| Under humid subtropical monsoon climate,the special hydrogeological structure of karst trough valley in southwest China leads to the complicated and rapid transformation process of"three rivers"in this area.It makes the development of high water storage structure more difficult,and the water resources leakage in the mountain areas of the trough and valley is serious.Then the strong interference of modern human activities is superimposed.As a result of the frequent drought and waterlogging disasters and the worsening of water pollution in the region,the development of local society and economy has been restricted to a certain extent.This paper takes the northeast of Langxi syncline karst trough in Yinjiang County,Guizhou Province,as the research area,through data collection,hydrogeological investigation,rainfall monitoring.The characteristics of rainfall and hydrochemistry in the study area are analyzed synthetically to clarify the dynamic characteristics of karst water.It provides data support and basis for the study of hydrochemistry in karst area with trough valley as the geological background.At the same time,combined with the local water situation,the protection and development of karst water are put forward.The specific research contents are as follows:First of all,to carry out field investigation based on the collected research areas related to hydrogeological data,further understanding of the geological structure characteristics of groundwater recharge,runoff and discharge conditions were found,the exposed.In the study area,analyzed and selected to replace the table of dynamic sampling and automatic spring monitoring.Secondly,in view of the large relative altitude difference in karst trough valley,we set up rainfall observation points at different elevations.Six rainfall stations were set up between500m and 1200 m above sea level,and Rain Water was collected regularly.The precipitation and the stable isotopic value of hydrogen and oxygen of Rain Water were measured.The altitude effect of rainfall and stable isotope value of hydrogen and oxygen in this area was studied systematically.Thirdly,the field monitoring,sampling and indoor test analysis of the main spring sites in Longxi Karst trough Valley are carried out.The field monitoring indexes mainly include water temperature?T?,electrical conductivity?EC?,pH value?pH?,Ca2+and HCO3-concentration.The contents of water sample test and analysis in laboratory mainly include the concentration of anions such as K+,Na+,Mg2+,and NO3-,SO42-,Cl-,and the hydrogen and oxygen stable isotopic values of spring water,and the regularity of hydrochemistry and isotope field of groundwater in the study area is summarized.Fourthly,the high time resolution automatic monitoring of typical karst springs has been carried out.The monitoring contents include rainfall,spring water flow,pH value,water temperature?T?,electrical conductivity?EC?and so on.Combined with the results of indoor test and analysis,the water carbon dioxide partial pressure?pCO2?and calcite saturation index?SIC?are calculated.The characteristics of hydrochemical seasonal variation and annual variation of typical karst springs are summarized.At the same time,the attenuation analysis of spring flow is carried out.The water storage capacity of different scale water-bearing media was studied.The main conclusions of the study are as follows:?1?The spring in the trough valley area is mostly exposed near the junction of Changxing formation and Wujiaping formation in the Permian,and the larger the dip angle is,the less the spring point is,mainly due to the greater the rock dip angle.Groundwater leakage is fast and not easy to be exposed.?2?The spatial distribution of precipitation is uneven,and there are three kinds of variation rules:linear type,inverse"S"type and irregular type at different elevations.The stable isotopes in precipitation have elevation effect and rainfall effect.?3?The main water chemical components are affected by water,rock and gas for different periods of time in the direction of karst water recharge,runoff and discharge.?4?Through the analysis of the flow recession,it is found that,The inner spring of Longdong Bay is a double water-bearing medium of pipeline and fissure and the sensitivity of karst water-bearing system makes the dynamic response of water quality and quantity to rainfall events rapid.The pH and EC values of the precipitation after a long period of no available rainfall increased first and then decreased. |
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