ABSTRACT

The Upper Cibolo Creek (UCC) karst watershed in Central Texas, USA, represents a portion of the drainage area that supplies water to the recharge zone for the Edwards Aquifer. However, the surface water–groundwater interactions along the UCC are not well quantified, and the hydraulic interactions are important for water budget and water quality of the aquifer. In this study, we investigated the evolution of hydrochemical and isotopic signatures (δ¹⁸O, δ²H and d-excess) from precipitation, surface water to groundwater in the UCC watershed from 2017 to 2019, and investigated surface water–groundwater interactions using samples from 14 creeks/spring sites. Factor analysis for the observed parameters demonstrates that changes in water hydrochemistry are primarily controlled by human activity, precipitation input, and water–rock interaction. Hierarchical clustering analysis of temporal isotope variations confirms that significant surface water–groundwater interactions occur in the UCC watershed. We identified relationships between nitrate concentrations at creek/spring sites and land-use conditions, and nitrate input sources were determined utilizing the dual-isotope analyses (δ¹⁵N and δ¹⁸O) of nitrate. This study provides capacity for a more precise assessment of water resources and water quality in Central Texas.

摘要

美国得克萨斯州中部的上 Cibolo Creek (UCC) 喀斯特流域代表了为 Edwards 含水层补给区供水的流域的一部分。然而，沿 UCC 的地表水 - 地下水相互作用没有得到很好的量化，水力相互作用对含水层的水收支和水质很重要。在这项研究中，我们研究了水化学和同位素特征（δ ¹⁸ O、δ ² H 和d-excess）从 2017 年到 2019 年 UCC 流域的降水、地表水到地下水，并使用来自 14 个小溪/泉水地点的样本研究了地表水 - 地下水的相互作用。观测参数的因子分析表明，水水化学的变化主要受人类活动、降水输入和水-岩相互作用控制。时间同位素变化的分层聚类分析证实，UCC 流域发生了显着的地表水-地下水相互作用。我们确定了小溪/泉水地点的硝酸盐浓度与土地利用条件之间的关系，并利用双同位素分析（δ ¹⁵ N 和δ ¹⁸O) 硝酸盐。这项研究为更精确地评​​估德克萨斯州中部的水资源和水质提供了能力。