This summer has been exceptionally hot, with record-breaking air temperatures. June 29th, Spokane reached 109°F (42.8°C), the highest temperature since records began 140 years ago. We also saw the warmest nighttime temperature of 78℉ (25.6℃) on June 30th. July 2021 was the hottest July on record for Spokane, with an average temperature of 77.5℉ (25.3℃). Climate change projections for Spokane predict our average annual mid-century temperatures will be 4.4℉ to 5.9℉ higher, depending on future levels of greenhouse gas emissions. We will also see an increased number of days reaching 90℉ or above.
We are concerned these high average temperatures and elevated nighttime temperatures will lead to an even warmer river. Spokane Riverkeeper has been monitoring temperatures in the Spokane River since 2015, and this summer marks some of the highest water temperatures we’ve seen in the last six years. To follow is a brief midsummer report summarizing temperature data from three locations in the Spokane River.
After reaching the all-time high air temperature on June 29th, water temperatures at Barker Road averaged 80°F (26.7°C) on July 1st and have reached daily maximum temperatures of 83°F (28.3°C) on eight separate days in July.
The graph above shows daily average temperatures in the Spokane River at the Barker Road bridge reaching 26.7°C (80°F) on July 1st and remaining consistently above 24°C (75°F) through the month of July 2021. Maximum water temperatures at this site have stayed above 27°C (80.6°F) for the majority of July.
Increased temperatures are expected at Barker Road, which is located in a losing reach of the river that only receives warm surface water from Lake Coeur d’Alene; however, even portions of the river that receive cool aquifer water were too warm for native fish populations like the Redband trout. On July 3rd, the water at Islands Trailhead reached 71°F (21.5°C), the highest we've ever recorded there! Where is a small fry (young fish) to go to hide from the heat?
The graph above shows the maximum daily temperatures recorded in the Spokane River at the Islands Trailhead (Centennial Trail) location. Temperatures reached record highs for this site in early July, exceeding 20°C (68°F), not typically seen in portions of the river receiving cool aquifer water.
Juvenile Redband trout
Image credit: Tim Connor photography
Washington State criteria for aquatic life lists a maximum daily temperature of 68°F (20°C) and a seven-day average maximum temperature for Interior Redband Trout at 64.4°F (18°C). Temperatures during the first week of July exceeded both of these standards.
In early July, maximum daily temperatures surpass the 20°C (68°F) daily threshold set by Washington to protect the health of native fish at all three of our temperature monitoring locations (Spokane River at the Barker Road bridge, Islands Trailhead to Centennial Trail, and Division Street bridge).
In early July, seven-day averages of daily maximum water temperatures also exceed the criteria set for healthy Redband trout habitat (18°C or 64.4°F) in all three of our monitoring locations (Spokane River at Barker Road bridge, Islands Trailhead to the Centennial Trail, and Division Street bridge).
Portions of the river that rely solely on surface water are being transformed by increasingly hot summers and drought conditions for eastern Washington. Although river reaches that have cold groundwater influxes are more resilient, large volumes of superheated surface water can raise temperatures above state standards. This phenomenon threatens populations of native trout that are already in a precarious position and whose populations are very low.
Global efforts are needed to combat the effects of climate change. Locally, we can protect the gaining reaches of the river by simply reducing our individual water usage in the spring and summer months. Keeping aquifer pumping down saves that water for the river and helps control temperatures in areas of the river receiving cool aquifer water. Our actions now influence how the Spokane River supports regional ecosystems in the future.