Dynamic variation characteristics of water chemistries and isotopes in a typical karst aquiferous system and their implications for the local karst water cycle, Southwest China

Abstract

The paper chose a typical karst aquiferous system in southwest China to study karst water cycle process to help the sustainable development and utilization of karst water resources. Different water bodies’ water chemistries and isotopes’ characteristics and their implications are analyzed based on the conceptions of transformations among “precipitation, vadose zone water flow, karst conduit water flow, and surface water flow” and the “recharge, runoff, and drainage”. Hydrological information can be obtained by analyzing water chemistries, δD and δ18O values, deuterium excess values, regression equations, influencing factors of all water bodies and precipitation in rainy season and dry season. Topography, geomorphology, and developed characteristics of karst areas affect circulation process of karst water resource, water chemistries and isotopes along the main conduit having a great fluctuation affected by changes of water dynamic conditions. Ca2+ and HCO3− are the main cation and anion in the karst aquiferous system, concentrations of Cl− and NO3− respond to the influence of human activities significantly, the dilution affection of precipitation recharging groundwater on the concentration of Ca2+ and Mg2+ is biggest, and affection of human activities on water bodies in rainy season is higher than dry season. δD and δ18O values have the increasing trend along the underground river flow path for the water–rock interaction; d values are higher and have more obvious fluctuating status along the main flow path in dry season for the long non-successive residence time. δD, δ18O and d values’ dynamic variation characteristics of cave drip water, epikarst springs, karst conduit water, and surface water in different seasons are mainly affected by recharging sources and evapotranspiration, the hydrological environment and fractionation, the developed location and evaporation, condensation and evaporation, respectively. Dynamic variation characteristics of water chemistries, isotopes, d values and their implications in the karst water cycle can help decision makers to take effective measures to protect and utilize karst water resources.