BGC) and the Hydrological Simulation Program-FORTRAN (HSPF) are combined to investigate the potential impact of climate change on the hydrology and ecosystems of the Guishui River Basin in Beijing China, under two emission scenarios A2 and B2 of the future period 2010–2099. The projected daily maximum and minimum air temperatures, precipitation and evapotranspiration ( ET ) of HadCM3 are downscaled on to local meteorological stations using the SDSM (Statistical Downscaling Model). The model calibration and validation results are in accord with observed data of surface runoff and Net Primary Productivity (NPP). Average climate projections based on two emission scenarios were used in simulations to assess future ecohydrological responses in the Guishui River basin. Also, the uncertainties in climate change impacts are discussed in detail. The predicted daily maximum and minimum air temperatures and evapotranspiration show a reasonable upward trend, while daily precipitation and surface runoff generally show a downward trend in the next 90 years. The changing rates of daily maximum and minimum temperatures, precipitation, evapotranspiration and surface runoff are 0.46 °C, 0.45 °C, −3.68 mm/year, 15.83 mm/year and −0.05 m 3 /s (0.26 °C, 0.26 °C, −4.99 mm/year, 9.36 mm/year and −0.04 m 3 /s) per decade under A2(B2) scenarios, respectively. The results also show that global warming impacts would decrease annual discharge and increase annual NPP (at the rate of 10–30%). These results present a serious challenge for water and land management in the basin and will provide support for regional water management. [ABSTRACT FROM AUTHOR]

Based on the standardized precipitation evapotranspiration index (SPEI), a significant increase after the mid-1990s is detected in the annual number of days with drought in the zonal belt from southern Xinjiang to southern Northeast China and North China. This change features the predominant mode of the annual number of days with drought in China. Meanwhile, two significant breakpoints in 1981 and 2001 indicate a continuous increase of days with drought in the meridional belt from eastern Northwest China to eastern Southwest China. The increase in days with drought is closely related to the significant warming in the zonal belt but is attributed to both the increase of temperature and the decrease of precipitation in the meridional belt. The typical circulation patterns responsible for the increase of days with drought comprise a wave train stretching from North Atlantic to East Asia, the generally anomalous high pressure over China, the northerly anomalies prevailing over northern and central China, and the suppressed convection in most of the zonal and meridional belt. Both the AMO and the PDO after the 1980s have a close relationship with the interdecadal variation of the number of days with drought. On one hand, either a positive AMO phase or negative PDO phase motivates the typical circulation patterns favorable for the occurrence of drought. On the other hand, both the AMO and PDO affect the warming in the zonal and meridional belt, and the PDO is also closely connected with the precipitation in the meridional belt. [ABSTRACT FROM AUTHOR]

It is important to understand the hydroclimate history of water‐deficient regions, such as the Alxa desert of northwest China. However, there are few high‐resolution proxy records for the hydroclimate changes over the past centuries in the Alxa desert. Fortunately, there are many tree‐ring hydroclimate reconstructions from the nearby mountains. However, the hydroclimate correlations between the Alxa desert and adjacent mountains are unclear. Here, we collected high‐quality data from 43 meteorological stations in northwest China (1960–2017). We found increasing mean temperatures in the study area, both on seasonal and annual timescales. We also found that while relative humidity had mostly decreased in the Mt. Qilian and Alxa desert, precipitation and the standardized precipitation evapotranspiration index (SPEI) increased mostly. In the Mt. Helan and Hasi ranges, relative humidity, precipitation, and SPEI all showed decreasing trends. Empirical orthogonal function analysis indicated that precipitation, relative humidity, and SPEI in the Mt. Qilian were similar to the corresponding conditions in the central and western Alxa desert. Hydroclimate conditions in the Mt. Helan and Hasi ranges were correlated with data from the eastern desert. Tree‐ring records of precipitation and SPEI from the mountains were used to validate the hydroclimate correlations during the instrumental period. We found strong similarities between hydroclimatic changes in the Mt. Qilian and those in the central and western Alxa desert, on both annual and decadal timescales, from 1877 to 2006. Tree‐ring width chronologies from mountainous areas were shown to faithfully represent the hydroclimatic history of the desert area. Plain Language Summary: Northwestern China has faced serious ecological challenges over the past five decades, including intensified desertification and declining lake levels. Understanding the regional hydroclimate history is necessary to manage water resources in this water‐deficient region. However, there are few climate proxies for these desert areas. In contrast, high‐resolution tree‐ring climate proxies have been studied intensively in the nearby mountains. This study attempts to find reliable correlations between mountain and desert hydroclimate. We found increasing mean temperatures over the entire study area. We also found that precipitation, relative humidity, and drought index data from the western and central desert were strongly correlated with data from Mt. Qilian, while data from the eastern desert were correlated with those from the Helan and Hasi mountain ranges. When relative humidity decreased mostly in the Mt. Qilian, precipitation and SPEI mostly increased; in the Mt. Helan and Hasi areas, relative humidity, precipitation and SPEI mostly decreased. Tree‐ring records from the mountains were compared to validate these correlations. Significant correlations were found between the precipitation reconstructions from the central desert and Mt. Qilian from 1877 to 2006. We also used tree‐ring width chronologies to show that they could represent the hydroclimatic history of the Alxa desert. Key Points: Precipitation and SPEI indicate wetter trends in Mt. Qilian but drier trends in Mt. Helan and Hasi ranges from 1960 to 2017Precipitation, relative humidity, and SPEI in western and central (eastern) Alxa desert resemble conditions in Mt. Qilian (Helan and Hasi)Tree‐ring proxies from nearby mountains can faithfully represent the hydroclimate history of the Alxa desert [ABSTRACT FROM AUTHOR]

