Science for Decision Making on Uranium Mining in Arizona

Increasing Understanding of Groundwater Flow in the Grand Canyon Region

Regional Studies

Owing to the remoteness and vastness of the Grand Canyon area and the complexity of the subsurface system there, several basic aspects of the groundwater hydrologic system remain unknown or uncertain including locations of recharge, direction and timing of flow paths, and locations of discharge. An improved understanding of the groundwater-flow regime is necessary to predict timing and location of potential subsurface transport from source areas (natural or mined ore bodies) to discharge areas (springs, Colorado River and tributaries). Conceptual models of groundwater flow synthesize what is known and hypothesized about the groundwater-flow regime into a framework that contextualizes past and present observations of the hydrologic system. Conceptual models also identify the unknown properties or conditions that contribute to the greatest uncertainties in understanding regional groundwater flow. In this way, conceptual models are used to guide the collection of additional critical data that would be required to develop a numerical groundwater-flow model capable of simulating potential effects of mining within a reasonable limit of uncertainty.

Questions this study could help answer

  • What do we understand about areas of groundwater recharge and discharge in the region?
  • What do we understand about the connection between perched and regional groundwater in the region?
  • How does geologic structure affect the occurrence and movement of groundwater?
  • Where would new groundwater monitoring wells, spring samples, or geophysical surveys provide the most useful information for improving understanding of groundwater flow in the area?


Status

Ongoing

Specific Tasks

Task 10: Update regional groundwater model

Principal Investigators

Jacob Knight
Hydrologist
Arizona Water Science Center
520.670.3336
jknight@usgs.gov

Fred Tillman
Hydrologist
Arizona Water Science Center
520.670.3312
ftillman@usgs.gov

Photo Gallery

Small falls along Havasu Creek 2

Regional Studies Gallery