Effects Of Farmland Irrigation Modes On Groundwater Recharge In Bayin River Basin

In arid regions,the rainfall is scarce and the water shortage is serious.Irrigation is an important measure to ensure the stability of agricultural production.Different irrigation modes have different effects on groundwater recharge.Studying the effect of different irrigation modes on groundwater recharge is an urgent problem in current production and practice.In this paper,on the basis of full field investigation,the lithologic structure of different gas zones and different irrigation modes in situ test are carried out.The soil unsaturated zone flow theory and the saturated zone flow equation are coupled to focus on the influence of irrigation on Groundwater Recharge under different irrigation methods,and the following understanding is obtained:(1)The piedmont plain in front of the piedmont basin is an important farming area,where the lithologic structure of the unsaturated zone is extremely complex.In this paper,for example,the sub-bottom coarse and coarse coarse sub-strands were used as examples to observe the migration process of soil moisture in the unsaturated zone using flood irrigation.The observation results show that:the infiltration rate of the soil under the clay layer is slowed sharply,and the irrigation water is enriched in the upper clay layer,which increases the lag time of the groundwater recharge of the groundwater.When the unsaturated soil in the unsaturated zone is loam and the deep layer is sand,the loam is highly water-retaining,and the water retained in the shallow loam after irrigation.When water penetrates the loam,the sand has extremely poor water holding capacity,and the irrigation water is rapidly supplied to the groundwater.(2)On the basis of the observation results,the water migration equation of unsaturated zone is established by combining the unsaturated theory of soil hydrodynamics,and the correction model is used to analyze different scenarios,which lays the foundation for analyzing the Groundwater Recharge under different irrigation modes.The results show that:in the flood irrigation mode,the soil water content of 0~40cm is increased by more than20%.After 147 days of the first irrigation in the growth period,the irrigation water began to supply groundwater,and the infiltration recharge coefficient was 0.3.In the furrow irrigation mode,the soil water content of 0~80cm under irrigation trenches responded to irrigation quickly;the water content of 0~80cm below the trench top was kept at 20%,close to the field water holding capacity.After 167 days of the first irrigation in the growth period,the irrigation water began to supply groundwater,and the infiltration recharge coefficient was 0.1.In the drip irrigation method,the maximum distance of water infiltration is 80 cm with the drip irrigation quota 358 m~3/hm~2.This irrigation system meets the lower limit of soil moisture required for each growth stage and does not produce effective recharge for groundwater.(3)The organic combination of the hydrological process model and the saturated water zone confirms the hysteresis of the aeration zone for groundwater recharge and improves the numerical simulation of the groundwater flow.