Downward Trend in San Francisco Bay Longfin Smelt

In my last posts on longfin smelt, I expressed some optimism about their recovery from the 2013-2015 drought based on 2017 and 2018 population data (Figure 1).1 I have changed my mind. In this wet water year 2019, the longfin have again crashed.

The long-term trend over four wet-year November adult trawl surveys, including this year (2019), continues downward (Figures 2-5). The trend portrays the underlying strong spawner-recruit relationship: the number of spawners (eggs) is the key factor that determines recruits. On top of that, poor recruitment in drier years (Figure 6) is driving recruitment-per-spawner down. There is 10-100 times higher recruitment from wetter years.

What is it about both dry years and wetter years like 2019 that is so bad? It is low Delta outflow and high exports in the November-December period.

Longfin smelt spawn in November-December in fresh water.2 When their freshwater habitat is in the San Joaquin channel in the central Delta upstream of Jersey Point (See location in Figure 2, Figures 7 and 8), the newly hatched larvae are highly susceptible to unlimited November and December exports. Although 2019 was a wet year, these conditions were present in November and December (Figures 9 and 10).

The prognosis for longfin smelt under current and planned water operations in the Delta is grim. The state and federal water projects need to increase Delta outflow and reduce exports in November and December to reduce spawning of longfin smelt in the central and south Delta.

Figure 1. Fall Midwater Trawl Index for longfin smelt, 1967-2018. Source: http://www.dfg.ca.gov/delta/data/fmwt/indices.asp

Figure 2. Catch distribution of longfin smelt adults in the November 1998 fall midwater trawl survey.

Figure 3. Catch distribution of longfin smelt adults in the November 2011 fall midwater trawl survey.

Figure 4. Catch distribution of longfin smelt adults in the November 2017 fall midwater trawl survey.

Figure 5. Catch distribution of longfin smelt adults in the November 2019 fall midwater trawl survey.

Figure 6. Longfin Recruits (Fall Midwater Trawl Index) vs Spawners (Index from two years prior) in Log10 scale. The relationship is very strong and highly statistically significant. Adding Delta outflow in winter-spring as a factor makes the relationship even stronger. Recruits per spawner are dramatically lower in drier, lower-outflow years (red years). Spawners in 2017 and 2018 were at record low levels. Recruits in 2011 and 2017 were relatively high because the Fall X2 provision in the 2008 Biological Opinion was implemented. Source: http://calsport.org/fisheriesblog/?p=2513.

Figure 7. Salinity (EC) in November and December 2017 at Jersey Point in the lower San Joaquin River channel of the west Delta. Spawning would occur in fresh water (below 500 EC).

Figure 8. Salinity (EC) in November and December 2018 at Jersey Point in the lower San Joaquin River channel of the west Delta. Spawning would occur in freshwater (below 500 EC), which occurred upstream of Jersey Point.

Figure 9. Salinity (EC) in November and December 2019 at Jersey Point in the lower San Joaquin River channel of the west Delta. Spawning would occur in freshwater (below 500 EC), which occurred upstream of Jersey Point.

Figure 10. Tidally filtered flow in two channels in the lower San Joaquin River upstream of Jersey Point, portraying net flows toward to the south Delta export pumps.

 

The Final Straw for Delta Smelt; Another Dagger for Longfin

Delta smelt and longfin smelt were not protected in the Delta in November-December 2019. High south Delta exports (Figure 1) and associated highly negative Old and Middle River (OMR) flows (Figure 2) pulled the spawning adult smelt toward the export pumps, likely significantly compromising what is left of the two populations. High exports and negative flows also pulled saltwater from the west Delta into the central Delta (Figures 3 and 4). This forced smelt to spawn further upstream in the fresher water of the central, east, and south Delta, sealing the fate of the numerous larval longfin smelt spawned there to the export pumps this winter. Young Chinook salmon, especially listed winter-run and spring-run entering the Delta in December, were also jeopardized.1

These circumstances were not allowed under the federal 2008 Delta smelt biological opinion (Figure 5) or the state’s longfin smelt incidental take permit (Figure 6). The new October 2019 Biological Opinion (BO) for the operation of the Central Valley Project (issued under the federal Endangered Species Act) does not preclude high exports or highly negative OMR flows. The pending new state Incidental Take Permit (ITP) for the operation of the State Water Project (to be issued under the California Endangered Species Act) follows the requirements of the federal BO for Delta smelt.

