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The exploration of variation trend of ground water resources is basic work to identify groundwater environmental problems and strengthen groundwater resource management. Based on the data of previous evaluation results of water resource survey and water conservancy statistical yearbook from local water conservancy departments, the change of groundwater resources from 1956 to 2016 and its influencing factors were analyzed. In addition, the causes of groundwater resource variation were investigated. The results showed that the amount of groundwater resources declined from 1956 to 2016 in the Xinjiang plain area. The dynamic variation of groundwater recharge was featured with stable natural recharge. Moreover, the surface water conversed recharge had a dramatically shrunk. Analysis from the structure of groundwater recharge showed that the significant decrease in canal seepage resulted in the decrease in groundwater resources, the increase in river seepage offset the decrease of groundwater resources. The increase in irrigation water consumption in plain area, which was led by the expansion of irrigation area, resulted in the decrease in groundwater resources. The impact of human activities on groundwater resources is greater than that of climate change. [ABSTRACT FROM AUTHOR]

To explore the mechanism of changes in the hydrologic cycle under the changing environment in eastern coastal areas of China,based on intensive observations from the hydrological station network and construction of experimental watersheds,we analyzed the distribution and responses of hydrological elements in areas of different land use and urbanization levels. The research results are as follows:① The spatial distribution of extreme rainfall exhibits differences,reaching 50 mm,and is mainly affected by the micro-topography and wind direction of the basin. ② For the runoff response for two basins with different urbanization levels,the flood response time,water level increase,and water level increase per unit rainfall of the highly urbanized basin are higher than those of the low urbanization basin,which is mainly affected by the size of the watershed and degree of urbanization. ③ Forest land plays a critical role in water conservation,and the decreasing process of soil moisture under forest land is slow,whereas the process in urban and cultivated land is faster;the average soil moisture lag times in 10 cm,20 cm,and 40 cm soil layers are 0-0.25 h,0.25-0.75 h,and 0.5-0.75 h,respectively,while the soil moisture response times for deep soil layers (60 cm and 80 cm) are more complex because of the influence of preferential flow. ④ The peak groundwater occurrence time has a hysteresis relationship with rainfall,and the lag time is 6.5-12 h. [ABSTRACT FROM AUTHOR]

The non-stationary nature of watersheds due to changing environments has invalidated the assumption that hydrological model parameters reflecting the physical characteristics of watersheds were time-invariant.To improve the performance of a hydrological model,it is thus necessary to consider the time variation of the model parameters.In this paper,the linear and nonlinear functions of five environment-related indicators(Normalized Difference Vegetation Index,population,gross domestic production,grain production,and irrigated area) were employed to describe the temporal variation of the parameters of the two-parameter monthly water balance model to reflect the impacts of vegetation change and human activities on hydrological processes.Impacts of four different scenarios of the temporal variation of two parameters were investigated for the upstream catchments of six hydrological stations,i.e.,Zhimenda,Zhangjiashan,Xianyang,Hengjiang,Danjiangkou,and Xiajiang,by comparing the model performances under different scenarios.Results showed that the hydro-meteorological characteristics of the study catchments was non-stationary during the period 1982-2006.Compared with the baseline scenario with all time-invariant parameters,the model with time-varying parameters could improve the monthly runoff simulations and provide more skillful predictions.Specifically,the Nash-Sutcliffe efficiency coefficient(NS) of the model with time-varying parameters improved by 10.3% and 8.8% in the calibration and validation periods,respectively,at the Zhimenda hydrological station.This research can provide the theoretical basis and technical support for reservoir operation and water resources planning and management. [ABSTRACT FROM AUTHOR]

