A Ridiculous Premise

Posted on December 8, 2021 by Tom Cannon

A recent post from the Center for California Water Resources Policy and Management (Center) discusses the extinction of the Delta smelt. The post starts by saying, “To be sure, the delta smelt’s numbers are in decline.” That is a real understatement, but it contains some acknowledgement of the facts.

The author goes on to say, “It might fairly be argued that prime contributors to the delta smelt’s distressed status are California’s resource agencies.” The ostensible rationale for this attribution is, first, that the resource agencies don’t look for smelt in the right places in the right way. Second, because the agencies can’t find the smelt, “they have resisted managing the species ‘adaptively’” based on the monitoring that they don’t do.

This ridiculous premise suggests the decline has not been caused by excessive exports of water from the Bay-Delta watershed over the past five decades, but by the resource agencies who don’t know where to find and thus protect the smelt.

The author argues: “The agencies persist in mobilizing trawler-based open-water fish surveys, originally intended to census juvenile striped bass, as their primary means of monitoring delta smelt and the Delta’s other protected fish species.” This statement is simply untrue. To provide better coverage of “open-water” pelagic smelt, the Interagency Ecological Program (IEP) in recent decades added the Larval Survey, the 20-mm Survey, the Kodiak Trawl Survey, and most recently the Enhanced Delta Smelt Monitoring Program (EDSM). All of these surveys, plus the historic Fall Midwater Trawl and Summer Townet Surveys (and 50 years of Delta Export Fish Salvage Surveys), show the smelt’s catastrophic decline and march toward extinction.

But the author insists that the smelt are out there somewhere. “The surveys sample neither the relevant habitat strata used by those fishes nor the extent of their ‘closed’ populations, which would allow for estimates of the sizes of their populations.” If the smelt are out there in “closed populations” whose numbers would change the conclusions about the smelt’s catastrophic downward trend, then surely the author and the water purveyors who have a vested interest in finding those populations can muster some evidence and show the agencies and the rest of the world where to look.

Basic review and analyses of the available information show the decline of Delta smelt is highly associated with increasing exports and associated factors (see my many posts on this subject). The partial truth in the notion that the resource agencies have been complicit in the decline of Delta smelt stems from agency inaction to cut back those exports consistent with biological sustainability. Agency managers don’t lack information and scientific method. They lack the political courage to deploy them.

More on the Delta Threat to Winter-Run Salmon – Fall 2021

Posted on November 25, 2021 by Tom Cannon

During early November, juvenile winter-run salmon were moving into the Delta after two short fall rainfall pulses (Figure 1). The allowed export of 65% of Delta inflow is not protective of these wild young winter-run salmon, which are in short supply this year. My October 30 post, in which I warned about the threat of rising Delta exports on this year’s production of juvenile winter-run salmon entering the Delta, is being borne out.

From November 9-12, south Delta exports exceeded 70% of Delta inflow,¹ with about 2000 cfs of calculated Delta outflow. The USGS measurement of Delta outflow on November 8-9 was as low as -3000 cfs. Delta exports were simply drawing from the Delta’s freshwater reservoir supplied by the recent rains. The cries of San Joaquin Valley farmers for the capture of the runoff before it was “wasted” into the Bay and Ocean were indeed being answered. The Delta export pumps were shipping 15,000-20,000 acre-feet of water south each day.

Up at the Delta Cross Channel (open) and Georgianna Slough, over half the daily flow was being diverted into the central Delta. With the False River Barrier installed, most of the diverted water (and young salmon) flowed south toward the export pumps. Since no young salmon were showing up in the export fish salvage collections, it is likely that few successfully made the 50-mile journey from the northern Delta through the predator-laden central Delta corridor.

Hopefully, the several hundred thousand winter-run hatchery smolts will have better circumstances when they are released this winter near Redding for their 300-mile migration to the ocean.

Figure 1. Capture of juvenile winter run salmon in the lower Sacramento River in 2021.

https://www.usbr.gov/mp/cvo/vungvari/doutdly.pdf ↩

Delta Smelt Status 2021

Posted on November 15, 2021 by Tom Cannon

The Enhanced Delta Smelt Monitoring (EDSM) caught only 1 Delta smelt in 2200 smelt-targeted net tows in 2021. This compares to 49 captured in 2020 and hundreds in prior years. None were captured in the Spring Kodiak Trawl 2021 survey (Figure 1). This year’s results indicate that Delta smelt are likely virtually extinct in the wild.

Figure 1. Spring Kodiak Trawl survey index of Delta smelt (2004-2021), in which none were caught in 2021. Only one was captured in 2020. (source)

Longfin Smelt 2021

Posted on November 15, 2021 by Tom Cannon

In a 6/15/21 post, I had a grim outlook for longfin smelt for the summer of critical drought year 2021. My concern has proven warranted.

The June Townet Survey (6/7-6/10) found longfin juveniles concentrated in the Sacramento River channel of the western Delta (Figure 1) in water temperatures of 19-21ºC (Figure 2), very close to stressful, low growth, poor survival conditions for longfin (>20ºC). The area was within the low salinity zone, where juvenile smelt concentrate in spring. In conditions of low Delta outflow in drought years like 2021, the low salinity zone encroaches into the western Delta, where the zone is prone to warming without the cooler Bay air temperatures. The zone remained in the western Delta through the summer of 2021, with sustained water temperatures of 21-23ºC.

The September Midwater Trawl Survey collected only one longfin smelt, a minimum catch for that survey (Figure 3). This catch total was similar to those observed in late summer of other drought years (07-08, 15, and 20).

A 2017 paper by UC Davis scientists concluded that extinction of Delta smelt and longfin smelt was not inevitable if the necessary recovery actions were soon implemented. The paper’s recommended actions have as yet not been implemented, and conditions have even become worse in recent years, especially in the 2021 drought. Delta smelt are now virtually extinct in the wild, with longfin smelt likely to follow soon.

Figure 1. Catch per unit effort of longfin smelt in survey #1 of CDFW/IEP Townet Survey in June 2021.

Figure 2. Water temperature in lower Sacramento River channel in western Delta in early June 2021.

The Next Threat to Winter-Run Salmon – Rising Delta Exports

Posted on October 30, 2021 by Tom Cannon

A modest production of winter-run salmon fry was achieved in the Sacramento River near Redding this summer (Figure 1).¹ With the recent storm that peaked on October 24, these young salmon are now moving down the river toward the Delta (Figure 2).

Upon entering the Delta, these young salmon face the grim fate of passing through the Delta Cross Channel (DCC)/and Georgiana Slough into the central and south Delta, where they are drawn to Delta pumps by sharply increased exports (Figure 3).

The diversion of Sacramento flows increases with the periodic opening of the Delta Cross Channel (Figure 4). On an outgoing tide, the diversion via the DCC and GS can be higher than 50% under these circumstances.

Once they enter the interior Delta, it is difficult for young salmon to navigate out to the Bay. Many are drawn with reverse net flows to the south Delta, especially in periods when the DCC is closed. The risks to salmon fry in Clifton Court Forebay (predation) and at fish facility screens are severe.

Closing the DCC during the flow pulse only increases flow through Georgiana Slough and traps any diverted salmon in the interior Delta. Keeping the DCC open minimizes the reverse flows in the interior Delta, but draws more salmon in. It is a tough call either way. So the best option for this first fall pulse of winter-run fry is to minimize exports. This type of protection has been considered many times in the past. It is currently required in the Incidental Take Permit (p. 80) for the operation of the State Water Project, but not until after December 1.