Knowledge of exchanges of energy and water over terrestrial surfaces is the first step towards understand the ecohydrological mechanisms, particularly in water‐limited ecosystems in dryland environments. However, patterns of energy exchange and evapotranspiration (ET) are not well understood in the oasis‐desert ecotone, which plays an important role in protecting oases against the threat of desertification in arid regions of northwestern China. Here, the continuous measurements of surface energy fluxes were made using eddy covariance in conjunction with auxiliary measurements for 2 years (2014–2015) in an oasis‐desert ecotone mainly covered by phreatophyte shrubs Haloxylon ammodendron, Nitraria tangutorum/sphaerocarpa, and Calligonum mongolicum in arid northwestern China. Based on the collated data for 2 years, statistical analysis on a 30‐min time scale indicated that approximately 50% of daytime net radiation (Rn) in the ecotone was dissipated as H on average, and one‐third of Rn was consumed by soil heat flux (G). Only 9% of Rn was consumed for latent heat flux (λE), which peaked in summer (21% in 2014 and 16% in 2015), corresponding to the highest rainfall season. Daily mean ET was approximately 1 mm days−1 during the growing season of the shrub species. Accumulated annual ET was 195 and 181 mm in 2014 and 2015, respectively, exceeding the corresponding precipitation (P) by approximately 87 and 77 mm, indicating that groundwater may be another important source of water for ET in the ecotone aside from rainfall. Results within provide valuable insights into the mechanisms responsible for sustaining energy and water balance in the ecotone, a potentially groundwater‐dependent ecosystem. These results also offer a foremost ecohydrological implication for water and land resources management and ecotone conservation, such as avoiding heavy groundwater pumping for extensive agricultural irrigation use to sustain groundwater availability for these shrub species in the ecotone. [ABSTRACT FROM AUTHOR]

The dry‐wet climate conditions of an area are mainly determined by the water input (e.g., precipitation, P) and output (e.g., potential evapotranspiration, PET). Based on three dry‐wet indices and the differential equation, this study designed a new attribution method to quantify the contributions of P and PET to the dry‐wet change, so as to determine the dominant factors of the dry‐wet change over whole China (CHINA) and various hydroclimate regions (i.e., arid region, AR; semi‐arid region, SAR; semi‐humid region, SHR; and humid region, HR) during 1960–2018 and six interdecadal periods. Results showed that the overall weak drying in CHINA was dominated by an increase in PET, while climate humidification in AR and HR was dominated by an increase in P, climate drying in SHR was dominated by the reduced P, and the weak drying in SAR was co‐dominated by P and PET during 1960–2018. The dominant factors of dry‐wet change over CHINA and each hydroclimate region varied in different decades. Briefly, climate humidification in CHINA and various hydroclimate regions was basically dominated by P in different decades, and the drying was mainly dominated by P in the 1960s–1980s, but the contribution of PET to climate drying began to become prominent after the 1980s. Besides, we found that P contributed more to dry‐wet change than PET on the station and regional scales, but the contribution of P to climate drying on a national scale was underestimated to some extent due to the regional offset effect of the increase/decrease in P during 1960–2018, as well as in the 1990s. These findings implied that the importance of research on the regional or local scale, and equal attention should be paid to the effects of P and PET changes in the future drought or dry‐wet change research. [ABSTRACT FROM AUTHOR]

