Temporal-Spatial Change of Precipitation in Upper and Middle Reaches of Yellow River and its Effects on Water and Silt Inflow of Sanmenxia Reservoir

The Yellow River is a world-known large river, its silt content is high, and its discharge and silt content affect strongly the Samenxia Reservoir located in its middle reaches. The situation of water inflow and silt inflow in the middle reaches of the Yellow River has been significantly changed since recent 20 years, which is mainly affected by precipitation and human activities in the upper and middle reaches. In this paper, the temporal and spatial change of precipitation in the upper and middle reaches of the Yellow River and its effects on the water inflow and silt inflow of the Sanmenxia Reservoir are analyzed using the empirical orthogonal function and correlation analysis based on the mteorological and hydrological data. The results are as follows: (1) There are three typical fields of the spatial distribution of precipitation in the upper and middle reaches of the Yellow River, and their trends and changing periodicities are different; (2) The temporal change of precipitaion is significant in the upper and middle reaches of the Yellow River, so both possibilities of drought and waterlogging exist; (3) The change of water inflow and silt inflow at the hydrological stations in the Sanmenxia Reservoir area is significant. The temporal coefficients of the typical spatial fields were generally reduced during the period from 1956 to 1995, correspondingly, the precipitation was also reduced, and the water inflow and silt inflow of the reservoir were decreased decade by decade; (4) The sand sources of the Sanmenxia Reservoir can be divided into 4 grades; (5) The water sources of the reservoir can be divided into 3 grades; (6) In the next 20 years, the precipitaion in the Yellow River Watershed and the water inflow and silt inflow of the Sanmenxia Reservoir will be gradually increased, and the soil erosion in the Yellow River Watershed will become more serious.