May 05 2011
Recharging the Spokane Valley-Rathdrum Prairie aquifer and the Spokane River with groundwater from near the southern portion of Lake Pend Oreille is technically feasible, according to a study just released. However, having the study results doesn’t mean this project will ever be constructed. The study presents an alternative for communities in Idaho and Washington to consider in the future.
The report is called the “Spokane Valley-Rathdrum Prairie Aquifer Optimized Recharge for Summer Flow Augmentation of the Columbia River.” The research was conducted for the Washington Department of Ecology by the state of Washington Water Research Center at Washington State University.
The research was done as part of ongoing efforts to ensure adequate water supplies in the SVRP aquifer and in the Spokane River in the face of population growth, ever-increasing groundwater pumping and expected effects of climate change. Large amounts of aquifer pumping have already decreased summer low flows in the Spokane River, the report says.
The Spokane Valley-Rathdrum Prairie aquifer serves nearly 600,000 people in the Coeur d’ Alene and Spokane areas. It is a federally-designated “sole-source aquifer,” meaning the region has no other sources of water and the aquifer needs special protection.
Given the sole source aquifer designation, few alternatives are available for increasing water supply to the region, the report says. Should conservation efforts fall short of meeting future demand, the pumping project appears to provide a technically viable option for enhancing summer flow conditions in the Spokane River and ensuring adequate water in the aquifer.
However, having the technical feasibility study done does not mean this project would move forward, according to senior hydrogeologist John Covert with Ecology’s Water Resources Program in Spokane.
“Knowing that it could be done doesn’t mean that it should or will be done,” said Covert. “This report simply gives us the technical information so that we can start a regional conversation about how to make up for the effects of groundwater withdrawals on the Spokane River during the critical, summer low-flow months.”
The study looked at three alternative sources for water to recharge the aquifer and the drier reaches of the Spokane River: the Spokane River during high flows; pumping aquifer water from a site in Washington up into Idaho; and using groundwater near the southern end of Lake Pend Oreille. Spring runoff water would be piped to Idaho and discharged to the aquifer, arriving in the Spokane River in the late summer.
The technically preferred source is the latter. The report concludes it would be feasible to implement this alternative by constructing a well-field adjacent to the southwestern tip of Lake Pend Oreille and conveying that groundwater down a pipeline to a location near Garwood, Idaho. Then it would be injected back into the aquifer.
Pumping wells next to Lake Pend Oreille would mean lake water would naturally replenish the withdrawn groundwater. Once in the SVRP aquifer, the groundwater would slowly move through the aquifer and end up discharging to the Spokane River, thereby augmenting summer low flows. The aquifer and the Spokane River are often considered one body of water because they flow in and out of each other.
The report indicates it would be cost-prohibitive to use Spokane River water as the source because that water would have to be treated first at considerable cost before being injected into the aquifer. Pumping groundwater from Washington upstream into Idaho to recharge the aquifer would fill in the depression in the aquifer that the pumping would create to supply the water – very little of this water would make it to the Spokane River.
In today’s economy, the report concludes that the cost of this project would be approximately $90 million plus $12 to 14 million per year to operate the system.