Research On Ecological Water Level Of Shallow Groundwater And Its Restoration Prediction In Xinxiang City

Groundwater restoration and management has presently become a common concern,increasing attentions are paying to the ecological value of groundwater.From the perspective of sustainable development,the dynamic characteristics and influencing factors of groundwater in Xinxiang Plain are analyzed to puts forward the threshold standard of groundwater ecological water level suitable for Xinxiang Plain on the basis of summarizing the existing theory of groundwater ecological water level.The groundwater numerical simulation model is established by FEFLOW software to analyze the groundwater dynamic evolution characteristics under different development and utilization scenarios,to explore a powerful scheme for groundwater ecological water level recovery.The main conclusions are as follows:1)In the 1970 s,the groundwater depth in Xinxiang Plain was between 2-6 m,and the overall flow field was from west to east,the groundwater level contours were basically distributed in strips.Since the 1980 s,the groundwater level line has gradually shifted to the west due to the continuous development and utilization of groundwater resources.The strip distribution was gradually broken by local protrusions with the generation and expansion of landing funnel.By analyzing the statistical data of natural and human factors such as precipitation,evaporation,groundwater supply and urbanization rate,the correlation between natural factors and groundwater depth is determined.In the study area,the correlation was good before the 21 st century;the influence degree of natural factors on groundwater depth has decreased with the continuous intensification of human activities.2)The upper threshold of groundwater ecological water level in Xinxiang plain area is 1.57-2.85 m,the lower threshold is 4.31-5.93 m,and the upper and lower threshold difference various between 1.42-4.36 m.The results of groundwater suitability evaluation show that the suitability area of groundwater status(2017)only accounts for 12.24 % of the total plain area of Xinxiang City.3)The urban area and Xinxiang County are selected as the simulation areas.According to the corresponding data from 2015 to 2017,the three-dimensional numerical model of groundwater is established by FEFLOW software to predict the changing characteristics of groundwater flow field in the coming five years under the current mining conditions(Scheme 1)and water saving and groundwater pressure mining conditions(Scheme 2).The simulation results show that the overall annual recovery rate of groundwater level is 0.4 m/a under Scheme 1 and 0.44 m/a under Scheme 2,respectively.The contribution of water saving,reduction of groundwater mining and other measures to the groundwater level recovery is as high as 10 %.4)By comparing the threshold of groundwater ecological water level,the suitability area of groundwater level in the simulation area accounts for 29.89 % of the total area in Scheme 1 and 30.97 % in Scheme 2,respectively.Under both scenarios,the groundwater recovery effect in funnel area is poor.It is suggested to appropriately establish surface water recharge projects and to strengthen the transformation of local surface water resources to groundwater resources according to the current situation of regional surface water resources.