Category Archives: Bay-Delta

Delta Outflow Measurement

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Delta outflow has been estimated by state and federal agencies for over 50 years.  The Department of Water Resource’s Delta Total Outflow is a daily-average algorithm calculated in cubic feet per second (cfs) for Station DTO, a hypothetical location near Chipps Island in Suisun Bay.  The federal Bureau of Reclamation’s Delta Outflow estimate is calculated similarly and presented as a daily average flow in cubic feet per second on Reclamation’s website.

Now a third estimate of Delta Outflow is available from the federal US Geological Survey on one of its websites (https://waterdata.usgs.gov/nwis/inventory?agency_code=USGS&site_no=380245121532301).  This site has daily average estimates for a “gage” near Chipps Island since summer of 2016.  The estimate is from tidally filtered flow/stage data.

A comparison of the DWR and USGS estimates is shown below in Figures 1 and 2.  The two estimates are very similar.  A closer comparison during the low-flow summer periods of 2018 (Figure 3) and 2019 (Figure 4) indicates significant differences, or at a minimum a modicum of uncertainty in one or both of the estimates.  The average flow in the DWR data for 2018 data is about 10% higher over the period than the USGS data.  The role of tides or tidal filtering in the USGS estimate is a likely factor in the difference.  Under high seasonal tide periods (termed spring tides), outflows can fall to near zero, with major ramifications to salinity and water over the entire Bay-Delta, especially in the high export summer season.

The state’s current water quality control plan for the Delta includes objectives for Delta outflow (Figure 5).  The objectives are stated as a monthly average.  The low level of the objectives 3000-8000 cfs should give one pause as to the level of protection that these objectives provide to public trust resources like fish.  The Water Resources Control Board is in the process of updating its plan and water quality objectives.

In past posts, I have advocated for daily salinity standards for the Delta rather than bi-weekly or monthly objectives for outflow, flow, export, and salinity.  Such daily standards could be readily planned for, managed, monitored, and assessed for effectiveness.

Figure 1. USGS estimate daily Delta outflow Sep 2016 to Sep 2019.

Figure 2. DWR estimated daily Delta outflow Sep 2016 to Sep 2019.

Figure 3. Estimated daily outflow by DWR and USGS summer 2018.

Figure 4. Estimated daily outflow by DWR and USGS summer 2019.

Figure 5. Delta outflow objectives in state’s water quality control plan.

It is Fall X2 Time Again

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The 2008 Delta Smelt Biological Opinion for Central Valley Project (CVP) and State Water Project (SWP) includes the Fall X2 provision to keep brackish water west of the Delta through October in wet years to protect Delta smelt.  X2 or the low salinity zone is defined as the location where salinity is 2 parts per thousand (about 4000 EC). Keeping X2 at Chipps Island (km 71 from the Golden Gate) benefits the longfin smelt and Delta smelt populations.  In wet years, the smelt are protected by Delta agriculture salinity standards through August 15.  The Fall X2 provision keeps X2 and the smelt west of the Delta through October.

This is the third wet year since 2008 (the others were 2011 and  2017) in which the provision for X2 in the Biological Opinion has applied.  When I last posted about the 2017 implementation, I remarked that the US Bureau of Reclamation had requested not to apply the provision because of the high cost of water and minimal benefit to the smelt populations.  In the end, the provision was applied, but in an unusual way that likely had some new negative consequences on smelt and their Bay-Delta critical habitats.

Reclamation has again requested exemption from the provision in wet year 2019.  Again, Reclamation referenced the high cost of water and minimal benefits to smelt, despite unequivocal evidence that smelt benefit (Figures 1 and 2).

The Fall X2 flows are being applied with extra releases from Shasta, Oroville, Folsom, and New Melones reservoirs (Figure 3).  Without the X2 requirement that is creating inflows to the Delta of about 25,000 cfs, Delta inflow would only need to be 15,000 cfs to meet 65% export-to-inflow requirement.  With lower reservoir releases, river flows and Delta outflows would be lower at the discretion of Reclamation.  In the past, Reclamation has also failed on many occasions to meet water temperature standards in the lower Sacramento River and the American River, as well as south Delta salinity standards.

Application of the Fall X2 provision benefits smelt and the fall upstream migration of salmon in the Sacramento and San Joaquin rivers and their tributaries.  In Suisun Bay and the western Delta, salinities and water temperatures would be higher without Fall X2 (Figures 4-6).  Fall X2 application also helps maintain the water temperature requirements in Reclamation’s water right permits and the water quality standards in the lower Sacramento River between Red Bluff and the Delta.

