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Baiyangdian Lake, the largest freshwater body in Northern China, is facing water shortage and eutrophication problems that threaten the lake&rsquo, s ecosystem. Environmental water releases from upstream reservoirs to the lake are important measures to provide the freshwater resources demanded by the lake ecosystem. However, knowledge is limited regarding the influences of such water allocations on the water quality of the upstream rivers that receive the reservoir water and transport it into Baiyangdian Lake. To improve our understanding of possible influences of environmental water releases from upstream reservoirs, the spatial variation of water quality in rivers upstream of the lake during environmental water release periods from reservoirs was explored in this study. Water samples were collected along the two routes of water allocation: the WangKuai reservoir route (WKR) and the XiDaYang reservoir route (XDYR) and water quality parameters related to organic pollutants, nitrogen and phosphorus were analyzed. In the WKR, the pollutant concentrations generally increased from upstream to downstream. Chemical oxygen demand, total nitrogen, and total phosphorous at the sampling site closest to Baiyangdian Lake could not meet the water quality target of the water function zone. For the XDYR, pollutant concentrations peaked downstream of the major urban region of Baoding city and then decreased or remained at a similar level further downstream and only the total nitrogen concentration was worse than the target. The dissimilarities in spatial variation patterns of water quality may be caused by the different spatial distribution of wastewater treatment plants in the two routes.

Sustainable management strategies for water resources rely on accurate knowledge about the dynamics of hydrological processes, especially in drylands, where freshwater is the limiting factor for the development of human society and ecosystems. The populated Loess Plateau (LP) in North China is a typical semi-arid region where competition for water between people and nature is worth noting because of afforestation promoted by the Grain to Green Program. In this study, changes in key components of terrestrial water storage (TWS) in the LP were explored using a multi-satellite approach, including Gravity Recovery and Climate Experiment (GRACE) observations and Earth observations of precipitation, evapotranspiration and soil moisture. By integrating data on human water use from different sources with satellite observations, we were able to examine the mechanisms driving these changes. The results demonstrated that, according to an evaluation based on reproducing TWS computed from the regional water balance in the LP, the mascon solution of the Center for Space Research (CSR) at University of Texas at Austin performed best out of the commonly used GRACE products. Regional TWS derived from the CSR mascon solution in the LP decreased significantly for the period 2003-2015. Significant decreases were also detected for regional ground water storage (GWS) estimated by decomposing the GRACE TWS using multi-sources remote sensing data. GWS made the greatest contribution to the changes in TWS. Increased plant transpiration was one reason for the decreasing trend of GWS. Because changes in precipitation, soil moisture and water consumed by irrigation were minor at regional scales, we concluded that the increase of transpiration is driven by deep-rooted trees planted, which use the part of precipitation that previously recharged groundwater. The findings from this study are valuable for water resource management and ecological restoration in semi-arid regions with high populations. (C) 2019 Elsevier B.V. All rights reserved.