Abstract
The Jinan Karst Spring System in Shandong province, China, has suffered to maintain groundwater level and spring flowing for decades. Recharge of river water to karst aquifer in Jinan is important for the outflowing of four large karst springs in the city center. Field investigations were conducted for two times in May and October, 2015, respectively and water samples were collected for hydrogeochemical and isotopic measurements. Results showed that (a) the water type was predominantly Ca-HCO3-SO4 for karst groundwater, and Ca-Mg-SO4 for river water; (b) the concentration of HCO3− and NO3− in karst groundwater were higher than that in river water, in contrast, the concentration of SO42− and K+ in karst groundwater were lower than that in river water; (c) the δ2H and δ18O values with average of −51.2‰ and −6.6‰ for river water is more enriched than the values in groundwater samples (−59.1‰ and −8.3‰), in that river experienced evaporation in the upstream reservoir; (d) Based on the distribution pattern of δ18O, groundwater near river bank was found to be recharged from river water and found a preferential flow path in karst aquifer situated from Dongkema to Manzizhuang near the river bank. This study provides useful information for understanding of the hydraulic connection between river water and karst aquifer, and benefit the protection and management of water resources.
Highlights
The evaluation of effect of river water recharge on karst aquifers has double significances: the scientific one in terms of the relationship between river water and karst aquifers and the applied one in terms of the assessment and protection of karst water resources
It is not easy to identify the effect of river water infiltration through the streambed on karst groundwater due to the complex hydrogeological conditions of karst systems [1,2]
The karst aquifer comprises a pattern of triple porosity, the matrix, fractures and conduits, which causes a high degree of heterogeneity on the hydraulic conductivity [3,4,5,6,7] and make it difficult to identify the flow paths and spatial effect areas of river water recharge in karst aquifers [8]
Summary
The evaluation of effect of river water recharge on karst aquifers has double significances: the scientific one in terms of the relationship between river water and karst aquifers and the applied one in terms of the assessment and protection of karst water resources. The recharge from the intermittent river is seasonally variable [9,10,11], which makes it difficult to reveal the temporal effect of river water recharge on karst groundwater [1,12]. Traditional hydrogeological investigations such as water level monitoring and river flow measurement result in uncertainty in evaluating the effect of river water recharge on karst groundwater. Inverse hydrogeochemical modeling can quantitatively study the theoretical mass transformation along the flow paths [17]
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