Study On Crop Water Demand Prediction And Anti-drought Operation Of Multi-reservoir In Longxi River Basin

In order to further efficiently utilize the agricultural production capacity of the Longxi River Basin,the water allocation and scheduling function of the reservoir complex in the basin is efficiently utilized to improve agricultural production and reduce the huge losses caused by the onset of drought.Through effective real-time drought monitoring technology and reservoir agricultural water supply irrigation,this thesis achieve optimal allocation of agricultural water resources and drought disaster mitigation in the region,and realize the harmonious development of people and nature in the Longxi River Basin.By studying the precise classification of land types and the agricultural water supply planning of reservoirs and hydropower stations in Longxi River Basin,the classification of main economic crops,dry land,planting area,and reservoir distribution in Longxi River Basin,the planning rules and water distribution priority of reservoirs in Longxi River Basin,it provides a theoretical basis for predicting agricultural water demand and scientifically determining the scheme.The main contents and conclusions of this study are as follows:(1)Based on the rainfall data,DEM,land use,and soil classification data of 7meteorological stations in the study area,a distributed hydrological model was constructed.The Longxi River is divided into 24 sub-basins,and the parameter calibration and accuracy verification are carried out by the measured runoff model of Liujiantan Hydrological Station from 2003 to 2014.After 1000 iterations,the results show that the NSE coefficient can reach 0.89,the determination coefficient R2 is 0.87,and the relative error(RE)of the total runoff is 5.4%.The daily runoff process of 24sub-basins from 1984 to 2014 is calculated.The variation of soil moisture content can be delayed,which shows that the constructed hydrological model of the Longxi River basin can simulate the production and sink flow in the study area.The drought index SMAPI was also calculated using soil water content,and the drought level reflected by the spatial and temporal characteristics of the mean SMAPI and decadal-by-decadal mean values during 2006 was more consistent with the real values.(2)Based on the weather data of seven weather stations in the Longxi River Basin,the FAO Penman-Monteith formula was applied to forecast the evapotranspiration of corn,rice,and sweet potato.The crop coefficient method was used to correct the reference crop evapotranspiration,and the water requirements of the crop growth period were 374 mm,624 mm,and 344 mm,respectively.Compared with the actual value,the relative error is less than 10%.Combined with the actual soil conditions in the study area,the USDA-SCS method was used to couple the actual rainfall with the crop water requirement,and an effective rainfall calculation model suitable for the study area was proposed.Compared with the traditional method,the complex deep seepage calculation process is simplified,and the results are reliable and simple.Finally,the irrigation water requirement of each crop is obtained through the crop water requirement and effective rainfall,which provides the data basis for the drought resistance scheduling of the reservoir group below.(3)This thesis introduces the concept,tasks,and rules of joint operation of reservoir group,as well as the calculation method of drought limit storage capacity and the formulation rules of operation chart.The optimal operation model of the reservoir group in Longxi River Basin and the drought relief operation model based on staged drought limit storage capacity are established.The POA algorithm is used to solve the two models.The rationality of the results is analyzed from the perspectives of the maximum water shortage depth,water shortage period,total water shortage,and various water use guarantee rates(annual guarantee rates)in long series and typical years.The results are compared and analyzed with the two models.The results are as follows:After the drought relief operation,the water shortage status of 22 reservoirs is reduced to varying degrees.The water shortage depth of Lion Beach decreased to 0.56,and the improvement degree was 41%.The water shortage depth of Yanjingkou Reservoir is reduced to 0.35,and the improvement degree is 51%.Through the optimization of the scheduling process by the drought limit storage capacity,the storage capacity(level of water)of each reservoir in the dry season has been improved,and the number of water shortage periods has been reduced.The water shortage period at the salt well mouth has been reduced by half from the water shortage in almost the whole year.The most obvious reduction in water shortage is the downstream Shizitan Reservoir,and the water shortage has been reduced by 636.751 10~4m~3.In the results of a typical dry water year in2006,the drought index system has been improved after drought resistance scheduling,and drought resistance measures have significantly reduced the drought risk during the year.From the perspective of the annual guarantee rate,the annual guaranteed rate after drought relief dispatching is higher than that before dispatching.The annual guarantee rate of urban,ecological,and agricultural water use before and after drought relief dispatching increases.After drought relief,the guaranteed rate of urban and agricultural water use in Yanjingkou Reservoir increases by 4%and 2.6%respectively,and the guaranteed rate of ecological water use remains unchanged.The urban water supply guarantee rate of the Gaodong power station increased by 2.3%,and the ecological water guarantee rate increased by 0.9%.The guaranteed rate of urban and agricultural water supply in the Shizitan hydropower station increased by 0.6%and 0.8%respectively,and the guaranteed rate of ecological water use increased by 1%.Therefore,the introduction of drought-limited reservoir capacity and reservoir group drought scheduling based on joint optimal scheduling of reservoir group are effective and have more outstanding drought resistance performance.Finally,the research content of this thesis is summarized,the shortcomings in the research process are explained,and the research methods and models used in this thesis are prospect.