Study On A Conjunctive Use Model Of Water Resources In Well-canal Combined Irrigation District

Irrigation district is an important support of regional economic development, and also animportant basis on regional ecological environment protection. Well and canal irrigation modecan utilize surface water and groundwater flexiblely, also can reuse irrigation canal seepagewater and regulate groundwater level. It has become a development direction of makingagricultural water utilized more efficiently in northern irrigation district. As the developmentand utilization of surface water and groundwater was not planed unified and allocatedscientifically, problems like groundwater mining disorders, deterioration of soil and waterenvironment have been appeared and seriously affect the sustainable development of irrigateddistrict. Therefore, researches about joint-control for surface water and groundwater in Welland canal irrigation district is helpful to regulate and utilize the limitted water resources morereasonable, also is significant to protect ecological environment and motivate sustainabledevelopment of irrigated district.In this paper, a typical well-cannal combined irrigation district named JinghuiquIrrigation District in Shaanxi province in northwestern China was chose as a research area.Considering the actual operation situation, the multi-objective model of optimal allocation ofwater resources was established on the basis of water supply and demand balance. Usingsurface water diversion and groundwater extraction volume as coupled variables, the optimalallocation model of water resources was combined with groundwater simulation modeleatsblished by visual modflow software, then a coupling water resource regulation model ofjoint optimization and simulation was established in irrigation district. The artificial fishswarm algorithm was used to solve multi-objective optimization allocation model and the bestmode of joint control of water resources for different level years was studied. The mainresearch contents and results showed as follows:(1) Water demand of industry, domestic and agriculture from different water sectors werecaculated and its monthly distribution were obtained by using quota method, also watersupply and demand balance was analyzed. The total water demand under50%guaranteed ratein2010is46994×104m3, the water demand is satisfied and no water shortage is appeared inirrigation district; The total water demand under75%guaranteed rate is62932×104m3, available water supply is61684×104m3, water deficit is1248×104m3. Scenario A(XijiaoReservoir doesn’t supply water for Sanyuan industry) and Scenario B(Xijiao Reservoir supplywater for Sanyuan industry) were developed to set the operating conditions of XijiaoReservoir in2020. The total water demand in2020under50%guaranteed rate is48199×104m3, the water demand is satisfied and no water shortage is appeared; The totalwater demand under75%guaranteed rate is62842×104m3. Available water supply ofscenario A is58631×104m3and water deficit is4211×104m3; Available water supply ofscenario B is59684×104m3and water deficit is3157×104m3; Comparing2020to2010, theratio of agricultural water demand is decreased, ratios of both domestic and industrial waterdemand are increased. The ratio of industrial water requirement increase significantly, whileratio of urban and rural living water requirement increase relatively slow. Under the conditionof75%guaranteed rate in2020, comparing scenario B to scenario A, the water deficit isreduced and water deficient ratio is decreased and it shows that the feasibility of planning tosupply water from Xijiao Reservoir for Sanyuan industry.(2)According to the actual situation and results of water supply and demand balance, toachieve the goal of minimum of total annual water deficit and quadratic sum of relative waterdeficient ratio, the multi-objective model of optimal allocation of water resources wasestablished. The artificial fish swarm algorithm was used to solve the model, then the monthlydistribution of water resources for different level years were acquired which provide a basisfor joint-regulation of water resource.(3)Using surface water diversion and groundwater extraction volume as coupledvariables, water balance calculation of optimal allocation results was done and input intogroundwater simulation model eatsblished by visual modflow, then groundwater levels weresimulated. Based on judgement of the annual change of groundwater level is less than anallowable value, the monthly distribution of water resources for different level years wereacquired through continually regulating the optimal allocation model of water resources. In2010, the water supply under50%guaranteed rate is46784×104m3. The ratio of surface watersupply to groundwater supply is3.24. The water deficit is210×104m3. The averagegroundwater level decrease0.097m; the water supply under75%guaranteed rate is60539×104m3. The ratio of surface water supply to groundwater supply is2.49. The waterdeficit is2393×104m3. The average groundwater level decrease0.379m; In the year of2020for scenario A, the water supply under50%guaranteed rate is47843×104m3. The ratio ofsurface water supply to groundwater supply is2.36. The water deficit is357×104m3. Theaverage groundwater level decrease0.091m; the water supply under75%guaranteed rate is57933×104m3. The ratio of surface water supply to groundwater supply is2.35. The water deficit is4909×104m3. The average groundwater level decrease0.415m. In the year of2020for scenario B, the water supply under50%guaranteed rate is47800×104m3. The ratio ofsurface water supply to groundwater supply is2.58. The water deficit is399×104m3. Theaverage groundwater level decrease0.108m; the water supply under75%guaranteed rate is58861×104m3. The ratio of surface water supply to groundwater supply is2.43. The waterdeficit is3980×104m3. The average groundwater level decrease0.405m. The water shortagefocus on irrigation and shortage period is mainly in June、July and August.