Given the December distribution of adult longfin smelt (Figure 7) and the likely distribution of the few remaining adult Delta smelt based on prior year surveys (Figure 8), the Smelt Working Group (SWG), Water Operations Management Team (WOMT), and the Director of the California Department of Fish and Wildlife (CDFW) should have limited south Delta exports in December. They did not.

The Trump administration’s new biological opinions simply do not protect these fish. The pending new state ITP for protection of these fish gives the Director of the California Department of Fish and Wildlife the last word in ordering changes to OMR flows. The CDFW Director’s non-decision in 2019 is a good indication of the level of protection that is likely under the new state ITP.

Figure 1. December 2019 state (HRO) and federal (TRP) south Delta exports. Note the maximum total rate of approximately 11,400 cfs was reached in the latter half of December.

Figure 2. December 2019 Old and Middle River (OMR) net daily flows.

Figure 3. Salinity (EC) in central Delta in December 2019.

Figure 4. Salinity (EC) in Old River in the south Delta in December 2019.

Figure 5. Page 281 of 2008 federal biological opinion for Delta smelt.

Figure 6. Page 10 of 2009 state Incidental Take Permit for longfin smelt.

Figure 7. Distribution of longfin smelt in December 2019 midwater trawl survey. These numbers are very low and show the present depressed level of the population.

Figure 8. Distribution of Delta smelt in December 2011 midwater trawl survey
showing likely distribution of remaining Delta smelt in 2019 (midwater trawl
survey found no Delta smelt in December 2019).

 

Fall X2 should extend through December

In a recent post, I described the Fall X2 provision in the 2008 Delta Smelt Biological Opinion that protects smelt by requiring a modest Delta outflow from mid-August through October in Above Normal and Wet years.  In the same post, I described how the 2019 Biological Opinion for smelt would move the compliance point for Fall X2 upstream into the Delta, reducing low salinity zone habitat.   In this post, I suggest that the Fall X2 requirement should not only be retained with the old compliance point, but also that the applicable time period should extend through December.

First, if the X2 provision is not extended into December, this is what happens:  (1) Delta outflow drops to zero or even negative, as occurred this past November 2019 (Figure 1); and (2) the low salinity zone moves up into the Delta via the San Joaquin River channel toward the export pumps (Figure 2).

Second, winter-run salmon smolts that pour into the Delta from the Sacramento River in November and December of all but the driest years (Figure 3) will have difficulty surviving and exiting the Delta for the Bay and ocean.

Third, what few Delta smelt that may be surviving will be put at risk of being drawn into the central and south Delta (Figures 4 and 5).

Fourth, longfin smelt will be at risk to being drawn into the Delta (Figures 6 and 7).

Fifth, the primary food of young Delta native fishes, calanoid copepod adults, which concentrate in the low salinity zone, would be drawn into Delta (Figure 8).  Bay-Delta pelagic plankton productivity would suffer.

In conclusion, there are presently few constraints on water project operations in the Delta in November-December.  Freshwater outflow to the Bay can be zero or even negative, as occurred this past month, November 2019.  The updates to the Bay-Delta Water Quality Control Plan and to state permits that regulate Delta exports should extend Fall X2 through December in order to protect Delta native fishes.  Compliance would entail Delta outflows in the 8000-10,000 cfs range and/or Jersey Point salinity of about 500 EC.

Figure 1. Tidally filtered flow in the Sacramento River channel at Rio Vista and Jersey Point in the San Joaquin channel in November 2019.

Figure 2. Salinity (EC) at Jersey Point in the San Joaquin channel of the west Delta in November 2019.

