Special issue: improving irrigation management across the Ogallala aquifer, USA
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EDITORIAL
Special issue: improving irrigation management across the Ogallala aquifer, USA Allan A. Andales1,3 · Daran Rudnick2 · José L. Chávez3 Published online: 22 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Introduction Groundwater stored in aquifers is a major source of irrigation water for many agricultural regions that receive insufficient precipitation for crop production. In the U.S.A., the High Plains aquifer (HPA) that underlies parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming supplies irrigation water for agricultural production. The HPA underlies around 450,658 km2 (174,000 mi2) of which the Ogallala aquifer is the principal geologic formation underlying 347,059 km2 (134,000 mi2) (Gutentag et al. 1984). The Ogallala aquifer is primarily a water table (unconfined) aquifer with saturated thickness ranging from 0 m to about 366 m (McGuire 2017). Average annual precipitation ranges from 400 mm in the west to 800 mm in the east of the Ogallala aquifer region (OAR), while mean annual pan evaporation ranges from 1500 mm in the north to 2700 mm in the south of the OAR (Zhang et al. 2019). Agriculture in the OAR is heavily dependent on irrigation with almost 88% of water withdrawal from the Ogallala aquifer used for crop production (Ajaz et al. 2020). Recent droughts have only exacerbated declines in groundwater (Zhang et al. 2019). Water pumped from the aquifer is primarily applied through center pivot sprinkler systems to irrigate major crops, such as alfalfa (Medicago sativa), maize (Zea mays), cotton (Gossypium hirsutum), soybean (Glycine max), winter wheat (Triticum aestivum), and sorghum (Sorghum bicolor) (Ajaz et al. 2020). Area-weighted state-wide * Allan A. Andales [email protected] 1
Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523, USA
2
Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
3
Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523, USA
average water level changes in the Ogallala aquifer from predevelopment (1950′s) to 2015 ranged from − 12.5 m (decline) in Texas to + 0.2 m (increase) in South Dakota, with an area-weighted average decline of − 4.8 m across the entire aquifer (McGuire 2017). However, local water level changes based on 3164 individual wells exhibited a larger range, with extremes of + 25.6 m rise in Nebraska to − 71.3 m decline in Texas during the same period (McGuire 2017). Sustainability of groundwater pumping to support irrigated agriculture varies across the OAR. Greater saturated thickness and recharge in the northern part of the aquifer (Nebraska and South Dakota) could feasibly sustain pumping while lower recharge and greater evaporative demand in the southern (Texas and New Mexico) and west-central (Colorado, Kansas, and Oklahoma) parts of the OAR make long-term pumping less sustainable (Deines et al. 2020). Although widely varying grou
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