Study On The Losses And Suiltable Level Of Ecological Base Flow Protection In The Main Stream Of Wei River Within The Guanzhong District

This paper taking Wei River main stream as an example to discuss the EBF(ecological base flow)security in Guanzhong section,the study included the followings:Influencing factors of the EBF insufficiency;direct influence both on agricultural economic and benefit of water supply,and indirect social impact caused by the EBF protection;in addition,based on the food security the suitable EBF security level is designed,and the effective contribution of agricultural water-saving potential in Baojixia Irrigation upper reaches District are discussed.The main achievements as follows:(1)The analysis of the main control section of the Wei river show that the ecological base flow in the upper reaches of the Wei River is seriously deficient,mainly concentrated in the Baojixia Irrigation District.The current controllable factor of ecological base flow guarantee is the water consumption in Baojixia Irrigation District.(2)The Solow’s improved Cobb-Douglas production function was expanded and improved in this paper,and the production function model were established by ridge regression analysis,and the marginal benefit of water supply on industrial and agricultural in Guaunzhong District were calculated.The results showed that:①The contribution rate of industrial and agricultural water supply was about 0.47 96‰～1.2‰,and 0.75‰～1.66‰ respectively,for every 1%growth in added value of themselves within Guanzhong District;②The efficiency of production water supply ate increasing year by year.In 2015,the industrial and agricultural water supply in per unit were Y41.1 and Y3.02,with an average annual growth rate of about 16%and 13%,and the total benefits reached ￥375 billion and ￥37.77 billion respectively.(3)Based on the present water conservation status of the Baojixia Irrigation District and the analysis results of the influence factors of EBF security,the agricultural economic losses and social impact caused by the protection of EBF on Linjuacun and Xianyang section were calculated respectively,calculation results shows that:①The EBF security consequence on winter wheat is much more serious than that of summer maize in general.With the hydrological frequency goes up and the EBF security level upgraded,the arable area suffered from the protection of EBF is gradually expanded;②The insufficiency conditon of EBF on Linjiacun section is tense.In Generally dry year(75%hydrologic frequency)to guarantee 4m3/s EBF,the direct economic losses will be reach to ￥0.913 billion yuan,and the price of water supply benefits will amount to ￥ 1.25 billion,and the social security burden going to add up to Y0.96 billion;③The relationship of EBF protection losses(under the full satisfaction of EBF security level)&EBF rate are plotted,refering to the loss-flow diagram,the direct economic losses,price of water supply benefits and social security burden corresponded with differen EBF security level can be seen directly,which can provide the corresponding cost reference for the decision of EBF protection in the upper section of Wei River.(4)The suitable EBF security level is based on the analysis of the regional food security and agricultural water-saving potential,calculation results shows that:①In order to balance the supply and demand of regional grain,to maintain the per capita grain availability between 385 and 390 kilogram,and according to that delimit the reasonable EBF security level in each typical year as follows,keep the EBF at 8m3/s during high flow year(25%hydrologic frequency),and 6m3/s during normal flow year(50%hydrologic frequency),and 4m3/s during low flow year(75%hydrologic frequency),and 3m3/s during excessive drought year(90%hydrologic frequency);②The comprehensive water-saving amount of Baojixia Irrigation upper reaches District are calculated by resource-based&efficiency-based water-saving potential,the effective contribution amount of the EBF protection on Linjiacun section is 26.2 million cubic meters during high flow year,and 46.04 million cubic meters during normal flow year,and 36.29 million cubic meters during low flow year,and 3477 million cubic meters during excessive drought year.The guarantee rate of EBF increased 11.9%an average of all typical year.It has good effect on reducing the dried-up riverway specially in dry year.In summary,the cost of EBF protection reaches its peak in extremely dry years,and the security burden is heavier in dry season of each typical dry year.