Variations in vulnerability across aquifer layers in a heterogeneous aquifer system

IF 4.9 Q2 ENGINEERING, ENVIRONMENTAL

Groundwater for Sustainable Development Pub Date : 2025-05-03 DOI:10.1016/j.gsd.2025.101456

Collins Kissi Asante-Sasu , Jon Turk , Seann McClure , Alexandra McLarty

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Abstract

The Columbia Plateau Regional Aquifer System (CPRAS) is a layered basalt aquifer system that underlies the Columbia River Basin in Washington, Oregon, and Idaho. The CPRAS covers a large spatial area and is undergoing water level declines that threaten water supply. It supports agriculture, economic development, and ecological systems. The heterogeneity of the aquifer system means each aquifer layer is experiencing different levels of groundwater storage change even at the same location. The goal of this study is to evaluate the magnitude and spatial variability of groundwater declines and vulnerability across the aquifer layers. We computed groundwater level trends using the Sen Slope estimator, in each aquifer layer and by subareas in the Washington portion of the CPRAS. The trends are projected into the future and combined with changes in available drawdown to evaluate groundwater vulnerabilities in the present (2020) and the future (2040) for each aquifer layer. The vulnerability assessment only uses trends that are statistically significant at a 95 % confidence level based on the Mann-Kendall test. The largest groundwater level declines were observed in the Grande Ronde aquifer layer, with a mean decline of 1.86 ft/yr, followed by the Wanapum aquifer layer with a mean decline of 1.61 ft/yr. Declines within the Saddle Mountains and Overburden layers are an order of magnitude smaller, with mean declines of 0.56 ft/yr and 0.22 ft/yr, respectively. Although there were higher groundwater level declines in the Grande Ronde layer, the available drawdown of this layer is greater, leading to lower levels of vulnerability. However, in the Overburden layer, the available drawdown is small, driving higher groundwater vulnerability. Evaluating groundwater vulnerability based on the available drawdown rather than total aquifer saturated thickness gives a more realistic assessment of vulnerability because groundwater below well depths is not accessible without infrastructure changes.

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非均质含水层系统中各含水层脆弱性的变化

哥伦比亚高原地区含水层系统（CPRAS）是一个层状玄武岩含水层系统，位于华盛顿州、俄勒冈州和爱达荷州的哥伦比亚河流域。CPRAS覆盖了一个很大的空间区域，并且正在经历水位下降，威胁供水。它支持农业、经济发展和生态系统。含水层系统的非均质性意味着即使在同一位置，每个含水层也会经历不同程度的地下水储量变化。本研究的目的是评估地下水下降的幅度和空间变异性以及跨含水层的脆弱性。我们在CPRAS的华盛顿部分的每个含水层和分区中使用Sen Slope估计器计算地下水位趋势。对未来的趋势进行了预测，并结合可用降水的变化来评估每个含水层现在（2020年）和未来（2040年）的地下水脆弱性。脆弱性评估仅使用基于Mann-Kendall测试的95%置信度的统计显著趋势。地下水位下降幅度最大的是Grande Ronde含水层，平均下降1.86英尺/年，其次是Wanapum含水层，平均下降1.61英尺/年。马鞍山和上覆层的下降幅度要小一个数量级，平均下降幅度分别为0.56英尺/年和0.22英尺/年。虽然Grande Ronde层的地下水位下降幅度较大，但该层的有效落差更大，导致脆弱性水平较低。然而，在覆盖层中，有效落差较小，导致地下水脆弱性较高。基于有效降水层而不是总含水层饱和厚度来评估地下水脆弱性，可以更真实地评估脆弱性，因为如果没有基础设施的改变，井底以下的地下水是无法获得的。

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来源期刊

Groundwater for Sustainable Development Social Sciences-Geography, Planning and Development

CiteScore

11.50

自引率

10.20%

发文量

152

期刊介绍： Groundwater for Sustainable Development is directed to different stakeholders and professionals, including government and non-governmental organizations, international funding agencies, universities, public water institutions, public health and other public/private sector professionals, and other relevant institutions. It is aimed at professionals, academics and students in the fields of disciplines such as: groundwater and its connection to surface hydrology and environment, soil sciences, engineering, ecology, microbiology, atmospheric sciences, analytical chemistry, hydro-engineering, water technology, environmental ethics, economics, public health, policy, as well as social sciences, legal disciplines, or any other area connected with water issues. The objectives of this journal are to facilitate: • The improvement of effective and sustainable management of water resources across the globe. • The improvement of human access to groundwater resources in adequate quantity and good quality. • The meeting of the increasing demand for drinking and irrigation water needed for food security to contribute to a social and economically sound human development. • The creation of a global inter- and multidisciplinary platform and forum to improve our understanding of groundwater resources and to advocate their effective and sustainable management and protection against contamination. • Interdisciplinary information exchange and to stimulate scientific research in the fields of groundwater related sciences and social and health sciences required to achieve the United Nations Millennium Development Goals for sustainable development.