Characterizing the transitory groundwater-surface water interaction and its environmental consequence of a riverside karst pool

Guanghui Jiang; Fang Guo; Liqiong Wei; Wanyi Li

doi:10.1016/j.scitotenv.2023.166532

Characterizing the transitory groundwater-surface water interaction and its environmental consequence of a riverside karst pool

Sci Total Environ. 2023 Dec 1:902:166532. doi: 10.1016/j.scitotenv.2023.166532. Epub 2023 Aug 23.

Authors

Guanghui Jiang¹, Fang Guo², Liqiong Wei³, Wanyi Li⁴

Affiliations

¹ College of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China; Key Laboratory of Karst Dynamics, MNR/GZAR, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China. Electronic address: bmnxz@126.com.
² Key Laboratory of Karst Dynamics, MNR/GZAR, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China; International Research Centre on Karst under the Auspices of UNESCO, National Center for International Research on Karst Dynamic System and Global Change, Guilin 541004, China. Electronic address: gfkarst@126.com.
³ Key Laboratory of Karst Dynamics, MNR/GZAR, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China; International Research Centre on Karst under the Auspices of UNESCO, National Center for International Research on Karst Dynamic System and Global Change, Guilin 541004, China.
⁴ Key Laboratory of Environmental Change and Resources Use in Beibu Gulf, Ministry of Education, Nanning Normal University, Nanning 530001, China.

PMID: 37625732
DOI: 10.1016/j.scitotenv.2023.166532

Abstract

Exchange between groundwater (GW) and surface water (SW) is a common occurrence in karst water systems through sinking stream disappearance or groundwater emergence. However, the transitory GW-SW interaction caused by river backflowing into a spring is poorly observed and understood. In this study, we present an approach for characterizing the influence of GW-SW interaction in a karst spring by integrating high-resolution hydrology, carefully selected hydrochemistry monitoring and precise microbe measurements. The spring-fed pool water conditions can be distinguished as high, medium, and low-water level periods in a hydrological year. The high-water level accounts for <1 % in a year, while it is associated with the hydrological regimes of backflooding states. The inflow of river backflow was found to be 4.4 times that of the natural discharge of spring water during a rainfall event. The duration of river intrusion into the spring or karst conduit could be assessed by jointly interpreting hydrography and physicochemical signatures, while the lasting environmental consequences should be evaluated together with biotic factors such as Escherichia coli. The GW-SW interaction induced by river backflow has led to the retention of river water in a pool, spring, and karst conduit for 132, 94, and 56 h, respectively. Despite turbidity returning to normal levels after 56 h, E.coli continued to persist for an extended duration. Our study reveals that despite the transient nature of GW-SW induced by river backflow on the hydrograph, they present a lasting risk of contamination from heavy metals, organic matter, and microorganisms. This extended influence can persist within a karst aquifer lacking a hyporheic zone. This research contributes to the quantification of processes involved in transitory GW-SW interaction in a karst spring, and it highlights the underestimation of GW-SW interactions in karst water systems, which might negatively impact water resources management.

Keywords: Flooding event; GW-SW interaction; Hyporheic zone; Karst spring; River backflow.