Back in April, I questioned whether Longfin Smelt, a state-listed endangered fish, are going extinct in the Bay Delta1. The June surveys are in. The Bay Midwater Trawl, the Bay Otter Trawl, the Townet, and the 20-mm Survey show Longfin are at record lows with only a few caught in the Bay2. One only has to compare 20-mm Survey results for June over the past three years to see the trend. Going, going, gone.
What does the May 21 TUCP mean for the Delta if the State Board adopts it for the summer? What would be the consequences of weakening the outdated standards for outflow and salinity do to the Bay-Delta ecosystem?
The location of X2, the critical location of the Low Salinity Zone center where salinity is 2 parts per thousand (ppt), is shown below for various Net Delta Outflow Indices (NDOI). The existing standards and proposed changes are as follows:
Location of X2 in Bay-Delta at various Delta outflows (NDOI cfs).
In June weakened standards from a previous TUCP were 4000 cfs NDOI, with X2 allowed at TMS. Water temperature at X2 location by mid-June reached 70-73°F, levels considered sublethal but stressful on Delta Smelt.
Early June 2015 water temperatures in X2 region.
On June 12, 2015, X2 reached Rio Vista Bridge (for first time this year) on high tide after midnight at 72°F (NDOI was 5200 cfs). Afternoon water temperatures at bridge at low tide had been >74°F. When EC was 2000 at TMS, the water temperature was 72°F. On this date in 2012, the X2 location was downstream of EMM, with an NDOI of 7100 cfs and a water temperature of 69°F. On this date in 2013, X2 was downstream of EMM, with an NDOI of 7500 cfs and a water temperature of 68°F. On this date in 2014, X2 was upstream of EMM, with an NDOI of 3150 cfs and a water temperature of 72°F. The pattern is consistent with the hypothesis that the further X2 is east, the warmer the water temperature will be. The pattern also indicates that the normal standard of 7100 cfs keeps water temperatures at X2 below 70°F, at least in late spring.
My prediction for water temperature for July through September in the X2 region is shown below. This conservative prediction is based on June 2015 and June-September 2014 data.
Predicted summer water temperatures in X2 region of the Delta under proposed weakened standards.
Delta Smelt, already on the brink of extinction, will be further stressed by near lethal water temperatures in the X2 region. We can assume that only a small number of smelt remain in the X2 zone going into summer 2015, as compared to 2012 (see following charts). Any remaining smelt in the X2 zone must be protected at least at the normal standards as in 2012. Any weakening of the critical year standards will jeopardize the existence of the species.
No Delta Smelt were collected from the X2 zone in late May 2015. Only 5 were collected at the northern Deep Water Ship Channel station.”
In contrast to 2015, the distribution of Delta Smelt in late spring 2012 shows higher numbers collected in the X2 zone below Emmaton under NDOIs of 8000-10,000 cfs. Water temperatures at that time in the X2 zone were <70°F.
Fall Run Chinook Salmon enter the Bay-Delta on their spawning migrations from the ocean in August-September. Expected near -lethal water temperature (>77°F) will delay and stress these fish. Expected water temperatures greater than 70°F will stop migrations and degrade subsequent adult salmon pre-spawn survival and egg viability. The proposed 2500 cfs outflow standard for September will result in water temperatures of 73-75°F in the X2 zone near Rio Vista in mid-September. In contrast, in mid -September 2012, outflow was 7100 cfs and water temperatures at Rio Vista and the X2 zone near Emmaton were <70°F.
During the past four years of drought little has been said about the specific effect of the drought on the Bay, especially the upper Bay. Suisun Bay is a very important part of the San Francisco Bay Estuary as it receives freshwater flow from the Delta and is the low salinity mixing zone of the Bay-Delta ecosystem. Suisun Bay is also critical habitat of many listed estuarine and anadromous fishes. The drought has brought something new: unprecedented high salinities to Suisun Bay from relaxed Bay-Delta Plan Delta outflow and salinity standards. In the chart below (Figure 1) salinity levels as measured by micro-mhos of electrical conductivity (EC) were high (>15,000 EC) at Port Chicago in west Suisun Bay in April and May 2014 and 2015. Normal dry year levels are shown by 2012, when the Delta Outflow standard is 7100 cfs and the Collinsville salinity standard is 2780 EC. In 2014 and 2015, the standards were relaxed to save reservoir storage. The Outflow standard was reduced to 4000 cfs. The salinity standard location was moved upstream into the Delta. Although unregulated flow dominated most of the Apr-May period in 2012 (Figure 2), the regular standards applied in the latter half of May.
Figure 1. Salinity (EC) in Suisun Bay in April-May 2012, 2014, and 2015.
The potential ramifications of these unprecedented low outflows and high salinities are wide ranging and substantial.
