Study On Groundwater Recharge Sources In Typical Groundwater Exploitation Reduction Area Of Heilonggang

The Heilonggang region（HLG）in Handan is a pilot area for groundwater exploitation reduction（GWER）in the North China Plain（NCP）,and the effect of GWER is remarkable.In this thesis,38 samples of atmospheric precipitation,35 samples of surface water and 1550 samples of groundwater collected in four field water samples were used to analyze the characteristics and influencing factors of isotopic changes in atmospheric precipitation,surface water and groundwater.Combination with multi-source information such as hydrochemistry and water level,the recharge sources of phreatic water,semi-confined water and confined water were quantitatively evaluated,and the groundwater circulation mode under the GWER conditions was clarified.The research results can provide a theoretical basic for the sustainable utilization and development of groundwater resources in NCP.The main research results include:（1）The isotopic composition of atmospheric precipitation is relatively rich and varies widely,which is strongly affected by evaporation.Ocean type water vapor transport and local type water vapor transport are the main sources of atmospheric precipitation.Temperature effect and rainfall effect are the dominant factors affecting the isotopic composition of atmospheric precipitation in winter and summer,respectively.The hydrochemical type of atmospheric precipitation is mostly Ca-HCO₃ type,and some are mixed type.（2）Total dissolved solids（TDS）of surface water ranging from 397.7 mg/L to 1389.9mg/L,and the hydrochemical type is mainly mixed type,and the hydrochemical type of some surface water is Na-Cl-SO₄ type.Surface water is strongly affected by evaporation,with an average evaporation ratio of about 37%.The average evaporation ratio of the Laosha River and the Laozhang River is 45%and 26%respectively.The isotopic composition of Dongfeng Canal,Minyou canal and Weilin Canal are affected by the mixing of water bodies and also by evaporation and the average evaporation ratio is 31%,32%and 42%respectively.（3）Considering that hydrogen and oxygen stable isotopes carry groundwater source information,this study conducted cluster analysis on hydrogen and oxygen stable isotopes and hydrochemical data of 150 groundwater samples,and successfully divided groundwater samples into shallow groundwater and deep groundwater,facilitating the classification of groundwater in the absence of well depth and filter tube depth data.The phreatic water is affected by certain evaporation,and the average evaporation ratio is about 25%.The phreatic water may be mainly recharged by semi-confined water（92%）and surface water（8%）.The semi-confined water may be a mixture of upper phreatic water（76%）,lateral runoff from the western mountains（9%）and lower confined water（15%）.Compared with the upper aquifer,the isotopic composition of confined water in closed state is obviously depleted,which means that the hydraulic connection between confined water and upper aquifer is weak.Compared with the groundwater in the Heilongdong Spring Basin in the west,the isotope of the deep confined water in HLG is more depleted,so it is speculated that the deep confined water may be the ancient groundwater formed in the late Pleistocene and Holocene.