CALIFORNIA WATER COMMISSION: A primer on State Water Project operations

The Banks Pumping Plant in the South Delta (Photo by DWR)
Presentation discusses the infrastructure and operational challenges of the State Water Project

At the June meeting of the California Water Commission, Tracy Petitt-Polhemus, Supervising Engineer with DWR’s SWP Operations Office, gave this presentation.  She provided an overview of the State Water Project facilities, project purposes, key agreements and requirements under which the State Water Project must operate, Delta operations, how the water allocation to our contractors is determined, and the challenges they face in operating the State Water Project.


Tracy Petitt-Polhemus began with a map showing the various water projects throughout the state of California.  The federal water projects, such as the Central Valley Project, are shown in brown; local projects, such as the Hetch Hetchy and the Los Angeles Aqueduct, are shown in green.  The facilities of the State Water Project are shown in blue; the major facilities are circled.

The State Water Project is the largest state-built and operated multi-purpose water and power system in the US.  There’s about 20-25 million residents in the state of California that take all or a portion of their water from the State Water Project.

The facilities of the State Water Project begin with the three upper Feather River reservoirs: Frenchman, Antelope Lake, and Lake Davis.  The Feather River then flows into Lake Oroville, the tallest dam in the US at about 770 feet.  From there, the Feather River flows down into the Delta.  The North Bay Aqueduct supplies state water contractors in Benicia, Vallejo, and Solano County.  The South Bay Aqueduct supplies state water contractors such as Santa Clara and Alameda.

The California Aqueduct begins at the Banks Pumping Plant in the South Delta.  South of the Delta, the San Luis Reservoir and O’Niell Forebay are part of a joint-use project shared with facilities shared with the Central Valley Project.

The Coastal Branch supplies the Central Coast areas of San Luis Obispo County and Santa Barbara.  The coastal branch terminates at the Vandenburg AFB.

Click here to take a photo tour of the Edmonston Pumping Plant.

At the base of the Tehachapis, the Edmonston Pumping Plant pushes the water over the Tehachapis and into Southern California where it birfurcates into the East Branch and the West Branch.  The East Branch terminates at Lake Perris and the West Branch terminates at Castaic Lake.

There are about 700 miles of canal and pipeline; 4 pumping/generating plants, 20 pumping plants, 5 hydroelectric plants, and 23 dams.  The State Project is the third largest generator of power in the State of California.

Municipal and industrial uses account for 70% of the State Water Project water; 30% is for agriculture.  Metropolitan is the largest urban contractor at 2MAF; Kern County Water Agency is the largest agricultural contractor at about 1 MAF.  Water from the State Water Project irrigates about 750,000 acres of crops.


The primary purposes of the State Water Project are water supply and flood control.  Secondary purposes are fish and wildlife enhancement and mitigation, Delta water quality and flow, recreation, and power generation.


There are several key agreements and requirements under which the State Water Project operates.  Some are individual obligations of the State Water Project; some of them are joint obligations with the Central Valley Project.

Individual agreements and requirements of the State Water Project are:

  1. The US Army Corps of Engineers oversees flood control and navigation. Three reservoirs within the State Water Project have received monies for flood protection from the US Army Corps: Lake Oroville, Del Valley Dam, and Los Banos.  Clifton Court has a permit for navigation.
  2. The Federal Energy Regulatory Commission issues hydropower licenses for the Lake Oroville facilities and our southern facilities.
  3. There is a 1983 agreement with the California Department of Fish and Wildlife agreement for both flow and temperature requirements in the Feather River.

There are also State Water Resources Control Board permit and conditions:  Water Rights Decision 1641 has water quality and outflow standards that both the Central Valley Project and the State Water Project have to meet; there is also a water quality certification for Lake Oroville as part of the hydropower relicensing.

