Basin-fill deposits, known as the Santa Fe Group, were derived from the adjacent mountain ranges, dune
deposits from windblown sand, and volcanic deposits from local volcanic areas. The Santa Fe Group aquifer
system is the primary aquifer in the URGB and is divided into three parts: the upper, middle, and lower.
Much of the lower part may have low permeability and poor water chemistry; thus, groundwater is mostly
withdrawn from the upper and middle parts of the aquifer. Only about the upper 2,000 feet of the aquifer
is typically used for groundwater withdrawal.
Water enters the Santa Fe Group aquifer system from mountain front recharge, seepage from the Rio Grande and
its tributaries, transmission losses from conveyance structures, and excess irrigation. Groundwater discharges
from the Santa Fe Group aquifer system from pumpage from wells, seepage into the Rio Grande and riverside
drains, springs, evapotranspiration, and subsurface outflow. If groundwater pumpage from an aquifer exceeds
recharge, water levels in the aquifer decline, as has been observed throughout the URGB. These declining water
levels can have adverse effects on long-term groundwater availability and sustainability, water quality, and
land subsidence. The approach to complete this study component is:
Hydrogeologic Framework
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Compile the digital boundaries of all subbasins in the URGB into a geodatabase. Some of the subbasins have
well defined digital boundaries, but many do not. Subbasin boundaries will be acquired as digital data files
from previous studies and (or) will be digitized in a vector format from figures in the literature.
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Create a table of existing hydraulic property data for hydraulic conductivity and (or) transmissivity,
Create a table of existing hydraulic property data for hydraulic conductivity and (or) transmissivity,
and storage coefficients.
Water Levels
- Compile historical water-level data from multiple sources
- Analyze water-level status and trends and create change maps for selected subbasins
- Develop water-level altitude maps for selected subbasins
Changes in Groundwater Storage
- Examine existing numerical flow models of the San Luis Valley, Espanola Basin, Albuquerque Basin, the Mesilla and Rincon Basins, and the Hueco Bolson, and report simulated changes in groundwater storage. No updates will be done to any of the groundwater flow models, and no new simulations will be run.
- Estimate water in storage for selected subbasins from water-level surfaces and hydraulic properties.
- Review study results pertaining to aquifer compaction and subsidence in the San Luis Valley, Colorado, the Albuquerque Basin, and El Paso, Texas for a better understanding of loss of water in storage.