Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL, 32306, USA.
Florida Geological Survey, 3000 Commonwealth Blvd #1, Tallahassee, FL, 32303, USA.
Ground Water. 2021 Nov;59(6):856-865. doi: 10.1111/gwat.13105. Epub 2021 Apr 29.
Oxygen and hydrogen isotopes were used in this study to detect a hydraulic connection between a sinkhole lake and a karst spring. In karst areas, surface water that flows to a lake can drain through sinkholes in the lakebed to the underlying aquifer, and then flows in karst conduits and through aquifer matrix. At the study site located in northwest Florida, USA, Lake Miccosukee immediately drains into two sinkholes. Results from a dye tracing experiment indicate that lake water discharges at Natural Bridge Spring, a first-magnitude spring 32 km downgradient from the lake. By collecting weekly water samples from the lake, the spring, and a groundwater well 10 m away from the lake during the dry period between October 2019 and January 2020, it was found that, when rainfall effects on isotopic signature in spring water are removed, increased isotope ratios of spring water can be explained by mixing of heavy-isotope-enriched lake water into groundwater, indicating hydraulic connection between the lake and the spring. Such a detection of hydraulic connection at the scale of tens of kilometers and for a first-magnitude spring has not been previously reported in the literature. Based on the isotope ratio data, it was estimated that, during the study period, about 8.5% the spring discharge was the lake water that drained into the lake sinkholes.
本研究利用氧和氢同位素来探测一个落水洞湖泊与一个岩溶泉之间的水力联系。在岩溶地区，流向湖泊的地表水可能会通过湖底的落水洞排入下面的含水层，然后在岩溶管道中流动，并通过含水层基质流动。在美国佛罗里达州西北部的研究地点，密科苏基湖立即流入两个落水洞。示踪剂实验的结果表明，湖水在距离湖泊下游 32 公里的一级泉——天然桥泉中排出。在 2019 年 10 月至 2020 年 1 月的旱季期间，从湖中、泉水以及离湖 10 米的地下水井每周采集水样，结果发现，当去除泉水同位素特征中降雨影响时，泉水同位素比值增加可以用重同位素富集的湖水混入地下水来解释，表明湖泊与泉水之间存在水力联系。这种在数十公里尺度上对一级泉的水力联系的探测在文献中尚无报道。根据同位素比值数据，估计在研究期间，约有 8.5%的泉水流量是排入湖落水洞的湖水。
