Managing turbidity for Delta smelt

Delta Smelt
Delta smelt
Metropolitan’s David Fullerton and Paul Hutton say there’s a relationship between turbidity and Delta smelt, and demonstrate that by cutting back Delta pumping at strategic times, they can avoid take of Delta smelt at the export pumps and gain water in the long-run

At the February 24th meeting of Metropolitan Water District’s Special Committee on the Bay-Delta, David Fullerton, Principal Resource Manager, and Paul Hutton, Senior Engineer, briefed the directors on the efforts to manage turbidity to reduce entrainment of Delta smelt at the export pumps in the south Delta.

3b_Presentation_Page_07David Fullerton began with an overview using a map of the Bay Delta system. He noted that the state and federal pumps are located toward the bottom of the map in the south Delta. “The Delta smelt basically live more or less in an arc from Cache Slough down into Suisun Bay and down to the bottom of Suisun Marsh; this is where they are most of the time,” he said. “However, during the winter, when we have storms, we can get a lot of turbidity coming into the system, particularly from the Sacramento River. If we get a lot of turbidity coming down the Sacramento River off these unregulated creeks that are pouring into that river after that big storms, it will pour into the Delta, and if simultaneously the exports are running at full blast, they are just sucking that turbidity south. The pumps are pulling the turbidity in and the Delta smelt are coming with that turbidity, and you can get a lot of salvage.”

There were a couple of years in the early 2000s where a lot of Delta smelt ended up at the pumps because of that scenario, he said. “Unfortunately, we don’t get a lot of water from the San Joaquin in some of these drier years, so when we pump water, it’s got to come from somewhere, and it’s coming from up the north; it brings turbidity and the turbidity brings fish,” he said.

Under the Endangered Species Act, there are very tight restrictions to try and keep the loss of Delta smelt to a minimum, Mr. Fullerton said. “The goal here is how do we protect Delta smelt and how do we stop from taking a lot of smelt, but at the same time manage to pump a reasonable amount of water for the projects?,” he said. “That’s the challenge and so meeting that challenge basically involves understanding what causes Delta smelt to move.”

The relationship between Delta smelt and turbidity

3b_Presentation_Page_04What we’ve learned over the last 5 or 10 years is that smelt are responding very heavily to turbidity levels,” he said, presenting a graph depicting the relationship between Delta smelt salvage and turbidity. The bottom axis is Secchi depth, a measure of turbidity. Mr. Fullerton explained that it’s going in the opposite direction from what you might expect, because the way that Secchi depth is measured, the larger the number, the less turbid the water is. “You can see a pretty clear pattern here where as the average turbidity in this system in the winter gets higher (or the Secchi depth gets lower) and it’s really mucky water, we take more smelts, so I think that is a very important insight if we’re trying to manage the salvage of smelt.”

3b_Presentation_Page_05Adult smelt salvage increases with reverse flows in the Old and Middle River or OMR. “Reverse flow is basically the lower San Joaquin River flowing backwards, because the San Joaquin River itself doesn’t have a lot of flow most years,” he said. “If we’re pumping a lot of water, the water is coming from the north, and that’s causing reverse flow.”

In years where we’re pumping a lot of water, we can even get up to as much as -10,000 cfs in Old and Middle River and those are the years where we tend to see a lot of salvage as well,” he said. “Interestingly, we can even get salvage when we have positive flow, so there’s something else going on, it’s not just Old and Middle River flow.”

3b_Presentation_Page_06But these two factors, turbidity and Old and Middle River flow, can be combined into a model that actually does a very good job of predicting the salvage each year from 1993 basically up to the present,” he said. He noted that the blue line on the graph is the measured salvage rate and the red line here is what the model predicted based on turbidity and OMR. “I think a lot of people feel very comfortable that turbidity and OMR are very important factors in controlling salvage.

The idea is that when the model predicts that there is a high risk, first of all reduce Old and Middle River flows, which slows or stops the turbidity coming into the south Delta. “You’re getting some synergistic effects by making very strategic cuts to exports, and we think you’re actually going to gain water while reducing salvage, so it’s kind of a win-win,” Mr. Fullerton said.

The cost of environmental constraints

3b_Presentation_Page_08This is what we estimate the loss is, this is due to all of the ESA listings and biological opinions, Chinook salmon as well as Delta smelt for different life stages, and you can see it adds up to a lot of water over the years, so we’re always trying to figure out ways where we can try and squeeze out more water while still complying with the Endangered Species Act,” he said.

