Bioenergy feedstock development scenarios & potential impacts on regional groundwater withdrawals

Authors: UDEN, DAN - University Of Nebraska; ALLEN, CRAIG - Us Geological Survey (USGS); Mitchell, Robert - Rob; GUAN, QINGFENG - Wuhan University; MCCOY, TIM - Nebraska Game & Parks Commission

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2013
Publication Date: 9/9/2013
Publication URL: http://handle.nal.usda.gov/10113/57904
Citation: Uden, D., Allen, C., Mitchell, R., Guan, Q., Mccoy, T. 2013. Bioenergy feedstock development scenarios & potential impacts on regional groundwater withdrawals. Journal of Soil and Water Conservation. 68:124-128.

Interpretive Summary: Irrigation has increased agricultural productivity worldwide, but has also stressed water resources. Drier conditions associated with climatic changes could strain finite water supplies in landscapes where human populations rely on groundwater for drinking, agriculture, energy and industry. In the North American Great Plains, rowcrops are utilized for food and bioenergy production and a large portion are irrigated with groundwater from the High Plains Aquifer System. Under projected future climatic conditions, greater crop water use requirements and diminished groundwater recharge rates could make rowcrop irrigation less feasible in some areas. Switchgrass is an alternative biofuel feedstock that could be produced in Great Plains agricultural landscapes with economic and environmental benefits, one of which is a reduced dependence on intensive irrigation. This study considers how drought tolerant bioenergy feedstocks could contribute to groundwater conservation efforts in an agricultural landscape under future climatic changes. We developed 3 biofuel–based agricultural landuse change scenarios for the intensely cultivated and irrigated Rainwater Basin region of south–central Nebraska, U.S.A., each driven by potential future climatic changes, irrigation limitations, commodity prices and ethanol demand. In climate change scenarios, annual groundwater irrigation withdrawals decreased by 3–6% in the study area, or by 10–19% in areas where irrigation limitations have been implemented and may be most severe under future conditions. In intensive agricultural landscapes where irrigation increases productivity, adopting drought tolerant bioenergy crops could provide income for farmers while conserving groundwater.

Technical Abstract: Availability of ample groundwater supplies for irrigation can increase the productive potential of agricultural landscapes; however, excessive withdrawals threaten sustainable use, and shortages could be exacerbated by drier future conditions in some regions. Throughout the North American Great Plains, irrigation has facilitated the conversion of grasslands to rowcrops and increased productivity, but has also decreased water table levels. Maize (Zea mays) grain is currently utilized for food and ethanol production in Great Plains agricultural landscapes, but switchgrass (Panicum virgatum) is a relatively drought tolerant, alternative biofuel feedstock that may be environmentally and economically superior to maize grain for ethanol production. Non–irrigated, small, marginally productive rowcrop fields are considered most suitable for conversion to switchgrass; however, under novel climatic conditions and ensuing agricultural policy adjustments, some larger, less productive irrigated rowcrop fields could also be converted. We developed 3 agricultural landuse change scenarios for the heavily cultivated and irrigated Rainwater Basin region of Nebraska, U.S.A., each driven by potential future climatic changes, irrigation limitations, commodity prices, and ethanol demand. For each scenario, we generated spatially explicit maps of rowcrop and switchgrass field distributions and identified registered groundwater irrigation wells. Under scenarios assuming climatic changes, annual groundwater irrigation withdrawals decreased by 3% – 6% in the entire study area, or by 10% – 19% in areas where irrigation limitations have been previously implemented and may be most severe under future conditions. In intensive agricultural landscapes where irrigation increases productivity, but may become further limited, the adoption of drought tolerant bioenergy crops could provide income for farmers while contributing to groundwater conservation efforts.