A Study on Influencing Factors of Runoff Effects in the Longmen Reservoir and Angezhuang Reservoir Watersheds
龙门水库和安各庄水库集水区不同径流效应的影响因子探究

Both the Longmen and Angezhuang reservoirs are located in the Baiyangdian watershed, and spatially close to each other. Concerning water capacity, the two reservoirs can be classified as big-II reservoirs according to the Chinese standard for reservoir classification. Decades ago, they were constructed primarily for flood control, combined with functions of irrigation and aquatic products. With changes in climatic factors and increasing pressure of human activities on these two watersheds, the functions of reservoirs have been changed accordingly. First, climate change is an obvious influencing factor for the recent water shortage. Understanding the runoff difference between the two reservoirs would be beneficial in improving an understanding of runoff effects within the Baiyangdian watershed. Even though they are spatially close, the runoff effect is completely different. The Angezhuang reservoir functions pretty well; however, the Longmen reservoir has suffered from a series of problems, like decreasing water coming from the upper reaches area. The authors analyzed hydrological data for the two reservoirs during the period 1961-2008 using regression analysis. Results indicate a decreasing trend in surface runoff for both reservoirs, especially the Longmen reservoir. Potential influencing factors resulting in the difference in surface runoff include climatic factor, topographic factor, vegetation factor, and human factor. The climatic and vegetation factors for the two reservoirs differ slightly because of similar geographic and natural conditions. The topographic and human factors might be the primary reasons for these differences since 1) the topographic factors, like river length, river width, and river slope, differ greatly; and 2) the human factors, like population density and arable land density, vary largely.