He then turned the floor over to Senior Engineer Paul Hutton. “As far as where we are today, our best estimate right now is for both biological opinions, we’re looking at a cost of around 400,000 acre-feet combined,” Mr. Hutton said. “If we hadn’t taken some voluntary actions this year, it would have been higher, and our estimate is around 70 to 200,000 acre-feet additional so instead of the 400,000 acre-feet so it would have been in the range of 470,000 to 600,000 acre-feet.”

Another number we took an estimate of, if we had a dual conveyance in the Delta right now, we would estimate that cost of 400,000 acre-feet would have been reduced down to 200,000 acre-feet,” he added.

Developing the tools to manage turbidity

Mr. Hutton then gave a brief history of the work Metropolitan has been doing to develop cost-effective concepts for controlling Delta smelt movements.

It was in 2007 that Judge Wanger threw out the 2005 Delta smelt biological opinion and set interim measures, which included restrictions on Old and Middle River flows. “These restrictions had triggers based on a calendar and based on turbidity levels as well,” he said. “Given those costs that you saw about the biological opinions, those were costs that we anticipated, so we started working on how could we manage turbidity in such a way and how could we come up with a procedure to meet the objectives of the biological opinion in a more cost effective way.”

The first effort was the Two Gates project, a proposal to install physical gates in the Delta channels to control the turbidity field and keep it from coming into the south Delta. An independent science panel gave the project mixed reviews in 2009, causing the project to be shelved, he said. In the meantime, in 2008, the biological opinion was updated, effectively keeping a lot of the same measures that Judge Wanger had put in back in 2007, he said.

So what we did is we scaled back from the Two Gate concept and just use the export pumps and modulating export pumping in such a way that we could try to manage the turbidity,” he said. “So we started focusing more on real time management and using real time data and forecast information on operations to try to help operators to decide when and how much we should throttle back the pumps to try to provide that protection.

Clifton Court Forebay  provides storage and regulation of flows into the State Water Project's Banks Delta Pumping Plant
Clifton Court Forebay provides storage and regulation of flows into the State Water Project’s Banks Delta Pumping Plant

We wanted to do this in a collaborative manner so we could get buy in and good ideas from all of the community, from the operators, from the regulators, and from our other water users,” Mr. Hutton said. “So, we worked with the operators and the water users very closely so that we could come up with what we believed would be a cost-effective solution. We worked very closely with Fish and Wildlife Service and with the science community to come up with an approach that we all believed would be protective of the smelt. Then lastly, we wanted to develop a procedure that we could actually transfer this technology from Metropolitan over to the operators because clearly we’re not running the show and we can’t be doing this indefinitely, so we needed to come up with a game plan to do that transfer.”

In 2010, Metropolitan staff begin work with consulting team to develop turbidity forecasting methodology, and by 2011, Metropolitan staff started sharing some of the forecasting pilot information being developed with Fish and Wildlife Service. “We were working closely with the operators to develop a concept, a voluntary pre-emptive action, where we would decide at this strategic time to throttle back the pumps voluntarily,” he said. “We’ll take a water hit at that time, but we would anticipate that by doing that, we wouldn’t trigger some of these biological opinion requirements and we would save water on the back end, so we developed that concept with the operators.”

Mr. Hutton said they were sharing the tools and the concept with the science community through presentations at technical conferences, and by 2012, the Department of Water Resources agreed to start using some of the forecasting tools on a pilot basis.

Click here to visit Bay Delta Live's turbidity page.
Click here to visit Bay Delta Live’s turbidity page.

In 2012, the Delta Conditions Team was assembled, comprised of the US Fish and Wildlife Service, National Marine Fisheries Service, Department of Fish and Wildlife, Department of Water Resources, the Bureau of Reclamation, and it also includes Metropolitan and the other state and federal contractors as well as NGOs; they meet weekly to provide advice and information. “This has been a very successful team to help provide some of our insights to fish and wildlife to help them make their determination,” he said.

Mr. Hutton said that an application has been developed on the website Bay Delta Live where those on the Delta Conditions Team (as well as the general public) can pull all the data that they need to help in the deliberations and to help in the discussions.