“The biomass of the larger copepods is less than it was before the introduction of the clam Corbula amurensis, because of competition for food and grazing by clams on the early life stages of copepods. The resulting low abundance of copepods of suitable size, and the long food chain supporting them, may be contributing factors to the decline in abundance of several estuarine fish species.”2
“Many scientists in the U.S. geological survey, who have been studying the Bay for decades, also concur with Strong, that the clam is likely the culprit”.3
Less inflow to the Delta and less outflow to the Bay also mean more nutrients, plankton, and fish are drawn to the South Delta export pumps. Even with restricted pumping at 1500 cfs limit, the effect is proportional and significant. In reality, Delta outflows are lower than the NDOI estimates provided by DWR and Reclamation. A 14-day running average relaxed standard of 4000 cfs often leads to “real” outflows closer to zero4.
More on the effects of outflow on Suisun Bay can be found at:
http://www.sfestuary.org/wp-content/uploads/2015/03/Estuary-MAR2015-v8a-finalWEB.pdf .
Figure 2. Delta outflow (NDOI) in April-May 2012, 2014, and 2015.
Despite a relatively cool May, the Delta is very warm under conditions of low river and Delta flows and low outflow to the Bay that the State Water Board has allowed by weakening flow standards. As in 2014, water temperatures in early June approach the lethal level for Delta Smelt of 73°F1 (Figure 1). The water temperatures now (and in 2014) are several degrees higher than in 2012, the last year in which the normal dry year flow standards were followed.
The first heat wave of summer, with air temperatures forecasted from 95-100°F, is predicted to begin early next week. Water temperatures in the entire Delta are expected to reach the lethal level of 73°F or higher. The water temperature may be further degraded in the north and central Delta by the opening of the Delta Cross Channel in combination with the new False River Barrier (FAL location on map).
Delta Smelt are presently confined primarily to the Sacramento Deep Water Ship Channel, where water temperatures are already near lethal levels (Figures 2 and 3). Reclamation scientists theorize that smelt can survive in deeper, cooler waters. I challenge Reclamation to prove this theory by monitoring water temperature and taking dissolved oxygen profiles throughout the Sacramento Deep Water Ship Channel all summer.
Figure 1. Water temperature in the Delta in first week of June 2015.
Based on water temperatures recorded at CDEC stations (blue dots).
Figure 2. Water temperature in the Sacramento Deep Water Ship Channel,
May 28 – June 6, 2015.
Figure 3. Distribution of Delta Smelt catch in 20-mm Smelt Survey May 2015.
All but three young smelt were captured in the Sacramento Deep Water Ship
Channel . Water temperature at the time of the net deployment in the
Channel was 65°F (at surface).
How are Delta and Longfin smelt doing after my earlier March and April poor prognoses? As predicted, late April – early May surveys indicated extremely low numbers (Figures 1 and 2), far fewer than the record low numbers of 2013-2014 (Figures 3-6).
In the May 4, 2015 Smelt Working Group meeting1, “Members did make a note of the single Delta Smelt larva from April 23, as well as the three Delta Smelt observed during the primary channel CO2 treatment [at Tracy Fish Salvage Facilities], providing that this is evidence of entrainment. These collections occurred despite at or below minimum exports levels, as defined in the Biological Opinion; OMR flows were also at or close to the most positive flows indicated in the Biological Opinion….Salvage of juvenile Longfin Smelt increased to 52 for the week of April 27 through May 3. Some increase was expected as south Delta water warmed. Between April 13 and 15, four juvenile Longfin Smelt were salvaged at the CVP and 12 at the SWP, at the same time, a single larva was observed in the larval fish samples at the CVP and four larvae at the SWP. During the period of April 17 through 23, seven Longfin Smelt larvae were observed at the SWP and one larva at the CVP in larval fish collections. Continued collections in salvage are expected. Overall, catches in the central and south Delta were not sufficient to reach concern levels based on density or distribution… Longfin Smelt larvae and small juveniles will continue to be detected at the salvage facilities until water temperatures surpass 22 deg C.” The fact that any smelt were collected at the two south Delta export facilities should be a grave warning of a larger and very significant “take” of smelt. As stated many times before, the odds of any young smelt reaching the south Delta export facilities without succumbing along the way are infinitesimal. In addition, no smelt will survive in any part of the Delta where water temperature reaches 25°C.
With the prescribed Net Delta Outflow Index at only 4000 cfs and measured outflow nearer to zero, the low salinity zone critical habitat of smelt is in the central Delta. Remaining smelt are being drawn across the Delta from north to south to the export pumps. Under these conditions the first heat wave of late spring will heat the central Delta to lethal 23-25°C levels for smelt. Unless these conditions are changed by increasing outflow and reducing exports, both smelt species may go virtually extinct2 this spring.
Figure 1. Delta Smelt density distribution in late April 20-mm Survey. Only three were captured in Sacramento Deep-Water Ship Channel, compared to 20 in previous week’s survey.
Figure 2. Longfin Smelt density distribution in late April 20-mm Survey
Figure 3. Delta Smelt density distribution in late April, 2014 20-mm Survey.
Figure 4. Longfin Smelt density distribution in late April, 2014 20-mm Survey
Figure 5. Delta Smelt density distribution in late April, 2013 20-mm Survey.
Figure 6. Longfin Smelt density distribution in late April, 2013 20-mm Survey.