Dissolved Oxygen Standards Don’t Adequately Protect Trout in the LDR, but You can do Something to Help!
Background:
Ever since Selective Withdrawal (SWW) Tower operations started at Round Butte Dam of Lake Billy Chinook in late 2009, there has been a well-documented decline in lower Deschutes River water quality due to the increased release of warm, polluted water from the surface of the reservoir into the lower Deschutes. The most obvious declines in water quality are increases in both pH and temperature following tower operations. However, dissolved oxygen (DO) is another important water quality parameter that is affected by warmer temperatures and operations of the 3-dam Pelton-Round Butte complex.
Aquatic animals require adequate DO to survive. The amount of available DO in water is affected by several factors, including water temperature, turbulence, and photosynthetic activity. In particular, cold water can physically hold more DO than warmer water. This means that warmer water temperatures seen in the lower Deschutes since SWW Tower operations started has reduced the water’s maximum amount of dissolved oxygen that it can hold. The concentration of DO necessary to support the life functions of fish (feeding, spawning, predator avoidance, etc.) varies among species and life stages. In cold water streams of North America, salmon and trout are typically the most sensitive and least tolerant species to low levels of DO.
Oxygen requirements for developing salmonid eggs are greater than for juveniles and adults. For this reason, Oregon’s water quality standards adopted under the Clean Water Act for DO are stricter during the most sensitive times of year: salmonid spawning and egg incubation periods. In the lower Deschutes, the spawning periods are designated as either Oct 15 – May 15 from Warm Springs River to the mouth, or Oct 15 - June 15 from the Reregulating Dam tailrace to the Warm Springs River. Oregon’s current DO criteria for the lower Deschutes River at the DRA monitoring site near Warm Springs are listed in Table A.
Beneficial Use
Dissolved Oxygen Criteria
Salmonid Spawning, including where and when resident trout spawn through fry emergence.
Not less than 11.0 mg/L 7-day mean minimum, or - *If intergravel DO (IGDO), as a spatial median, is 8.0 mg/L or greater, then DO criterion is not less than 9.0 mg/L absolute minimum, or -If conditions of barometric pressure, altitude and temperature preclude achievement of the criteria in mg/L, then 95% saturation applies
Cold-water Aquatic Life (includes salmon and trout rearing).
8.0 mg/L as a 30-day mean minimum, 6.5 mg/L as a 7-day minimum mean, and 6.0 mg/L as an absolute minimum. All three requirements must be met, or -If conditions of barometric pressure, altitude, and temperature preclude achievement of 8.0 mg/L, then 90% saturation applies
*This is the standard that has been applied in the lower Deschutes River
As described in Table A, the criterion applied during spawning periods can depend on intergravel dissolved oxygen (IGDO) concentration. IGDO is the amount of oxygen dissolved in the water that flows within the stream substrate. Adequate oxygen within streambed gravels is critical for developing salmon and trout eggs and incubating fry. Through a series of interim agreements between PGE, the Confederated Tribe of the Warm Springs (CTWS), and ODEQ the DO standard currently being applied by ODEQ for the lower Deschutes River during steelhead and salmon spawning is the lower standard of 9.0 mg/L minimum concentration since intergravel DO studies completed by PGE show that intergravel DO has been above 8.0 mg/L. While the DRA has concerns about the quality and accuracy of these intergravel DO studies (for example, data were only collected near the reregulating dam tailrace and not throughout the lower Deschutes), even when the 9.0 mg/L minimum is applied, serious departures from the DO standard occur on an annual basis. Particularly if trout spawning is considered as it should be, as discussed below.Table A. State of Oregon’s dissolved oxygen criteria for the lower Deschutes River from the Reregulating Dam tailrace to the mouth of the Warm Springs River.
The Problem:
ODEQ’s current application of the DO standard in the lower Deschutes with a hard spawning end date of May 15 or June 15 does not protect resident trout spawning/incubation as required in Oregon’s water quality standards. Oregon’s water quality standards for DO mandate that when determining the DO standard for a particular water body, resident trout spawning must be included. Oregon Administrative Rules (OAR 340-041-0016) states:
“The following criteria apply during the applicable spawning through fry emergence periods set forth in the tables and figures and, where resident trout spawning occurs, during the time trout spawning through fry emergence occurs.”
In other words, Oregon’s DO standard requires that the DO criteria of 11.0 mg/L 7-day mean minimum or 9.0 mg/L absolute minimum concentration must be applied not just in the identified salmon and steelhead spawning time and place, but also during resident trout spawning through fry emergence. Trout spawning is known to take place at a minimum from February through the end of August in the lower Deschutes. Therefore, ODEQ’s standards should reflect this instead of the current hard end dates in May and June.