This study investigated the attribution of terrestrial water storage (TWS) variations across China to changes in groundwater and human water use. As one vital storage component, the groundwater storage (GWS) derived from the Jet Propulsion Laboratory's GRACE (Gravity Recovery and Climate Experiment) mass concentration solution compared reasonably well with the in situ groundwater table depth, with the correlation coefficients ranging from −0.83 to −0.18, all of which were statistically significant at the 95% confidence level. About 71% of the trends in derived GWS had the same sign as those of observations, without systematic deviation, across China. The GWS variation contributed a large portion of the TWS trend in most regions of China, and the majority of contribution values reached 50%–150% in the Hai River basin, the Loess Plateau, and the middle portion of the Yangtze River basin. The dominant role of GWS is closely related to the detected long-term "memories" in both TWS and GWS. The increase of irrigation consumption accelerated the TWS depletion trend by 13.4% in the Huai River basin, while the decrease of consumptive agricultural water use alleviated the TWS decline rate by 4.1% in the Hai River basin. Importantly, the correlation coefficients reached 0.74–0.95 between the TWS change and the residual of precipitation, evapotranspiration, flow into the sea, and irrigation consumption in the four river basins of particular interest. The findings of this study are helpful for understanding regional water cycles in China. [ABSTRACT FROM AUTHOR]

Quantifying evapotranspiration (ET) and its components are particularly crucial to reveal the eco-hydrological processes in arid and semi-arid regions, such as the Horqin Sandy Land in China, but is lacking in existing literature. This study applied the Shuttleworth-Wallace (S-W) model to simulate and partition the ET at the representative landform-soil-vegetation formations (i.e., mobile dune, semi-fixed dune, and fixed dune) in Horqin Sandy Land based on the in situ data sampled by the meteorological monitoring system. Eddy covariance technology was used to validate the performance of the model. The results showed that the performance of the S-W model for clear days was better than that for cloudy or rainy days, and the S-W model would underestimate ET in rainy days. During 2017 growing season, ET showed as mobile dune (308 mm) < semi-fixed dune (333 mm) < fixed dune (352 mm), which was consistent with canopy coverage. Evaporation (E) showed as mobile dune (176 mm) > semi-fixed dune (84 mm) > fixed dune (75 mm), accounting for 57.1%, 25.2%, and 21.3% of ET, respectively. With the increase of canopy coverage, the effect of leaf area index (LAI) on E/ET increased; conversely, the effect of soil moisture decreased. There were significant differences in the variation of ET in the dry and wet periods. During the dry period, the desert vegetation maintained low water consumption and showed obvious "midday break." Compared with transpiration from canopy, evaporation from soil was more sensitive to precipitation. [ABSTRACT FROM AUTHOR]

The investigation of concentration characteristics of reference evapotranspiration (ETref) is important for water resources management. The concentration index (CI), concentration degree (CD) and concentration period (CP) are used to investigate the concentration characteristics of ETref and the relationship between ETref concentration and precipitation concentration at sub-monthly timescale based on the daily climatic variables from 1966 to 2015 in 27 meteorological stations at the southern and northern slopes of Tianshan Mountains in China. It was found that the CI of ETref is about 0.40 and less concentrated than precipitation in the study area. At the southern slope, the maximum ETref appears in late June and is earlier than the maximum precipitation (early July), ETref distributes more equally than precipitation, and the CI, CD and CP of these two variables do not show significant change based on the Mann-Kendall test. At the northern slope, both the maximum ETref and precipitation appear in early July, and ETref is more dispersed than precipitation. During the study period, the maximum ETref at the northern slope tends to appear earlier due to the impacts of wind speed, relative humidity, sunshine duration, and air temperature. ETref concentration does not match the precipitation concentration in the study area, particularly at the southern slope. The mismatch between ETref and precipitation concentration within a year reveals the water resources pressure on environmental, social and economic sustainability in the study area. [ABSTRACT FROM AUTHOR]