Figure 1. Delta smelt spawner-recruit relationship. Note strong recovery in 2011. Source: http://calsport.org/fisheriesblog/?p=1966

Figure 3. Bay-Delta hydrodynamics in late August 2019 under Fall X2 operations. Flows are average daily cfs. South Delta exports are in red. Red circle is location of X2.

Figure 2. Longfin smelt spawner-recruit relationship. Source: http://calsport.org/fisheriesblog/?p=2513

Figure 4. Water temperature and salinity (EC) in eastern Suisun Bay, August 1, 2017 through November 1, 2018. Fall X2 was applied in 2017 (red outlined box). Note lower salinity and lower water temperature in 2017 compared to 2018.

Figure 5. Water temperature and salinity (EC) in the lower Sacramento River channel of the west Delta near Decker Island August 1, 2016 through November 1, 2018. Fall X2 was applied in August-September 2017 (red outlined box). Note lower salinity and slightly lower water temperature in 2017 during Fall X2 application compared to 2016 and 2018 without Fall X2.

Figure 6. Water temperature and salinity (EC) in the lower San Joaquin River channels near Jersey Point in the western Delta from August 1, 2016 through November 1, 2018. Fall X2 was applied in August-September 2017 (red outlined box). Note lower salinity and slightly lower water temperature in 2017 during Fall X2 application compared to 2016 and 2018 without Fall X2.

 

Striped Bass Status – Summer 2019

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I last reported the status of striped bass in 2016.  The prognosis was not good after four years of drought (2012-2015).  Today, after a sequence of water years (2016-2019) that were below normal, wet, below normal and wet, the prognosis has not improved, notwithstanding the remarkable resilience of striped bass.

After improving in below-normal 2016 and wet year 2017, the below-normal 2018 fall index equaled that of below-normal 2010, the lowest since 2000 (Figure 1).  A similar pattern occurred in the 2018 summer index (Figure 2).

The summer-to-fall recruitment relationship (Figure 3) shows a continuing strong relationship between the summer index and fall recruitment.  Furthermore, the relationship continues to show a positive response in wet years (2011 and 2017), but a poor response in the below normal years (2010, 2016, and 2018).  This indicates that summer conditions in these below-normal water years is depressing  the fall recruitment of striped bass.

Early indicators for wet year 2019 give me pause and further concern for striped bass recruitment this fall.  First, numbers and densities in the 2019 late spring 20-mm survey were way down as compared to 2017.  Second, despite high south Delta exports in July 2019, juvenile striped bass salvage is also lower compared to July 2017 (Figure 4), consistent with the lower 20-mm survey results.  The summer and fall indices for 2019 will help complete the story.

Figure 1. Striped bass fall index 2000-2018.

Figure 2. Striped bass summer index 1959-2018.

Figure 3. Striped bass Fall Midwater Trawl Survey Index (log10[index+1]) versus prior Summer Townet Index (log10). Select years labeled, with color of number showing year type: blue=wet, green=normal, and red=critically dry.

Figure 3. Striped bass Fall Midwater Trawl Survey Index (log10[index+1]) versus prior Summer Townet Index (log10). Select years labeled, with color of number showing year type: blue=wet, green=normal, and red=critically dry.

Figure 4. Striped bass salvage at south Delta export facilities with export levels (acre-feet) summer 2017-summer 2019. Note near maximum export levels in July 2017 and 2019.

Delta August Adjustment

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The State of California has markedly increased inflows to the Delta and reduced exports in early August 2019 (Figure 1). There is no announced reason for this major hydrologic adjustment that has had a major effect on Bay-Delta habitat. The likely reason was to maintain the 14-day average salinity standard of 450 EC at Jersey Point,1 which was exceeded on a daily basis beginning on August 10 (Figure 2).

“Adjustments” to Delta inflow and exports began at the end of July as daily Jersey Point salinity began to exceed the 450 EC standard. The federal Central Valley Project made little or no contribution to this correction.

These recent changes are a textbook example of why the 14-day salinity standard needs to change to a daily standard. State water managers gamed easily controlled parameters, using the 14-day average to squeeze out more exports through July. This operation caused a major system reaction with far-reaching consequences to the State Water Project system and to the Bay and Delta.

The state could have maintained a daily 450 EC limit with gradual small system adjustments and support from the CVP.

