This drone photograph shows the completed temporary emergency drought barrier for the West False River in the Delta in Contra Costa County. The 750-foot-wide rock barrier will help deter the tidal push of saltwater from San Francisco Bay into the central Delta. Photo taken July 13, 2021 by Jonathan Wong / DWR
DELTA STEWARDSHIP COUNCIL: DWR discusses plan to keep Delta drought barrier in place
Additional barriers in the Northern Delta being contemplated if conditions remain dry
Despite the wet weather, California is still experiencing dire drought conditions and concerningly low storage levels in the state’s largest reservoirs. DWR is responding to the continuing drought conditions with modifications to how they plan to operate the emergency drought barrier currently installed in the Delta, as well as planning for continued drought conditions.
At the October meeting of the Delta Stewardship Council, Jacob McQuirk, DWR Project Manager for the 2021 Emergency Drought Barrier, provided an update on the implementation and some of the observed impacts of the 2021 barrier and other actions DWR is taking in response to the evolving drought emergency in California.
He began by noting the dry conditions and the low reservoir levels, particularly in Shasta and Oroville, the state’s largest reservoirs.
The Emergency Drought Barrier was installed in June of 2021. Due to continued dry conditions, DWR is currently working toward obtaining approval from the regulatory agencies to leave the barrier in place with modifications. The plan is to cut a notch in the barrier in early January and reestablish the full drought barrier in April. DWR plans to remove the barrier in its entirety by November 30, 2022.
Proposed notch in existing barrier
In considering what size to cut the notch in the barrier, they did a lot of hydrodynamic modeling with different designs, running a model to estimate what velocities would occur through the barrier. They decided on a sizeable notch that will bring the barrier down to -12 feet elevation, keeping the velocities low and making conditions more favorable for passage in a small vessel.
“With that large of a notch, the barrier really isn’t doing its job anymore,” said Mr. McQuirk. “But what it is doing is enabling fish passage and vessel passage, and the draft here would be over 13 feet at a low spring tide. So there’s plenty of draft. And it also will enable us to rebuild that barrier much faster, as well as with less impacts to the environment.”
The Department has developed criteria for when the drought barrier would no longer be needed, which is 73 inches of precipitation on the 8-station index, about 140% of average, and 6.5 million acre-feet storage in Orville and Shasta storage combined. Both of those triggers would have to be met by April 30 of 2022 for the drought barrier to be removed.
Mr. McQuirk acknowledged the concerns over high discharge (or river flows) coming into the Delta with the drought barrier in place. “The West False River is really a tidal slough, and so the changes in elevation associated with West False River are dominated by the tides, not by the inflow from either the Sacramento or the San Joaquin River,” he said. “We did do an analysis looking at the high flow events of 2017, which had virtually no stage changes in West False River.”
Recognizing the concerns over monitoring with the 2015 drought barrier, the Department has a robust monitoring plan in place with this barrier installation. Most monitoring utilizes existing monitoring conducted by DWR and the Interagency Ecological Program, including fish, water quality, phytoplankton, and zooplankton. The monitoring will look at both the physical and biological changes that occur and get at questions such as the difference between drought effects, TUCP effects, and drought barrier effects.
Harmful algal blooms will be monitored by visual assessments, microscopy (grab samples), satellite data, and fluoroprobes used during USGS and DWR water quality cruises. Additional cyanotoxin samples will be taken in Franks Tract and other areas of the Central Delta should a bloom be detected.
In addition to the monitoring plan, they will be looking at the effects of the barrier on out-migrating salmonids and predation events in the area. In particular, the notched barrier could provide a “predator hot spot,” so predation event recorders will be used to track predation events and determine if there is any difference with or without the barrier in place, with the barrier notched, and when the notch is refilled.
They are also working on acoustic telemetry studies to detect fish presence and movements across the barrier.
Temporary Urgency Change Petition (TUCP)
The temporary urgency change petition (TUCP is a process at the State Water Board for DWR to request to modify or relax the water quality standards in D 1641. Mr. McQuirk said that both the TUCP and the barrier are needed to maintain the water quality in the interior Delta with less upstream reservoir releases.
DWR is preparing the TUCP for 2022 and is considering requesting modifications for Net Delta Outflow index (NDOI) reduction, Flexible Delta Cross-Channel gate operations, Combined project export caps, and Vernalis minimum flow requirement reduction.
The Department is working towards a December 1 submittal of the TUCP petition; they hope to have the TUCP change order by February. If conditions remain dry, DWR will seek another TUCP that would go into effect in May.
Additional drought barriers
If drought conditions continue to degrade, the Department is considering additional drought barriers in the Northern Delta in 2022. After meeting with landowners who gave their recommended locations, they are considering constructing barriers on Miner Slough and Steamboat Slough to help maintain water levels in the Delta. The barriers would have operable culverts to allow some downstream flow to augment the flow through the barrier itself. There would be a boat portage facility similar to what we have in the South Delta at the Grant Line canal barrier at the Steamboat barrier; no portage is proposed for the Miner Slough barrier. The earliest the North Delta barriers would be installed would be in June of next year, which is after flood season and avoids most impacts to out-migrating salmonids.
