The Changes Of The Runoff And Its Element And The Response To The Vegetation Restoration In The Typical Hilly-gully Area

The hilly-gully area of the upper reaches of Beiluo River was selected as the research area in this paper, and the meteorological, hydrological and remote sensing data were collected.to analyze the distribution patterns and phase characteristics of the annual rainfall,runoff and base flow of the year of 1959 to 2011 in different time of scales, and discussed about their response to the vegetation restoration, and explores influence to the different eras of human activities and the implementation of national policies and the hydrological cycle. the study could be the reference on maintaining ecological balance of watersheds,water resources protection and rational utilization. The main conclusions are as follows:1. the precipitation of the upper reaches of BeiluoRiver are uneven distribution. The average rainfall in the year of 1957-2009 is 450.8mm, which concentrates in July and August, and 63.2% of the annual rainfall centralized in summer(June-August). The reduction of the annual rainfall on time series exhibits no significant trend. Spring, summer,and autumn precipitation was not significant decreasing trend and the rate of change respectively was-0.05,-0.02, and-0.15 mm/a. Winter precipitation was significant increasing trend, the rate of change of 0.06 mm / a. With the passage of years especially,annual precipitation has stabilized.2. The annual runoff volume in Wuqi, Zhidan, and Liujiahe hydrological stations showed a significant decreasing trend in the annual rate of change-0.287 mm / a, accounting for 38.6% of runoff for many years both. Base flow of Wuqi station showed a significant increasing trend(p = 0.05), Zhidan station remained stable, and Liu River Station was a significant increasing trend(p = 0.01), the average annual change rate of 0.053 mm / a. The entire data sequence divided into P1, P2 and P3 periods. Trends and distribution of runoff and base flow compared in different periods, found that runoff showed a decreasing trend after the first increase in three periods, a significant increase in deep of the base flow in the stages P1, no significant changes in the stage P2 and P3, remaining relatively stable.3. Runoff coefficient showed an increasing trend in the P1, P2 period, and appearanced a decreasing trend in the P3 period. Full-time precipitation is relatively stable, and runoffreduced significantly, which indicated that Soil and water conservation and Conceding the Land to Forest(grass) Project play a positive role in reducing runoff of P2 and P3 periods.Base flow index showed increase, decrease, and tendency to increase three periods respectively, which indicated that the trend of runoff and base flow is not consistent, and base flow index increase significantly in P3 period.4. The annual distribution of runoff in three stations of BeiluoRiver has a feature of double maximum, and the peak of runoff and base flow are both occurred in March and August. The unevenness of runoff distribution weaken gradually as time goes by within a year, and the proportion of flood runoff decreases in flood season and increases in spring and winter. Base flow trends in different seasons of the three stations was not obvious. Base flow index of Four Seasons during P1-P3 were tested the increasing trend which indicated that the proportion of base flow accounted for runoff increases gradually.5. With the increasing vegetation coverage in BeiluoRiver upstream basin, the runoff coefficient decreases and base flow increases. In decade of the Conceding the Land to Forest(grass) Project, Beiluo River upstream precipitation remained unchanged, and runoff reduced the rate of 58.2%, base flow depth reduced the rate of 28.3%, runoff coefficient reduced significantly, and a significant increase occurred in base flow index. There exists a quadratic non-linear relationship between the deep of runoff and vegetation coverage in upstream of BeiluoRiver, and there exists a negative linear correlation between the base flow and vegetation coverage. Every 10% increase of vegetation coverage in base flow depth increases 1.29 mm. Changes of vegetation coverage caused changes in the composition ratio of runoff, which reducing the total runoff while increasing the base flow index, and improve the ability of soil and water conservation.6. The national policies and human activities have a significant impact on the stability of the hydrological cycle. Protecting the watershed vegetation and building soil and water conservation facilities have a significant effect on enhancing the ability of withstanding heavy rain and soil conservation capacity, and do better to maintaining ecological balance and sustainable development of the hydrological cycle watershed health.