2014-12-11_HYDROLOGY - M1979059 - Laserfiche WebLink

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Peter Wayland Page 3 of 7 Brownwood SWSP December 11, 2014 Loveland Storage Reservoir water as decreed in case no. 82CW202A, and Colorado Big Thompson ("C-BT") Project water. In the event that Loveland plans to use C-BT water as a replacement source, Loveland shall comply with the Interim Rule issued by the Northern Colorado Water Conservancy District ("Northern District") in May 2005, regarding the use of C-BT Project water in substitute water supply plans. Prior to the use of C-BT Project water, Loveland is required to notify this office, the division engineer and the water commissioner of the amount of C-BT Project water dedicated to this plan and provide a copy of the Northern District's approval letter as required by paragraph I(g) of the Northern District's May, 2005 Interim Rule. A review of the irrigation practices at Brownwood Farm, which overlaps nearly exactly with the parcel that is now the Brownwood Pit, indicates that 2 shares of the BTDMC were used to irrigate approximately 139.68 acres. Of these shares, the Applicant owns 5/6 of a share and is claiming a credit based on 16.76 acres of dry up. The dry up of 16.76 acres is associated with 0.24 shares of the water right. The historical consumptive use was estimated using the Modified Blaney-Criddle methodology in the IDS Consumptive Use Model, using the average monthly diversion from 1951 through 1979. The northern portion of the farm was mined beginning in 1980. A mixture of silage corn, pasture grass, and alfalfa were grown on the farm in different proportions over the study period. Ditch loss was considered to be 15 percent, which is consistent with the ditch loss assumed in case no. 2002CW392. Temperature and precipitation data was taken from the Fort Collins weather station. Crops were irrigated through wild flood and furrows, therefore the irrigation efficiency was assumed to be 60 percent'. Water in excess of the irrigation requirement was added to the soil moisture bank, which was assumed to be three feet deep with a water holding capacity of 1.92 inches/feet, based on NRCS soil survey data. Of the irrigation water historically applied to the farm, a portion ran off the fields (surface return) and a portion seeped into the ground below the root zone of crops (deep percolation). Return flows were assumed to consist of 50 percent of surface return flow and 50 percent of deep percolation. The timing of surface return flows was assumed to be instantaneous to the stream system. The timing of deep percolation return flows was estimated using the AWAS model alluvial aquifer boundary condition option with the following aquifer parameters: transmissivity (T) = 44,883 gallons per day per foot and specific yield, (SY) = 0.2, the distance from the centroid of the farm = 798 feet, and the location of the parallel impermeable boundary was estimated to be 2,000 feet from the stream. The average year analysis shows that on an average year the historic net stream depletions as a result of the 0.24 shares are 22.03 acre-feet per year. This would provide a credit of 24.39 acre-feet during the irrigation season, and a return flow obligation of 2.36 acre-feet during the non-irrigation season (see attached Table AI.3). During a dry year, the current 25-year lease with Loveland may not be sufficient during the irrigation season. The ' If the Applicant applies to use the BTDMC shares next year, the maximum irrigation efficiency should be substantiated using an analysis of slope, soil type, and irrigation method, or another engineering analysis.