A delicate balance: Rainfall and groundwater in Nebraska during the 2000-2005 drought

Recent decreases in rainfall and the accompanying decreases in groundwater levels since 1999 indicate heightened vulnerability to drought in Nebraska and the surrounding Great Plains. Precipitation across Nebraska during 2000-2005 ranged from 72% to 108% of the 30-year normal value, with fully 90% of 150 stations reporting below-normal precipitation. Simultaneously, groundwater levels declined more than 9 m in the most heavily impacted areas, most of which were already experiencing declines due to extensive irrigation development and low recharge rates. Thus, recovery from the drought and long-term intensive land use will be particularly challenging in densely irrigated areas of Nebraska. In contrast, contemporaneous groundwater-level changes in areas with little groundwater irrigation were comparatively modest. These observations demonstrate that drought mitigation efforts in the central and northern Great Plains must consider the combined effects of area-specific reduced recharge, local geohydrology (especially as it affects recharge), and increased groundwater withdrawals.