Category Archives: Smelt

What is wrong with summer water transfers?

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Summer water transfers are predominantly made with water released from Shasta and Oroville reservoirs.  Instead of being used by Sacramento Valley CVP and SWP contractors, water is sold to South of Delta contractors who take the water via the South Delta CVP and SWP export pumps.  Non-project water transfers are also facilitated by CDWR.  Transfers usually occur in drought years when allocations to South of Delta contractors are low and excess export capacity exists at the South Delta pumping plants.  Purchasers must also pay for an additional 15-25% of “carriage” water to limit salinity intrusion into the Delta that would occur with export of transfer water.

Under existing “rules”, up to 600,000 AF of water may be transferred through the Delta during the allowed summer transfer “window”.  In 2014, 110,000 AF of CVP water from Shasta Reservoir was transferred from July through November (Reclamation was granted a temporary change to transfer water in the Oct-Nov period in 2014).  In 2014, approximately 300,000 AF of transfers were conducted by CDWR during the summer.  In 2015 CVP transfers of Shasta water are expected to be 240,000 AF, while SWP transfers are expected to be less than they were in 2014.

So what are the problems with water transfers from an ecological perspective1?

  1.  Transfer water is released from reservoirs in summer where during drought years there may be a limited cold-water pool to sustain downstream fish populations through the summer and fall. In 2014, the brood year for Winter Run Chinook Salmon was lost when the Shasta cold-water pool was exhausted at the end of August (Figure 1).  Some would argue that the water would have been released in any case to downstream ag contractors.  However, there are other options that would keep the water in the reservoir (e.g., fallowing programs, water purchase, deferring transfers).
  2. The water is released from multi-year storage, thus limiting the amount of carry-over storage in the coming years that is needed to sustain fish and their habitat, as well as water supplies for public health and safety.
  3. Transfer water exported from the Delta is not the same water released from the reservoirs. Water exported is a combination of Sacramento River inflow, San Joaquin River inflow, and Delta low-salinity (brackish) water from the North, Central, and West Delta.  Sacramento River inflow includes flows from the Feather, Yuba, and American rivers, as well as many smaller rivers.
  4. The already inadequate protections that apply to “normal” export water don’t apply to transfer water. Transfers increase the flow towards the Delta pumps, pulling fish with them.  But the ratio of inflow to outflow that generally limits exports doesn’t count transfer water; there are no restrictions in moving transfer water through the Delta other than carriage water requirements.  Transfer water can make up 25% or more of Delta inflow.
  5. Transfer water exported thus takes water with fish from many Central Valley habitats. Most prominently is the taking of Delta Smelt from the brackish and freshwater zones of the North, Central, and West Delta. Transfer water essentially must pass through the Delta’s designated critical habitats to get to the South Delta export facilities (Figure 2).
  6. When water quality standards for inflow, outflow, and salinity are relaxed, the process is further aggravated. Adding transfers during drought conditions with barriers, DCC open, low exports, low inflows, and low outflows worsens the effects of transfers by bringing in added warm, fresh, low turbidity water to the Low Salinity Zone from the north, while exporting turbid, brackish, higher turbidity, more biologically productive water from the south (Figure 2).
  7. Delta Smelt are highly vulnerable in the summer of drought years because the entire population is within the Delta (figure 3), where water temperatures are near or above lethal levels.
Figure 1. Water temperature of Keswick Dam releases in summer 2014. Chart depicts rapid rise in water temperature in early September as Shasta cold-water pool was exhausted. (Chart Source: NMFS)

Figure 1. Water temperature of Keswick Dam releases in summer 2014. Chart depicts rapid rise in water temperature in early September as Shasta cold-water pool was exhausted. (Chart Source: NMFS)

Figure 2. Freshwater inflows to the Delta (blue arrows) including transfer water must mix first with many other source waters including brackish waters (green lines) from San Francisco Bay. South Delta exports draw water across the Delta (red arrows).

Figure 2. Freshwater inflows to the Delta (blue arrows) including transfer water must mix first with many other source waters including brackish waters (green lines) from San Francisco Bay. South Delta exports draw water across the Delta (red arrows).

igure 3. Catch distribution of Delta Smelt in CDFW Summer Townet Survey, July 2014. (Source: http://www.dfg.ca.gov/delta/data/townet/ )

Figure 3. Catch distribution of Delta Smelt in CDFW Summer Townet Survey, July 2014. (Source: http://www.dfg.ca.gov/delta/data/townet/ )

Are Longfin Smelt Going Extinct?

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long fin smelt

Longfin Smelt are a native Bay-Delta fish and are listed under the California Endangered Species Act as “threatened”. Like the Delta Smelt, Longfin have undergone dramatic declines over the past several decades starting with the 1987-92 drought, then the 2001-2005 dry period, the 2007-09 drought, and the most recent 2012-15 drought (Figure 1). A strong recovery occurred in the wet years of 1995-2000. Modest recoveries occurred in 2006 and 2011 (wet years).

The Winter Kodiak Trawl Survey of adult Longfin Smelt provides the first clue as to how the population is faring in the 2015 drought after the second lowest fall index on record. The number of adult Longfin captured in the three winter surveys (Jan-Mar) are low but not unlike other low abundance years in the past decade (Figure 2).