Due to spatial and temporal heterogeneity in moisture conditions, the responses of arid/humid climate regions (AHCR) to climate change are complex. In this study, we delineated the AHCR of China using information about the balance of the atmospheric water supply and demand collected from 581 meteorological stations over the past 50 years. We also analyzed inter-decadal shifts and linear trends in the AHCR and examined the influence of precipitation and reference evapotranspiration. The results indicate that the semi-arid region expanded significantly over the last five decades, mainly in northwest China, northern China, and the Tibetan Plateau and, by the 2000s, had increased by 33.53% relative to its extent in the 1960s; in contrast, the arid region shrank by 20.75%. The semi-arid region grew mainly because of transfers from the arid region in western China and the sub-humid region in eastern China. The decreased reference evapotranspiration and significantly increased precipitation together contributed to the expansion of the semi-arid region in northwest China and the Tibetan Plateau over the last 50 years. In contrast, the expansion of the semi-arid region in Inner Mongolia and northern China reflects the counteractive influence of decreased reference evapotranspiration and decreased precipitation. [ABSTRACT FROM AUTHOR]

Drought/wetness conditions are fundamental not only for agricultural production but also ecology, human health, and economic activity. Dryness/wetness is a function of precipitation, temperature, vegetation and potential evapotranspiration. Regions with low moisture are often characterized by aridity which, in turn, reflects the degree of meteorological drought. Observed climatic data from eleven meteorological stations in and around Shiyang River basin, China, were used to calculate the aridity index (AI) which was defined as the ratio of potential evapotranspiration (ET) to precipitation (P). ET was calculated using the Penman-Monteith method. The ordinary kriging method was used to interpolate the spatial variability of ET, P and AI. The Mann-Kendall test with a pre-whitening method was employed using the Yue and Wang autocorrelation correction to detect temporal trends. The Theil-Sen estimator was used to estimate the slopes of trend lines. Results showed a higher AI in the north basin and a lower AI in the Qilian Mountain region. Annual ET and P had increasing trends with a slope of 0.672 and 0.459 mm per year, respectively, but trends were not statistically significant for most stations. While annual AI had a slight decreasing trend with a slope of −0.01 per year, the trend was not statistically significant for all stations. The decreasing trends in winter AI (at a rate of −0.313/a) was more significant than that in other seasons. The study indicates that the Shiyang River basin is getting slightly wetter, especially in winter. [ABSTRACT FROM AUTHOR]

Soil moisture is a consideration for soil conservation, agricultural production and climate modelling. This article presents a simple method for estimating soil moisture storage under water stress and storage depletion conditions. The method is driven by the common agro-hydrologic variables of precipitation (PPT), irrigation (IRR) and evapotranspiration (ET). The proposed method is successfully tested for the 152 000 km2 floodplain region of Hai River Basin using 48 consecutive months (2003-2006) of data. Soil moisture data from global land data assimilation system/Noah land surface model are validated with ground-truth data from 102 soil moisture monitoring sites. The validated soil moisture is used in combination with in situ groundwater data to quantify total water storage change (TWSC) in the region. The estimated storage change is in turn compared with gravity recovery and climate experiment-derived TWSC for the study area. The soil moisture and TWSC terms show favourable agreements, with discrepancies of <10% on the average. While there is no consistent seasonal trend in soil moisture, TWSC shows a strong seasonality. It is low in spring and high in summer. This trend corresponds with the IRR-PPT season in the study area. Change in groundwater and total water storage indicates storage depletion in the basin. Storage depletion in the region is driven mainly by groundwater IRR and ET loss. Despite the low PPT and high ET, there is narrowing seasonal trend in soil moisture. This is achieved at the expense of groundwater storage. IRR pumping has induced extensive groundwater depletion in the basin. It is therefore vital to develop cultivation strategies that aim at limiting IRR pumping and ET loss. Water management practices that not only reduce waste but also ensure high productivity and ecological sustainability could also mitigate storage depletion in the region. These measures could reduce further not only the seasonal trend in soil moisture but also that in groundwater storage. [ABSTRACT FROM AUTHOR]

