2025-07-21_HYDROLOGY - M2008082 (2)

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Morton Lakes Substitute Water Supply Plan Renewal (Amended) July 21, 2025 Page 8 of 17 Reservoir Construction at Stage 5 It is projected that the final reservoir construction for Stage 5 will require 41.98 acre- feet as shown on attached Table 2, Column 6. Since water will be pumped and metered directly from the stream for the construction at Stage 5, no lagged depletions will occur from this use. The reservoir construction of Stage 5 has been delayed, and is anticipated to begin in July and continue through the end of this amended plan period. The reservoir construction at Stage 5 will primarily consist of earthwork and soil compaction to build the reclamation slopes. During the construction process, water will be needed to increase the moisture content of the soil to achieve the desired compaction. Water will also be needed for dust suppression and repair of the slurry wall. Total Consumptive Use (Unlggqed Depletions) The total consumptive use at the site for this amended plan period is 105.30 acre-feet, as shown on attached Table 2, Column 7. Lagged Depletions The IDS AWAS stream depletion model was used to determine the lagged depletions from dewatering, evaporation, and operational losses at the Morton-Holton Lakes site to Big Dry Creek and the South Platte River, using the following Glover parameters: • Specific yield = 0.2 • Transmissivity = 150,000 gpd/ft based on pumping test data in Colorado Ground Water Circular No. 11 • Distance from centroid of the Stage 1 mining area to Big Dry Creek = 300 feet • Distance from centroid of the Stage 2 mining area to Big Dry Creek = 1,150 feet • Distance from centroid of the Stage 5 mining area to Big Dry Creek = 318 feet • Distance from centroid of the Stage 6A mining area to the Big Dry Creek = 1,356 feet