Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2010
Publication Date: 12/15/2010
Citation: Scanlon, B.R., Reedy, R.C., Gates, J.B., Gowda, P. 2010. Impact of agroecosystems on groundwater resources in the Central High Plains, USA. Agriculture Ecosystems and Environment. 139(4):700-713. Interpretive Summary: Sustainable management of fast depleting groundwater resources in the Texas High Plains is needed. It requires a quantitative understanding of all the inputs to and outputs from the underlying Ogallala Aquifer. In this study, we quantified recharge rates in different agricultural systems in the northern Texas High Plains. Recharge is controlled by soil texture and land use. Limited or no recharge was found beneath natural systems. Moderate recharge rates were found under rain-fed agroecosystems. Irrigation increased recharge rates in all soils. Overall, recharge rates in the northern Texas High Plains is too low to allow sustainable development of the Ogallala Aquifer water.
Technical Abstract: Agroecosystems impact water resources by changing water partitioning at the land surface and by consuming most fresh water through irrigation. The study assesses impacts of agroecosystems on groundwater resources in the Texas High Plains (37,000 km2 area). Borehole samples beneath different agroecosystems were analyzed for matric potential and water-extractable chloride and nitrate to quantify groundwater recharge. Percolation/recharge is controlled by soil texture and land use. In fine-medium grained soils, there is no recharge beneath natural ecosystems or rain-fed agroecosystems; however, recharge is focused beneath playas and drainages. In medium-coarse grained soils, percolation/recharge beneath natural ecosystems is low (median 4.8 mm/yr, 1% of precipitation) and beneath rain-fed agroecosystems is moderate (median 27 mm/yr, 5% of precipitation). Irrigation increased percolation/recharge under all soil types (median 37 mm/yr, 4% of precipitation plus irrigation). Irrigation has resulted in large scale declines in groundwater levels since the 1950s (>/= 15 m over 11,400 km2 area) with declines </= 1.3 m/yr in wells. Total water-storage decline since the 1950s (57 km3) exceeds regional recharge (3.1 km3) by approximately 20 times. Regional recharge is too low (approximately 5 mm/yr) to allow sustainable irrigation and groundwater abstractions constitute mining of the aquifer, which is being managed as a nonrenewable resource.