Managing Groundwater to Ensure Ecosystem Function

Abstract

Groundwater is a critical resource not only for human communities but also for many terrestrial, riparian, and aquatic ecosystems and species. Yet groundwater planning and management decisions frequently ignore or inadequately address the needs of these natural systems. As a consequence, ecosystems dependent on groundwater have been threatened, degraded, or eliminated, especially in arid regions. There is growing acknowledgment that governmental protections for these ecological resources are necessary, but current legal, regulatory and voluntary provisions are often inadequate. Groundwater management premised on "safe yield," which aims to balance human withdrawals with natural recharge rates, typically provides little to no consideration for water needed by ecosystems. Alternatively, the "sustainable yield" concept aims to integrate social, economic and environmental needs for groundwater, but the complexity of groundwater systems creates substantial uncertainty about the impact that current or future groundwater withdrawals will have on ecosystems. Regardless of the legal or regulatory framework, guidance is needed to help ensure environmental water needs will be met, especially in the face of pressure to increase human uses of groundwater resources. In this paper, we describe minimum provisions for planning, managing, and monitoring groundwater that collectively can lower the risk of harm to groundwaterdependent ecosystems and species, with a special emphasis on arid systems, where ecosystems and species may be especially reliant upon and sensitive to groundwater dynamics.

The vulnerability of springs and phreatophyte communities to groundwater level declines in Oregon and Nevada, 2002–2021

“…Groundwater can provide ecological stability to groundwater dependent ecosystems under climate variability by providing fairly constant aquatic environments, enabling the evolution of assemblages of endemic taxa (Cantonati et al, 2020), but excessive groundwater withdrawals can dry springs and lead to the elimination of springs-dependent taxa (Williams and Sada 2021). Monitoring at appropriate temporal and spatial scales can provide early warning for impacts and can help resource managers make appropriate decisions to maintain sustainable yield, learn from management actions, and mitigate risk to GDEs (Saito et al, 2021). This study demonstrates that groundwater levels between 2002 and 2021 were frequently declining in Oregon and Nevada, and substantial proportions of springs and phreatophytes near monitoring wells could be impacted by the declines.…”

Sustainable Use of Groundwater May Dramatically Reduce Irrigated Production of Maize, Soybean, and Wheat

“…In areas with considerable depth to water, it would likely be decades before environmental flows have an impact. To what extent water levels would rise and where, and complicating factors such as post-development aquifer changes, environmental flows, and vulnerable shallow domestic wells, make narrowing the range of recharge accessible, and in turn the uncertainty in our findings, difficult (Bredehoeft, 2002;Saito et al, 2021).…”

“…As soon as the pump is turned on, it is the local hydrogeology, which includes but is not limited to recharge (e.g., discharge, transmissivity, pumping rate), that determines the dynamic response of the aquifer (Bredehoeft, 2002). Further, even if we assume that the water table after pumping remains constant and is therefore sustainable from the perspective of human water use, if discharge to the lake is diminished it may not be sustainable from the perspective of environmental water use (Saito et al, 2021). Scanlon et al (2002) also note that aquifer recharge rates are difficult and expensive to measure, which limits both the evaluation and improvement of recharge estimates for the continental US.…”

Ecohydrology of coastal aquifers in humid environments and implications of a drying climate

“…Integrating abiotic and biotic indicators into assessments of groundwater regime modification will prove useful in defining resultant alterations to ecosystem processes (Korbel & Hose, 2017). To preserve ecosystem function, research must aim to uncover the minimum provisions for planning, managing and monitoring groundwater across coastal catchments (Saito et al, 2021).…”