Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley

Abstract

International audienceAquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ∼50% of groundwater depletion in the United States since 1900. A newly developed High Plains recharge map shows that high recharge in the northern High Plains results in sustainable pumpage, whereas lower recharge in the central and southern High Plains has resulted in focused depletion of 330 km3 of fossil groundwater, mostly recharged during the past 13,000 y. Depletion is highly localized with about a third of depletion occurring in 4% of the High Plains land area. Extrapolation of the current depletion rate suggests that 35% of the southern High Plains will be unable to support irrigation within the next 30 y. Reducing irrigation withdrawals could extend the lifespan of the aquifer but would not result in sustainable management of this fossil groundwater. The Central Valley is a more dynamic, engineered system, with north/south diversions of surface water since the 1950s contributing to ∼7× higher recharge. However, these diversions are regulated because of impacts on endangered species. A newly developed Central Valley Hydrologic Model shows that groundwater depletion since the 1960s, totaling 80 km3, occurs mostly in the south (Tulare Basin) and primarily during droughts. Increasing water storage through artificial recharge of excess surface water in aquifers by up to 3 km3 shows promise for coping with droughts and improving sustainability of groundwater resources in the Central Valley

Potential climate change effects on groundwater recharge in the High Plains Aquifer, USA

“…If groundwater depletion is spread over the entire High Plains Aquifer, it would result in a mean water table decline of 4.2 m; however, there is almost no depletion in the north, and water table mounds are found near parts of the Platte River, whereas depletion is focused in the CHP and SHP with water table declines of as much as 70 m in Texas [McGuire, 2009]. The spatial variation in storage depletion is primarily controlled by differences in recharge from the NHP to the SHP, which in turn is strongly affected by variations in soil texture [Scanlon et al, 2012].…”

“…[4] Previous studies on climate change and recharge in the High Plains have mainly focused on paleoclimate and how current recharge (particularly in the Southern High Plains (SHP) and Central High Plains (CHP)) is much lower than it has been under past climatic conditions during the Pleistocene [McMahon et al, 2006;Scanlon et al, 2012]. There have only been two previous studies that have investigated recharge under a future climate for the High Plains.…”

“…The aquifer is unconfined across its extent, and the preagricultural development depth to water varied from less than 5 m along rivers (predominately in the NHP) up to 100 m for parts of the CHP and SHP [Scanlon et al, 2012].…”

“…However, groundwater extractions currently exceed recharge by up to a factor of 10 in some areas, resulting in depletion of storage mostly in the central and southern High Plains. Depletion has averaged 5.7 km 3 yr À1 since irrigation development began in the 1950s [Scanlon et al, 2012], making the High Plains a globally significant hotspot of groundwater depletion [Wada et al, 2010].…”

Eos, Transactions, American Geophysical Union Volume 94, Number 1, 01 January 2013

“…His term "feasible" may have anticipated many current issues about aquifer sustainability. Papers published this year on the Ogallala aquifer in the central United States and on the global groundwater "footprint" [Scanlon et al, 2012;Gleeson et al, 2012] focus on recharge as an index of sustainability and have been featured in the popular press. However, I argue in this Forum that natural recharge rates alone cannot serve to address the core policy question regarding sustainable aquifer conditions in response to well field stresses.…”