Category Archives: Bay-Delta

Spring 2018 – Unusual at Best

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Flow conditions into and through the Delta are creating an unintended adaptive management experiment this spring. The San Joaquin River is providing half of the 20,000 cfs of Delta inflow. Exports and other water diversions are each taking about 3000 cfs from the Delta, leaving 14,000 cfs for outflow to the Bay. The Delta has been free of salt (Collinsville has been fresh at 200 EC, but salt is now encroaching). These are good conditions for the Delta and the San Joaquin, but horrendous for the Sacramento. Such conditions are highly unusual.

The Bureau of Reclamation’s decision to save water in Shasta reservoir, combined with a low water level in Oroville Reservoir because of ongoing repairs, have led to poor flows and high water temperatures in the lower Sacramento River. Flow at Wilkins Slough on the Sacramento River above Feather River confluence has fallen to 4000 cfs (Figure 1). Flow in the Sacramento River at Verona, below Feather River confluence, is only 7000 cfs (Figure 2). Water temperatures have reached 60°F at Red Bluff and 70°F at Wilkins Slough. Water temperatures above 56°F are detrimental to spawning winter-run salmon near Red Bluff. Water temperatures above 65°F are detrimental to out-migrating juvenile salmon, steelhead, and sturgeon.

A recent increase in releases from Shasta Reservoir is accommodating agricultural diversion demand in the upper Sacramento River below Shasta (Figure 3), while flows decline in the lower river. The increase in the upper river has stimulated emigration of wild juvenile salmon from the upper river, as shown by increased catch at the Red Bluff screw traps (Figure 4). The problem is that two-thirds of river flow is being diverted for Sacramento Valley agriculture, and river temperature rises 10°F along the way. Sacramento River salmon that reach the Delta, along with other Central Valley wild and hatchery salmon, are subject to south Delta exports (Figures 5 and 6). Though south Delta exports have been reduced, their effect remains significant because of low Sacramento River inflow to the Delta.

As I have suggested in past posts, Shasta Reservoir releases should be increased or water diversions from the upper Sacramento River reduced by several thousand cfs, in order to increase lower river flows and reduce water temperatures to no higher than the state water quality standard of 68°F. If this action is not taken, we will simply be feeding most of the young salmon to the abundant stripers that thrive in warm water conditions between Redding and the Bay (Figure 7).

Figure 1. Sacramento River flow at Wilkins Slough in spring 2018.

Figure 2. Sacramento River flow at Verona in spring 2018.

Figure 3. Sacramento River flow below Shasta/Keswick dams in spring 2018.

Figure 4. Catch of juvenile salmon in screw traps, water temperature, river flow, and turbidity near Red Bluff in Sacramento River.

Figure 5. Juvenile Chinook salmon salvage at south Delta export facilities in spring 2018. Red circle outlines recent salvage of wild juvenile spring- and fall-run smolts.

Figure 6. Juvenile Chinook salmon salvage at south Delta export facilities in spring 2018.

Figure 7. Striper limits from late April 2018 guide trip on lower Sacramento River. Source: James Stone.

Spring Hatchery Salmon Releases – Feather River

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Hatchery fall-run salmon smolts being released into the Sacramento River at the mouth of the Feather River at Verona on May 2, 2018. SacBee photo.

The California Department of Fish and Wildlife released spring-run and fall-run salmon smolts raised at the Feather River Hatchery into the lower Feather River from late March to early May 2018. The initial spring-run releases were accompanied by a flow pulse up to 14,000 cfs into the lower Feather River.1 The early May release2 of fall-run was made without the benefit of a flow pulse.

Past performance of hatchery spring-run smolt releases is shown in Figure 1. The 2011 successful smolt release was accompanied by 8,000-17,000 cfs Oroville Dam flows (Figure 2) and wet year conditions in the Bay-Delta. The 2012 modestly successful smolt release was accompanied by a 3000 cfs flow pulse. The 2007 to 2009 smolt releases also had an accompanying 3000-5000 cfs flow releases, but flows that followed fell to 1000-2000 cfs. There was no flow pulse in 2010.

The early April 2018 flow pulse in the Feather River was followed by falling flows (14,000 cfs in early April down to 1000 cfs flow in late April – Figure 3). The latest release of fall-run smolts on May 2 was made near the mouth of the river because of low Feather River flows. Flows in the Sacramento River were also low (less than 10,000 cfs – Figure 4), and water temperatures were marginal at 65°F. The evidence summarized in Figures 1 and 2 suggests that smolts should be trucked to the Bay in non-wet years without strong flow pulses. Survival would be further increased if the smolts are barged from the mouth of the river.3

We can expect good survival from the earlier releases that were accompanied by flow pulses and poor survival from the early May release without a flow pulse. The latter release should have been trucked to the Bay.

