Agricultural water rights for irrigation of 17,500 acres in the Cache la Poudre basin were acquired by the City of Thornton. Northern Colorado Water Conservancy District (NCWCD) objected to the change of the water rights from agricultural use to municipal uses so that it could ensure that no injury would occur to other water rights in the basin. W. W. Wheeler and Associates, Inc. was retained to provide engineering analysis of the surface water portion of the proposed change.

The major focus of the Wheeler investigations was to determine the amount of water that was historically consumptively used. Wheeler quantified the amounts of irrigation water attributable to transmountain, reservoir storage, native direct flow sources and surface and ground water inflow into the WSSC system. Wheeler performed extensive field and operational studies to quantify canal seepage losses, river and farm headgate deliveries, on-farm water use, historical crop evapotranspiration (ET), on-farm irrigation efficiencies, tail water reuse, farm, field and sector runoff, deep percolation losses, and historical groundwater pumping. Key elements of this work included the development of procedures and computer models to calibrate a reference crop based daily crop evapotranspiration model for determina-tion of historical crop evapotranspiration. Using the collected data, Wheeler developed a comprehensive hydrologic computer model of the irrigated farm land, which was used to quantify the historical water use of the purchased water rights.

Wheeler provided a full range of water resources engineering services for this litigated water rights transfer case, including hydrologic investigations related to water supply sources, agricultural engineering related to crop evapotranspiration, field investigations to determine canal seepage losses and on-farm irrigation efficiencies, and expert witness testimony in the Water Court.