Utah Water Science Center
Navajo Sandstone recharge study
Project Number: 97169CD
Cooperating Agency: Washington County Water Conservancy District
Project Chief: Victor Heilweil, USGS Salt Lake City, Utah
Project Period: 2001-2005
Problem: Southwestern Utah is the warmest and driest part of Utah. Average annual precipitation at
St. George, Utah, is about 8 inches per year. According to the U.S. Census Bureau (1990, 2000), the population of Washington
County increased from 49,000 to 90,000 from 1990 to 2000. This 86 percent increase is more than six times the national average
increase of 13.2 percent over the same 10-year period (Perry and Mackun, 2001). The population of Washington County is expected to exceed 200,000 by 2020. The combination of rapid population growth and the dry climate of Washington County require local water managers to develop additional water resources. The Navajo Sandstone aquifer is the main ground-water source for municipal water supply in Washington County. This natural water source is being increasingly used to meet growing needs. However, there is little information on the primary source of recharge to this aquifer - diffuse infiltration of precipitation. In addition, aquifer storage and recovery projects are underway to utilize storage within the unsaturated zone of the Navajo Sandstone. However, little is know of the factors controlling how recharge moves through the unsaturated zone and what are the rate-limiting factors for estimating artificial recharge rates.
Collecting pore-water samples from shallow sandstone, Washington county,
Utah |
Objectives: Evaluation of natural and artificial recharge to the
Navajo Sandstone Aquifer of southwestern Utah.
Relevance and Benefits: This study will be of relevance for evaluating both natural and artificial
recharge to various fractured bedrock aquifers throughout the desert southwest.
Approach: Natural recharge will be evaluated by collecting both unsaturated-zone and aquifer water
samples and using environmental tracers to evaluate the timing and location of diffuse infiltration of precipitation.
Artificial recharge will be evaluated by both infiltration experiments and variably-saturated flow modeling.
Products: Study results are documented in USGS reports and journal articles. |
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