C150094 Red Mesa Aquifer Groundwater Study 2002

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Red Mesa Aquifer Groundwater Study — Interim Report 2002 after irrigation ceases showing a one to three month lag in irrigation recharge (see Figure 9). Mounds and troughs in the water table develop (see Figure 5). The water table then adjusts to this recharge event. Low water table conditions typically occur during the winter and early spring. The water table is more uniform during this period (see Figure 6). (2) The groundwater flow direction is generally northeast to southwest from Breen to Red Mesa. Groundwater flow paths and groundwater divides generated from water table maps indicate that most of the groundwater return flows accrue to Long Hollow and its tributaries. Many flow paths converge on Church Hollow and the Marvel Spring. Groundwater west of a line approximated by Highway 140 flows to the La Plata River. A substantial portion of this flow is derived from irrigation near the Town of Red Mesa. This water is provided from Red Mesa Ward Reservoir and the Joseph Freed, Revival and Warren-Vosburgh ditches. (3) The total amount of groundwater in storage in the Red Mesa Aquifer was estimated to be approximately 165,000 af, with 82,500 af in transient storage and available for withdrawal. The location, amount and timing of groundwater discharges to surface streams can be modified by irrigation recharge and infiltration of water at recharge basins. The aquifer reasonably could be expected to store 250,000 af with 125,000 af available for withdrawal. If saturated from the bedrock to the surface, the aquifer could store more than 414,000 af with 207,000 af in transient storage and available for withdrawal. These estimates were made using water level and bedrock elevations from wells in the study area as well as some seismic refraction data. Since no measured porosity values were available, an estimate of porosity was made based on the lithology of the deposits. A specific yield value of 15 percent was used for the study. Therefore, 991-077/031 Wright Water Engineers, Inc. Page 13 Interim Report