Simulation And Analysis Of Water And Salt Balance In Bohu Irrigation District In Yanqi Basin

Bohu County Irrigation District in Yanqi Basin is located in the lower reaches of Kaidu River.It is an important commercial grain and oil production irrigation area in Yanqi Basin.This irrigation area accounts for more than 90%of the total water consumption.It is a typical dry and water-deficient oasis agricultural irrigation area.In recent years,due to the more and more serious shortage of water resources and the increasing non-agricultural water consumption,the amount of Kaidu River used for irrigation is obviously decreasing,so it is imperative to develop water-saving agriculture.Therefore,this paper takes the irrigation area of Bohu County as the research scale,based on field investigation,literature review and water and salt monitoring data in the study area,and uses the calibrated and verified Saltmod model to simulate,predict and analyze different irrigation and drainage in the next 15 years.Under the same conditions,the arable land and saline wasteland soil salinity,groundwater depth and other inter-annual dynamic changes in the irrigation area,and proposed irrigation and drainage development recommendations suitable for this study area,and at the same time it can improve the soil salinization in the oasis irrigation area of Yanqi Basin,and improve the scientific theoretical basis for the efficient utilization of water resources and the sustainable development of agricultural ecological environment.The main research results are as follows:(1)Through the 4-year calibration and 3-year data verification of the Saltmod model,it shows that the model simulation results fit well with the measured values.The Saltmod model has good applicability in the simulation and prediction of the long-term interannual dynamic changes of soil salinity.It is used to simulate and predict the inter-annual changes of water and salt dynamics in the study area in the future.(2)After model calibration and verification,the natural drainage(Gn)is 0.10 m3/(year·m2),the root layer leaching rate(Flr)is 0.80,and the transition layer leaching rate(Flx)is 0.50;The results show that the soil salt content of cultivated land will increase by 2.64 dS/m in the next 15 years,and the salt content of salt wasteland will increase by 8.60 dS/m.the salt wasteland has become a concentration area of salt in cultivated land,which plays an irreplaceable role in the movement and control of salt in the study area;However,the groundwater depth in the growing period is shallow,less than 1.0 m.(3)Considering the salt control,crop water demand and water-saving measures in the study area,without causing major changes in groundwater level and rapid increase in soil salinity,research and analysis show that irrigation quotas during the current growth period It is a more suitable irrigation combination plan for this study area to reduce the irrigation quota by about 15%(3910 m3/hm2)and increase the winter irrigation quota by about 15%(3910 m3/hm2).This plan can avoid too much irrigation quota during the growth period.The waste of resources can give full play to the superiority of winter lavage salt.At the same time,based on the consideration of increasing the drainage and salt discharge capacity,reducing channel leakage,and reducing project investment costs,it is believed that the most reasonable drainage depth in this study area should be about 2.0 m,and the canal utilization efficiency reaches about 0.60,which can effectively inhibit the increase of soil salinity.(4)Through model simulation analysis,the degree of mineralization of irrigation water in the study area can be appropriately increased to avoid waste of water resources.Appropriate exploitation of brackish underground water for mixed irrigation can not only alleviate the shortage of water resources in the irrigation area,but also reduce Depth of groundwater and reduce the accumulation of groundwater salt in the upper soil.Based on the comprehensive consideration of the simulation data and the actual situation of the irrigation area,it is concluded that the irrigation water salinity in this study area can reach about 1.1dS/m to effectively play the role of irrigation,and will not cause a rapid increase in soil salinity,which is the most suitable for this study.The mixed irrigation ratio of brackish ground water and Kaidu River water in the district is about 1:1,and the groundwater depth is basically maintained at a balanced state of about 2.0 m.