Study On Groundwater Circulation Characteristics In Guohe River Basin (Henan Section)

The Guohe river basin?south section?is an important base of grain,cotton and oil in China,which is the upper reaches of the huaihe river basin.It gives play to a key effect in the utilization of resources,ecology and geological environment,and playing an important role in the development of the river basin economy and society.Due to the influence of climate change and the increase of human activity intensity,the groundwater recharge,runoff and discharge in the Guohe river basin have undergone great changes.Therefore,it is of great significance to study the cyclic characteristics and evolution law of groundwater in the Guohe river basin for the development,utilization and protection of groundwater in the basin.Based on the Henan 1:50,000 Lankao amplitude and Qi county amplitude hydrogeological survey project,this paper analyzes the characteristics of water quality and circulation evolution of surface water and groundwater in the Guohe river basin through hydrochemistry,isotopic tracing and numerical simulation techniques and methods.The main conclusions are as follows:?1?From shallow groundwater to deep groundwater in the wohe river basin,the over proof components and the overstandard rate of components in the water samples are reduced,which are basically smaller than the surface water.The salinity of the water samples is basically lower than 1g/L,and the whole water quality is well.From shallow to deep,the hydrochemical types of water samples change from HCO₃·SO₄·Cl—Na·Mg·Ca type to HCO₃-—Na·Mg·Ca type and then to HCO₃-Na type.The quality uniformity of surface water is good,shallow groundwater is affected by surface water and human activities,water chemical types are more complex,the hydrochemical types of the middle groundwater changed in the northwest and near the southern boundary,deep groundwater is less affected and does not change much.The dominant ions of water chemistry in water samples were Na⁺and HCO₃^-,while the contents of Ca²⁺,Mg²⁺,Cl^-and SO₄^2-in shallow groundwater are higher than those in surface water,and those in surface water are more abundant than in medium and deep groundwater.The main ions in the water are significantly correlated with the salinity,and the interrelationship between the ions in shallow groundwater is high.The surface water and shallow groundwater in the region are affected by water rock action and evaporation,and they are mainly affected by water rock action.The chemistry of middle and deep groundwater is controlled by water rock action,that is,the water rock action is strengthened from shallow to deep.The sources of Na⁺in the water include dissolution of rock salt and other ores-containing sodium.The main sources of Ca²⁺and Mg²⁺are the dissolution of evaporite and silicate minerals and the dissolution of other calcium and magnesium minerals.Cation exchange adsorption occurred in surface water and groundwater at different depths.?2?The main source of the Guohe river is the replenishment of atmospheric precipitation,and due to the influence of evaporation,from upstream to downstream,the isotopes are increasingly enriched.With the increase of groundwater depth,the smaller the hydraulic connection with the upper water,the more closed the occurrence environment and the smaller the isotope value.Shallow groundwater is mainly supplied by meteoric precipitation and the infiltration of surface water,and a few areas are affected by other factors,such as irrigation infiltration,fish pond leakage,etc;the main source of middle groundwater is meteoric precipitation,and in the area near the Yellow River in the north and Taikang county in the south,there is an overcurrent recharge from shallow groundwater;while deep groundwater is relatively stable,whose replenishment source is atmospheric precipitation in ancient history.From northwest to southeast,the degree of isotope enrichment in shallow groundwater gradually increases along the direction of groundwater.The vertical influence depth of surface water on groundwater is about 50m,and when there is overcurrent recharge,the influence depth can reach up to 300m.And the horizontal influence range is about 20km?30km.The isotopic content of groundwater in the study area has not changed much in recent years.?3?Most of the surface water in the basin is replenished in the 1960s and 1970s.And most of the shallow groundwater is the mixture of pre-1953 supply water and modern water,a small part of it is replenished in the 1960s and 1970s and in the past five years.The middle and deep groundwater is the mixture of pre-1953 supply water and modern water.It can be seen that the age of middle and deep groundwater>the age of shallow groundwater>surface water?s.The influence of nuclear explosion test has gradually weakened from atmospheric precipitation to the deep groundwater.?4?It is good that the imitative effect of simulated flow field and observation hole of the numerical model of water flow in the study area,and the model accords with the actual hydrogeological conditions of the research area.The general trend of the groundwater flow field in the study area is from northwest to southeast.The recharge of shallow groundwater in the basin was 133627.17×10⁴m³,and the excretion was 143724.83×10⁴m3.The recharge of mid-groundwater in the basin was20198.06×10⁴m³,and the excretion was 25992.56×10⁴m3.The recharge of deep groundwater in the basin was 112.03×10⁴m³,and the excretion was12913.79×10⁴m3.The total difference of equilibrium was 28693.92×10⁴m³.All regions are in a negative equilibrium state,and the water level is declining.