Characters of Precipitation Variation in Jinghe Watershed
泾河流域降雨量变化特征分析

In the last 100 years, global climate is on the tendency of warming that will influence the water circulation and lead to variation including precipitation, run-off, and frequencies of flood or drought. Jinghe watershed lies in the northwest of China which belongs to arid and semi-arid area. And water resource in that region is the main limiting factor of both social economic and ecosystem, which has significantly positive inter-relationship with precipitation. Therefore, it is important to make it clear what the precipitation will change in concerned area under the impact of global warming. This paper attempts to detect the trends and spatiotemporal characters of precipitation in the Jinghe watershed. The monthly precipitation data from 1961 to 2004 was collected from meteorological stations in Jinghe watershed and the surrounding areas. By using the analysis methods of linear regression and Mann-Kendall test, the results show that the precipitation in Jinghe watershed fluctuates greatly. The positive and negative distance to the mean value of precipitation alternates every ten years. Furthermore, it appears that from 1990s till now precipitation is prominent in the decreasing period. In the last more than 40 years the negative trend of precipitation has no significant effect through Mann-Kendall test and the declining rate is about 4.7mm every ten years. However, the negative trend of precipitation in autumn and positive trend of precipitation in winter can be observed among the upper, middle and lower Jinghe watershed. And the decline of precipitation in autumn may be the main cause leading to annual precipitation decline. The spatiotemporal variation of precipitation in Jinghe watershed is closely related to global warming, which may intensify the east asian monsoon to move northward, regional different topography and surface. The results also indicate that in the majority part of the watershed, precipitation changes little comparing the average contour of precipitation between two stages, which is in turn from 1981 to 2004 and from 1961 to 1980. The negative areas are mainly situated at the northwest and southwest part of Jinghe watershed such as Guyuan, Huating and Qianyan. The positive areas are located in the middle-lower watershed which is agriculture high yield region. Changwu and Xianyan seem to be the two central places of precipitation enrichment regions. And it will help to increase these areas agriculture production.