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

There are Endangered Species Act and the California Endangered Species Act requirements which are met jointly with the Central Valley Project.  The US FWS issued a biological opinion for Delta smelt that came into effect in December of 2008; the National Marine Fisheries Service issued a biological opinion that came into effect in June of 2009.  The California Department of Fish and Wildlife issued a permit for longfin smelt which came into effect in 2009.

The Coordinated Operations Agreement is a 1986 agreement that defines the methodology of how both projects will meet in-basin demands and how they will share the responsibilities.

The San Luis Joint Use Facilities Operating Agreement specifies how the joint use facilities will be operated, such as the scheduling of power and water at San Luis and at the O’Niell Forebay.

Ms. Petitt-Polhemus then presented a table for the State Water Board’s D-1641 which captures the timing and requirements that the State Water Project needs to operate under.  “It’s for both flow and water quality standards, the beneficial purposes or uses of this water and it’s for the fish and wildlife, agriculture, and municipal and industrial,” she said.  “This is all on a monthly basis; sometimes the averaging period can be a 3-day, a 7-day, a 14-day, or monthly, but this tells you on a monthly basis what kind of standards we’ll be operating to.”

The standards are tied to what water year type it is:  Wet, above normal, below normal, dry, and critical dry.  Outflow can have a range depending on the year types.  “You’ll have more water under a wet year that you need to provide than in a dry year,” she noted.  The water year type affects not only flow but also how the Delta cross channel gates are operated.

There are water quality standards for things such as chlorides that must be met throughout the year.

This graph shows the criteria for the biological opinions for Delta smelt and salmon that both the State Water Project and the Central Valley Project must operate under.  “One thing in managing for fish, we’re seeing more of increasing requirements for fish protection and enhancement, but we’re also seeing actions upstream and in the Delta,” Ms. Petitt-Polhemus said.  “The US FWS biological opinion contains requirements to operate to an Old and Middle River flow requirement, and also additional outflow in the fall for Fall X2.  And that’s in effect from September through the end of November.”

The NMFS requirements are calendar based.  “They also have an Old and Middle River flow target, but they also include technical team developments, additional studies, and operations of the Delta Cross Channel gates; also the operation in April and May of the San Joaquin River, and then flow to export ratio,” she said.  “While the US FWS has more of a triggers tied to real-time conditions, the NMFS Service is more calendar based, so come January 1, we will be operating to this criteria.

We are seeing more of adaptive management approach in managing the fish,” she said.  “How we manage to meet those criteria is we look at real-time conditions such as flow and temperature, or if we see any salvage or observed fish at the export facilities, as well as the fish distribution.”  She noted that they have been looking at the genetics of the fish are salvaged.

The other thing is we’re seeing is the criteria is becoming more based on real-time observed data, and because it’s made on real-time, it’s more challenging to try to forecast the behavior of the fish.  We’ve had challenges trying to predict the fishery behavior and then also trying to modify operations in a timely manner.  The other thing too is that we’re starting to see competing species starting to be competed both upstream and downstream in the Delta.”


There are a number of tools that can be used when there is a shift or change in Valley demands or in the Delta.  “We use them when we see an increase because of effects of tides on chlorides or salinity, electrical conductivity, and also for fishery.”

Increase inflow: Inflow can be increased from the different reservoirs, Ms. Petitt-Polhemus said.  “You can think of Shasta as the freight train; the travel time is about 5 days away.  Oroville is like a truck; it’s 3 days away. Folsom is more like a sports car at about a day away, so if we need to make changes we’ll tap into Folsom if possible and then we’ll start balancing off all the other reservoirs after the initial response.”

Export reductions: The export pumps at the Jones Pumping Plant (Central Valley Project) are single-speed, so once they are on, they are harder to adjust versus the Banks Pumping Plant (State Water Project), she noted.  The units at Banks Pumping Plant are variable speed; the state facilities also include Clifton Court Forebay, which gives them more flexibility in operations than the Central Valley Project.