Figure 3. Cumulative catch of winter-run Chinook salmon at Knights Landing rotary screw traps in fall-winter of water year 2017. Source: DOSS 2017.

Figure 4. Trawl catch distribution of Delta smelt fall 2011, the last time Delta smelt were relatively common.

Figure 5. Salvage of Delta smelt pre-spawn adults in fall-winter of water year 2003.

Figure 6. Longfin smelt trawl catch distribution in November 2011.

Figure 7. Longfin smelt trawl catch distribution in December 2011.

Figure 8. Adult calanoid copepod catch distribution in November 2011 zooplankton survey.

The Good, the Bad, and the Ugly in the New Non-Jeopardy Biological Opinions for CVP/SWP

The Endangered Species Act (ESA) directs all federal agencies to work to conserve endangered and threatened species and to use their authorities to further the purposes of the Act. The purpose of the Act is to protect and recover imperiled species and the ecosystems upon which they depend. Protect means to not allow “take” of listed species. If some take occurs despite best efforts, then “reasonable and prudent” alternatives (RPAs) may be needed to protect the threatened or endangered species.

The US Bureau of Reclamation and its partner the California Department of Water Resources (permittees) operate the federal Central Valley Project (CVP) and the State Water Project (SWP) under federal and state ESA “take” permits issued in 2008-2009 biological opinions that included RPAs. The RPAs constrained water supply deliveries and other project operations during the past decade to protect listed salmon, smelt, sturgeon, and steelhead.

Over the past decade, the parties have reinitiated consultation to revise take permits and RPAs. The initial motivation for reinitiation was that RPAs and take limits were not protecting or recovering the listed species. The US Fish and Wildlife Service (USFWS) and the National Marine Fisheries Service (NMFS) recognized that more stringent measures were needed. A series of draft opinions were developed with further protections, culminating with a July 1, 2019 draft jeopardy opinion from NMFS on Reclamation’s proposed action as of that time. A jeopardy opinion occurs when an action is reasonably expected, directly or indirectly, to diminish a species’ numbers, reproduction, or distribution so that the likelihood of survival and recovery in the wild is appreciably reduced.

Reclamation updated its “proposed action” in response to the draft jeopardy opinion. “It must also be acknowledged that the current status of all these species continues to be imperiled, and that one of the objectives of the proposed action is to maximize the available supply of water for irrigation, municipal, and industrial deliveries.”1 Reclamation doubled down. Reclamation’s most recent proposed action includes some provisions of the 2008/2009 biological opinions’ RPAs and recent jeopardy draft BO. In response, the Services relented under pressure from the Trump administration, replaced technical staff with a new group of managers, and recently issued final non-jeopardy opinions.

The new proposed action from Reclamation can now go into effect without RPAs that would hinder Reclamation from maximizing water deliveries. The new Biological Opinions will govern project operations under a wide array of vague commitments to protect and recover listed species: some good, some bad, and some simply ugly.2

The Good (Well, as Good as it Gets)

