Hydrologic‐Economic Trade‐offs in Groundwater Allocation Policy Design

Abstract

Groundwater is an essential source of water supply worldwide, supporting human and environmental needs for water including agricultural, municipal, industrial, and habitat functions. It can be a primary source of water, or a supplementary one that serves to buffer against variability of rainfall or surface water availability in years of drought or scarcity. In either case, however, groundwater pumping can induce a number of negative environmental and social consequences, called externalities, such as depletion of aquifer storage, degradation of hydrologically connected surface water, seawater intrusion, well interference, and land subsidence (Bierkens & Wada, 2019). To curb such externalities, groundwater management agencies increasingly are implementing policies to manage and regulate rates of extraction (Gorelick & Zheng, 2015). Restrictions on groundwater use, called allocations, can and often have been designed with more inter-annual flexibility compared to typical surface water allocations. In the absence of significant built storage infrastructure (e.g., reservoirs), surface water supplies typically are highly variable from year to year (Ho et al., 2017; Pagano & Garen, 2005). Physical limits therefore exist to how much surface water can be diverted for irrigation in any given year in many regions. In contrast, groundwater resources generally respond much more slowly to inter-annual weather variability (Russo & Lall, 2017), providing natural storage that can be drawn down in dry years and recharged in wet years. Such physical differences in the temporal availability of surface water and groundwater have important implications for the design of allocations. In general, surface water allocations or rights in water-scarce regions impose fixed limits on withdrawals in any individual year or season. In contrast, groundwater allocations exhibit much greater heterogeneity in the time periods over which pumping limits are imposed. In some regions, groundwater allocations are imposed as strict annual or seasonal quotas in a manner identical to surface water, in which the allocation binds every year (hereafter referred to as a "hard cap"). Single-year groundwater allocations are observed in a number of agricultural regions within the western Abstract A common environmental externality of groundwater pumping is streamflow depletion. To manage impacts of groundwater pumping on hydrologically connected surface water systems, regulators often impose quotas, or allocations, limiting the rates of groundwater extraction. Allocations vary in their temporal flexibility, ranging from single-year "hard caps" to multi-year "soft caps". Soft cap allocations allow greater flexibility for farmers, the primary users of groundwater, to adjust irrigation rates from one year to another, potentially providing greater resilience to drought but also altering hydrologic impacts of pumping. In this study, we integrate agronomic, economic, and hydrologic models to evaluate optimal irrigation decisions for a range of equivalent hard and soft ...

Estimating non‐market values of protecting groundwater in a constrained environment

“…The first level, uniform reduction, is commonly used due to its ease of implementation (Tisdell, 2010). This approach has been used to reduce groundwater allocations in Nebraska, USA (Upper Republican Natural Resources District, 2019; Young et al., 2021), and in Spain (Blanco‐Gutiérrez et al., 2011). The second level, a reduction in groundwater allocation proportional to ecological impact, was developed based on theoretical and empirical studies on groundwater spatial externalities (Brozović et al., 2010; Lan et al., 2021b; Pfeiffer & Lin, 2012).…”

Evaluating Distributed Policies for Conjunctive Surface Water‐Groundwater Management in Large River Basins: Water Uses Versus Hydrological Impacts

“…Furthermore, such policy adjustment can reduce the variation and uncertainty in water availability to the downstream area of the basin. The important role played by adjusting the time window in policy implementation was also evidenced by a recent study that compared soft and hard water use constraints for GW management in the Republican River Basin of the United States (Young et al, 2021). Hydrological outcomes can be changed by adjusting water policies between dry and wet years.…”

Introduction to Special Section: The Quest for Sustainability of Heavily Stressed Aquifers at Regional to Global Scales

“…These restrictions are typically applied as part of efforts to protect higher priority surface water users and maintain environmental flows, but defining appropriate implementation strategies is difficult (Bredehoeft, 2011). Young et al (2021) use agronomic, economic, and hydrologic models to examine the impacts of various strategies for implementing restrictions on groundwater use in aquifers in hydraulic connection with streams.…”

“…Young et al. (2021) use agronomic, economic, and hydrologic models to examine the impacts of various strategies for implementing restrictions on groundwater use in aquifers in hydraulic connection with streams.…”