Further discussion of the effects follows below.

Figure 1. Sacramento River Delta inflow at Freeport (FPT flow), Delta outflow (DTO resflow), state exports (HRO pumping), and federal exports (TRP pumping), 7/1-8/9, 2019. Note only state exports were affected.

Figure 2. Salinity (EC) at Jersey Point near mouth of San Joaquin River in the Delta 7/14-8/10, 2019.

Delta Inflow
Sacramento River inflow to the Delta at Freeport increased about 3000 cfs to just over 20,000 cfs (Figure 3).  The extra flow came from the Feather River (Oroville Reservoir of the SWP).  The higher inflow coincided with a drop in water temperature at Freeport from 23oC to 21oC.

Delta Outflow
Delta outflow rose about 9000 cfs from near 7000 cfs to 16,000 cfs (3000 from inflow and 6000 from reduced exports, Figure 1).  Outflows rose in the Sacramento channel at Rio Vista (Figure 4) and San Joaquin channel (Figure 5).  Water temperatures also fell about 1oC.

Interior Delta
Flow also increased and water temperature fell in Georgianna Slough (Figure 6).

Suisun Bay
Salinity and water temperature fell in Suisun Bay west of the Delta (Figure 7).

Figure 3. Flow and water temperature in Sacramento River at Freeport 7/1-8/10, 2019.

Figure 4. Flow and water temperature in Sacramento River at Rio Vista, 7/1-8/10, 2019.

Figure 5. Flow and water temperature in San Joaquin River at Jersey Pt, 7/1-8/10, 2019.

Figure 6. Flow and water temperature in Georgianna Slough in the central Delta, 7/1-8/10, 2019.

Figure 7. Salinity and water temperature in Suisun Bay near Pittsburg, 7/1-8/10, 2019.

 

  1. The standard applies for wet years through August 15. ↩

Delta Science Plan – It’s not that complicated

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From Delta Science Plan Figure 1-1 | Network map of collaborative groups in the Delta

From Delta Science Plan Figure 1-1 | Network map of collaborative groups in the Delta

The new Delta Science Plan (Plan) is a “call” for more collaborative science to improve government decision making affecting the Delta ecosystem.  The first page announces the vision for the plan as being “One Delta, One Science.”  Really?

Science is not just one thing; it is many things.  Science is knowledge.  Delta science is knowledge on what makes up the Delta and how it all works together.  There is science for all Delta social, economic, and ecosystem components.  There is Delta smelt science.  There is Sandhill Crane science.  There is science on water quality, water supply.  There is science on roads, farming, and flood control.  There is science on large ship movement through the Delta.  The Science can be good, bad, or simply inadequate; it is only as good as the predictions and decisions that one can make from it.

What is missing from the current Plan is a presentation of the major actions that will affect the Delta ecosystem and the ramifications these actions would have on the ecosystem.  Also missing is a description of key decisions to be made relating to these actions and the associated science needed to make the decision.

Each ecosystem component should have science and advocates that can assess how specific actions can affect the resources related to that component.  Delta smelt should have its science and advocates.  These folks need not communicate with the crane folks.  On the other hand, the smelt folks may need information from the water folks.  Each action should have its own science and science group to understand what the action entails and how it might affect other ecosystem components.  Each decision process and decision group should have its science.  Each group may need information from other science groups.

The Plan should include a compilation of each ecosystem component’s science and needs, and a clear depiction of the important actions and decisions under consideration for that component.  A good plan would summarize the science of each ecosystem component, each major action being considered, and each major decision being contemplated.

The overall success of the Plan will depend on how good the science is in predicting outcomes.  Each science group is responsible for its own science, as well as how other groups use it.

Stakeholders need a Plan that instills confidence that each ecosystem group knows its science.  Stakeholders also need to know what actions are being planned and how decisions will be made.

Personally, I want to see what the smelt science indicates that smelt are lacking in the Delta ecosystem.  I want to see a description of how the USFWS/CDFW plan to restore Delta smelt.  I want to see how the State Board plans to set new Delta water quality standards.  I hope to see how Delta levees will be addressed.  I want to know whether Delta flow barriers are being considered and what factors may affect that decision.  I am interested in the future for Sandhill Cranes and the factors that may affect that future.  And I want to know how each ecosystem component will address climate change.

In summary, I want to see a plan that includes a description of our understanding of each key Delta ecosystem component, what actions involving the Delta are being considered, and what decisions that might affect the Delta are being contemplated.