Lower Deschutes River pH Exceeds DEQ limits again
The Deschutes River Alliance science team's preliminary review of the 2022 water quality data shows once again, pH levels in the lower Deschutes River consistently exceed Oregon Department of Environmental Quality (DEQ) standards.
DRA 2022 lower Deschutes River water quality data including pH and temperature.
Similar to results DRA has seen in prior years, Figure No. 1 shows that 2022 pH in the lower Deschutes River was above DEQ's protective maximum standard of 8.5 for the majority of DRA's monitoring season (April-Nov). The pH level is an important proxy of river health since high pH levels are indicative of excessive nutrient loads that are bad for the native ecosystem. DEQ set the maximum pH standard at 8.5 in the lower Deschutes River in order to protect aquatic organisms from excessively high pH.
DRA 2021 lower Deschutes River water quality data including pH and water temperature plus Selective Water Withdrawal Tower data. Note that the increase in pH above 8.5 at the beginning of October is likely explained by what is called lake turnover, where the surface and bottom water temperatures equalize and water from the surface mixes with bottom water.
While DRA does not have the 2022 tower blend data from the operators yet, our thorough review of the 2021 blend data with respect to pH tells us a lot about how tower operations affect pH in the lower Deschutes River. Figure No. 2 includes the 2021 SWW tower operation blend data plus pH and temperature from the same DRA monitoring site in the lower Deschutes River. In 2021 the increase in the bottom draw in early July resulted in decreases in pH and temperature. The high pH drops into compliance starting around the same time the percent bottom draw increases to "maximum" at 60 percent. The black boxes in Figure No. 2 emphasize this.
Prior to SWW tower operations, only cool, clean water from the bottom of Lake Billy Chinook was released into the lower Deschutes River. Results from previous DRA water quality reports and the existing data record clearly establish that surface water releases from the tower have had a rapid and negative impact on pH in the lower Deschutes River. Since the SWW tower operation started, pH has consistently exceeded DEQ standards relative to pre-tower operations. This issue is discussed at length in our 2021 Water Quality Report.
The DRA has monitored water quality in the lower Deschutes River after a number of long-time anglers noticed significant changes to the river more than 10 years ago. The changes coincided with the installation of the (SWW) tower that releases water from Lake Billy Chinook into the lower Deschutes River.
The decrease in pH in conjunction with the increased bottom draw indicates that with tower operational changes, operators can better manage pH and help solve the water quality issues on the lower Deschutes River.
Deschutes River Alliance: Cooler, cleaner H2O for the lower Deschutes River.
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