Lower Deschutes River Update – Wednesday 9/13/2023

• Data through: Sunday 9/10/23

Key Findings:

As noted in previous updates, increasing cool, clean bottom water releases from Lake Billy Chinook show immediate improvements to water quality in the lower Deschutes. Since Thursday, 8/17, there has been a dramatic drop in both pH (Figure 9) and temperature (Figures 1-2) near the reregulating reservoir dam tailrace at our “Warm Springs” station. pH has been in compliance with the maximum standard of 8.5 at this station since the initial drop. A similar, but less dramatic, drop in temperature and pH readings occurred on 8/31. Based on similar occurrences in previous years, it’s clear that water quality can be improved by increasing the release of bottom water from the Selective Withdrawal (SWW) Tower in Lake Billy Chinook.

Interestingly, while there was a similar decline in pH (Figure 10) and temperature (Figures 3-4) at our monitoring site at Maupin 8/17 and 8/31, the reduced pH levels were not long-lasted as levels returned to a daily maximum level of around 8.75 on subsequent days. Note that there was still a violation of the maximum 8.5 pH standard at the Maupin station on 8/17 and 8/31 since levels were over 8.5 starting at midnight and going on into the first few hours of the day. Like the Warm Springs site, temperature is still cooler in Maupin relative to levels earlier in August (Figures 3-4).

Aside from the recent exceptions noted above, there have been daily violations of the pH standard in the lower Deschutes for the duration of our monitoring in 2023, which has unfortunately been a common occurrence since the DRA started continuous water quality monitoring in the lower Deschutes back in 2016.

Directly below is a summary table of pH, dissolved oxygen (DO) and temperature at our two monitoring stations to date for the 2023 monitoring season. Note that our Maupin telemetry unit is currently down due to communication issues. Data below is through Sept 7, but rest assured that the water quality meter is still collecting data. Live readings will be updated in early October.

Background

The relative increase in water quality standard (particularly pH and temperature) violations are representative of the negative shifts that have been observed in the lower Deschutes River following SWW Tower operations in 2009, including the increased abundance of nuisance algae, decline in sensitive aquatic insect abundance and shift in emergence, and increased prevalence of fish disease and parasites.

Summary:

This document will be updated ~1-2 weeks to report on the current conditions in the lower Deschutes River. It includes water quality conditions at each of our two monitoring sites near Warm Springs and Maupin, weekly flow snapshots from the USGS Madras and Moody gauges, and an update on the latest aquatic insect hatches occurring throughout the river based on entries we receive from the public on our Aquatic Insect Hatch App. Please consider keeping your fellow anglers informed by making entries to our hatch app while you are on the lower river!

Outline:

The following data will be provided in this weekly update:

• Water quality update:
  • Tables 1-2 provides an overview of the water quality violations for pH, temperature, and dissolved oxygen (DO) observed by the DRA in the lower Deschutes River at our two monitoring stations so far during the 2023 monitoring season.
  • Figures 1 – 10 depict current graphs of temperature, dissolved oxygen (DO) and pH at our two monitoring stations during the 2023 monitoring season. Data gaps were periods where (1) flow levels are too high to safely have equipment deployed or (2) technical difficulties with the water quality meters or transponder equipment – i.e. battery levels.
• Flow update: Figures 11 -12 depict the last thirty days of flow data from the USGS Madras (near Warm Springs) and Moody (near the mouth) gauges in the lower Deschutes
• Aquatic insect hatch data: summarizes the most recent hatches occurring on the lower Deschutes based on entries received from our aquatic insect hatch app

Public Portal:

You can view the current water quality conditions at each of our two monitoring sites on our Public Portal. Conditions are updated every 10 minutes.

Note that our Maupin telemetry unit is currently down due to communication issues. Last available data point on the public portal is from Sept 8, but rest assured that the water quality meter is still collecting data. Live readings will be updated in early October.

For Additional information:

Our Public Portal Help Sheet contains the following:

1. How to use the Public Portal
2. Additional background information
3. What the aquatic life use designations mean
4. What the water quality standards are in the lower Deschutes and why they are important

For more information on how the river ecosystem has changed in the lower Deschutes following SWW Tower operations as a result to declining water quality, please read our annual 2022 Lower Deschutes River Water Quality Report, or watch our recent State of the Lower Deschutes webinar.

Water Quality Update

Table 1.  Running tally of water quality standard violations in the lower Deschutes River recorded by DRA water quality sondes at the Warm Springs station. Tally organized by parameter, and the various standards that apply in the lower Deschutes for each parameter.

Table 2. Running tally of water quality standard violations in the lower Deschutes River recorded by DRA water quality sondes at the Maupin station. Tally organized by parameter, and the various standards that apply in the lower Deschutes for each parameter.

