2025-07-21_HYDROLOGY - M2008082 (2)

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Morton Lakes Substitute Water Supply Plan Renewal (Amended) July 21, 2025 Page 6 of 17 Depletions The projected depletions for Stages 1, 2, 5, 6A, 6B, 6D, 7A and 7B result from evaporation, dewatering, dust control, water used to wash the mined product, water lost in the mined product, reservoir construction, and slurry wall repair at Stage 5. Evaporation The Applicant proposes to replace evaporation from exposed groundwater at the Morton- Holton site based upon evaporation atlases in NOAA Technical Report NWS 33 and the State Engineer's Office ("SEO") monthly distribution factors for sites below 6,500 feet, as shown in attached Table 1. Gross annual evaporation at these gravel pit locations is estimated to be 44.27 inches per year based on the NOAA NWS 33 Evaporation Atlas mapping. Net evaporation is defined as gross evaporation less the consumptive use of water by vegetation that naturally occurred at the site prior to construction of the pit. The historical consumptive use was assumed to be equal to the effective precipitation of 9.25 inches, which was estimated based on the data from the Fort Lupton 2SE (ID 3027, record 1950- 1976) and Brighton 1 NE (ID 950, record 1976-2014) NOAA weather stations. The projected maximum monthly exposed groundwater surface area at each stage is described in Table A below: Table A - Maximum monthly exposed groundwater surface area (acres) Stage 5 Stage Stage Stage Stage Stage Stage 1 Stage 2 Total 6A 6B 6D 7A 7B 11.0 15.0 1.0 1.0 1.0 2.0 1.0 1.0 33.0 The net evaporation rate for the exposed water surface is estimated to be 2.92 acre-feet/acre, as shown on attached Table 1. Total net evaporation for this amended plan period is 50.30 acre feet, as shown on attached Table 2, Column 2. Mined Product