Maven’s Minutes: The Delta Watermaster presents his latest report, Gates and Barriers, to the State Water Board
The landmark Delta Reform Act of 2009 made many changes to governance in the Delta, including a provision that required the appointment of a Delta Watermaster. The legislation charged the watermaster with several functions, including the responsibility for the administration of water rights in the Delta, enforcement activities, and monitoring and reporting of water diversions within the Delta watershed. The Water Code also gave the watermaster the responsibility to submit regular reports to the State Water Board and the Delta Stewardship Council on water issues, such as water rights administration, water quality, and conveyance operations.
The watermaster’s latest report, Gates and Barriers in the Delta, is the seventh such report written by Delta Watermaster Craig M. Wilson since his appointment in 2010. At the April 23 meeting of the State Water Board, Mr. Wilson presented the report to the Board, explaining that while most of the previous reports dealt with water rights issues, this report is more technical in nature and is more relevant to the water quality issues and conveyance operations.
“Gates and barriers are seeking to modify the hydraulics in the Delta in a beneficial way,” said Mr. Wilson, noting that the three major influences on hydrodynamics in the Delta are tides, river flows into the Delta, and exports from the Delta; of these three, the tides are by far the most dominant.
Conveyance, export, and inflows into the Delta do raise issues dealing with water quality and fish: “Some of the conveyance and operations have altered the normal east-west tidal flow to have a more north-south flow that has created both salinity and fish in supply corridor issues,” said Mr. Wilson. Gates and barriers have been used in the Delta to address both water quality issues and keeping fish out of water supply corridors. “It’s kind of hard to greatly influence what Mother Nature is doing but some of these gates and barriers have proved to be of benefit in tweaking some of the water quality and fishery issues,” he said.
Mr. Wilson then discussed existing gate and barrier projects in the Delta.
The Suisun Marsh Salinity Control Gates were one of the earliest gate projects in the Delta and one of the more successful projects, he said, explaining that due to the geography and configuration of the channels in Suisun Marsh, there was a net movement of water during the tidal cycle from the west to the east which drew salt water towards the east. By operating the gates in connection with the tides, a net movement from east to west can be created, bringing more freshwater into the Suisun Marsh area and improving water quality. “Basically when flows are high, the gates can be closed on the flood tide to keep the salt water from intruding, and opened on the ebb tide to let more freshwater in,” he said, noting that locks were constructed to help navigation around the gates.
The Delta Cross Channel was constructed in the Central Delta to try to improve the export projects by allowing water to get more directly to the pumps, as well as improve some of the water quality in the south Delta. While the main purpose of the Delta Cross Channel was to provide a freshwater corridor to the export projects, “there were the unintended consequences of the migrating fish being drawn out of the Sacramento River corridor and into the channel and towards the pumps, and so the Board many years ago, in one of its water rights decisions, required the project operators to close the gates at certain times to keep the fish out of the supply corridors and it’s worked pretty well for that project,” he said.
There are three projects in the south Delta whose main purpose is to increase water levels in the southern Delta. These are more primitive projects in that basically every year, rocks are thrown across these water courses to create a barrier, he said.
“One of the barriers keeps fish out of the southern Delta so they won’t be drawn toward the pumps; the others, the main purpose is to increase water levels in the south Delta,” he said, adding that they can be used and operated to better the circulation by tying open some of the culverts and allowing more circulation, which can help with salinity issues in the South Delta.
Possible improvements to existing facilities include improving the Delta Cross Channel gates to make them more flexible in their operation and building permanent operable gates in place of the south Delta temporary barriers.
However, one of the issues with gates and barriers is that they tend to be a stopping point where fish tend to congregate, and so there have been predation issues and a lot of studies are underway to see what can be done.
Non-physical barriers which use a combination of light, sound, and bubbles have been used to address predator concerns, Mr. Wilson said, adding jokingly, “I heard a rumor that the best sound to deter fish was bagpipe music; I kind of take offense to that as I am of Scottish background, but I think they are actually studying different types of music and different types of strobe lights.” These barriers have been used at the Head of Old River and at Georgiana Slough, and have proven to be effective in pilot studies, he said. “There may have some predator concerns because anywhere we have fish lingering in an area, it’s an issue, but I think they will continue to study these and perhaps make wider use of them in the future because they have the obvious benefit of not affecting boating and navigation and they are effective and serve their main purpose of keeping fish out of the water supply corridors.”