In recent years, the problem of urban waterlogging has become more and more serious as the environment has changed through both climate change and urbanization. The fundamental assumption of stationarity in municipal engineering may be invalid because changing environments have changed the frequency and intensity of extreme rainfall in urban areas. For this reason, analysis of the impacts of changing environments on extreme urban rainfall and drainage infrastructure is important to urban water resources management, municipal engineering design, and disaster prevention and mitigation. The present study summarizes the advances in future projection of short-duration (sub-daily) rainfall and design criteria for urban drainage system and also reviews both the evolution of laws concerning urban short-duration rainfall and current research into studies of the impacts of changing environments on drainage infrastructure. We also explored the physical mechanism underlying the impact of changing environments on urban short-duration extreme rainfall. Besides, we summarize the methods for analyzing of impacts of changing environments on urban region and emphasized what type of future research is required:(1) strengthening physical mechanisms research focusing on impacts of climate change and urbanization on short-duration extreme rainfall; (2) improving the capability of climate models to describe the interactions between urban land surface and local climate, and strengthen the applications of kilometer-scale convection-permitting models in urban areas; (3) strengthening the study of design criteria for urban drainage infrastructure in changing environments; and (4) comprehensively evaluating the impacts of changes in extreme rainfall and urbanization on urban drainage infrastructure including pipes' surcharges, pollution and water security. [ABSTRACT FROM AUTHOR]

Ｔｈｅ ｉｎｔｅｎｓｉｆｉｅｄ ｉｍｐａｃｔ ｏｆ ｃｌｉｍａｔｅ ｃｈａｎｇｅ ａｎｄ ａｎｔｈｒｏｐｏｇｅｎｉｃ ａｃｔｉｖｉｔｉｅｓ ｈａｓ ｃｈａｎｇｅｄ ｔｈｅ ｓｔａｔｉｏｎａｒｙ ｃｈａｒａｃｔｅｒｉｓｔｉｃｓ ｏｆ ｔｈｅ ｈｙｄｒｏｌｏｇｉｃａｌ ｅｘｔｒｅｍｅ ｓｅｒｉｅｓ， ｔｈｕｓ ｐｏｓｉｎｇ ａ ｃｈａｌｌｅｎｇｅ ｏｎ ｔｈｅ Ｔｒａｄｉｔｉｏｎａｌ Ｈｙｄｒｏｌｏｇｉｃａｌ Ｆｒｅｑｕｅｎｃｙ Ａｎａｌｙｓｉｓ （ＴＨＦＡ） ｍｅｔｈｏｄ． Ｔｈｅｒｅｆｏｒｅ， ａ ｎｅｗ ｔｈｅｏｒｙ ａｎｄ ａｐｐｒｏａｃｈ ｉｓ ｒｅｑｕｉｒｅｄ ｆｏｒ ａｎａｌｙｚｉｎｇ ｎｏｎ⁃ｓｔａｔｉｏｎａｒｙ ｈｙｄｒｏｌｏｇｉｃａｌ ｆｒｅｑｕｅｎｃｙ． Ｉｎ ｔｈｉｓ ｐａｐｅｒ， ｆｕｒｔｈｅｒ ｄｉｓｃｕｓｓｉｏｎｓ ａｒｅ ｃｏｎｄｕｃｔｅｄ ａｂｏｕｔ ｔｈｅ ｆｕｎｄａｍｅｎｔａｌ ｉｄｅａ ｏｆ Ｅｑｕｉｖａｌｅｎｔ Ｒｅｌｉａｂｉｌｉｔｙ （ＥＲ） ａｐｐｒｏａｃｈ， ａｎｄ ＥＲ ａｐｐｌｉｃａｔｉｏｎ ｆｏｒ ｔｈｅ ｄｅｓｉｇｎ ｆｌｏｏｄ ｅｓｔｉｍａｔｉｏｎ ｕｎｄｅｒ ａ ｃｈａｎｇｉｎｇ ｅｎｖｉｒｏｎｍｅｎｔ ｈａｓ ｂｅｅｎ ｅｘｐａｎｄｅｄ． Ｔｈｅ ＥＲ ａｐｐｒｏａｃｈ ｉｓ ｅｘｐｅｃｔｅｄ ｔｏ ａｄｄｒｅｓｓ ｔｗｏ ｋｅｙ ｉｓｓｕｅｓ： ① ｔｏ ｅｓｔｉｍａｔｅ ｔｈｅ ｄｅｓｉｇｎ ｆｌｏｏｄ ｗｉｔｈ ａ ｇｉｖｅｎ ｄｅｓｉｇｎ ｓｔａｎｄａｒｄ ｆｏｒ ａ ｐｒｏｊｅｃｔ ｙｅｔ ｔｏ ｂｅ ｃｏｎｓｔｒｕｃｔｅｄ； ② ｔｏ ａｄｊｕｓｔ ｔｈｅ ｄｅｓｉｇｎ ｆｌｏｏｄ ｆｏｒ ａｎ ａｌｒｅａｄｙ ｃｏｎｓｔｒｕｃｔｅｄ ｐｒｏｊｅｃｔ ｆｏｒ ｉｔｓ ａｄａｐｔａｔｉｏｎ ｔｏ ｔｈｅ ｃｈａｎｇｉｎｇ ｃｏｎｄｉｔｉｏｎｓ． Ｔｈｅ ５９ ｙｅａｒｓ ｏｆ １５⁃ｄａｙ ｆｌｏｏｄ ｖｏｌｕｍｅ ｓｅｒｉｅｓ ｆｒｏｍ １９５６ ｔｏ ２０１４ ｉｓ ｕｓｅｄ ｔｏ ｄｅｍｏｎｓｔｒａｔｅ ｔｈｅ ＥＲ ａｐｐｒｏａｃｈ， ａｎｄ ａｎａｌｙｓｉｓ ｉｓ ｃｏｎｄｕｃｔｅｄ ｆｏｒ ｔｈｅ ｉｍｐａｃｔ ｏｆ ｐａｒａｍｅｔｅｒ ｕｎｃｅｒｔａｉｎｔｙ ｏｎ ｄｅｓｉｇｎ ｆｌｏｏｄ． Ｔｈｅ ｒｅｓｕｌｔｓ ｓｈｏｗ ｔｈａｔ ｔｈｅ ｄｅｓｉｇｎ ｆｌｏｏｄ ｗｉｔｈ ａ ｇｉｖｅｎ ｒｅｔｕｒｎ ｐｅｒｉｏｄ ｕｎｄｅｒ ｎｏｎ⁃ｓｔａｔｉｏｎａｒｙ ｃｏｎｄｉｔｉｏｎｓ ｖａｒｉｅｓ ｗｉｔｈ ｔｈｅ ｅｎｇｉｎｅｅｒｉｎｇ ｄｅｓｉｇｎ ｌｉｆｅｔｉｍｅ， ａｎｄ ｔｈｅ ｕｎｃｅｒｔａｉｎｔｙ ｏｆ ｔｈｅ ｄｅｓｉｇｎ ｆｌｏｏｄ ｅｓｔｉｍａｔｉｏｎ ｉｎｃｒｅａｓｅｓ ｗｈｅｎ ｔｈｅ ｅｎｇｉｎｅｅｒｉｎｇ ｄｅｓｉｇｎ ｌｉｆｅｔｉｍｅ ｅｘｔｅｎｄｓ． [ABSTRACT FROM AUTHOR]

