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Another Chance for Delta Smelt – 2017 Comeback?

In 2010 Delta smelt started a two-year comeback after three years of drought.  The fourth lowest fall index on record (2009) brought a modest increase in the normal water year 2010 summer and fall indices that in turn led to the modest 2011 wet year recovery.  Another comeback may be in the making with the wet fall-winter of water year 2017.  After the record low 2015 summer and fall indices, and what were perceived to be record lows in 2016, the remaining smelt seem to be making a run of it this wet fall-winter as they did in 2010 (Figures 1 and 2).  In 2010 exports were constrained by the 2009 Smelt Biological Opinion (BO) limits on OMR of -5000 cfs or below (Figure 3).  Only one Delta smelt was observed in December and January at the south Delta fish salvage facilities that year (most likely due to the export restrictions).  So far this year prescribed export restrictions and recommendations from the Smelt Working Group on OMR flows per the BO have been ignored, in part due to relaxations allowed in the new water bill the President signed last week.  Exports and negative OMR flows remain high (Figure 4).  With such high winter exports and associated highly negative OMR flows, it remains to be seen if salvage numbers remain low (none so far) and a comeback occurs in 2017.

Figure 1. Delta smelt distribution in January 2010 Kodiak Trawl Survey 2010. Source: CDFW.

Figure 1. Delta smelt distribution in January 2010 Kodiak Trawl Survey. Source: CDFW.

Figure 2. Delta smelt distribution in December 2016 Kodiak Trawl Survey. Source: CDFW.

Figure 2. Delta smelt distribution in December 2016 Kodiak Trawl Survey. Source: CDFW.

Figure 3. Old and Middle River net flow in the central Delta downstream of the South Delta export pumps 12/2/2009-1/28/2010. Negative flows are caused by reverse flows in these river channels toward the pumping facilities. Source: CDEC.

Figure 3. Old and Middle River net flow in the central Delta downstream of the South Delta export pumps 12/2/2009-1/28/2010. Negative flows are caused by reverse flows in these river channels toward the pumping facilities. Source: CDEC.

Figure 4. Old and Middle River net flow in the central Delta downstream of the South Delta export pumps 11/21/2016-12/21/2016. Negative flows are caused by reverse flows in these river channels toward the pumping facilities. Source: CDEC.

Figure 4. Old and Middle River net flow in the central Delta downstream of the South Delta export pumps 11/21/2016-12/21/2016. Negative flows are caused by reverse flows in these river channels toward the pumping facilities. Source: CDEC.