Efficient use of water resources in semi-arid agro-ecosystems of the Central Plains of the U.S.A. has emerged as an important issue because of the rapid depletion of freshwater resources and drought conditions, and degradation of groundwater quality in recent years. In the Central Plains of the United States, 90% or more of the precipitation is returned to the atmosphere by evapotranspiration (ET). Accurate and consistent estimation of ET is one of the key elements for better planning and managing water resources. Accurate quantification of ET in irrigated agriculture is critical in the context of crop production, water allocations, scheduling of irrigation, evaluation of the effects of changing land use on water yields, and environmental assessment by developing best management practices for surface and groundwater quality protection. Thus, accurate quantification of ET is important for predicting the status of the soil water supplies and their allocation and efficient use. Better allocation and management of the region's water resources will ultimately affect the region's economy.
Water is the life support of irrigated agriculture in Nebraska and the state's irrigated lands are extremely vital to the state's economy. The Nebraska Department of Natural Resources (NDNR) has declared some watersheds fully appropriated under the provisions of the state law LB962, which requires Natural Resources Districts (NRDs) associated with these watersheds to develop integrated management plans, rules and regulations that may prevent drilling new wells and restrict or closely regulate irrigation on existing irrigated acres. As a result, some growers are limited to pump only 50 to 70% of the full irrigation water requirement for maximum yield, forcing adoption of some kind of deficit irrigation strategy in response to limitations on groundwater withdrawal.
The Central Platte Natural Resources District stretches 175 miles east from the Lincoln-Dawson county line near Gothenburg to Columbus and has 2.1 million acres, which is the largest NRD in the state in terms of irrigated land and number of wells. Most of the land in the CPNRD is irrigated with center pivots and the district has over 17,000 active irrigation wells. Some of the major irrigated crops in the district are field corn, seed corn, sorghum, and soybeans. CPNRD has been working on projects to provide science-based information to the users to assure an adequate supply of water for feasible and beneficial uses through proper management, conservation, development and utilization of the District's water resources. CPNRD has been involved in groundwater level observations, administering irrigation runoff regulations, groundwater quantity and quality management, groundwater modeling and development of a surface water flow model which will all lead to a complete groundwater and surface water management program. This project will be supplementary to aforementioned projects and will provide improved crop water use information for some key cropping systems in the district.
