Study On The Hydraulic Relationships Between Groundwater And Lake Water In The Typical Wetland Of Poyang Lake

The high dynamic change of water level is the unique hydrogeological characteristic of Poyang Lake,which leads to the seasonal alternation of dryness and wetness in wetland,and brings a quite sensitive dynamic response of the hydrological system of beach wetland.The study on the relationship between groundwater and lake water and the mechanism of interaction is of great importance to the management of lake water resources and maintenance of the stability of lake ecosystem.The key point of the study on the interaction between groundwater and lake water is the relationship between water supply and drainage and the regular pattern of their transformation.Study on the relationship between groundwater and Lake Water transformation in Poyang Lake and its main influencing factors has a great practical significance on the study on the appropriate hydrological rhythm for the scientific protection and restoration of Poyang Lake ecology,maintain the health of Poyang Lake wetland ecosystem,and the evaluation of water environment and water resources in the lake area.This paper goals to reveal the relationship between groundwater and lake water transformation in Poyang Lake and explores the relationship between groundwater and lake water in different typical areas,with research strategy combining multiple methods.Firstly,the field monitoring of groundwater level and lake water level is carried out,and the velocity and direction of groundwater flow are measured by field monitoring method,and the dynamic change of groundwater level is analyzed by collecting groundwater and lake water sample isotopic analysis.According to the hydrochemical data and the characteristics of the groundwater flow,the relationship between groundwater and lake water and the transformation pattern between them are revealed.Based on all above this paper explores the applicability of ground penetrating radar detection technology and high density resistivity method in typical wetland of Poyang Lake,and shows the variation characteristics of groundwater level process line,along the gradient of the section,under different seasonal conditions in Poyang Lake by using the ground penetrating radar and high density resistivity method,and analyzes the lithology of aeration zone,the characteristics of groundwater distribution and the spatial distribution of groundwater.Finally,the hydraulic relationship between lake water and groundwater in different typical areas of Poyang Lake is estimated by Darcy's law and statistical method and mainly results as following:?1?The comprehensive analysis of ground penetrating radar and high density electric method shows that,in the average sense,the typical beach wetland in Poyang Lake is from1.7m to 2.65m for rock layer and 3.5m for diving level.It is shown that the ground penetrating radar has the ability of high resolution shallow exploration and is sensitive to detecting the medium with obvious horizontal development of stratification.Therefore,the ground penetrating radar can accurately characterize the depth of the underground layer of the wetland.?2?The experimental results of high density resistivity method show that the topography of the study area is gradually inclined from land to lake with a same direction with that of lake water receding,and the apparent resistivity of near-surface strata increases with the direction of strike and depth.The results obtained from the polar distance of 3 m is precise and the depth of the polar distance of 6 m is deep.?3?The analytic results of water samples from typical study area of Poyang Lake show that the groundwater and lake water in the riparian zone are weakly acidic.The chemical composition of both is basically the same,of which the main anions include SO₄^2-,Ca²⁺and Mg²⁺.The results of velocity and flow meter combined with Surfer software show that the flow direction of groundwater in the study area is from the hilly area to the Poyang Lake area,and the hreatic surface is an oblique surface which is inclined to discharge area from recharge area.The water chemical composition and groundwater flow direction indicate to some extent that there is a transformation relationship between groundwater and lake water.?4?The analysis results of the monitoring data of groundwater level,indicate that the groundwater level is obviously changing dynamically in the study area.The level of groundwater decreases gradually from upstream to downstream.The maximum velocity of groundwater in the hilly area far from the lake area and the river is 19.5 m/d,the average velocity of groundwater near the downstream lake area is about 5.1 m/d,and the flow direction of groundwater is basically the same with the change of topography.The results show that the groundwater in the study area is likely to be discharged to Poyang Lake and recharge the lake water during the dry season,which further indicates that there is a transformation relationship between the groundwater and the lake water.?5?The field monitoring data and the quantitative results of Darcy's law and statistical method show that the groundwater and lake water in the typical wetland of Poyang Lake have a close relationship from June and September during the high-water period.There is a positive correlation between lake water level and beach wetland water level change,which means that the change of lake water level is the main factor affecting the change of wetland groundwater level.The variation of water level and groundwater level of typical beach lake is consistent with that of groundwater level,indicating that there is a more obvious hydraulic gradient between them.In addition to July,there has always been a large water level difference between the groundwater level and the lake water level,which indicates that the discharge intensity of groundwater in the riparian zone of Poyang Lake has seasonal difference.The groundwater level in the riparian zone is higher than that in Poyang Lake during the whole monitoring period.The water level difference between the two will lead to the groundwater flowing to the lake at different rates,that is the groundwater recharges the lake water,and the transformation relationship between the lake water and the groundwater is seasonal.