| The Shijiazhuang Plain is located on the eastern side of the Taihang Mountains and is an important part of the North China Plain.It is also an important area for the production of winter wheat and summer maize in China.Almost all of the water needed for irrigation of winter wheat and summer maize comes from shallow groundwater,resulting in continuous shallow groundwater levels decline and a series of ecological and environmental problems.It is of great significance to clarify the current status of shallow groundwater resources in Shijiazhuang Plain,and to reasonably limit the usage of agricultural irrigation water in future years,to slow down the rate of decline of the shallow groundwater level in Shijiazhuang,and to improve the current situation of overexploitation of groundwater.Based on the collection of predecessor research data and further understanding of hydrogeological conditions,the thesis establishes a conceptual hydrogeological model,and then uses GMS simulation software to establish a long-term numerical simulation model of groundwater flow in Shijiazhuang Plain from 2010 to 2018.After validation of the model,we analyzed groundwater balance and evaluation.The results show that the average annual storage change during the simulation period is-5.67×10~8m~3/a,which is under a negative equilibrium state.After 2015,the groundwater loss has been significantly reduced,which is 6.94×10~8m~3 less than in2010;the multi-year average groundwater replenishment resource is 14.00×10~8 m~3/a,rainfall infiltration replenishment is the main source of replenishment,accounting for 47.37%of the total replenishment;the multi-year average extractable amount of groundwater is 12.60×10~8m~3/a,of which Xinji County has the largest amount of extractable resources,which is 1.75×10~8m~3/a,accounting for 13.86%of the total extractable resources,Yuanshi has the smallest extractable resources,with a value of 0.31×10~8m~3/a,accounting for 2.48%of the total extractable resources.Predict the water level and water volume changes of Shijiazhuang Plain under different conditions,especially agricultural irrigation with limited water.First,a prediction model for 2019-2028 under current mining conditions and planned compression mining conditions was established,the results of the analysis are as follows:Under the conditions of maintaining the current mining and planned compression pumping scenario,the average annual change rate of the shallow groundwater level in the Shijiazhuang Plain is-0.1m/a and-0.01m/a,respectively.The overall water level is still under a state of declining,and the average compensation and drainage difference for many years is different.It is-2.18×10~8m~3/a,-1.16×10~8m~3/a,and the overall situation is still under negative equilibrium,the groundwater extraction coefficients are 1.16 and 1.09 respectively,and the overall situation is still over-exploited;Secondly,according to the results of the water level and water volume under the planned restricted extraction,the restricted extraction prediction model for the next ten years under the condition of limited water irrigation of winter wheat was further established.First,the rainfall level during the growth period of the winter wheat under the multi-year average rainfall in the districts and counties was analyzed,based on the rainfall level to determine the irrigation scheme in all districts and counties under the condition of limited water irrigation,while the reduction of winter wheat production is not more than 20%and the rate of groundwater level drop is the smallest,the results show that the average annual change rate of groundwater level in the shallow layers of the Shijiazhuang Plain is 0.17m/a,the overall water level is rising,and the multi-year average compensation and drainage difference is 1.01×10~8m~3/a,which is generally under a positive equilibrium state,the groundwater exploitation coefficient is0.92,and overall in a state of dynamic adjustment of water level recovery.The study results show that after the implementation of agricultural water-restricted irrigation,the water level restoration effect in Shijiazhuang is obvious,which can significantly improve the current situation of groundwater overexploitation.If the output level of winter wheat needs to be maintained,a certain amount of externally transferred water needs to be added as a supplementary irrigation water source. |
