Runoff Variation And Its Influence Factor Analysis In Lanhe River Basin

The river runoff had undergone significant change under the background of global warming and human activities enhanced, the shortage of water resources were exacerbated, and lead to the deterioration of the ecological environment. It was of great significance to cognitive runoff variation and analyze the influence of climate change and human activities on runoff for easing the water crisis, protecting the ecological environment and achieving the sustainable development of socio-economic. Therefore, according to the special subject of national key technology R&D pillar program in the12th five year plan of China (2012BAB02B00):"Analyze the reason of runoff drop into the Yellow River from Fenhe river", this paper selected Lanhe basin as the typical study area upstream of Fenhe river, carried out the study of runoff variation and its influence factor analysis in the Lanhe river basin. In the paper the main research contents and results were as follows:(1) The basic characteristics of hydrometeorological factors in Lanhe basin was analyzed. Based on long-term observations of precipitation, temperature, evaporation and other factors, and applied statistical methods to analyze the changes characteristics. The results showed that the distribution of precipitation was very uneven during the year, and annual variation was also lager, precipitation showed a downward trend, the average annual temperature and annual evaporation volume tended to increase.(2) The regularity of runoff variation in Lanhe basin was researched. Uniformity coefficient, concentration and centralization period were allocated for analyzing distribution characteristics of runoff during the year, and stochastic theory, mathematical statistics and wavelet analysis were applied to analyze the tendency, mutagenicity and cyclicity of runoff changes, thus which revealed the regularity of runoff change in the Lanhe basin under the changing environment. The results showed that the distribution of runoff was uneven and concentrated mainly in the flood season. The runoff significantly reduced year by year in the overall trend, and the runoff mutated in1982, and had4years,8years and15years multi-time scale change cycle.(3) BP neural network model for simulating the natural runoff during human activities influence period was constructed. On the basis of the previous research results, the BP neural network model and genetic algorithm was combined, the BP neural network model based on genetic algorithm was adopted to simulate the natural runoff during human activities influence period. The results showed that the simulation accuracy of the model was high, percent of pass reached88.89%, and could be used as a new method of runoff simulation.(4) The influence of climate change and human activities on runoff in Lanhe basin was researched quantificationally. Based on measured and simulative runoff data, separation evaluation method was used to estimate the influence of climate change and human activities on runoff. The results showed that the influence quantity of climate change and human activities on runoff was29.93%and70.07%respectively. This showed that human activities was primarily reason which caused runoff decrease in the Lanhe basin.