Charaterzing Surfater Water-groundwater Interactions Using Isotopic Techniques In The Anyang River Watershed

The interaction between surface water-groundwater is a hot topic in hydrology research,and it is very important for scientific management of water resources.The Anyang River Basin includes most of Anyang City.The urban area is located in the middle of the Anyang River alluvial fan.The rich water resources of the basin support the rapid economic and social development of Anyang City for many years.Because the unreasonable development and utilization,it has caused some of the water resources issues.It is of great significance to find out the interaction between surface water and groundwater in the Anyang River Basin and provide technical support for the scientific development and management of water resources in the Anyang River Basin.Based on the field hydrological survey and hydrogeological survey,a total of111 water samples were collected in August 2016?summer?and January 2017?winter?.Among them,there are 26 atmospheric precipitation samples,18 surface water samples,9 shallow groundwater samples,55 medium and deep confined water samples,and 1 spring water sample.Using the stable isotope technique,the isotope and water chemistry characteristics of surface water and groundwater were characterized by the graphical method.The recharge elevation method was used to determine the recharge elevation area of the aquifer.The mixing ratio method was used to calculate the mixing ratio of surface water and groundwater.The technology calculates the age of the groundwater.Through the above research,the following main conclusions are drawn:1)The spatial hydrogen and oxygen isotopes(?D,?¹⁸O)in the surface water and groundwater in the study area are spatially distinct.The isotope in the upstream water is more depleted,and the middle and lower reaches are more abundant.The?D and?¹⁸O values of surface water are close to the average of local atmospheric precipitation data(?D is-44.31‰,?¹⁸O is-6.60‰),indicating that the surface water in the Anyang River Basin is derived from local atmospheric precipitation.The isotope value of deep confined water varies greatly,from the point close to the precipitation value?21,33 and 45?to the point affected by the?evaporation?or the extraneous water?23,25 and 36?.The difference of?D values in August 2016 is29‰,the?¹⁸O value differs by-4.9‰;in January 2017,the?D value differs by-30‰,and the?¹⁸O value differs by-4.8‰,indicating that there are different sources of water infiltration in the Anyang River alluvial fan to the fan front.2)The groundwater samples in the alluvial fan are closely distributed on both sides of the regional atmospheric precipitation line except for individual points,indicating that the groundwater is closely connected with the outside world,and the local part is obviously affected by human activities.The main source of recharge of river water and shallow groundwater is atmospheric precipitation;according to the elevation effect of atmospheric precipitation,the recharge elevation of medium-deep groundwater is 185-1301m,and the western mountainous area is the recharge zone of deep confined water in this area.Hydrogen and oxygen isotope and water chemical analysis shows that atmospheric precipitation is the recharge source of surface water and shallow groundwater,and the western mountainous area is the source of deep pressurized water.Calculated by the ratio of surface water to shallow groundwater mixing,the proportion of Anyang River water to shallow groundwater in the August2016 flood season was 56%,while the lateral recharge rate of other rivers and upstream shallow groundwater accounted for 44%.3)The chemical composition of the Anyang River is located on the left side of the diamond-shaped area of the Piper diagram,showing that the water chemistry type is HCO₃·SO₄-Ca·Mg type,and the chemical composition content changes little.The seasonal variation of the chemical composition of groundwater indicates that there is a significant change in groundwater in the vicinity of the fan roof of the alluvial fan in the middle of the Anyang River.Among them,the water content of the water samples with higher Cl^-content?23,25 and 36?is as high as 18%¹46%in summer,and the water chemistry type is HCO₃·Cl·?SO₄?-Ca·?Mg?.It is the highest point of the?evolution?in the Cl+SO₄ area on the Piper diagram.In the alluvial fan,as the groundwater flows downstream,the groundwater changes from submersible to confined water,and downstream Cl and SO₄ ions decrease,and HCO₃+CO₃ ions increase.The upstream and downstream of Ca ions did not change much,and HCO₃-Ca·Mg type water was formed.The groundwater quality of the Anyang River alluvial fan is only affected by surface water infiltration in the local part of the trailing edge,and the content of Cl and SO₄ ions is high.The groundwater pressure characteristics of the frontal margin of the alluvial-producing fan located in the lower reaches of the Anyang River are characterized by weak surface infiltration and good groundwater quality.4)The atmospheric precipitation devaluation before the 1953 study area was 10TU.In 2017,the weighted average of 11 TUs of the measured values of the three hydrological stations was used.The age of the diving samples is 3.8?35.5a,which is the recharge of atmospheric precipitation since the peak of atmospheric precipitation has subsided.It is speculated that the average residence time of the Xiaonanhai spring water system is 20?30a.The overall distribution of confined water age is increased from the alluvial fan to the southeast and the eastern fan.The intersection of Anyang River and South-to-North Water Transfer is the upper part of the fan.The pressure water age is 40⁵0a,and the east is in Anyang River.The area between Chapogou and Flood River increased to 50⁶0a or>60a,and the age along the flood river sample and the downstream of the Anyang River increased to 60a or older until the nuclear explosion experiment.