Hydrologic Settings

Image Provided by: Utah Department of Natural Resources

Figure 1. Map of Colorado showing location of the Denver Basin. (USGS Groundwater Atlas of U.S., 1995)

Regional Extent of The Dawson Aquifer

The Dawson Aquifer is the smallest aquifer in the upper portion of the Denver Basin. It is one of four contributing aquifers to the Denver Basin. Several of the components that contribute to the characteristics and nature of the Dawson Aquifer are the same traits that contribute to the basin as a whole. In Figure 3, the extent of the aquifer is illustrated: the upper unit (blue), the confining unit (pink), and the lower unit (orange).

Figure 2. Conceptual block diagram of the Denver Basin aquifer system (Paschke, 2011)

Figure 3. Google Earth Imagery containing both the Upper and Lower portion of the Dawson Aquifer including the confining unit.

Regional Climate

As previously mentioned, many features of the Dawson Aquifer share the same traits as those of the Denver Basin. As the uppermost portion of the basin, the Dawson Aquifer reflects these regional qualities:

Semiarid
- Evaporation
  - Five times larger than annual precipitation
- Precipitation
  - Runoff in streams is evaporated from the soil surface
  - Vegetation Consumption
  - A small amount percolates downward and recharges the groundwater system
  - Recharge occurs mostly in highland areas
    - Southern Portion of the basin
      - Greater precipitation
      - Dawson Arkose soils allow for deeper percolation
        Local
        Water moves from the highland recharge areas through shallow sandstone beds
        Discharge goes into nearby stream valleys

- - - - Regional
        Water moves from the recharge areas into deeper parts of the aquifer
        Moves greater distances through aquifer
        Discharge is many miles away

Recharge & Discharge

Water moving upward and downward through confining units of mudstone or shale located within or between the four aquifers.
- Mudstone and shale beds allow for some vertical water movement through or around the beds
- Discharge occurs postly from wells and inter-aquifer movement of water from bedrock to overlying alluvial aquifers

Statistics

Around 5 million ac-ft of water falls as precipitation each year on the Denver Basin
- 99.2% is lost to evaporation, transpiration or surface runoff
- 0.8% recharges the four aquifers

(USGS Groundwater Atlas of U.S., 1995)

Surface Water Bodies

The Denver Basin does not contain any large lakes, rivers, or extensive wetlands. Instead, it features several creeks that flow into its aquifers. This emphasizes that the only source of recharge for the basin comes from the limited precipitation it receives throughout the year.

Figure 4. Hydrological settings within the Dawson Aquifer. (Paschke, 2011)

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