Additionally, the current Dissolved Oxygen Management Plan of the ODEQ permit for tower operations (401 Certification) states that salmonid spawning standards for DO should apply year-round:
“The ODEQ and CTWS salmonid spawning DO criterion will apply to the Deschutes River downstream of the PRB Project during the periods of salmonid spawning and incubation, which in the lower Deschutes River is the entire year.” (from ODEQ’s 401 Certification Water Quality Management and Monitoring Plan)
In March 2020, PGE submitted an application to ODEQ to revise the 401 certification, which in part requested reducing the year-round spawning requirement for dissolved oxygen. After almost three years ODEQ has yet to draft a new 401 permit, and in the meantime have ignored the requirements of the current permit.
Figure A below depicts the DRA’s DO data collected in the lower Deschutes near Warm Springs the last three years from 2020-2022. It also depicts the two different minimum DO standards during spawning depending on IGDO data. These data show that there are serious violations (>30days per year) of both protective DO standards of 11.0 mg/L 7-day mean minimum or 9.0 mg/L absolute minimum, particularly when trout spawning is considered (dashed lines).
Figure A. Daily minimum DO concentration (mg/L) in the lower Deschutes River near Warm Springs from 2020-2022. The red and yellow lines show the minimum dissolved oxygen basin standards based on two separate criteria: (1) without intergravel DO data the 11.0 mg/L 7-day mean minimum applies during spawning (red line) and (2) if intergravel DO (IGDO) data indicates associated DO levels are above 8.0mg/L, then the 9.0mg/L water column DO minimum during spawning applies (yellow). Solid red line depicts when ODEQ applies the DO standard in the LDR during the designated salmon and steelhead spawning and incubation period of October 15- June 15from the Reregulating Dam tailrace to the confluence with the Warm Springs River. Dashed red and yellow lines depict the extension of the DO standard to the known spawning/incubation period of trout in the LDR.
Regardless of whether the 11.0 mg/L or 9.0 mg/L DO standard is applied, an in-depth review of all of the DRA’s continuous DO data confirms that trout spawning is not being protected. Table B depicts the number of days that the 9.0 mg/L absolute minimum protective standard was violated annually from 2016-2022 based on three separate categories: (1) the June 15 hard end date of salmonid spawning that is currently applied by ODEQ; (2) the Aug 31 end date of salmonid spawning based on the available data record for trout spawning; (3) the year-round application of the spawning standard as outlined in the current ODEQ permit for tower operations since the last interim agreement expired in 2020. Since 2016, the DRA DO data indicates that an average of 56 days of violations per year of the 9.0 mg/L DO minimum standard has occurred when trout spawning is considered (Table B). This mismanagement cannot be allowed to continue, particularly when there is a simple solution.
Year
# Days Minimum 9.0 mg/L DO Spawning Standard was Violated With:
June 15 End Date (Jan 1 – June 15, Oct 15- Dec 31)
Aug 31 End Date (Jan 1 – Aug 31, Oct 15- Dec 31)
Entire Monitoring Season
2016
2
65
91
2017
0
56
56
2018
26
78
78
2019
0
55
70
2020
16
62
86
2021
0
44
64
2022
0
33
42
Total
44
393
487
Average
6
56
70
Table B. Number of days the minimum DO level fell below 9.0 mg/L, categorized by salmonid spawning end date.
The Solution:
Fortunately, the dissolved oxygen problems described above can be easily fixed by spilling water over the Reregulating Dam, the third and last dam of the 3-dam Pelton-Round Butte complex, to entrain oxygen as it is released into the lower Deschutes River; when water and air mix due to turbulence (including waterfalls, white water, and spill from dams) oxygen from the air entrains in the water, increasing its concentration. However, ODEQ needs to do their job and require PGE to make this change and adequately protect aquatic life.
If you have been following the DRA’s recent emails and posts, you know that for the first time in 20 years, ODEQ are updating their aquatic life use designations that determine when and where the protective spawning standards for dissolved oxygen and temperature apply throughout Oregon, including the lower Deschutes. The current draft rules still do not protect trout spawning because they keep the hard end dates of May 15th or June 15th. Because of this, and other concerns detailed in this blog post, it is vital that you make your voice heard to ensure that all water quality standards, including dissolved oxygen, adequately protect aquatic life.
How to make your voice heard:
- Sign up for DRA’s email blasts: This is the best way to receive updates, reminders and how to attend the meeting and submit comments.
- : DRA has a list of concerns based on these draft rules. Our recent blog post, “DRA’s Top Concerns with DEQ’s Proposed Aquatic Life Rules”, details these concerns. If you are signed up for our newsletters, our May newsletter contains a public comment insert that you can fill out and mail to ODEQ to register your comments. You can also submit comments via email to aquaticlife.2022@deq.oregon.gov. All comments are due by 5pm June 23.
ODEQ’s current regulations on DO and beneficial use maps can be found at: OAR 340-041-0016, OAR 340-041-0016 - TABLE 21, OAR 340-041-0130 – Beneficial Use Maps. For more information, please read our 2022 Lower Deschutes River Water Quality Report and/or watch our State of the Lower Deschutes Webinar