Wood River Valley Hydrologic Trends and Comparisons

Science Center Objects

Wood River Valley residents rely on groundwater for domestic supply, either from domestic or municipal-supply wells. The rapid population growth since the 1970s has caused concern about the long-term sustainability of the groundwater resource.

In cooperation with local agencies and organizations, we analyzed trends in ground-water and surface-water data, documented 2006 hydrologic conditions, and compared 2006 and historic groundwater data. To do this we:

  • Analyzed mean annual water levels for trends in three wells with more than 50 years of semi-annual measurements
  • Analyzed mean annual and monthly trends in streamflow at three streamgages
  • Measured water levels in 98 wells and streamflow at 13 sites in October 2006
  • Constructed water-level maps of the confined and unconfined aquifers for:
    • Partial development conditions (1952-86)
    • October 2006 conditions
    • Water-level changes between the partial-development and October 2006 conditions

 

Statistically significant declining trends were identified in mean annual water levels in three wells (all with more than 50 years of measurement data) that seem representative of general conditions in the aquifer system.

  • The Big Wood River at Hailey streamgaging station (13139500) showed an increase in mean monthly base flow for March over the 90-year period of record, possibly because of earlier snowpack runoff.
  • Low-flow analyses for the Big Wood River near Bellevue streamgaging station (13141000) showed a mean decrease of about 15 cubic feet per second since the 1940s, whereas the mean monthly discharge showed decreasing trends for the winter months.
  • The Silver Creek at Sportsman Access near Picabo streamgaging station (13150430) showed decreases in annual discharge, as well as mean monthly discharge for July through February and April, during the 1975–2005 period of record. Because Silver Creek and its tributaries are fed primarily by groundwater through seeps and springs, seasonal fluctuations in groundwater levels affect streamflow.