Depletion and Capture: Revisiting “The Source of Water Derived from Wells”

Abstract

A natural consequence of groundwater withdrawals is the removal of water from subsurface storage, but the overall rates and magnitude of groundwater depletion and capture relative to groundwater withdrawals (extraction or pumpage) have not previously been well characterized. This study assesses the partitioning of long-term cumulative withdrawal volumes into fractions derived from storage depletion and capture, where capture includes both increases in recharge and decreases in discharge. Numerical simulation of a hypothetical groundwater basin is used to further illustrate some of Theis' (1940) principles, particularly when capture is constrained by insufficient available water. Most prior studies of depletion and capture have assumed that capture is unconstrained through boundary conditions that yield linear responses. Examination of real systems indicates that capture and depletion fractions are highly variable in time and space. For a large sample of long-developed groundwater systems, the depletion fraction averages about 0.15 and the capture fraction averages about 0.85 based on cumulative volumes. Higher depletion fractions tend to occur in more arid regions, but the variation is high and the correlation coefficient between average annual precipitation and depletion fraction for individual systems is only 0.40. Because 85% of long-term pumpage is derived from capture in these real systems, capture must be recognized as a critical factor in assessing water budgets, groundwater storage depletion, and sustainability of groundwater development. Most capture translates into streamflow depletion, so it can detrimentally impact ecosystems.

Land subsidence and recovery in the Albuquerque Basin, New Mexico, 1993–2014

“…Groundwater generally leaves the groundwater system through pumping from wells (though some of this reenters the groundwater system as return flow), seepage into the Rio Grande and (or) riverside drains, evapotranspiration, and subsurface outflow to the downgradient Socorro Basin to the south (Bartolino and Cole, 2002). The effect of pumping may cause outflow from the system to exceed inflow; the difference will be compensated by flows into the system from aquifer-system storage and (or) captured flows from other inflow sources, reduced outflow through evapotranspiration, stream/groundwater exchange, and subsurface groundwater flow (Konikow and Leake, 2014). Flows from aquifer-system storage cause groundwater levels to decline and may cause susceptible sediments in the aquifer system to compact and land subsidence to occur.…”

Groundwater intensive exploitation and mining in Gran Canaria and Tenerife, Canary Islands, Spain: Hydrogeological, environmental, economic and social aspects

“…In relatively large extent and moderate to low permeability aquifers these modifications produce a slow and progressive decrease in groundwater reserves (Custodio, 2002;Konikow and Leake, 2014). When groundwater abstraction does not exceed recharge under current exploitation circumstances, a final steady state can be attained in what refers to water quantity.…”

Hydrology and numerical simulation of groundwater flow and streamflow depletion by well withdrawals in the Malad-Lower Bear River Area, Box Elder County, Utah

“…The term "capture" was defined by Lohman and others (1972, p. 3) as the combination of decreased discharge and increased recharge. The term capture has been used by many others, including Leake and others (2010) and Konikow and Leake (2014) to describe the effects of groundwater pumping on surface water.…”