  1. Delta Smelt Conservation Hatchery
    This is long past due. However, the proposal is vague and limited in potential scope and funding commitment.
  2. New Habitat
    Most measures that require new habitat in the new BO were prescribed in past BOs. Now there are new vague commitments. Some listed species (e.g., Delta smelt) have populations too small to benefit from new habitat.
  3. Hatchery Management
    New and updated old prescriptions, though vague, are badly needed, especially for converting the program focus from mitigation hatcheries to conservation hatcheries.
  4. Proposed Funding for research and restoration
    The BOs contain an estimated total of $1.5 billion dollars in proposed funding to support threatened and endangered fish survival and recovery through research and restoration actions. However, the proposed funding is not dedicated and is vague, particularly in that much of the effort and funding may go to prior commitments that have not been funded.
  5. Delta Cross Channel Improvements
    Proposed upgrades to the Delta Cross Channel Gates are helpful but vague. The Delta Cross Channel should be screened, as should nearby Georgiana Slough.
  6. Modifying the Head of Old River Scour Hole
    This action is OK but addresses only one of many predation hotspots for salmon and steelhead caused by human actions and man-made structures in lower San Joaquin River.
  7. Fish Passage on Deer Creek (a non-Project watershed)
    This is one positive action for listed spring-run salmon among many in NMFS’s Central Valley Salmon Recovery Plan. All of the actions in the Recovery Plan should be included and funded. Deer Creek, a tributary to the lower Sacramento River, has a spawning run of wild spring-run salmon. Deer Creek does not have a project dam on it, but Deer Creek salmon pass through the lower Sacramento River and Delta. Deer Creek salmon and all other salmon-bearing tributary populations are thus affected by project operations.
  8. Adult Straying Barrier on the Knights Landing Outfall Gate (a flood and drainage system)
    This was constructed under prior commitments but failed.
  9. A “drought toolbox” to prioritize a proactive approach to drought planning, including early coordination with senior water right users
    Proactive coordination is fine and good, but the BOs contain no commitment to reduce diversions by senior Settlement and Exchange contractors or any others during droughts.
  10. Support for NMFS Steelhead Monitoring and Collaboration Activities with Non- Project Tributaries
    Monitoring may inform mitigation. However, monitoring in itself is not mitigation. All recovery plan actions should be supported because CVP/SWP operations and facilities have had major adverse effects on all Central Valley steelhead populations.
  11. $14 million commitment to expedited implementation of the Battle Creek Restoration Project including reintroduction of winter-run Chinook salmon
    The commitment to fund actions on Battle Creek is long overdue, but the funding in the BO is inadequate by an order of magnitude.
  12. A stronger commitment to actions maintaining low-salinity habitat in the Delta Smelt Summer-Fall Habitat Action with commitments regarding Suisun Marsh Salinity Control Gate (SMSCG) operations and projects for other elements of habitat
    It is important to acknowledge the importance of summer-fall habitat representing half of the smelt life-cycle, but the commitment in the BO is vague and likely ineffective as formulated. Rather than being used more often, the SMSCG should simply be removed. It has been a detriment to smelt, salmon, steelhead, and sturgeon populations since its use began in 1989.