Frank’s Tract is a possible location for a future possible gate project, said Mr. Wilson, explaining that Frank’s Tract used to be an island in the Delta, but it was not reclaimed after a levee break several years ago. “It’s a situation similar to Suisun Marsh in that there’s a net flow from the west to the east that brings in higher salty water into the interior of the Delta; also it’s a more direct route for the fish to get to the export pumps, so there’s been some studies of some possible gates or barriers that would serve two purposes: to stop the area from becoming salty as it does now and to keep the fish away from the pumps,” he said.
While most gate and barrier projects ‘nibble around the edges’, this next project is a bit more provocative, he said.
The Maeslant tidal surge barrier built on the Rhine River corridor in the Netherlands is one of the largest engineering feats in the history of mankind; it was built after disastrous tidal surges caused billions of dollars of damage and loss of thousands of lives in the 50s and 60s. “This project is open most of the time; it operates kind of like the flappers on an old pinball machine; the gates can be closed within an hour if a tidal surge is coming in, but in most cases it stays open so it doesn’t affect fish or navigation,” he said. “It’s only been closed once for reasons other than operational maintenance in its history … but they theorize that even though the project cost upwards of $1 billion, it probably saved many times that in damage and obviously saved lives, so it’s basically an insurance policy.”
A similar structure could potentially be constructed at the confluence of the Sacramento-San Joaquin Rivers near Chipps Island, he said, noting that the Chipps Island area is narrower than the project in the Netherlands, so obviously it would be feasible from an engineering standpoint.
Mr. Wilson recalled that when he’s discussed a western tidal barrier with people, they generally laugh and say it’s been studied and rejected, “but the more I looked at it, the project that was studied and rejected many years ago was basically throwing a permanent rock structure across the Sacramento River downstream of the confluence of the rivers that would obviously totally impeded both fish and navigation … There were multiple problems with it and it was soundly rejected,” he said. “This idea is totally different from that. These operable gates would remain open almost all the time. They would be an insurance policy against a catastrophic event, such as a major levee failure where the interior of the Delta would become very salty; it would be an insurance policy, not only to protect the water supply projects but also protect the Delta itself.”
Mr. Wilson said the idea has undergone a little bit of study, but there's not a lot of information about it and it’s not included in the BDCP, “but I thought it was an interesting idea to bring up about a barrier or gate project in the Delta that is more than just these ‘nibbling at the edges’ projects that we’ve talked about in the past.”
As far as recommendations, “the existing gates and barriers have served a useful purpose. They have been shown to improve water quality and protect fisheries, and they can keep fish out of the water supply corridors, and they can help regardless of which types of conveyance operations are implemented through BDCP,” he said. “Additional projects that can help, such as Frank’s Tract and the expansion the nonphysical barrier projects; but obviously the predation issue has to be dealt with and navigation concerns have to be addressed.”
“I think what we need to look for are projects that get you two things for the price of one, as a lot of these projects can not only address water quality issues but also fish protection by keeping them away from export operations.”
A board member asks if Mr. Wilson could walk through the possible projects as they relate to the BDCP – are any included in the BDCP's current draft … ? What about Two Gates?
Two Gates was an idea of throwing some kind of temporary gate structures in the Delta that could be put in and taken out rather quickly, Mr. Wilson replied, but the proposed locations caused a lot of navigation concerns which caused the project to be put on the back burner. “Navigation is something that has to really be considered in determining where these projects are constructed … a lot of times location can matter.”
In regards to the BDCP, “there is some brief discussion of gates and barriers and a lot of it is couched in the concept of adaptive management, stating that these projects have proved to be of some value, we're going to continue to study them and maybe put some in as needed in various places.”
Mr. Wilson noted that he hadn't seen a lot of opposition to the Frank's Tract project so that one could possibly go forward for further study. “It's actually been studied to the extent that it's pretty much a shelf-ready item if people were ready to put it in,” noting that these projects aren't cheap and so it's a question of whether it's an appropriate mitigation and which location is appropriate.
“I think the three major things you are looking for are one, can it help water quality, can it help protect fish and keep them away from the adverse impacts of project operations, and can you locate them in places where navigation is not a concern,” he said.
Question from Board member: Do we have permitting authority?
Mr. Wilson answers that yes, they would have to go through permitting, although he wasn't how much permitting authority the Board would have, but they would be subject to CEQA analysis, and certainly Army Corps permits, and others.