2011-06-23_HYDROLOGY - M1980149 - Laserfiche WebLink

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Page 3 of 7 Ms. Michelle L. Hatcher June 22, 2011 Weld County uses ground water from the southwestern reclaimed cell to irrigate landscape at the Weld County Southwest Service Center. Weld County conducted a field survey on February 7, 2008 and reported that the landscaped area consists of 0.15 acres of blue grass and 5.5 acres of native grass. This area will be irrigated using water pumped from the cell during the growing season of April through October. According to a Modified Blaney- Criddle analysis, the potential crop consumptive use for the 0.15 acres of blue grass is 0.30 acre -feet, and the potential crop consumptive use for the 5.5 acres of native grass is 9.35 acre -feet. Since the irrigation occurs directly around the reclaimed cell, the plan assumes that irrigation retum flows will return to the river in the same timing as the depletions. The total consumptive use of ground water associated with the Hokestra Pit is estimated to be 182.9 acre -feet, consisting of 173.3 acre -feet of evaporation loss from 67.87 acres of post - '81 exposed surface area and 9.6 acre -feet of water used for irrigation at the SWSC. The depletions from evaporation losses were lagged to the Saint Vrain River usi gallons Glover analysis. The following parameters were used in the model: transmissivity (T) per day per foot, specific yield (SY) = 0.2, the distance from the exposed ground water to the . river (X) = 250 feet, and the location of the parallel impermeable boundary to the stream (W) = 6,600 feet (based on the USGS Depth to the Water Table in the Boulder -Fort Collins - Greeley Area, Front Range Urban Corridor, Colorado map). The depletions due to irrigation were similarly lagged to the river using a distance from the point of irrigation to the edge of the dewatering trench for the 35.0 -acre cell (X) = 800 feet. The attached Table 4 provides a monthly schedule of lagged actual depletions to the river system, together with a schedule of replacement requirements. This SWSP accounts for actual depletions determined to accrue to the stream system during this plan period. The total lagged stream depletions from evaporation and irrigation is 183.0 acre -feet. For the purposes of this SWSP, the distance to the exposed ground water surface from the river Is accepted; however, should the Applicant seek to renew this SWSP, the Applicant must demonstrate that the depletions were calculated based on the distance to the centroid of the ground water ponds. Replacements The sources of replacement water are 3.75 shares in the Rural Ditch Company owned by the County, storage of excess credits in Varra Companies' 112 Pit, fully consumable water leased from Saint Vrain Left Hand Water Conservancy District ( "SVLH "), and fully consumable water leased from the City of Greeley ( "Greeley "). The 3.75 shares of the Rural Ditch Company will be used directly to replace depletions between May and September. In order to claim credit for the delivery of the 3.75 shares of the Rural Ditch to the river, the shares must be measured to the satisfaction of the water commissioner. You have indicated that the County's Rural Ditch farm headgate has been improved and that construction plans are being developed to pipe the return ditch and install appropriate measuring devices. Until the pipeline and measuring devices are installed, which is anticipated within this plan period, the applicant proposes to run the 3.75 shares of the Rural Ditch through Varra Pit No. 112, which Iles directly to the south of the Hokestra Property and across the Rural Ditch, use the measuring device already installed in the 112 Pit, and return the shares back to the river for replacement. This proposal is accepted for this SWSP; however for any subsequent renewal request the applicant must demonstrate to the satisfaction of the water commissioner that a turn -out structure has been installed on the existing farm diversion point on the ditch used to divert water to the historically irrigated lands.