The BAD

  1. Drought Mitigation
    Drought mitigation in the BOs focuses on maintaining Shasta Reservoir’s cold-water-pool. The proposed action drops mitigation actions for wet years such as Fall X2. The proposed action drops previous OMR constraints that provided some protection in drought years. The one-hand-giveth-while-the-other-taketh-away approach is an old tired gambit. The ostensible improvement at Lake Shasta eliminates numeric targets for Shasta carryover storage.
  2. Real time management – protect when and where the fish are
    This is poor prescription because some listed species populations are so low that they are undetectable (e.g., Delta smelt). Larval life stages also go undetected. Past detection rates even for larger populations have been poor, and actions to reduce impacts have been gamed and trimmed to the bone. Real time detection does not protect primary productivity and food sources and other elements of critical habitats. The managers charged with managing have a long history of choosing water supply over fish protection.
  3. A more detailed description of Shasta Dam operations and a commitment to Cold Water Management Tiers
    This prescription does not protect listed winter-run salmon in droughts from thermal shock or dewatering of redds, which are the primary factors in recent low survival and production. Prior RPA and Recovery Plan requirements to fix problems with Spring Creek powerhouse (Whiskeytown Lake thermal curtain) and Shasta Dam warm water power releases are not included in the new salmon BO.
  4. “New” Science
    A commitment to maintaining long-term monitoring programs and recognizing past and present science is needed. “New” science funded and conducted by water contractors or federal/state project operators will ensure any new science will be biased – foxes assessing their effects on the henhouse. The science and its presentation and analyses have become more and more controlled by water supply entities, and less and less by resource agencies. The BOs give more control of science to water suppliers. The revisions to the draft BOs are clear evidence of the new realignment of roles and new controls on science.
  5. Performance Metrics for managing Old and Middle River reverse flows to limit salmonid loss to similar levels observed under the previous BiOp through explicit reductions in export pumping.
    The BOs’ performance measures for reverse flows are vague, ineffective, and unenforceable. Wild components of salmon populations were hard hit in droughts under previous BOs. “Similar” levels of loss are not protective and will not promote recovery.
  6. Performance Metrics for incubation and juvenile production of salmonids under the proposed Shasta Cold Water Pool Management strategy
    The BOs’ performance measures for cold water management at Lake Shasta are vague, ineffective, and unenforceable.
  7. Commitments to manage Old and Middle River reverse flows for limiting larval and juvenile delta smelt entrainment based on modeled recruitment estimates
    OMR rules have been one of the major restrictions on exports under the past BOs. The rules proved beneficial to the listed species survival (primarily reduced salvage and improved through-Delta survival of tagged salmon smolts). The new strategy would allow changes that would allow greater levels of exports under OMR reverse flow prescriptions. The poor survival of San Joaquin salmon under existing rules would remain poor or further decrease. Entrainment of young smelt (not measured under existing rules), an existing serious concern, would only worsen. Modeling entrainment risk has not worked and has not been verifiable. The main risks to smelt are pulling larvae into the central Delta with its poor habitat (not just to the south Delta pumps) and the destruction of their critical pelagic rearing habitat.
  8. Independent Review Panels to evaluate the science behind actions and outcomes
    This is nothing new. There have been so many “independent” review panels. I remember working with Pete Chadwick back in the mid-70s. He consulted on my projects on the Hudson River Estuary. He and his CDFG staff working on the Bay-Delta were on the cutting edge of estuary science. They trained the next generation and they in turn trained the next. Outsiders have only verified what CDFG already well understood. Same goes for NMFS and the USFWS, as well as UC Davis. Together as IEP they manage Bay-Delta and Central Valley science more than adequately with the help of a huge cadre of capable scientists among NGOs. Water agencies and other water suppliers just can’t handle the truth, so they hire their own consultants and many outside “independent” consultants.
  9. Ramping rates specificity for reservoir releases to reduce the risk of stranding
    Ramping rates do not work for eggs and fry salmon that are in gravel beds for up to several months. Reductions in flows from Keswick Reservoir after winter-run fry have left their nests (redds) in the fall strands up to 80% of new fall-run redds.

The Ugly

  1. Commitment to implement appropriate actions after two years of low winter-run Chinook salmon egg-to- fry survival.
    Shasta operations in the 2014 and 2015 drought killed 90-95% of the egg production of winter-run salmon. The new Salmon BO would make that acceptable under the ESA. It would stretch the no-take standard to no take in more than two years out of three.
  2. More specificity on collaborative planning with specific habitat restoration and facility commitments.
    More planning for habitat restoration and facilities is not needed. Reclamation, DWR and other responsible agencies should get on with prior commitments. The history of foot-dragging on habitat restoration in the Central Valley is a worthy rival to the foot-dragging by PG&E in maintaining and upgrading its infrastructure.
  3. A commitment to sediment supplementation and food-web studies for the protection of delta smelt.
    As proposed the supplementation of sediment would come in the form of the discharge of warm, polluted agricultural drainage water full of non-native predatory fish into critical habitats of listed fish.
  4. Dynamic, real-time monitoring of changing conditions and potential species impacts, within an improved scientific and adaptive-management-based decision-making framework; avoiding or minimizing fishery impacts while increasing operational flexibility.
    Real time management will not work for rarer listed species like Delta smelt. This has been tried for three decades and has not worked. The adaptive managers will be the same managers who produced the revised non-jeopardy BOs. “Operational flexibility” is a buzzword for increased diversions, primarily Delta exports.
  5. Operational rules that lay the foundation for eventual voluntary agreements on water flows for rivers that feed into the delta. Those agreements promise even greater protections and investments in fish and the environment.
    Most of the “even greater protections” will have to backfill the protections that these BOs took away. The Voluntary Agreements offer pennies on the dollar in terms of necessary flow through the Delta into the San Francisco Bay.
  6. Eliminating or Modifying Existing RPAs and Take Limits
    • Modifying year-round temperature and Shasta reservoir storage management program to minimize effects to endangered winter-run salmon.
      NMFS and CDFW were just starting to get it right. NMFS’s 2017 draft RPA for Shasta would have required stronger carryover storage requirements.
    • Long-term passage prescriptions at Shasta Dam and re-introduction of winter-run to its native habitat in the McCloud and/or Upper Sacramento Rivers.
      They were ready to start this program after promising initial feasibility studies. The foot draggers strung it out until Trump administration officials threatened in 2019 to arrest DWR personnel who were installing equipment to begin a pilot implementation.
    • Old and Middle River flow levels that limit the strength of the reverse flows
      There will be less of the needed restrictions under Reclamation’s new plan.
    • Prescriptions for additional technological measures at the facilities to enhance screening and increase survival of fish.
      There will be fewer planned upgrades to project facilities to protect fish than were promised under the previous BOs.
    • Prescribed additional measures to improve survival of San Joaquin steelhead smolts, including both increased San Joaquin River flows and export curtailments.
      No longer apply.
    • Prescribed flow management standard, a temperature management plan, additional technological fixes to temperature control structures, and, in the long term, a passage at Nimbus and Folsom dam to restore steelhead to native habitat.
      No longer apply.
    • Prescribed year-round minimum flow regime necessary to minimize project effects to each life-stage of steelhead, including new springtime flows that will support rearing habitat formation and inundation, and create pulses that allow salmon to migrate out successfully.
      No longer apply.
    • The Fall X2 provision has been eliminated.
      This flow-salinity RPA protected longfin and Delta smelt in summer and fall of wet years.
    • Take limits have been eliminated.
      They should have been revised to be more protective.

