Characteristics Of Runoff Changes And Its Attribution Analysis In Enjiang River Basin

Currently, global change is a momentous environmental problem that humansociety faces, including both climate change and the effect of human activities onenvironment. Affected by climate warming and human activities, the stream runoffprocess has changed profoundly in recent years. Due to the determinacy and intenserandomicity of runoff process, the flood and drought disasters happen frequently.While, society, economy and environment change accordingly, aquatic ecosystemsdegenerate and its service function brings down which will affect the developmentand use and rational distribution of water resources, cause a huge financial loss forhuman, even lead to life-threatening situation. Therefore, the study on the tendency ofrunoff variation and the effect of climate change and human activities on waterresources has become the hot spot issue for the whole society.Firstly, the statistical methods of cumulative filter, Mann-kendall test, rescaledrange analysis and wavelet analysis are used to study on the general characteristics,variation tendency, mutation characteristics and periodic characteristics of runoffbased on the temperature data, rainfall data, evaporation data and runoff data ofdifferent hydrological stations and weather stations from1956to2004. The resultsshow the runoff amount is not distributed evenly in a year and it has been decreasingon the whole. The mutation points lie in the early1960s, around1984and the late1990s. Multi-time scale analysis shows there exists three time-scale period in theJiangqiao Station, they are20-35year time scale whose scale center is about25years;8-15year time scale whose scale center is about11years, and about5years time scale.According to the wavelet coefficient figure of25years time scale, this paper concludepreliminary the NenJiang River Basin will enter the high water period in2013.Next, this paper adopts a method integrating qualitative analysis withquantitative analysis to analyze the effect of climate change and human activities onrunoff. The results show the most significant climate factor that affect runoff israinfall, secondly is evaporation, and then temperature. The runoff of Nenjiang RiverBasin affected by significant human activities from1977, the responsiveness degreeof runoff to human activities changes from time to time. The contribution rate of human activities to runoff is30.07%from1986-1997;51.99%from1999-2004;97.86%from1956-2004. Overall, the human activities has increasing influence onrunoff over time, the rainfall has decreasing influence on runoff.The factors that affect runoff are quite complicated. This paper is short ofquantitative study of human activities, such as hydraulic engineering and vegetationcover. So coupling analysis of climate change and human activities will be the focusin the future.