Category Archives: Smelt

Sacramento River Low Flows and High Water Temperatures Violate State Standards for lower Sac River and Delta - Lethal for Salmon and Smelt

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Low flows in the lower Sacramento River above the Feather River and warm flows from the Feather River are compromising the summer habitat of smelt and salmon in the lower Sacramento River and the Delta, violating state and federal water quality standards.

Lower Sacramento River at Wilkins Slough

The Sacramento River at Wilkins Slough at river mile 118, 63 miles upstream of the Sacramento Delta, has low flows and high water temperatures (Figure 1).  The high water temperatures are a violation of the 68oF (average daily) water quality standard and are stressful to migrating salmon.

Lower Sacramento River at Verona below mouth of Feather River

The lower Sacramento River 50 miles downstream of Wilkins Slough at Verona, just downstream of the mouth of the Feather River, has near lethal water temperatures, far above the water quality standard (Figure 2).  The high temperatures are likely due in part to recent increased releases from Oroville Reservoir to lower water levels for the spillway repair project.

Lower Sacramento River in Delta

The lower Sacramento River at Freeport in the north Delta, 25 miles downstream of Verona, has near lethal water temperatures for Delta smelt (Figure 3).   The high temperatures are likely due in part to recent increased releases from Oroville Reservoir to lower water levels for the spillway repair project.  The north Delta water temperatures are also high in part due to lower than normal net river flow (as measured at Rio Vista 20 miles downstream of Freeport – Figure 4).  The low flows have also led to encroaching salinity at Emmaton several miles downstream of Rio Vista (Figure 5), also in violation of water quality standards.

Figure 1. Sacramento River at Wilkins Slough flow and water temperature in May-June 2018. The water temperature standard for the lower Sacramento River is 20°C (68°F).

Figure 2. Sacramento River at Verona water temperature 6/15-6/26, 2018. The water temperature standard for the lower Sacramento River is 20°C (68°F).

Figure 3. Sacramento River at Freeport water temperature 6/15-6/26, 2018. The water temperatures above 72°F are stressful to Delta smelt.

Figure 4. Rio Vista daily average historical and 2018 flow May-June.

Figure 5. Salinity (EC) at Emmaton near Rio Vista. The standard of 450 EC (uS/cm) was exceeded from 6/15 to 6/18, 2018. The standard is necessary to keep the low salinity zone, critical habitat for Delta smelt. west of the Delta.

Enhancing Pelagic Habitat Productivity in the North Delta Is it too late to save the Delta smelt?

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The Bureau of Reclamation recently released an Environmental Assessment for the Sacramento Deep Water Ship Channel Nutrient Enrichment Project. The proposed project would directly release nitrogen nutrients into the Ship Channel, which runs from West Sacramento to Cache Slough, north of Rio Vista.  The project is designed to stimulate plankton blooms in the North Delta as part of the Delta Smelt Resilience Strategy, which describes the goal as follows:

The purpose is to determine if the addition of nitrogen can stimulate plankton (fish food organisms) production in a section of the ship channel, which is isolated from the Delta in terms of water flow.

Adding nitrogen to the ship channel will indeed stimulate plankton productivity.  Only a few miles away, regional governments have spent decades in removing nitrogen (most recently, ammonia) from the effluent of the Sacramento Regional Wastewater Treatment Plant to reduce production of blue-green algae in the Delta.  The City of West Sacramento already seasonally releases high nutrients, metals, and salts into the Ship Channel.  Adding more nitrogen could easily increase toxic blue-green algae problems in the Delta, similar to the bloom that recently led to the recreational closure of southern California’s Diamond Valley Reservoir, which receives Delta water.

There is higher plankton productivity in the Ship Channel than in nearby Delta channels because the Ship Channel has longer residence time, higher nutrients,  and higher water temperatures.  The broken gate on the Ship Channel’s northern entrance contributes to these conditions.  However, lack of circulation also leads to nitrogen depletion and declining plankton production, and there is limited seasonal replenishment of nitrogen.

The Delta Smelt Resilience Strategy is considering increasing flows into the north Delta from the Colusa Basin Drain, Fremont Weir, and the Ship Channel to stimulate Delta plankton blooms.  The biggest problem with these sources is high spring-through-fall water temperatures (Figures 1-3).  Water temperature is certainly the greatest limiting factor in the north Delta for Delta smelt; adding nitrogen will not fix this problem.