Another indicator is results of the Smelt Larval Survey. The abundance and distribution of larvae in the Bay-Delta is representative of spawning success and potential of this year’s production to contribute to the population. So far in March 2015, survey capture densities have been generally below 100 per 1000 cubic meter sampled (Figures 3 and 4). These densities were slightly lower than for the same surveys in 2014 (Figures 5 and 6). Much higher densities occurred in years 2009-2013 (not shown).

The Juvenile or 20-MM Smelt Survey is another indicator of how Longfin Smelt are faring. Its first survey was recently completed (Figure 7), and the densities are again down from 2014 (Figure 8). Densities in 2014 and 2015 are again significantly lower than in surveys over the previous decade (not shown).

Based on these trends, we can expect another poor recruitment year, perhaps even a record low Fall Index. The population was able to rebound after low Fall indices in 1992 and 2007. It remains to be seen whether the population can rebound after declining since 2006 and after record low numbers of larvae and juveniles in 2014 and 2015. As in 2014, water quality standards for Delta outflow and exports, as well as salinity, have been relaxed, which will further stress the population toward possible extinction. This “canary in the coal mine” for the San Francisco Bay-Delta Estuary, like the Delta Smelt, remains on “life support”.

We will keep you posted as to how the year progresses for Longfin Smelt. To keep up to date on upcoming surveys, check out CDFW’s web site. (https://www.dfg.ca.gov/delta/data/)

Longfin Smelt Fall Midwater Trawl Index – 1967-2013.

Figure 1. Longfin Smelt Fall Midwater Trawl Index – 1967-2013. The 2014 Index was 16. (CDFW data)

Figure 2. Catch of adult Longfin Smelt in Winter Kodiak Trawl Survey, Jan-Mar 2015.

Figure 2. Catch of adult Longfin Smelt in Winter Kodiak Trawl Survey, Jan-Mar 2015.

Figure 3. Longfin Smelt catch distribution in Smelt Larval Survey #5, early March 2015. (CDFW data summary)

Figure 3. Longfin Smelt catch distribution in Smelt Larval Survey #5, early March 2015. (CDFW data summary)

Figure 4. Longfin Smelt catch distribution in Smelt Larval Survey #6, late March 2015. (CDFW data summary)

Figure 4. Longfin Smelt catch distribution in Smelt Larval Survey #6, late March 2015. (CDFW data summary)

Figure 5. Longfin Smelt catch distribution in Smelt Larval Survey #5, early March 2014. (CDFW data summary)

Figure 5. Longfin Smelt catch distribution in Smelt Larval Survey #5, early March 2014. (CDFW data summary)

Figure 6. Longfin Smelt catch distribution in Smelt Larval Survey #6, late March 2015. (CDFW data summary)

Figure 6. Longfin Smelt catch distribution in Smelt Larval Survey #6,
late March 2015. (CDFW data summary)

Figure 7. Longfin Smelt catch distribution in 20-mm Survey #1, mid March 2015. (CDFW data summary)

Figure 7. Longfin Smelt catch distribution in 20-mm Survey #1, mid March 2015. (CDFW data summary)

Figure 8. Longfin Smelt catch distribution in 20-mm Survey #1, mid March 2014. (CDFW data summary)

Figure 8. Longfin Smelt catch distribution in 20-mm Survey #1, mid March 2014. (CDFW data summary)

Are Delta Smelt Going Extinct?

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Recently Dr. Peter Moyle (UC Davis) suggested we “prepare for the extinction of delta smelt”1. Record low summer and fall abundance indices in 2014 following declines over the past decade in the key survey indices have led to major concerns about the future of this endangered species. The first three survey of this winter’s trawl survey brought record lows for January and March (Figure 1). Dr. Moyle and many others are particularly concerned with the March catch of only six adult smelt.

Winter Kodiak Trawl Survey, Delta Smelt Adults

Figure 1. Catch statistics from Winter Kodiak Trawl Survey Jan-Mar 2002-2015. (CDFW data)

Will the record low numbers of Delta Smelt adults be sufficient to bring some recovery when the rains come again as in 2010 and 2011, the last two years with abundant rain and snow before the present drought? As Dr. Moyle pointed out, it is too early to tell. March larval smelt surveys in 2010 and 2011 captured few larvae, as have larval surveys so far this March. This year is different in that the present drought continues whereas the previous drought ended in 2010 and 2011.

Will another year of drought spell disaster for the smelt? That very well may be the case if the State Water Resources Control Board accepts the recent Temporary Urgency Change Petition submitted by the US Bureau of Reclamation and the California Department of Water Resources to change Delta water quality standards. The petition requests relaxation of Delta inflow, outflow and salinity standards, all of which are designed to protect water quality and Delta fish and their habitats, in order to sustain water deliveries to water contractors during the present drought. The changes will undoubtedly lead to higher losses of smelt and further degradation of their freshwater and low-salinity habitat, which could lead to even sharper declines than those apparent during the present and previous droughts. Stay tuned, as we will be keeping close track of events and the Delta Smelt, as well as preparations for their possible extinction.