Analysis For The Characteristics Variety Of Water Cycle Factors In Shiyang River Basin

Water resources are the support of national economy and ecological environment, and are also the material base of sustainable development. These years, the Global Warming and the more and more human activities make important influence, the inland arid region which has special weather and environment has been influenced deeply. Hence, the analysis for the characteristics variety of water cycle factors in the background of climate change and human activities are essential for deeply knowing the water resources formation and evolution rules, rational exploitation and utilization and environment protection.This thesis is based on the typical inland arid region ----Shiyang River Basin. The data is from 8 weather stations (Minqin, Yongchang, Wuwei, Alashanyouqi, Gulang, Tianzhu, Menyuan and Jingtai) and 9 hydrologic stations. Data for rainfall and evaporation is from1960 to 2005 and data for runoff is from 1950 to 2000. The main methods for analysis are Kendall rank test, by which we can know the degree of the change of Water Cycle factors, EOF (empirical orthogonal function) and EOF-SVD method, though which we will know the rainfall and evaporation spatial distribution in this basin. After that, the principal component regression model and ANN model have been built to simulate the runoff of Hongyashan Reservoir and analysis the main influence factors (nature and human activities) of it. The main results are as follows:(1) Rainfall is not even in the year, it is highest in summer (56% of the year) and lowest in winter. The multi-year average precipitation shows the uptrend, but trend is not significant. From 1970s to 1990s the rainfall remains a stable level, 1960s to 1970s and early 1990s it fluctuates obviously. The multi-year average precipitation has three spatial distribution types: south-north decrease, east-west opposite and south-north opposite. The relative humidity and vapor pressure influence the rainfall significant and Minqin and Alashanyouqi are the areas where rainfall is influenced significantly.(2) Evaporation is highest in summer and spring, (32% and 41% of the year respectively) and lowest in winter; the multi-year average evaporation shows the significant downtrend, and in summer it changes the most. From late 1960s to late 20th century the evaporation remains a stable level; before 1960s and early 21st century (2000-2005) it fluctuates obviously. The multi-year average evaporation has two spatial distribution types: around-center type and east-west opposite. The wind speed influences the evaporation significant and Minqin, Alashanyouqi, Menyuan and Tianzhu are the areas where evaporation is influenced significantly.(3) Runoff is highest in the period from June to September which is 58%of the year. From 1950s to 1970s runoff shows significant downtrend; from 1970s to 1990s a little downtrend; after 1990s down obviously again, but less than the first period (1950-1970). Except West River and Dajing River, all the rivers show significant downtrend and the Hongyashan Reservoir down the most. For the eight river, the nature factors in Qilian Mountain are the main reason for reduce, but for the runoff in Hongyashan Reservoir, human activities are another important reason.(4) Base on the foregoing analysis, the principal component regression model and ANN model have been built to simulate the runoff of Hongyashan Reservoir. And the analysis shows human activities have 59% of the power and nature factors have 41% of the power. That is to say the human activities are the main influence factor for Hongyashan Reservoir runoff change. Both the two model has good effect in the simulation, although comparatively speaking the ANN model has better precision in simulation.