Delta Science Plan – It’s not that complicated

Posted on July 26, 2019 by Tom Cannon

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.

Delta June 2019

Posted on July 19, 2019 by Tom Cannon

Water year 2019 has been a very wet year. Yet salmon and sturgeon survival was compromised by low flows and high water temperatures in the Sacramento River this spring.¹ Young salmon survival has been further compromised by low flows, high exports, and high water temperatures in the Delta this past June.

Many of the wild smolts produced in Central Valley rivers this year entered the Delta in May and left (or died) by the end of June, as observed in Delta export salvage collections (Figure 1). Many of the wild smolts captured in the south Delta likely originated from San Joaquin tributaries. South Delta exports were near maximum at 10,000 cfs, about 70-80% of San Joaquin inflow to the Delta and 20% of total Delta inflow. The high exports caused lower flows and associated high water temperatures (>20^oC) in the Delta channel of the lower San Joaquin River (Figure 2), and contributed to similarly high temperatures in the lower Sacramento River channel (Figure 3).

The high Delta water temperatures (>20^oC) compromised the survival of the salmon smolts in June. Reducing the export limit to 5000-6000 cfs in June of this wet year would have kept the water temperature near a 20^oC limit. The water quality standards in the 1980’s and 1990’s under D-1485 had a 6,000 cfs June export limit. In the past two decades under D-1641, the June export limit changed to 65% of total inflow.

New Delta water quality standards should provide export limits and inflow/outflow minimums that protect salmon through the spring months.

Figure 1. Chinook salmon salvage at south Delta export facilities in 2019. Note the prevalence of wild (non-hatchery) smolts in May-June.

Figure 2. Water temperature and tidally-filtered flow at Jersey Point in the lower San Joaquin River channel of the Delta in June 2019.

Figure 3. Water temperature and tidally-filtered flow at Rio Vista in the lower Sacramento River channel of the Delta in June 2019.

http://calsport.org/fisheriesblog/?p=2673 ↩

Delta Smelt – Spring 2019 Status

Posted on July 5, 2019 by Tom Cannon

Late April and early May 20-mm Surveys provide an excellent picture of the status of Delta smelt population in the estuary. Since 2017, some surveys collected no Delta smelt (Figures 1-3) in the San Francisco Bay-Delta estuary. The 2018 and 2019 survey catches (Figures 1 and 2) are a new low for Delta smelt, lower even than the 2017 survey catch (Figure 3), and the lowest in the 1995-2019 survey period.

The outlook for the Delta smelt population remains grim after these lows. Despite good conditions in spring 2018 and 2019, the severely depressed number of adult spawners indicates a continuing weak potential for recovery.

Figure 1. Catch and lengths of Delta collected in the 20-mm Survey in spring 2019. None were collected in survey 3.

Figure 2. Catch and lengths of Delta collected in the 20-mm Survey in spring 2018. None were collected in surveys 4 and 5.

Figure 3. Catch and lengths of Delta smelt collected in the 20-mm Survey in spring 2017.

Napa River Smelt Sanctuary

Posted on June 29, 2019 by Tom Cannon

The Napa River and its estuary are an important spawning and rearing area for longfin and Delta smelt, especially in wet years. Wet years, with their high Delta outflows (Figure 1) and modest Napa River flows (Figure 2) provide spawning habitat for the smelt in the Napa River and its estuary (Figures 3-6).

Wet year 2019 shows use by longfin (Figure 3), but little use by Delta smelt (Figure 7), which likely reflects their low population abundance.

Because the smelt populations have strongest recruitment in wet years,¹ the Napa River estuary likely is an important contributor to their overall population health and abundance. The Napa River estuary deserves more attention in smelt recovery strategies. However, that should not take away from improving upper Bay-Delta estuary habitat conditions in all water year types.

Figure 1. Delta outflow in recent wet years 2011, 2017, and 2019.

Figure 2. Napa River flows 2009-2019.

Figure 3. 20-mm Survey results for Longfin smelt March 2019. Source

Figure 4. 20-mm Survey results for Longfin smelt March 2017.

Figure 5. 20-mm Survey results for Delta smelt April 2011.

Figure 6. 20-mm Survey results for Delta smelt April 2017.

Figure 7. 20-mm Survey results for Delta smelt April 2019.

http://calsport.org/fisheriesblog/?p=2513; http://calsport.org/fisheriesblog/?p=1858 ↩

Why is Water Temperature in the Delta so important? Why there should be a water quality objective in the Delta for water temperature.

Posted on June 25, 2019 by Tom Cannon

The rivers flowing into the Delta are generally cool. The Bay is generally cool. But the Delta gets warm (>20^oC, 68^oF) from late spring into early fall. Rivers have a water quality standard limit of 68^oF.¹ The Delta should too.

Salmon, smelt, and steelhead are cool water fish that use the Delta for major portions of their life cycle. Water temperatures above 68^oF are stressful, leading to poorer growth, higher predation, lower survival, and early exits from Delta critical habitats. One reason for the stress is that warmer water holds less dissolved oxygen. When water temperature exceeds 68^oF, dissolved oxygen falls below 8 parts per thousand (ppt), which is stressful to fish. In eutrophic (high organic loads with lots of aquatic plants) waters like the Delta, dissolved oxygen can get even lower, near the minimum state standards (6-7ppt), especially at night.

Delta waters are cooler in wet years because of higher flows and generally cooler spring air temperatures. There is no doubt that low river inflows, higher exports, and low Delta outflows can exacerbate high Delta water temperatures, especially during hot periods of summer. There is also plenty of evidence that higher inflows, lower exports, and higher outflows during exceptionally warm weather can help minimize high water temperatures.

Delta waters are cooler when inflows are higher and cooler. The lower reaches of rivers that enter the Delta are cooler with higher flows. Maintaining high river inflows with the associated cooler water helps maintain Delta water temperatures. It takes approximately 20,000 cfs of Sacramento River inflow at Freeport to the Delta to maintain inflow water temperature near 68^oF in summer (Figures 1-3).

The central Delta flow inputs are also cooler in late spring under higher Delta inflows, as exemplified by water temperature and flow comparisons between dry 2015 and wet 2011, 2017, and 2019 (Figures 4 and 5). This comparison dispels the argument that that water temperature in the Delta is wholly dependent on air temperature and is not affected by flow.

There is evidence that increasing diversions and decreasing flows in warmer weather (Figures 1 and 3) increases water temperatures. This is another reason to increase Delta river inflows during warm weather. A Delta water temperature standard/objective would potentially require episodic higher Delta inflows to offset higher warm weather diversions, in addition to a sustained inflow near 20,000 cfs in summer.