Delta Cross Channel Gates:  The last option is the Delta Cross Channel gates and whether they are kept open or closed.  “If we keep them open, it provides fresh water from the Sacramento to help with salinity and conditions in the Delta, and if we keep them closed, they help with the passage of fish as they go through the Sacramento River.”

Ms. Petitt-Polhemus noted that they can also use a combination of the three tools.

The hard part is when things can happen, while we do look at all these tools, trying to make changes on a pre-scheduled basis, Shasta is 5 days away for travel time but you’re looking at 2 to 3 days for power scheduling, so you’re looking at Shasta as 7 days, Oroville as 5 days, and Folsom potentially 3 days, so knowing in advance these actions that need to be taken helps.  But export reductions, we can make those changes.  When you think of the tidal influence within the Delta, sometimes these kinds of changes from project operations has a more gradual effect, but it will get there.”


Much of the Delta is below sea level, so there are levees that protect it.  There are over 1100 miles of waterways within the Delta.  There is also a network of gauges that monitor water quality and flow.  The Sacramento River flows in from the north; three-quarters of the water in an average year is from the reservoirs; in drier years, up to 90% of the inflow coming into the Delta is from reservoir releases, Ms. Petitt-Polhemus said.

The San Joaquin flows in from the southeast; there are also east side streams which come into the Delta.

Another tool that helps in managing the Delta is the series of gauges on CDEC that monitor both flow, stage, temperature, preset, and turbidity.  “We use forecasts to help with our inflows or flows, and that helps with planning and how we operate in the Delta.  We also use simulations; we have a tool that we use, the Delta Simulation Model II, and that models the hydrodynamics in the Delta and we use that for tidal forecasts.”

The Delta is a tidally-influenced estuary, and Ms. Petitt-Polhemus pointed out that there are huge tidal surges that come in that are in multiple hundreds of thousands of cfs coming in and sloshing back and forth at least twice a day; project operations are only several thousands of cfs, as compared to the hundred thousands of cfs from the tides.

There’s a lot of variability in the Delta,” she said.  “We talk about inflow and that’s not only from our reservoir releases, but it’s also the unregulated flows that come in from tributaries that are near the Sacramento and through the San Joaquin.  There is also the Delta consumptive use and return flow from the over 1800 agricultural diversions in the Delta; they are taking water out, and then you have their return flow coming from their irrigated lands, and so that has an effect on water quality and flow and the hydrodynamics within the Delta.”

There are also the tidal conditions.  “We have big surges of tides and that does affect the hydrodynamics of the Delta, water quality, and the fish,” she continued.  “And you have the channel flow in the Delta which are affected by tides and diversions.  The water quality salinity gradients – these are all affected by tides and diversions and the return flows.  Then you have the effects on the tides from wind velocity, wind speed, and air pressure (if it’s a low pressure or high pressure system), and that affects the flow and the fish and the water quality within the Delta, and the water levels.

Head of Old River barrier (photo by DWR)

There are also are four barriers installed in the Delta that help with operations.  In the spring and in the fall, the Head of Old River barrier is a fish barrier that helps with the outmigration of the San Joaquin salmonids; there are three agricultural barriers that help with water levels and water quality.  These barriers in conjunction with export operations have an effect on the hydrodynamics, water quality, and the fish in the Delta.

As we manage to the standards on a real-time, we’re finding the criteria is more based on observed data, so we’re managing to the real time observation of criteria so forecasting is a little more challenging,” said Ms. Petitt-Polhemus.  “We’re managing our limited resources with increasing demands in this very dynamic environment.  There are a lot of tradeoffs that are occurring and we are evaluating what effect those tradoffs have on future actions in meeting our Delta operations and compliance to these current standards.  It’s based on this integrated upstream reservoirs that we do have, and so any actions that we do take, if there’s any delay, we can see a large action will need to be taken but also the longer time frame to manage in order to be in compliance.”