Fixing the gate at the north end and allowing cooler Sacramento River water (strong American River influence) into the channel (Figure 4) would reduce water temperatures in the Ship Channel.  Just a few degrees can be life or death for Delta smelt.  Increased entry into the Ship Channel of Sacramento River water would also introduce more nitrogen, potentially reducing the need to fertilize the Ship Channel with crop dusters.

Figure 1. Water temperature in the Yolo Bypass downstream of the entrance of the Colusa Basin Drain.

Figure 2. Water temperature in the Sacramento River Deep Water Ship Channel.

Figure 3. Water temperature in the lower Yolo Bypass toe drain canal near Liberty Island.

Figure 4. Water temperature in the Sacramento River near Freeport downstream of the entrance to the Sacramento River Deep Water Shipp Channel.

And then there were none…

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ARE DELTA SMELT FINALLY EXTINCT? HAS THE CANARY SUNG ITS LAST SONG?

In late April and early May 2018, 20-mm Surveys collected no Delta smelt (Figure 1) in the San Francisco Bay-Delta estuary. It’s a new low for Delta smelt since the survey began in 1995, worse even than the 2017 survey catch (Figure 2). The outlook for the population as indexed by the summer and fall surveys looks grim after record lows from 2012-2017. Despite good conditions in spring 2018, the number of adult spawners was too low, indicating a weak recovery potential.

Figure 1. Catch and lengths of Delta smelt collected in the 20-mm Survey in spring 2018. None were collected in surveys 4 and 5

Figure 2. Catch and lengths of Delta smelt collected in the 20-mm Survey in spring 2017.

Delta Smelt Spawning Run – Record Low February 2018 Index

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Despite three straight non-drought winters (2016-2018) the Delta smelt spawning run shows no sign of recovery based on the Kodiak Trawl Survey (Figure 1). The February 2018 survey brought a record low catch of only 4 adults (compared to 125-287 from 2011-2013). The March index was “1”. As in my last post, the prognosis for Delta smelt remains grim. The next check is the spring 20-mm Smelt Survey index to determine if this years spawning run production of juvenile smelt continues the pattern of four years of near record lows (Figure 2).

Figure 1. Kodiak Trawl Survey catch of Delta smelt in winter 2002-2018. Source: CDFW survey data.

Figure 2. CDFW 20-mm Survey Delta smelt index 1995-2017. Source: https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=147044

 

Longfin Smelt February 2018

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In April 30, 2017 post on longfin smelt, I wrote that it appeared that longfin were making a comeback after the 2012-2015 drought. In this post I compare the 2017 comeback to those in the two previous wet years, 2006 and 2011.

First: The number of adult longfin smelt collected in the December 2017 trawl survey (Figure 1) was substantially less than the number collected in the December 2011 survey (Figure 2).

Second: The number (density) of larval longfin smelt collected in the late January 2018 larval fish survey (Figure 3) was substantially less than the number collected in the late January 2012 survey (Figure 4).

Third: The 2017 index, though higher than the dry years that immediately preceded 2017 and indicative of some recovery, remained below the recent wet years (06, 11) and continued a long-term trend of progressively lower indices (Figures 5 and 6).

Figure 1. Catch distribution of adult longfin smelt in the December 2017 trawl survey. Source: CDFW survey online report.

Figure 2. Catch distribution of adult longfin smelt in the December 2011 trawl survey. Source: CDFW survey online report.

Figure 3. Catch distribution of larval longfin smelt in the late January 2018 larval fish survey. Source: CDFW survey online report.

Figure 4. Catch distribution of larval longfin smelt in the late January 2012 larval fish survey. Source: CDFW survey online report.

Figure 5. Fall Midwater Trawl Index for Longfin Smelt, 1967-2017. Source: CDFW FMWT Survey.

Figure 6. Longfin Recruits (Fall Midwater Trawl Index) vs Spawners (Index from two years prior) in Log10 scale. Note the progressive decline in recruits in the last three wet years (06, 11, 17). The relationship is very strong and highly statistically significant. Taking into account Delta outflow in winter-spring makes the relationship even stronger. Recruits per spawner are dramatically lower in drier, low-outflow years (red years). Source: http://calsport.org/fisheriesblog/?p=1360 .