Under the background of global warming, does the effect of the rising global surface temperature accelerate the hydrological cycle? To address this issue, we use the hydro-climatic data from five sub-basins in Poyang Lake basin in the southeast China over the past 50 years, to investigate the annual and seasonal trends of streamflow and the correlations between streamflow and climatic variables. The Theil-Sen Approach and the non-parametric Mann-Kendall test are applied to identify the trends in the annual and seasonal streamflow, precipitation and evapotranspiration series. It was found that annual and seasonal streamflow of all the stations had increasing trends except Lijiadu station in wet season. Only 37.5% hydro-stations in annual streamflow increased significantly, while most stations increased at 95% significance level in dry season. Trends in annual and seasonal precipitation during the whole period were generally not as significant as those in evapotranspiration. The correlations between streamflow and climate variables (precipitation and evapotranspiration) were detected by the Pearson's test. The results showed that streamflow in the Poyang Lake basin are more sensitive to changes in precipitation than potential evapotranspiration. [ABSTRACT FROM AUTHOR]

The Heihe River Basin (HRB), located on the northeastern edge of the Tibetan Plateau, is the second-largest inland river basin in China, with an area of 140,000 km2. The HRB is a coupling area of the westerlies, the Qinghai–Tibet Plateau monsoon and the Southeast monsoon circulation system, and is a relatively independent land-surface water-circulating system. The refined characteristics of moisture recycling over the HRB was described by using the Weather Research and Forecasting (WRF) model for a long-term simulation, and the "finer box model" for calculating the net water-vapor flux. The following conclusions were drawn from the results of this study: (1) The water vapor of the HRB was dominantly transported by the wind from the west and from the north, and the west one was much larger than the north one. The net vapor transported by the west wind was positive, and by the north wind was negative. (2) The precipitation over the HRB was triggered mainly by the vapor from the west, which arose from the lower vertical layer to higher one during transporting from west to east. The vapor from the north sank from a higher layer to a lower one, and crossed the south edge of the HRB. (3) The moisture-recycling ratio of evapotranspiration to precipitation over the HRB was much higher than the other regions, which may be due to the strong land–atmosphere interaction in the arid inland river basin. [ABSTRACT FROM AUTHOR]

Water budget plays an important role in ecological functions and biogeochemical cycles on the Qinghai‐Tibet Plateau (QTP). However, the key factors that govern the water budget across spatiotemporal scales in natural conditions are poorly understood, especially in the alpine region. To advance our understanding of how and why the water budget varies at the ecosystem and catchment scales, this study measured and modeled the main water budget components in the Qinghai Lake Basin (QLB) and further investigated the key factors for evapotranspiration and streamflow. The results showed that most monthly precipitation from June to September was greater than the corresponding evapotranspiration from the high‐altitude Kobresia meadow (KMd.) and Potentilla fruticosa shrub (PFSh.) ecosystem, and vice versa for the low‐altitude Achnatherum splendens steppe (ASSt.) ecosystem. The mean annual proportions of evapotranspiration of precipitation for the KMd., PFSh., and ASSt. ecosystems were 0.83, 1.06, and 1.02, respectively, from 2014 to 2015. The study highlights that the high‐altitude KMd. ecosystem is the main contributing area for runoff generation in the QLB. From ASSt. to PFSh. and then to the KMd. ecosystem, the key factors for evapotranspiration switched from water conditions to temperature conditions with the increase in elevation. The future scenario of climate warming and precipitation increase may cause a rise in evapotranspiration and streamflow in the QLB. Moreover, the increasing precipitation may be consumed mainly by evapotranspiration in the high altitude with low slope and by transfer into streamflow in the area with high slope. Key Points: The high‐altitude Kobresia meadow ecosystem is the main runoff‐producing area in the Qinghai Lake BasinThe key controlling factor for evapotranspiration changed from water conditions to temperature conditions with an increase in elevationThe increasing precipitation will be mainly consumed by evapotranspiration in the high altitude with low slope and by transfer into streamflow in the area with high slope [ABSTRACT FROM AUTHOR]