Figures 1 – 2. Instantaneous temperature (top) and rolling 7-day average daily maximum (7-DADM) temperature (bottom) at the Warm Springs site depicted by the blue lines in the two graphs above. The rolling 7-DADM temperature is what is applied for the temperature standards throughout Oregon. Red line in bottom graph depicts the maximum 13 °C standard that applies during the designated salmon/steelhead spawning period of October 15 – June 15 at this site. Orange line depicts the maximum 16 °C core cold-water standard that applies June 16 – October 14 at this site. Note the violation of the temperature standard at the Warm Springs site from 5/30/23 to 6/15/23.

Figures 3 -4. Instantaneous temperature (top) and rolling 7-day average daily maximum (7-DADM) temperature (bottom) at the Maupin site depicted by the blue lines in the two graphs above. The rolling 7-DADM temperature is what is applied for the temperature standards throughout Oregon. Orange line depicts the maximum 18 °C salmon/trout rearing and migration standard that applies May 16 – October 14 at this site. The salmon/steelhead spawning period is designated October 15 – May 15 at this site. The first 7-DADM data point did not occur until May 29, which why the spawning standard is not included in the bottom graph.

Figures 5-6. Dissolved oxygen concentration near Warm Springs in mg/L (top) and percent saturation (bottom) depicted by blue lines in the two graphs above. The absolute minimum 9.0 mg/L and 95% saturation dissolved oxygen standard that applies during the salmon/steelhead spawning period of October 15- June 15 at this site are depicted by the red lines. Note that the percent saturation standard only applies if conditions of barometric pressure, altitude, and temperature preclude achievement of the 9.0 mg/L standard. The large daily swings in %DO saturation (about 25% ) are indicative of excessive aquatic plant/algal growth and point to excess nutrients in the river (eutrophication). Starting August 25, the large daily swings in DO decreased due to an increase in the daily minimum DO from around 8 mg/L and 75% to around 10.5 mg/L and 95%.

Figures 7-8. Dissolved oxygen concentration at Maupin in mg/L (top) and percent saturation (bottom) depicted by blue lines in the two graphs above. The absolute minimum 95% saturation dissolved oxygen standard that applies during the salmon/steelhead spawning period of October 15- May 15 at this site is depicted by the red line in the bottom graph. Note that the percent saturation standard only applies if conditions of barometric pressure, altitude, and temperature preclude achievement of the 9.0 mg/L standard. Also note that there was not enough data collected at the Maupin site during the spawning season (3 days, 7 days needed) to calculate the 7 day mean minimum DO in mg/L, which is 11.0 mg/L at this site during the designated spawning/incubation period. The large daily swings in %DO saturation (almost 30%) are indicative of excessive aquatic plant/algal growth and point to excess nutrients in the river (eutrophication).

Figures 9-10. pH readings near Warm Springs (top) and Maupin (bottom) depicted by the blue lines in the two graphs above. The absolute maximum pH standard of 8.5 that applies throughout the Deschutes Basin is depicted by the red lines. At the Warm Springs site, the standard has almost been continuously in violation of the maximum standard since monitoring started in mid-March until August 17, when presumably percent bottom draw from the SWW Tower was increased. At the Maupin station, aside from one day the pH standard has been violated on a daily basis with the natural daily swing that occurs in pH values due to photosynthetic activity in algae and aquatic plants.

Flow update:

Higher than average (over the last two decades) snowpack caused peak spring flows to be the highest since 2019 at 6800 cubic feet per second (cfs) just downstream of the Pelton-Round Butte (PRB) dam complex and 10,600 cfs near the mouth of the lower Deschutes on May 1, 2023. Unsurprisingly, due ongoing drought, flows have reduced to about 3600 cfs just downstream of the PRB complex and 4100cfs near the mouth, which is lower than the median for the period of record. There have been a couple small spikes in flow in the lower Deschutes over the past 30 days, but they remain lower than the median for the period of record.

Screenshots from the last 30 days discharge data in cubic feet per second (cfs) from the USGS Madras Gauge (just downstream of the Pelton-Round Butte complex) and Moody Gauge (near the mouth of the lower Deschutes) are shown in Figures 11 – 12 below.

Figure 11. Graph depicting discharge (cfs) at the USGS Madras gauge from Aug 13 to Sept 10

Figure 12. Graph depicting discharge (cfs) at the USGS Moody gauge from Aug 13 to Sept 10

Current hatches on the lower Deschutes:

Since 2013, DRA has collected macroinvertebrate hatch data to help track shifts in timing and abundance. The last entry into our lower Deschutes Hatch App was on 7/26/2023. See the conditions update from Aug 23 for details.

We highly encourage you to fill out this survey each time you are out on the lower Deschutes to keep your fellow anglers informed, and provide the DRA with invaluable data. For more information, please see our hatch app webpage. Prior to filling out your first survey, we ask that you watch the following identification training video.