Projects by Discipline / Water Resources Engineering

Groundwater Management, Eastern Snake Plain, Idaho

The eastern Snake River plain in Idaho overlies a prolific basalt aquifer estimated to contain up to 500 million acre-feet of water.  The Eastern Snake Plain Aquifer (ESPA) is adjacent to the Snake River, and discharges to the river through large springs in several locations.  Early surface water irrigation development in the area dramatically increased incidental recharge of the aquifer and, consequently, the discharges from springs.  Starting in the 1950s, an extensive aquaculture industry was built around these enhanced spring discharges.

Also after World War II, plentiful electric power and changes in pumping technology permitted effective irrigation development of the groundwater resources of the ESPA.  In recent years, this pumping from the ESPA has come under increasing scrutiny by spring and surface water users concerned with its impact on their water sources.  The Idaho Department of Water Resources (IDWR) has developed conjunctive management rules to support joint administration of surface and groundwater rights where stream/aquifer interactions are significant.

Hydrosphere was retained by groundwater users to evaluate historical data on basin water uses and the potential effects of groundwater withdrawals on other water uses.  Among the findings of this investigation was that the existing groundwater model of the basin was not well-suited to answer the management questions that were being asked.  Hydrosphere subsequently provided technical oversight of the development of a new model of the aquifer.  The new model uses a substantially finer grid than the original model, and incorporates a GIS-based set of tools for creation of well files.  The model was calibrated (transient) to observations of aquifer water levels and spring discharges over a 22-year period using the PEST automated calibration routine.

Hydrosphere is currently supporting ground water users in ongoing negotiations with spring and surface water users over pumping effects and suitable mitigation activities.  We are also providing technical support to members of a special Interim Committee of the state legislature tasked with developing a framework for long-term management of the aquifer.