| Karst water is one of the most important production and living water sources for human being,which exists and runs in the karst rock strata.Karst hydrological system,as an important part of the earth surface water circulation system,has the characteristics of fragility,sensitivity and complexity.Deciphering the the hydrogeochemical dynamic change law of shallow karst groundwater is of great significance to understand the karst water cycle process and the sustainable development of karst areas.Based on weekly sampling and online monitoring,hydrology,hydrochemistry and stable isotope data were obtained in Yellow Dragon Spring Region of Aziying Township,Kunming City.The characteristics and rules of hydrological dynamic change of shallow karst groundwater are revealed by using the indexes of annual non-uniformity coefficient,complete regulation coefficient,concentration degree and concentration period and time series method.Based on the time series method,Piper trigram,PCA-mixed end element method,?D-?18O diagram and many other methods,the characteristics of Yellow Dragon Spring water were discussed to reveal the recharge source and hydrological infiltration and migration process of typical karst spring water.The research conclusions are as follows:(1)The annual inhomogeneity coefficient,complete adjustment coefficient and concentration degree of spring area show the general pattern of precipitation,cave dripping,spring water vertical decline,in which seasonal dripping>sensitivity dripping>ability dripping;The concentration period of dripping water and spring water in the cave is 2 months later than that of precipitation.The retention and response time of cave water drop and spring to precipitation are stable water dropping>seasonal dropping?spring dropping>sensitive dropping;The response time of spring water to cave dripping is seasonal dripping>sensitivity dripping>ability dripping.The water in the karst key zone has the seasonal characteristics of alternating abundant and dry periods and the hydrological zoning of vertical migration of precipitation,water drop and spring in the cave.(2)The hydro-chemical type of spring area belongs to HCO3-—Ca2+or HCO3-—Ca2+·Mg2+;In flood season,the Yellow Dragon Spring water is supplied by rain-leached karst surface water,which leads to higher Ca2+,K+,Al,Fe,HCO3-,Cl-,F-,Br-,NO32-and total carbon in flood season than in dry season.The concentration of Mg2+,Na+,Mn and other cations in spring water is higher in dry season than in flood season,and the concentration of Mg2+,Mn,Al,Fe,SO42-,F-,Br-in spring water is the highest in normal season.Most of the hydro-chemical components such as Ca2+,Mg2+,HCO3-,Mn,inorganic carbon are mainly dissolved in carbonate;Ca2+,F-,SO42-are from fluorite,fluorapatite,etc.;Br-,Cl-,Na+are from bromate or brine.Yellow Dragon Spring water and river water have similar recharge sources.In the dry season,they are replenished by deep formation water and fissure water,and in the rainy season,they are replenished by leaching and mixing of rain water,soil water and surface karst water,leading to an increase in the concentration of chemical ions in water at first and then a decrease.(3)The?D and?18O of spring area show the following rules:spring water?river waterspring dropping>river water>water.The?D,?18O,?17O and d-excess of Yellow Dragon Spring water all show that:flood season>normal season>dry season.?D and?18O water drop in the cave tend to be negative in the rainy season and positive in the dry season,flood season>normal season>dry season,the self-sensitive water drop increases to the stable water drop.The?D and?18O of Yellow Dragon Spring water drop are more positive in rainy season and more negative in dry season.(4)The water of Yellow Dragon Spring and the river have the same recharging source.The main recharge sources are meteoric precipitation and karst groundwater,which is recharged by leaching and mixing of cave water,pipe,fissure and pore water in rainy season,and by deep formation water and karst fissure water in dry season.The recharging process of spring water goes through soil,surface karst zone water,aeration zone,saturated zone,and the stream water comes from surface karst zone water.The hydrological,hydro-chemical and isotopic data of springs were collected to form three clues for the analysis of Yellow Dragon Spring Basin.The purpose of this study was to compare and discuss the hydrogeochemical dynamic characteristics of typical karst springs,Interpret the response law of karst aquifer to precipitation,and to reveal their recharge sources and the circulation mechanism of shallow karst groundwater.Further enrich the hydrological research theory of karst key zones,and provide scientific reference for the protection of water resources,flood control and drought resistance,and drinking water safety of people and animals in the vast karst areas. |
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