Groundwater Numerical Simulation And Multi-source Allocation In Northeast Paddy Field Irrigation Area Based On Water Consumption Balance

With the increasing global demand for food,irrigation water for agricultural production is becoming more and more important.Nowadays,supply and demand of surface water resources in many areas are unbalanced,and groundwater resources have become the main water source for agricultural water consumption.Groundwater overexploitation is becoming increasingly prominent,and groundwater resource failure has become an important bottleneck affecting food security in China.Northeast China is one of the three major black soil regions in the world and also one of the main grain production areas in China.In order to alleviate groundwater overexploitation in the main grain production areas of Northeast China and promote scientific allocation of surface water and groundwater resources.In this study,taking Qingan County and Heping Irrigation Area in Heilongjiang Province as typical irrigation areas,a groundwater numerical simulation model based on water consumption balance was established,and the model was validated and identified with measured data.On this basis,22 scenarios were simulated under the two irrigation modes using the model.Through the establishment of groundwater numerical model,the threshold value of reasonable exploitation scale and water supply ratio of groundwater when water consumption equalization is achieved under two irrigation modes in typical irrigation area,and the reasonable reduction proportion of irrigation area when water consumption equalization is achieved under extreme conditions without surface water supply,are studied to control groundwater overexploitation in the main grain production area of Northeast China.Provide decision support for rational allocation of water resources and food security.The main conclusions are as follows:(1)Under constant irrigation mode,when groundwater supply ratio is less than 66.5 %,groundwater level rises and groundwater in irrigation area recovers;when groundwater supply ratio equals 66.5 %,groundwater level is in fluctuating and stable state.Therefore,when the ratio of groundwater supply is less than or equal to 66.5 %,groundwater balance can be realized in paddy field irrigation area.(2)In water-saving irrigation mode,when the proportion of groundwater supply is less than 67.9%,the groundwater level rises and groundwater in irrigation area recovers;when the proportion of groundwater supply equals 67.9 %,the groundwater level is in a fluctuating and stable state.Therefore,when the ratio of groundwater supply is less than or equal to 67.9 %,groundwater balance can be realized in paddy field irrigation area.(3)In constant irrigation mode,the ground water supply is restricted when the proportion of groundwater supply equals 66.5%.Under the condition that there is no surface water supply and only groundwater is used as irrigation water,43% of irrigation area in irrigation area can be reduced and groundwater balance can be realized in paddy field irrigation area.(4)In water-saving irrigation mode,ground water supply is restricted when the proportion of groundwater supply equals 67.9%.Under the condition that there is no surface water supply and only groundwater is used as irrigation water,31% of irrigation area in irrigation area can be reduced and groundwater balance can be realized in paddy field irrigation area.The results show that the proportion of groundwater resources in irrigation water has a significant impact on the water consumption equilibrium state of the irrigation area.With the increase of groundwater resources,the total amount of recharge and discharge difference in the irrigation area has gradually decreased to negative value in 20 years.When the local surface water supply is constrained,proper reduction of irrigation area can also make the irrigation area reach the water consumption equilibrium state.