Rio Grande Basin FAS

Upper Rio Grande Basin Focus Area Study



The Rio Grande Basin is composed of a sequence of alluvial sub-basins that formed in the Rio Grande rift approximately 30 million years ago. The Rio Grande rift is a north-south trending structural feature that developed during a period of tectonic extension where the Earth’s crust was pulled apart and a series of normal faults created alternating mountain ranges and basins.

Study Component Lead

Natalie Houston

USGS Texas Water Science Center

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 Much of the lower part may have low permeability and poor water chemistry; thus, groundwater is mostly withdrawn from the upper and middle parts of the aquifer.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

  1. 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.
  2. 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

  1. Compile historical water-level data from multiple sources
  2. Analyze water-level status and trends and create change maps for selected subbasins
  3. Develop water-level altitude maps for selected subbasins

Changes in Groundwater Storage

  1. 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.
  2. Estimate water in storage for selected subbasins from water-level surfaces and hydraulic properties.
  3. 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.