Figure 1. Survival (% return) of spring-run salmon tag-release groups from 2007-2013 spring smolt releases. Source of data: http://www.rmpc.org/

Figure 2. Flow (cfs) in the lower Feather River at Gridley in Apr-May 2007-2013.

Figure 3. Flow (cfs) in the lower Feather River at Gridley in Mar-May 2018.

Figure 4. Flow (cfs) in Sacramento River just below mouth of Feather River at Verona in Mar-May 2018.

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

 

Miracle March/April for Water Supply and Fish

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It has been a “Miracle March-April” for water supply and fish in the Central Valley. Over 2 million acre-feet of water was added to Central Valley storage reservoirs. Many major reservoirs reached flood capacity, with large releases and rivers spilling over into flood bypasses. The snowpack doubled to over 50% of average. Water year 2018 cumulative precipitation nearly doubled (remains 10 inches short of average at about 80% of normal).1 Water Year 2018 will likely stack up as “below normal,” not unlike 2010, 2012, or 2016.

Without the added precipitation so far this spring, water conditions would be similar to critically dry 2015. The prognosis for salmon, smelt, and sturgeon would be poor with yet another drought year. The fish have yet to recover from the 2012-2016 drought.

In the next three months, tens of millions of wild and hatchery juvenile salmon and steelhead will be leaving Valley rivers for the Delta, Bay, and ocean. Millions of young smelt and sturgeon will be trying to reach their Bay low salinity nurseries. Adult fall, winter, and spring run salmon and green and white sturgeon will be seeking their upriver spawning grounds. All of these populations are in real trouble and need help after years of stress.

Some of the Miracle March-April water added to Central Valley storage should be set aside for the fish. Fish need higher river flows and Delta outflow through summer than would normally be allocated in a sub-normal water year like this. Lower Sacramento River flows (Figure 1) should be kept near 8000 cfs, not the projected 5000-6000 cfs. San Joaquin River flows should be kept near 1000 cfs (Figure 2). The Delta outflow minimum should be 8000 cfs (Figure 3), not 5000 cfs, by allowing the added river flows to pass through the Delta. The “extra” water would amount to about a quarter of Mother Nature’s gift to the reservoir supply added so far this spring. That would seem more than reasonable and fair. In most cases it means meeting already prescribed flow and water temperature standards for the Central Valley rivers and Delta. These standards have been more than regularly ignored in recent years. So let’s do the fish a favor for once – call it “adaptive management” – and see if it helps.

Figure 1. Flow in lower Sacramento River at Wilkins Slough over past decade.

Figure 2. Flow in lower San Joaquin River at Vernalis over past decade.

Figure 3. Delta outflow at Pittsburg over past three years.

San Joaquin River Spring-Run Salmon at Risk

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Give them a chance.

Soon after spring run salmon smolts were released from the new San Joaquin River Spring-Run Recovery hatchery at the beginning of March, they began appearing in south Delta export salvage facilities (Figure 1). The number salvaged is unusually large, about one percent of the 87,000 released1, in salvage historical records as indicated in Figure 1. The salvage rates of recovery for the other winter 2018 Central Valley hatchery releases are much lower. The high rate of salvage of the March 1 San Joaquin River spring-run release reflects the vulnerability of young salmon that are drawn into the south Delta, where they are at risk to the State Water Project (SWP) and Central Valley Project (CVP) export facilities.

That risk comes from high export levels in winter-spring. Salvage of the spring-run smolts increased sharply as combined SWP and CVP exports reached high levels (8000-10,000 cfs) in late March (Figure 2). Such high exports were allowed this spring because of the increase in San Joaquin flows in late March (Figure 3). Tying export limits to San Joaquin flows2 and OMR flows is obviously not protecting San Joaquin salmon emigrants. The flow pulse may be the trigger that moves the young salmon down to the Delta. Exports should be reduced, not increased, during such pulses. But both current requirements as prescribed in the OCAP Biological Opinion for the Delta operations and requirements proposed under WaterFix allow increasing exports as flows increase.

Figure 1. Salvage of salmon at south Delta export fish facilities August 8, 2017 to April 5, 2018.

Figure 2. Salmon salvage and export rates from state and federal export facilities in south Delta March 1, 2018 to April 5, 2018.


Figure 3. San Joaquin River flow at Mossdale December 10, 2017 to April 7, 2018.

  1. Note: the actual rate of tagged fish recovered is much higher because salvage numbers are estimated from subsamples, and many fish are lost in Clifton Court Forebay prior to reaching salvage facilities. ↩
  2. Exports are also limited by Old and Middle River negative flow limits (-5000 cfs), which were exceeded in late March ↩