2014-03-27_HYDROLOGY - M2001090 - Laserfiche WebLink

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Steamboat Sand and Gravel Pit SWSP March 21, 2014 Page 4 of 8 through October based on the quantification provided in the decree in Case No. 2008CW94 and is presented in the attached Table 5. In order to determine how much credit is available from the dry -up of the lands historically irrigated by the Weiskopf Ditch, a ditch -wide historical consumptive use analysis was performed for the period of 1950 through 2005, which was considered to be representative as it includes wet, dry and average years. The annual irrigated acreage during the study period was 126 acres for the Weiskopf Ditch. The crop irrigated by the ditch was entirely pasture grass. The consumptive use credit associated with the Weiskopf Ditch was calculated using the Modified Blaney - Criddle Method with daily temperature and precipitation data from the nearby Steamboat Springs weather station. TR -21 crop coefficients were used in the Blaney - Criddle analysis. The ditch loss was assumed to be 10% for the Weiskopf Ditch. The maximum irrigation efficiency was assumed 50% reflecting the flood irrigation practices historically used in this area. Based on the soil type and effective root depth, the available soil moisture capacity of the field irrigated under the subject ditch is estimated to be 0.125 inches /inch. The average annual historic stream depletions that occurred due to irrigation of the acreage under the Weiskopf Ditch are estimated to be about 137.74 acre -feet, or 1.09 acre - feet/acre (Table 6). However, as noted above, Alpine does not propose to use any dry - up consumptive use credits under the Weiskopf Ditch during the requested SWSP period, but may propose to utilize dry-up consumptive use credits in future SWSPs. The dry -up areas are in close proximity to Grouse Creek and the Yampa River. These areas are underlain by alluvial sand and gravel deposits which have a high transmissivity of ground water. Therefore, for purposes of this SWSP, you assumed that 100 percent of the historical return flow will accrue to the stream system within the same month that water is applied to the ground, which is consistent with the determination made in the decree in case no. 2008CW94. Conditions of Approval hereby approve the proposed substitute water supply plan in accordance with § 37 -90- 137(11), C.R.S., subject to the following conditions: This plan is approved with the effective date of February 1, 2014 and shall be valid through January 31, 2015 unless otherwise revoked or modified. If this plan will not be made absolute by a water court action by the plan's expiration date, a renewal request must be submitted to this office with the statutory fee (currently $257) no later than December 1, 2014. 2. Well permit 76189 -F was issued for the gravel pit in accordance with § 37 -90- 137(2) and (11), C.R.S., on June 28, 2012, and remains in good standing. 3. The total surface area of the groundwater exposed at the Steamboat Sand and Gravel Pit site must not exceed 1 acre in the dewatering trenches, which results in a maximum evaporative annual loss of 1.94 acre -feet.