Spokane Community Indicators e-Newsletter


The Spokane Valley - Rathdrum Prairie (SVRP) Aquifer provides water to over 500,000 residents of Kootenai County, Idaho and Spokane County, Washington. As the SVRP Aquifer is the only source of drinking water for at least 50% of local residents, in 1978, it was the second aquifer in the nation to be designated a "sole source aquifer" by the Environmental Protection Agency (EPA). This designation initiated special management practices such as working to eliminate septic tank systems and pre-treating storm water on the ground above the aquifer.

Although formed naturally over millions of years, the SVRP Aquifer was shaped more recently during the last Glacial Age (approximately 12,000 to 18,000 years ago), due to a pattern of ice dams formed and melted.

As new ice dams would form, some believed to be 2,000 feet or taller, researchers estimate as much as 500 cubic miles of Glacial Lake Missoula water would form behind them. As the backwater pressure increased, the ice dam would eventually break resulting in cataclysmic flooding. With each flooding event, gravels, cobbles, and rocks were picked up by the flood waters and deposited in places where the flow slowed enough to let some of the heavier sediments drop.

Ultimately, forty or more separate flood events formed the 370 square miles of SVRP Aquifer we depend on today for all of our water needs. Constantly monitoring aquifer water quality, quantity, and consumption will help us prepare to meet both current and future demand for water.

Doug Greenlund, Environmental Analyst with the City of Spokane says "Although our sole source aquifer has an ample supply of water, it is not unlimited. This precious resource needs to be managed in order to provide high quality water into the future."

The SVRP Aquifer naturally has some of the cleanest water in the world, but pollutants at the surface are a concern. Above the aquifer is a thin layer of topsoil and highly permeable gravel allowing pollutants to easily seep into the aquifer.

Rob Lindsay, Water Programs Manager with Spokane County Environmental Services, says the biggest pollution threat is "untreated stormwater infiltrating the aquifer."

Looking at the Aquifer Level and Total Water Consumption indicator on the Trends website, we see that aquifer levels have remained relatively the same while consumption has increased. Aquifer levels represented in this indicator are actually the distance from a fixed point in the well to the water. The well is located near the corner of Denver and Marietta Streets in the City of Spokane. During 2016, the distance from the fixed point in the well to water was 83.4 feet, increasing slightly from 82.7 feet during 2009, or by less than 1.0%.

Total water consumption in Spokane County during 2016 was 37.9 billion gallons, increasing from 34.7 billion gallons during 2009, or by 9.2%.

One positive aspect seen in this indicator is that increased water consumption did not lead to a decline of SVRP aquifer levels during the time period offered (2009-2016). However, with a projected additional 72,000 people living in Spokane County by the year 2025, there are simply no guarantees consumption will never exceed production.

The Ogallala Aquifer is one of the largest aquifers in the world spanning from South Dakota to Texas. It is the main water source for the majority of the Western U.S. Plains where 20% of all agriculture production in the U.S. occurs. Even with a variety of conservation efforts in effect, consumption has consistently exceeded production posing serious questions about the long-term sustainability of the Ogallala Aquifer.

Most, but not 100% of water consumed in Spokane County is pumped directly out of the SVRP aquifer and groundwater is still by far the primary source of water for Spokane County residents. The City of Spokane, the largest consumer of SVRP Aquifer water, also sells water to nearby cities such as Medical Lake and Airway Heights. Places in the county not drawing water directly or indirectly from the SVRP Aquifer, such as Deer Park, still get their water from groundwater sources.

The relationship between the SVRP Aquifer and the Spokane River are now well established. County water consumption, especially during the dryer summer months, lowers the Spokane River levels as more river water is drawn below ground to replenish lower aquifer levels.

Greenlund says "Outdoor landscape irrigation is the largest use of water. The peak irrigation season occurs when river flows are the lowest."

Lindsay says "When we think about the aquifer, we need to think about the river too because they are connected."

As much 50% of water used outside is wasted from inefficient watering methods so people looking for ways to conserve water might start with making sure outside watering methods are efficient.

Greenlund said homeowners can still have beautiful landscaping with lower water demand. He said SpokaneScape was created for this very purpose. City of Spokane residents can earn a maximum of $500 in credits off their water bills for removing lawn turf and replacing it with SpokaneScape landscaping. People who do not live in the city can still reduce their water consumption by integrating SpokaneScape practices and recommendations.

Lindsay said "Reducing water use for irrigation of lawns in the summer will keep more water in the river, thus supporting flows and river habitat."

Making changes in when and how we water our yards seems to be a good place to start - especially now that we in the time of year where water demand is at its highest recharging of the aquifer is at its lowest.

Lindsay says that while we are becoming more efficient regarding our water consumption, we need to continue seeking ways to conserve water because our "community is growing and water use will increase in the future."

A special thank you to the Spokane Valley Rathdrum Prairie 2015 Atlas for providing many of the geological and statistical details presented in this article. The Atlas and other aquifer resources can be accessed from the Spokane County website by clicking here.

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