They are working with the Army Corps on the permitting process; a Section 408 permit is needed because the barrier would modify a flood control project levee.
In conclusion …
Mr. McQuirk concluded his presentation by noting that DWR is dealing with the current drought emergency while planning for future drought conditions, so the Department isn’t perpetually operating in emergency mode. This includes developing a CEQA document that analyzes up to two 2-year installations in a ten-year period for West False River; that document is anticipated to be released for public review in the spring or summer of 2022. It wouldn’t take effect until 2023 at the earliest.
They also plan to work towards non-emergency permits for the North Delta barriers as well.
“Even if we get more precipitation and we can call these off, we will still be working on getting those levee modification permits and standard individual permits to allow us to be able to make those channel closures if we need them,” said Mr. McQuirk. “We will come up with a schedule for CEQA, and there will be plenty of opportunity for public involvement public comment.”
QUESTION: Commissioner Virginia Madueño asked what would happen if the barrier is in place and we have continued storm activity. What is the risk to the adjacent communities and islands?
Mr. McQuirk: “The West False River really is a tidal slough; it’s not like the Sacramento River … the Sacramento River, we all know that you get a good discharge on the Sacramento, the stage really comes up. That is not the case with West False River; it’s really the high tide that increases the stage. So we see no risk to the local communities of leaving that barrier in place.”
“We did develop the hydrologic triggers that would indicate that we no longer need the barrier. And they are pretty high. One is 73 inches on the 8-station index; I think we’re currently at 12. And a combined 6.5 million acre-feet at Orville and Shasta. I haven’t looked at the storage today, but I know at least at Oroville, we’re still well below 1 million acre-feet. So those would be the hydrologic triggers. At that point in time, if we reach those, we would agree to go ahead and remove that barrier. The Department could choose to remove the barrier with less precipitation, but at that point, we would do it.”
QUESTION: Dr. Laurel Larsen asked about the barriers being contemplated in the North Delta, particularly at Steamboat Slough. “Those sloughs are increasingly regarded as critical for the survival of out-migrating Chinook salmon because that represents the first significant diversion they encounter. Survival probabilities are enhanced if they move through Sutter and Steamboat Slough because they’re less likely to enter the South Delta pumping facilities. So there’s been a lot of attention given to management actions that might enhance fish passage through that region. And I’m wondering how those plans might interact with plans for installing a barrier at Steamboat Slough?“
Mr. McQuirk: “On salmonid survival and the movement of out-migrating juveniles down Steamboat Slough, we agree. We’re also working on barriers like the Georgiana Slough bioacoustic fish fence to keep fish out of Georgiana Slough. We’re evaluating floating fish guidance structures to push fish into Steamboat Slough. And so, at this point, the first real measure that’s going to help is having the barrier installed later. We’re looking at installing that barrier after the peak migration has happened. Then we’re still working on a study or evaluation to look at the effects of the barriers on the movement of juvenile salmonids. It’s still in formulation at this point; we are looking at working with some of our consulting team and USGS on that. And there would be some culverts open that would potentially allow us for some passage through the barrier as well.”
QUESTION: Dr. Larsen asked if the barrier does go in in June, when is it likely to come out?
Mr. McQuirk: At this point, we are looking at having the barriers entirely removed by November 15.
QUESTION: Executive Officer Jessica Pearson asked about those hydrologic triggers. Would that change the hydrologic triggers for the West False River barrier if the North barriers are put in?
Mr. McQuirk said the northern barriers are incremental, so the hydrology has to continue to worsen. “We’re working on looking at the hydrology that would tell us at what point would we be able to call off the need for this emergency channel closures. It’s definitely a very dry situation. I don’t have those numbers right with me today. We are working the analysis on to kind of figure out what point – it’s a whole lot less than the 73 inches that the 8-station index when we can say, we just need the West False River, we don’t need to move forward with this Steamboat or the Miner slough barriers work in progress.”
QUESTION: Jessica Pearson asked what feedback they are hearing from adjacent Delta residents or boaters.
Mr. McQuirk: “We did go out and meet with some concerned residents. I’ve heard both that the markings for the barrier are more than adequate, but we’ve also heard that others say that they could be more so, so we are moving forward with some additional buoy lines. I’m still getting a schedule for that. So we’re going to go ahead, and we’re going to deploy an additional line of buoys both upstream and downstream of the barrier. There’ll be lighted flashing buoys … they’re considerably further upstream than the float lines.”
CONCLUDING THOUGHTS: “There was a comment made about more green solutions,” said Mr. McQuirk. “We do see Franks Tract Future as a potential solution here as it would provide nearly the same benefits that the barrier would. And so we have done a lot of modeling and analysis. And the great thing about Franks Tract futures is it works every day of the year. So we’d be it would be helping, even without any additional actions from DWR. But then, if we really needed to get the full effects that we’re getting from West False River, we could go in there with very small channel closures that would require a lot less work and money.”