Hydrogeology of the Tusas Mountains, Rio Arriba County, New Mexico
— Finch, Steven T., Jr.

 The Tusas Mountains in Rio Arriba County provide a significant portion of the streamflow for the Rio Chama, however most communities in the Tusas Mountains obtain groundwater from saturated stream alluvium, which is typically localized and limited in supply. Groundwater occurs in four geologic settings: 1) alluvial deposits, 2) Tertiary sediments and weakly cemented volcanic rocks, 3) regional NW-SE trending fault and fracture systems, and 4) localized fractured, brittle Precambrian rocks such as quartzite. In many areas the Precambrian rocks and Tertiary sedimentary and volcanic rocks are not water bearing or do not sufficiently yield water to wells. The solidified and cemented Tertiary rocks typically are not water bearing or have poor groundwater yield (< 1gpm), the weakly cemented Tertiary rocks commonly have fair groundwater yield (1 to 10 gpm), and the unconsolidated Tertiary sediments have good groundwater yield (> 10 gpm).