Modeling the joint distribution of hydrological drought associated with non-stationary drought properties under the effects of uncertain drought events and low flow variability is difficult. Daily streamflow data from gauging stations in Dongjiang River basin, South China are used. On the basis of run theory for truncating drought events, alterations are analyzed in terms of mean values for hydrological drought properties and their non-stationary statistics with changes in pooling and exclusion ratios. Bivariate copula functions are built for modeling the joint distribution of hydrological drought according to the test method of Cramer-von Mises statistics associated with Rosenblatt transfer. Furthermore, a pair of designed drought values for predefined joint return periods is calculated using the equalized probability method. Changes in drought properties associated with dependence and joint distribution, as well as water shortage under a changing environment in Dongjiang River basin, are investigated by comparing two subseries of droughts separated by the change point in low flow. Results demonstrate that the pooling and exclusion ratios set to 0.1 and 0.3, respectively, are rational. Despite positive dependence between drought properties, the bivariate and univariate models for hydrological droughts vary under different time series and variable pairs. The remarkable decrease in drought duration and water shortage in the middle and lower streams is attributed to the regulation of water reservoirs, particularly the Xinfengjiang Reservoir. When the joint return period exceeds the threshold by 2 years, the designed duration periods, total volumes, and daily maximum water shortage levels decrease by 63%-71%, 71%-84%, and 30%-47%, respectively. However, they still account for 12-18 d, 61.14-90.30 million, and 7.150-9.290 million m3, respectively, provided that instream flow satisfies the water demand in Dongjiang River basin. [ABSTRACT FROM AUTHOR]