Ms. Petitt-Polhemus then explained the procedure for determining water for the State Water Project contractors.  The State Water Project is contracted to deliver about 4.2 million acre-feet; the allocation is stated as a percentage of the Table A amount that the contractors receive.

What goes into our allocation process are these assumptions and inputs,” she said.  “We look at hydrology.  From the Department’s Division of Flood Management, we receive a water supply forecast, and they give us a suite of exceedance probabilities, so 10, 25, 50, 90, and 99.  We process that exceedance probability, and we can come up with an operations plan for the year, that includes releases and exports throughout the year.”

We base our allocation on the 90% exceedance probability with the idea it’s the most conservative and it’s with the chance that it will become wetter as the months progress,” she said.  “What happens is, when you think of the exceedance probabilities, you have 50 and a 90, and eventually the 50 is going to go the 90 or the 90 is going to up to the 50, and we’ve seen that this year in our allocations, we had a lower allocation and our final allocation is 100% for north of Delta and 85% for south of Delta, and that’s because the 90 moves up to the 50%.

Storage conditions are also considered, not only what’s in State Water Project reservoirs, but also the reservoirs within the Central Valley Project.  “Our operations are integrated with each others,” she said.  “What they are going to do will affect us and what we’re going to do will affect them.

Water demand is also considered: every October, they receive a plan of what kind of delivery would contractors would like under various allocations, a 30, a 50, a 60, and 100%., and those are included in our studies.

Then we look at the environmental constraints – those regulatory requirements,” she said.  “Trying to model or predict fishery behavior is challenging and so in our studies, we do bookends with the most restrictive action and the least restrictive actions, so that gives you a sense of what kind of range we can deliver under the various suite of different hydrologic probabilities.”

By December 1, the initial allocation is determined and announced.  The allocation is updated on a monthly basis, and increased or decreased, depending on the conditions at the time.  “The Director determines the allocation every month, every time we update, and our final allocation.  The water supply forecast that we receive from flood management is basically from December through May, and so we make our final allocation by May.”


There are a lot of operational challenges for the State Water Project.  The biggest challenge is the hydrologic uncertainty and variability.  “Variability can be both where the water is made available, such as where it comes from in Northern California, but also where it’s needed and that’s where the conveyance facilities of the State Water Project come into play,” said Ms. Petitt-Polhemus.  “There is also seasonal variability, so it’s available in the wintertime and spring, but it’s not needed until the summer for agricultural use, so you have that mismatch.  That’s where our reservoirs can capture the water and make it available when it’s needed.”

There are also competing project objectives, such as flood control and water supply.  “If you release too much, if you release too little, how do you balance the two?” she noted.

Lake Oroville; Photo by DWR

There are also conflicting standards and objectives.  “There are times where we’ve operated to one of the State Water Resources Control Board objective versus a biological opinion, and we’ve seen that conflict, or a trade-off in the sense that if you take an action now for Delta smelt, how is that going to affect the fall salmonids, so you can have conflicting standards on species.”

There are also changing in-basin demands, the timeliness of real-time monitoring, Delta uncertainty and variability, power scheduling, and facility outages, as well.  “When we develop this water operations plan, we try to plan outages and power.  Sometimes, you can plan for a unit or the work that you have to do, but we have those unplanned events – an emergency or unit, something happens, so you can’t really plan for that.”

During the brief discussion period, Commissioner David Orth commented, “I sit here and think about what we’re going to do here in the next six to 12 months relative to assessing benefits, and those two schedules in particular indicate to me the importance of us having some solid understanding with the agencies that are going to administer and help us quantify these benefits, when in fact you’re operating a dynamic system with real-time observed data driving decisions, and we’re supposed to try to translate that into a quantified public benefit that’s going to last over the life of an investment.  That’s going to be incredibly challenging.  I think the only way that happens is through clear, defined agreements with Fish and Wildlife, State Board, and the other administering agencies.”



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