Study on the Variation Property of the Runoff and Sediment Yield and Its Influence Factors of the Upper Reaches Watershed of Guanting Reservoir

Guanting reservoir is the first reservoir that built in the abundant sediments river.It is very important that to study the properties of the runoff and sediment yield to the management of the Guanting reservoir.The runoffand sediment yielding in the upper reaches of the watershed is studied.It's results show that the fifties 20th century was the exuberance period of the runoff and sediments yielding,the amounts of runoff and sediments yielding decreased in the sixties,seventies,eighties and nineties,and the nineties runoff and sediments yielding amounts were the smallest.Why yielding amount of runoff and sediments show the degradation law,it mainly due to regular variation of the precipitation amount in the watershed from the 1920s to 2000s and human activities.