Evaluation of potential of floodwater utilization in the middle and lower reaches of the Weihe River

Water shortage,flood prevention and disaster mitigation are important problems awaiting to be dealt with in the Weihe River of Shaanxi Province.Under this situation,floodwater utilization would become an important way to realize comprehensive management of resources and the sustainable development of regional economy.In Guanzhong area which is located at the lower reaches of the Weihe River.The Weihe River is the biggest branch of the Yellow River,passing through Gansu,Ningxia and Shaanxi provinces.The middle reaches of the Weihe River is located in Shaanxi Province,with broad water ways,many shoals and scattered water flow.The lower reaches of the Weihe River is located in Xianyang,with serious channel siltation and small gradient.The flood resulted from heavy rain is the major disaster in these two areas.In general,the floodwater takes up about 33.1%-39.3% of the total runoff annually;the silt is about 60.1%-74.3%,where all data are mean values.It can be seen that a great deal of water and silt comes from the floodwater.By analyzing features of water,the quantity of silt coming from the upper reaches of the Weihe River,and the channel siltation,we establish the criteria as the initial values to evaluate the floodwater utilization;that is,the flood peak with a velocity of 2000m3/s in the middle reaches of the Weihe River,and that of 3000m3/s in the lower reaches of the Weihe River.According to these criteria,based on calculations we obtain the annual average quantlity of the available floodwater and silt from Linjiacun to Wijiabao is 4.038×107m3,and 6.83×106 t respectively,the quantlity of the available floodwater and silt from Weijiabao to Xianyang is 9.139×107m3,and 6.05×106 t respectively,and the quantlity of the available floodwater and silt from Xianyang to Huaxian is 1.617×108m3,and 1.843×107t,respectively.It is necessary to establish the risk management system to gain the optimal effects of flood prevention,water supply and ecological protection.