2025-07-09 ワシントン州立大学 (WSU)
＜関連情報＞
- https://news.wsu.edu/press-release/2025/07/09/wsu-study-offers-detailed-look-at-declining-groundwater-in-regional-aquifer-system/
- https://www.sciencedirect.com/science/article/pii/S2352801X25000530
不均質帯水層系における帯水層間の脆弱性の変化 Variations in vulnerability across aquifer layers in a heterogeneous aquifer system
Collins Kissi Asante-Sasu, Jon Turk, Seann McClure, Alexandra McLarty
Groundwater for Sustainable Development Available online: 3 May 2025
DOI:https://doi.org/10.1016/j.gsd.2025.101456
Graphical abstract
Highlights
- Groundwater vulnerability is quantified based on the amount of groundwater accessible by existing well infrastructure.
- Groundwater trends and vulnerability vary by aquifer layer, even in the same geographic location.
- Groundwater studies and management need to account for vertical and spatial heterogeneity in groundwater systems.
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.
