2024-02-01_HYDROLOGY - M2010071 - Laserfiche WebLink

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Goose Haven Reservoir#2 Expansion SWSP Page 2 of 7 February 1, 2024 based on average monthly temperatures less than 32°F taken from the Longmont 2 ESE, NOAA weather station (record 1960-2004). However, for the purpose of this SWSP, the Applicant shall replace the net evaporation depletions from the exposed groundwater surface area that may occur during the assumed ice covered period (the months of December and January) for any time that the pit is not completely covered by ice. The Applicant must include in their accounting daily verification of percent ice cover. Computation of the net evaporation during any time that the pit is not completely covered by ice shall be determined as the pro-rata amount of the monthly gross evaporation rate distribution amount identified in the State Engineer's General Guidelines for Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro-rata amount of the effective precipitation for that period. Currently, the following areas in each cell are exposed with the following net evaporations from the exposed water surfaces (as shown in Table AI.1, column 7): • Cell 2A: Approximately 3.61 acres are exposed in Cell 2A (shown on attached Figure 2 as areas 1-12) with a net evaporation of 9.07 acre-feet. • Cell 2: Approximately 3.61 acres are exposed in Cell 2 (shown on attached Figure 2 as areas 13-16) with a net evaporation of 9.07 acre-feet. • Cell 4: Approximately 2.24 acres are exposed in Cell 4 (shown on attached Figure 2 as areas 17-23) with a net evaporation of 5.63 acre-feet. The total estimated evaporative depletions are 23.77 acre-feet for 2023. The total net evaporation through November 2023 was 23.06 acre-feet according to the Applicant's accounting. Dust Suppression The total estimated depletions from use of groundwater for dust control are 3.75 acre-feet for 2023 as shown on attached Table AI.2. Water used for dust suppression must be measured in accordance with condition #5. The total water used for dust suppression through November 2023 was 3.93 acre- feet, though adequate replacement water was provided according to the Applicant's accounting. The total estimated unlagged depletions are 27.51 acre-feet for 2023. The total unlagged depletions through November 2023 were 26.99 acre-feet according to the Applicant's accounting. Lagged Depletions The Alluvial Water Accounting System ("AWAS") model was used with the alluvial aquifer boundary condition option to lag depletions to Boulder Creek. The following parameters were used in the model: transmissivity (T) = 44,883 gallons per day per foot, distance (X) from the centroid of the surface of the exposed groundwater to the river = 3,709 feet, distance (W) from the aquifer boundary through the exposed groundwater to the river channel = 4,400 feet, and specific yield (SY) = 0.2. The location of the stream depletion is assumed to be perpendicular to the river. The total modeled lagged depletions due to evaporation and dust control are 28.16 acre-feet for 2023. The depletions to occur in this plan period are summarized on attached Tables AI.1, AI.2 and AI.3. The total lagged depletions through November 2023 were 24.53 acre-feet according to the Applicant's accounting. The Applicant proposes to replace an additional 25% of lagged depletions to account for potential deviations from the plan as well as an additional 15% of lagged depletions to account for transit losses. Therefore total unreplaced lagged depletions to be replaced under this SWSP are 39.43 acre-feet for 2023 as shown on attached Table AI.2, column 7. The actual total replacement