Putting it into action … a tale of two years

Dave Fullerton then returned to the floor to talk about how the theory works in practice. He began with the caveat that there is only one Delta, so it isn’t possible to run any controlled experiments. “We don’t know what would have happened if we had acted differently, but we try to guess and model it and infer what might have happened, and try to learn every year,” he said.

3b_Presentation_Page_13He started with a slide showing Sacramento River flow in December of 2012. “We had a very early storm, right at the beginning of December,” he said. “Through the fall, Sacramento flow was running between 10 and 15 thousand cfs, not very high. Then there was a big storm in early December and we had a spike in flow up to about 60,000 cfs. We had a second storm getting close to Christmas, which then tailed off over the next weeks or month.”

3b_Presentation_Page_14He added two lines to the graph, a pinkish line depicting the pumping response to the storms, and a gray line showing OMR flow. He noted that the OMR flow is kind of a mirror image of the pumping, and explained, “When the San Joaquin River is running low, as it was that year, these two will tend to be mirrors of each other, because if we’re pumping a lot, it’s coming through Old and Middle River in a reverse direction.”

Mr. Fullerton pointed out the dramatic cut in the last half of December. “This is what killed the year in terms of water supply,” he said. “We had to cut way back, and then we were kind of stuck in the 3,000-4,000 cfs pumping range for weeks and months after that.”

3b_Presentation_Page_15He then added a graph of turbidity and Delta smelt salvage, noting that the blue line represents turbidity near Clifton Court and the orange line represents Delta smelt salvage at the pumps. “You can see that as soon as the turbidity in Clifton Court went above 12, we started getting salvage,” he said. “It started spiking up very quickly and as soon as it started getting high, the regulatory agencies dramatically cut our pumping. Then basically it worked for awhile, but we basically had smelt dribbling in for the whole rest of the winter. It was this long agonizing process of each day or two, you’re getting more and more smelt coming in. The turbidity stayed high all winter long down in the south Delta.”

Mr. Fullerton said that it catalyzed them to think about how it could have been done better, and their conclusion was that they should have cut pumping earlier. “The nice thing about turbidity, it’s not like salt; once there’s salt there, it’s there,” he said. “Turbidity will settle out, so the thing about turbidity if you can keep it away from the projects for a period of time, a lot of it will settle to the bottom and it will disappear out of the system. If you can get the water to clear up on its own, we believe the smelt are going to swim away back downstream, so you’re going to be reducing the risk.”

3b_Presentation_Page_16That’s basically what happened that year,” he said. “I call it pumping into trouble, because I think we probably pumped for about two weeks two long during that year. We brought a lot of turbidity into the south Delta, and then every time there was a little bit of wind, it got kicked up again, so the turbidity just kept torturing us all winter long.”

3b_Presentation_Page_17What we did this year was quite different,” he said. “We had an early storm again this year, and then we had another big storm right on the heels of it just about two months ago.  You can see that turbidity was low but it was starting to creep up over time. The difference here is that we made a moderate cut pretty early, well before the turbidity was getting up to high risk levels this year, and as a result, the turbidity took many weeks to actually reach the south Delta.”

We did have a little smelt event basically around New Years which might have been avoided if there hadn’t been an enormous windstorm in the Delta, which was very unfortunate,” he said. “We believe this was very successful. By making a very strategic small cut here, we were able then to basically avoid having much more stringent reductions in exports imposed upon the projects by the Fish and Wildlife Service.”

He said there’s been a process of cooperation and discussion basically every day. “I think there’s been some trust developed this year, and as a result, we believe that these early moderate cuts saved very stringent cuts that would have occurred a week later if we had waited that would have actually cost a lot more water in the end,” he said. “We think that we generated a net benefit of between 70 and 200 or 270 extra acre-feet of water while probably reducing Delta smelt salvage at the same time, so basically it comes down to understanding what causes Delta smelt to move and then trying to manage around that characteristic.”

The SWP's Harvey O. Banks Pumping Facility
The SWP’s Harvey O. Banks Pumping Facility

We think to the extent that we’re successful in keep adults out of the south Delta, we’re going to keep the larvae out of the south Delta too,” Mr. Fullerton said. “This is about the time they are starting to lay their eggs so you want them to lay their eggs as far away from the projects as possible so that you’re not taking the next generation as well, so you’re getting a double benefit by managing turbidity to keep smelt out of the south Delta.

