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Drought propagation is very significant for short-term drought forecast and water resources management. However, the law of drought propagation is still unclear, especially with human activities. In this study, we calibrated and validated the SWAT model in the Luanhe River basin controlled by the Luanxian hydrological station, where there are three large reservoirs upstream and water diversion to Tianjin city. The variable threshold level (VTL) method was employed to identify meteorological and hydrological events both under natural and reservoir-influenced conditions. Drought occurred more frequently, drought duration became longer, and drought deficit became larger with the influence of reservoir regulation and water diversion to Tianjin city. The lag time of hydrological drought onset was shorter and termination longer, i.e., the drought period was more persistent. Multiple regression was used to establish the relations between hydrological drought and the driving factors both under natural and reservoir-influenced conditions. The coefficient of determination is high enough to explain drought propagation. The driving factors were different under the two conditions. The results could provide valuable information for water resource managers. [ABSTRACT FROM AUTHOR]

Annual runoff in Luanhe river basin was detected a downward trend and caused water crisis in Tianjin, China. To quantify the decreased runoff volume, Mann-Kendall test and Pettitt test were employed to check whether there existed significant trend and change points for annual rainfall and runoff time series in Panjiakou reservoir basin and 8 sub-watersheds. It was found that the annual runoff time series had a significant downward trend at 5 % confidence level, and the change point was at 1979 in Panjiakou reservoir watershed. Then double mass curve of annual rainfall and annual runoff was plotted, and two lines were fitted before and after 1979, respectively. Based on this method, the comprehensive effects of land use/land cover change on annual runoff were estimated. To further quantify the contributions of each main factor to annual runoff decrease, water stored in check dams and social water use in different periods were surveyed first. And then multi-linear regression was used to develop the relations between annual runoff and the driven factors. Water area decrease was identified to be the main factor contributing to annual runoff reduction. The results in this study can provide valuable information for water resources planners and policy makers. [ABSTRACT FROM AUTHOR]

A large quantity of pollutants is washed off by stormwater during rainfall events. Polluted storm runoff deteriorates the water quality of receiving water bodies, which is becoming a main threat to urban water environment. In this work, five rainfall events were monitored to clarify the characteristics of land surface pollution in Wuqing district, China. Four pollutant indicators of storm runoff samples, including chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN) and ammonia nitrogen (NH 3 -N), were analyzed and then used to validate the parameters of a model established by Infoworks integrated catchment modeling (ICM). The land surface pollutant loads of metropolitan area for four different rainfall scenarios and the variations in pollutants concentration in urban rivers were illustrated based on the model. The simulated results showed that the volume of runoff increased from 31.8 × 104 m3 to 139.7 × 104 m3 with the increase in the return period. The EMCs (Event Mean Concentration) of pollutants, however, were negatively correlated with return periods and the maximum drop was approximately 67%. Furthermore, the increased runoff enhanced the dilution effect and reduced the residence time of pollutants in rivers, which were the main reasons for the decrease of the pollutants concentrations. The results suggested that the runoff should be taken into account when considering the effects of surface pollution on urban river water quality. [Display omitted] • Field experiments were conducted to confirm the surface pollution characteristics. • The simulated pollutant concentration decreases when storm return period increases. • The peak of pollutant concentration in rivers is higher for 1-year return period. • Rainfall runoff significantly affects the concentration of pollutant in rivers. [ABSTRACT FROM AUTHOR]

Urban flooding and waterlogging are becoming increasingly serious due to rapid urbanization and climate change. The stormwater management philosophy of low-impact development (LID) has been applied in urban construction to alleviate these problems. The selection and placement of LID designs are the most important tasks. In this study, LID experiments were performed to calibrate the Storm Water Management Model (SWMM). Then, a multi-objective optimization model, which adopted the minimum surface runoff coefficient, surcharge time, and investment cost as objectives, was established by coupling the SWMM and non-dominated sorting genetic algorithm-II (NSGA-II). Hydrological simulations were performed with the SWMM, and optimal calculations were conducted with NSGA-II. Real-coded optimal variables containing detailed size and location information of multiple LID measures were generated, and a decision space for LID design selection was obtained. The optimization designs reduced the surface runoff coefficient from 0.7 to approximately 0.5, the conduit surcharge duration was reduced from 1.62 h to 0.04–0.47 h, and the total investment cost only ranged from 395,000–872,000 ¥. Thus, the optimization model could achieve synchronous optimization of all objectives. This study could provide valuable information for LID design with the aim of urban flooding and waterlogging control. [Display omitted] • Calibrating SWMM parameters based on LID experiments in the area without measured data. • The surcharge status of drainage systems is taken into account in LID optimization. • The structure of optimal variables is suitable for optimization in small-scale communities. [ABSTRACT FROM AUTHOR]