What is Missing

So much is missing that is within state and federal governments’ power and authority in the final approved Reclamation proposal. Here is a limited selection.

  • Effective Management of Shasta Cold-Water Pool
    Missing from the BOs are controls of Spring Creek powerhouse warm water releases into Keswick Reservoir, modifications to hydropower operations, long term Shasta storage rules, and modifications of water contractor deliveries. Combinations of these actions would have alleviated winter run salmon recruitment failures in 2014 and 2015. Reclamation’s approved proposal would allow such drastic recruitment failures in future droughts.
  • Commitment to comply with water quality standards on flow, water temperature, salinity, and export restrictions
    Reclamation has made no commitment to comply with state water quality standards or other state laws.
  • Commitment to provide needed pulsed flows
    Coordinated pulsed flows are needed to increase survival of hatchery and wild salmon. None are included in Reclamation’s plan, with the possible exception of a pulse from Shasta when it is likely to spill anyway.
  • Commitment to implement recovery plan actions
    Recovery, not just protection, is needed and is required by the ESA. These BO’s do not address recovery plans. The ESA goes beyond simple mitigation. The ESA focuses on minimization of effects, enhancement, and recovery.

In Conclusion: Ugly

Reclamation’s proposed action has been approved by the Services. The proposed action includes some good concepts for protective measures (though generally the requirements are vague, underfunded and not enforceable), and a suite of bad and downright ugly actions that will harm affected listed fish species. The overall mix will lead to much confusion, wringing of hands, blaming, ignoring of responsibility, initial lawsuits, and (if the initial lawsuits fail) further lawsuits when fish metrics fail to show improvement. Some actions will take time to implement, while some are already too little too late.

The Services should have issued jeopardy opinions with a suite of appropriate RPAs. That did not happen. Instead, the Services are allowing further risk of extinction to the listed species. The best example of this is allowing expected temperature-dependent egg mortality levels for Sacramento River winter-run Chinook salmon to occur in “Tier 3 and 4 years.” Mortality due to allowed temperature exceedance was a major cause in the recent decline in the winter-run salmon population, one of the few species listed as “endangered” rather than the more common “threatened” designation. The effect the salmon BO will allow is entirely avoidable and within the control of the state and federal agencies involved in permitting the CVP. NMFS has designated winter-run as a “Species in the Spotlight”; it’s more likely that it is now a “Target for Extinction.”

