The Simulation Of The Kaidu River Runoff Process And The Study Of The Response Of The Kaidu River To The Climate Change

Yanqi basin is located in the drought northwest area. Its ecological environment has become worse and worse over the years. In the recent decades, irrational exploitations of the water and soil have worsened the soil secondary salinization problem, the deterioration of water quality problem, and the flood problem, etc. Kaidu River is at the northern rim of the Yanqi basin, with an average runoff volume 34.86×108m3/a, accounting for 87.5% of the total runoff of the basin. How to efficiently use Kaidu River is pivotal for the sustainable development of the ecology environment, agricultural irrigation, and economics of the Yanqi basin. The analysis of how the runoff of the Kaidu River affecting the climate and valley runoff is an important foundation for the rational use of the water resource, the flood control and disaster mitigation.The hydrological model is a good way to study the valley runoff. The daily runoff simulation is conducted in this thesis, using the Xin'an River model with the snow melt structure for the runoff process of Kaidu River Dashankou hydrological station from 1979 to 1987. In the meanwhile, parameter calibration is performed to enhance the performance. The temperature of the Kaidu River has an ascending trend over 1979 to 1987. The precipitation is low, about 70 to 80 percent of which is from May to August. And the runoff volume is comparatively small on an annual basis, evenly distributed within one year and does not vary much over the years. There is no strong correlation between precipitation and runoff. However, temperature and runoff are strongly correlated. For instance, the runoff goes up while the temperature is increasing in the summer, and the runoff goes down while the temperature is decreasing in the fall and winter.At the same time, different climates and precipitations are configured in this thesis, under which conditions the runoffs are simulated. It is found that the temperature is main factor of the climate. Given constant precipitation and 1 centigrade increment of temperature, the annual runoff increases by 25.78%, 24.98%, 25.65%, 44.1% and 22.1% from 1983 to 1987, with an average increment of 28.52%. Given constant precipitation and 2 centigrade increment of temperature, the annual runoff increases by 34.67%, 33.94%, 34.83%, 63.45% and 31.08%from 1983 to 1987, with an average increment of 39.59%. Given constant temperature and 20% decrement of precipitation, the annual runoff varies by-5.6%, 2.12%,-10.78%, 8% and 4.9%, with an average variation of-1.36%. Given constant temperature and 20% increme nt of precipitation, the annual runoff varies by 5.3%, 8.9%,-3.4%, 21.2% and 11.3%, with an average varia tion of 8.66%. Given constant precipitation and varying temperatures, significant changes of runoff are observed. The reason behind is that the runoff of the Kaidu River is fed by snow meltwater, rainfall and underground water. And the temperature has the greatest impact on the snow meltwater. With constant temperature and varying precipitation, the runoff does not vary much and is totally random. This is because the impact of precipitation to the runoff with many glaciers and much snow is delayed, not as obvious as the temperature change.This thesis is meaningful for the conversion between the ground water and the underground water of the Kaidu River and the efficient development of the water resource of the Yanqi basin.