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The changes of impervious surface from 1986 to 2006 and the relationship between those changes and hydrological response were studied in the Qinhuai River Basin (2631 km 2 ), which is located in the southwest of Jiangsu Province, P. R. China. A series of Landsat imagery during that period was employed to extract impervious area using the Linear Spectral Mixture Analysis. The results showed that impervious area increased from 2.9% in 1986 to 12.1% in 2006. The annual runoff and precipitation of the basin were collected to analyze the relationship between impervious surface area and annual runoff. Based on the regression analysis, it was found that the average annual runoff depth has increased by 26% since 2003 due to the increase of impervious area.

Flooding is the most prevalent and costly natural disaster in the world and building reservoirs is one of the major structural measures for flood control and management. In this paper, a framework was proposed to evaluate functions of reservoirs′ locations and magnitudes on daily peak flow attenuation for a large basin of China, namely Ganjiang River Basin. In this study, the Xinanjiang model was adopted to simulate inflows of the reservoirs and flood hydrographs of all sub-catchments of the basin, and simple reservoir operation rules were established for calculating outflows of the reservoirs. Four reservoirs scenarios were established to analyze reservoirs′ locations on daily peak flow attenuation. The results showed that: 1) reservoirs attenuated the peak discharges for all simulated floods, when the flood storage capacities increase as new reservoirs were built, the peak discharge attenuation by reservoirs showed an increasing tendency both in absolute and relative measures; 2) reservoirs attenuated more peak discharge relatively for small floods than for large ones; 3) reservoirs reduced the peak discharge more efficiently for the floods with single peak or multi peaks with main peak occurred first; and 4) effect of upstream reservoirs on peak attenuation decreased from upper reaches to lower reaches; upstream and midstream reservoirs played important roles in decreasing peak discharge both at middle and lower reaches, and downstream reservoirs had less effect on large peak discharge attenuation at outlet of the basin. The proposed framework of evaluating functions of multiple reser-voirs′ storage capacities and locations on peak attenuation is valuable for flood control planning and management at basin scale.

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