  1. USFWS summary, p. 13.
  2. The US Fish and Wildlife Service’s summary of both its own Biological Opinion for smelt and the National Marine Fisheries Service’s Biological Opinion for salmon, steelhead and green sturgeon is available at: https://www.fws.gov/sfbaydelta/cvp-swp/documents/ROC_on_LTO_Summary_FINAL.pdf
    For the complete USFWS and NMFS Biological Opinions and appendices, go to: https://www.fws.gov/sfbaydelta/CVP-SWP/index.htm

Analyzing Fish Population Dynamics in the Bay-Delta

I have been analyzing the declines in Bay-Delta and Central Valley fish populations for over 40 years. Fish population dynamics were the focus of my college education and my 50-year career in environmental impact assessment. I have participated in all the major efforts to understand the Bay-Delta fish population declines. From all of these efforts, it is clear to me what has caused the major fish population crashes.

Pre-1970

First and foremost are the well known historic factors, the original sins pre-1970s of diverting water, building levees and dams, urban development, gold mining, cutting forests, polluting rivers, over-fishing, and introducing non-native species. These explain many of the major native fish population declines and extinctions such as the Sacramento perch and San Joaquin spring-run Chinook salmon, and the near extinctions of Delta smelt, green sturgeon, winter-run and spring-run salmon, and steelhead.

Post-1970

Since 1970, there have been dramatic declines in salmon, steelhead, smelt, sturgeon, splittail, and striped bass, often described as “recruitment failure” or failure to reproduce. While some of the blame most certainly is on continuing effects of the aforementioned original sins, the major post-1970 shifts were the consequence of a new array of stresses that hit the whole fish community, especially native fish populations. Most certainly the droughts of 76-77, 87-92, 01-02, 07-09, and 12-15 were a major underlying factor; however, it was the man-made responses to the droughts that caused most of the damage. Asian clam and other non-native aquatic invertebrate invasions to the Bay-Delta in the 80s were another stress, in part brought on by the aforementioned factors. Poor water management response to these new threats has caused further damage. The big culprits of change were the water management stresses described below.

1. State Water Project

The addition of the State Water Project (SWP) in the mid-1970s nearly tripled Delta export capacity (4400 to 11,400 cfs pumping rate1) and annual exports (2 million acre-feet to 6 million acre-feet annual exports). The additional Delta exports had huge fish population effects in the mid-70s from salvage mortality and entrainment of young fishes, as well as on fish habitat conditions in the rivers, Delta, and Bay. These stresses resulted in major population declines, which in turn resulted in the imposition of export restrictions in new water quality standards in 1978 (D-1485), and eventually to species listings under the Endangered Species Act in the 1990s.

2. Reservoir Operations

The increase in exports changed reservoir operations, including within-year reservoir release strategies and long-term multiyear reservoir storage patterns. Reservoir storage was depleted faster in droughts because of higher water supply demands. These effects continue today.

3. Water Supply Demands

Ever-increasing water supply demands from agricultural and municipal users have reduced river flows, Delta outflow, and reservoir storage. It’s not only the Delta’s 6 million acre-feet of exports, but the more than 20 million acre-feet from other Central Valley water diversions.

4. Invasive Species

Invasions of non-native clams, shrimp, fish, and zooplankton species since the 1970s have occurred in-part due to changes in Bay-Delta hydrology and water quality, as well as physical and biological habitat conditions. Delta pelagic (open water) habitat is now dominated by low-productivity reservoir water. The low salinity or mixing zone of the estuary became far less productive because of species invasions and reservoir water moving through to the south Delta export facilities, taking productive low-salinity habitat with it. The Delta is warmer from higher warm river inflows from spring through fall to feed water project exports, further favoring non-native warm-water fishes. Turbidity is lower, favoring non-natives. Invasive aquatic vegetation benefits from low turbidity, and the vegetation further favors non-native fishes over native fishes.