I was very impressed by the level of trust and cooperation this year,” he said. “We made voluntary actions and, basically in recognition of our goodwill and our willingness to sacrifice, the FWS in turn didn’t impose things as harsh as they might have otherwise if we hadn’t taken those actions. We’re going to continue to work on the modeling, we’re going to continue to learn from this year, but I think most people view this as quite a successful year. Even though we have taken some smelt in the salvage, it could have been a lot worse.”

This was a textbook year for a big event. When I saw the storm, I was thinking it was going to be bad, and I think we were able to manage around it with a relatively moderately low level of salvage this year,” concluded Mr. Fullerton.

Discussion highlights

One of the directors says to Mr. Fullerton that he had heard that because of the drought, the amount of water lost to regulations has been minimal, and yet this is continuing to show large numbers … ?

My quickie answer would be that even in dry years, there are a couple of storms, and we’re severely limited by this Old and Middle River standard and the question is if you can take advantage of those few storms that come by or whether you have to let the water go,” said Mr. Fullerton, handing the question then over to Mr. Hutton.

Skinner Fish Facility Screens Nov 2011 #2
The Skinner Fish Facility collects fish that are drawn to the pumps.

It is true in dry years, the biological opinions tend to have a much lower impact on us than they would in wetter years, so it tends to be the D1641 objectives in the drier years,” said Mr. Hutton. “However, I brought up the number 400,000 for example; so that sounds like a lot, but when you compare it to 1.5 MAF or something like that – we haven’t had a lot of wet years since 2008, I guess that’s one thing to bring up, so I don’t think we’ve really seen the full extent of what could happen, so when you line up 400,000 with 1.5MAF, it’s a smaller number.”

The same director says it seems like they hadn’t had a lot of regulatory or legal success. “It’s great that we can work with people. In essence, this is all voluntary, just trying to get fish agencies to be more cooperative, that’s how we’re achieving this success?,” he asks.

I think that there is discretion within the law, and the regulatory agencies accept that, and so what we’re trying to do is work within that discretion within the law,” said General Manager Jeff Kightlinger. “At the end of the day, the Endangered Species Act is a fairly black and white law, but still there’s a fair amount of discretion in how they implement those restrictions, so what we’re trying to do is through cooperative efforts with the regulatory agencies using what we think is the best most sound science is to show them how they can implement their discretion, and we have had some success with that.”

Director Beard asks, “On slide 8, Impacts of Regulation, you show numbers for the State Water Project and Central Valley Project that are not only not equal but variable from year to year, I was curious … in some years, the losses on the CVP are one-third the state’s losses. Why are the variables so large … ?”

This is a question that comes up all the time because the language that we use for sharing of these water costs is a 50/50 split of these costs, but as you can see here, that terminology doesn’t always reflect what happens,” replied Mr. Hutton. “Bear with me, this gets down into the weeds, but effectively when we say we’re sharing 50/50, is we (meaning the state and federal projects), we’re sharing the ability to pump water. So if the total we can pump is 400,000 acre-feet, the state can pump 200,000 and the feds can pump 200,000, so the question comes then why does it look like the state is getting hit harder? The reason is because the state has larger pumps, so during these times when we have these high flows, under unregulated conditions, the state project would have had the opportunity to have pumped a lot more water than they would have, so by sharing the available pumping 50/50, the state project is actually getting hit harder because they have the ability to have pumped more.”

Delta smelt

It’s a complex issue,” said Mr. Kightlinger. “What you have to look at losses versus gains, so the gains are even. In other words, we each receive the same amount of water, but losses are greater to the SWP because the SWP historically moves more water and it has bigger pumping capacity and it has more customers and more territory and land, so while each got, say if we split it evenly and there was a 1 MAF and we each got 500,000 AF, the SWP would normally moved close to 3 and they’d have moved closer to 2, so the losses fall more heavily on the SWP. What we received is equivalent, but the losses are greater.”

Another way of looking at it, the federal pumping facility can pump about 4600 cfs and then they can’t go any higher, that’s all the pumping they have,” said Mr. Fullerton. “We have about 10,000 cfs of pumping at the Banks, although we rarely use all of that, so as the flows get higher and higher, at least historically, we were able to keep pumping more and more and they (the CVP) topped out, so the state system is always very effective at catching these winter storms and taking advantage of them, so that’s why the OMR restrictions have been so devastating to the state, whereas the fed is more of a baseload system. They just keep going.”

For more information …

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