Post-1990

Since 1990, there have been steps backward that have undermined effective strategies and actions that had been undertaken beginning in the late 1970s to help depressed fish populations. Below are five examples in a long list of actions/changes.

1. Changes to D-1485

Beginning In 1978, Delta water quality standards in Decision 1485 placed restrictions on Delta exports, improved Delta outflows, and set salinity standards that had benefits for native fishes. Beginning in the 1990s, these post-1970 constraints on water diversions were changed, ignored, or eliminated. For example, new standards in D-1641 (1995 Accord) dropped the D-1485 June-July export restrictions.

2. Eliminating VAMP Export Restrictions and Higher Outflow Requirements in April and May

The Vernalis Adaptive Management Plan (VAMP) from 2000-2009, and its operational precursors under the CVPIA (1991) and the 1995 Accord, sought to protect Central Valley salmon and Delta native fishes by reducing April-May Delta exports and increasing spring Delta inflows and outflows. During the VAMP years, exports were restricted to less than 2000 cfs in April-May to protect fish (Figure 1). In the post-VAMP decade, restrictions were lifted and exports increased, especially in post-drought recovery wet years 2011 and 2017 (Figure 2).

3. Temporary Urgency Change Petitions (TUCPs) and Orders

Temporary urgency change orders during the recent drought allowed April-May Delta outflow to fall to around 5000 cfs in 2014 and 2015, from the normal near-10,000 cfs lower limit (Figure 3). Such low outflows in combination with Delta exports are devastating to Delta native fishes and Central Valley salmon and steelhead.

4. Delta Channel Barriers

The operation of the Delta Cross Channel, Head of Old River, South Delta, and False River barriers helps to keep export salinity down by funneling the fresher Sacramento River water to the south Delta export pumps. This increases the efficiency of exports in taking reservoir water in drier years and seasons. With the exception of the Head of Old River, barrier operation also funnels Delta native fish production (pelagic eggs and juveniles) and migrating young salmon (and their low salinity habitat and food sources) directly to the export pumps instead of to the Bay.

5. Suisun Marsh Salinity Control Gates

Since the installation of the Suisun Marsh Salinity Control Gates (SMSCG) in Montezuma Slough in 1989, the Slough and Marsh no longer function as critical low salinity habitat in drier years and seasons. Without high freshwater inflow, the Slough and Marsh no longer maintain the high biological production the once contributed to the Bay. The following excerpt from a DWR 2019 blog post inadvertently describes how limited the benefits of Suisun Marsh have become in the absence of flow:

DWR launched a pilot project last year that directed more fresh water flow into Suisun Marsh. The action involved opening salinity control gates in the summer months instead of during fall and winter, as is customarily done to reduce salinity in the marsh for migrating ducks and other waterfowl. The Delta smelt relies on low-salinity water – opening the salinity control gates allowed the smelt to enter the marsh from the Sacramento River, where it can access greater amounts of food and shelter.

Extinction looms so closely over the Delta smelt population that the project could have been considered a success even if it didn’t lure any countable Delta smelt to the marsh, said DWR Lead Scientist Ted Sommer. Just creating the conditions that allow smelt to thrive – that is, low salinity levels, lots of food, and high turbidity or muddy water that magnetizes smelt – would have been a cause for celebration.

Conclusion

There are many, many other examples of adverse changes that have put fish population dynamics in the Delta in a perpetual downward spiral. Since 1970, almost of all them involve reduction of Delta inflow and outflow, elimination of measures to mitigate the effects of reduced Delta inflow and outflow, and/or the biological response to reduced Delta inflow and outflow.

Figure 1. State south Delta exports (Harvey Banks pumping plant) in spring 1997-2010.

Figure 2. State south Delta exports (Harvey Banks pumping plant) in spring 2011-2019.

Figure 3. Delta outflow April-May 2007-2009 and 2013-2015 droughts.

 

 

 

  1. Initially exports were even higher with the new 11,000 cfs export capacity of the State Water Project. Total exports reached 12,000-14,000 cfs