Proposition 1 of 2014 dedicated $2.7 billion for investments in water storage projects, which the California Water Commission administers through the Water Storage Investment Program (WSIP). Projects approved under the Water Storage Investment Program are funded based on the public benefits they deliver. One such benefit is supplying pulse flows to the Feather River to benefit salmon. Three groundwater storage projects in the South San Joaquin Valley and Southern California have committed to providing these flows in exchange for funding.
But how can a groundwater project in Southern California contribute to pulse flows on the Feather River? This question was answered at the May meeting of the California Water Commission, where Kristal Davis Fadtke, Environmental Program Manager at the Department of Fish and Wildlife (DFW), and David Okita, Special Consultant with the Department of Water Resources (DWR), explained the mechanics behind the pulse flows.
HOW MUCH WATER WOULD BE PROVIDED?
Three of the WSIP projects are proposing to provide pulse flows:
- The Chino Basin Program is proposing to provide 50,000 acre-feet per pulse flow for a total of 375,000 acre-feet over a 25-year term;
- The Willow Springs Water Bank proposes to provide 29,000 acre-feet per pulse flow for a total of about 450,000 acre-feet over a 50-year term; and
- The Kern Fan Groundwater Storage Project proposes to provide 18,000 acre-feet per pulse flow for a total of 125,000 acre-feet over a 50-year term.
WHERE PULSE FLOWS WOULD BE RELEASED
When releasing water from Lake Oroville, the Department of Water Resources (DWR) has two options: they can release water from the dam into the low-flow channel or from the Thermalito Afterbay into the high-flow channel, as illustrated on the map. Flows released into the low-flow channel eventually merge with the high-flow channel downstream.
Pulse flows are designed to be released into the low-flow channel where the Feather River Fish Hatchery is located. Typically, this channel is maintained at a flow rate of 600 cubic feet per second (CFS). However, pulse flows can offer several ecological benefits, such as improving water temperatures, diluting pathogens, aiding spring-run salmon migration out of the low-flow channel, or attracting adult salmon returning to the hatchery, where they are collected for broodstock and tagging.
These pulse flows are planned for the spring of drier year types and will continue downstream through the Delta, contributing to Delta outflow.
“The flows will be following and supporting salmon on their journey out to the ocean,” said Ms. Fatdke. “We will likely time these with the release of the hatchery spring run, as we know that this will lead to an increase in survival and some of the other benefits of pulse flows in the spring.”
WHEN PULSE FLOWS WOULD OCCUR
The Department of Fish and Wildlife (DFW) determines the conditions under which a pulse flow will be initiated. Factors such as prevailing conditions, river temperature, and the timing of hatchery fish releases are all considered. While pulse flows are often targeted during drier years, the flexibility of adaptive management allows for targeting in other year types as well.
Once the need for a pulse flow is identified, DFW collaborates with the Department of Water Resources (DWR) to plan key details, including the duration of the pulse flow and how it will ramp up and down.
DFW also evaluates the amount of water available from the pulse flow projects. There is potential to combine water from all three projects to generate a significant pulse of up to 100,000 acre-feet or to implement two separate pulses within the same year.
“We have a lot of flexibility with what these three projects will provide, and we will be looking on a regular basis at how we can combine those pools of water to get the maximum benefit, depending on what the projects have available,” said Ms. Davis Fatdke. “So we will make the request of DWR. Then, in the end, we will take the responsibility for evaluating the effectiveness of these pulse flows, and that will be information that we will be providing to the commission and sharing with the project proponents.”
HOW THE PROJECTS WILL PROVIDE THE WATER
David Okita then explained the complicated exchange process for how groundwater projects will provide the water for the pulse flow on the Feather River.
Each project has a different method of depositing water into its respective groundwater bank, labeled as “Introduction” in the graphic. The projects have a State Water Project (SWP) contractor partner who, during pulse flow years, has agreed to take supplies from the groundwater bank instead of water that would have been delivered by the State Water Project.
When the California Department of Fish and Wildlife (CDFW) requests a pulse flow, the Department of Water Resources (DWR) releases the water as needed. To account for the pulse flow release, DWR compensates by forgoing the delivery of an equivalent volume of water from Lake Oroville to the partner SWP contractor because the contractor has received their water allocation from the groundwater bank.
The San Luis Reservoir, highlighted in the graphic, plays a key role as a regulating reservoir, facilitating this exchange process. Ultimately, Lake Oroville’s water balance remains unaffected, and the SWP contractor receives their full water allocation via the groundwater bank.
CARRIAGE WATER
The Delta is heavily influenced by tidal movements, with saltwater from San Francisco Bay flowing in and out of the region twice daily. To limit the intrusion of saltwater—which can negatively affect agriculture, local water users, and water intended for export—the Department of Water Resources (DWR) and the Bureau of Reclamation release water from upstream reservoirs. This freshwater flow pushes back the saltwater, ensuring the Delta’s water remains fresh and suitable for use.
All Delta water exporters, including Water Storage Investment Program (WSIP) projects, are required to contribute to these reservoir releases, a portion known as “carriage water,” to help prevent saltwater intrusion. However, during a pulse flow year, the water that would typically travel through the Delta is instead delivered directly to the partner contractor. As a result, carriage water contributions are not required in those instances.
“That’s a savings that results from the efficiencies of the WSIP program,” said Mr. Okita. “The State Water Project and the Central Valley Project benefit from not having to put that extra carriage water into the Delta. So the idea is that DWR and Reclamation would credit the WSIP projects for that carriage water that doesn’t have to be provided. It’s a large amount – 20 to 35% of the pulse flow. So it’s quite meaningful to the project, and we have to work out exactly how that will be done.”
EXCHANGES WON’T IMPACT THE STATE WATER PROJECT
The fundamental principle is that this exchange process must not interfere with the operations or finances of the State Water Project. Mr. Okita emphasized that the State Water Project is obligated to protect its contractors from any negative impacts caused by external projects.
Therefore, several conditions must be met by the Department of Water Resources (DWR) before initiating a pulse flow:
- There will be summer releases from Lake Oroville that can be reduced to recover spring pulse flow;
- All SWP regulatory and contractual requirements can be met, particularly temperature and flow in the Feather River;
- The exchange does not cause San Luis Reservoir to spill or reach a low point; and
- The WSIP Projects can deliver stored groundwater to their partner State Water Project contractor
Mr. Okita said that in critically dry years, it’s unlikely there will be a pulse flow. “We’re reducing flows in the summer to make up for that spring pulse flow,” said Mr. Okita. “If there aren’t going to be any releases from Oroville in the summertime, we can’t do a pulse flow. In a critically dry year, Oroville is not used to provide water for export from the Delta, so it’s very unlikely we’ll be able to do a pulse flow.”
MANY AGREEMENTS NEEDED
To implement the pulse flow, the following DWR agreements are necessary
- DWR/CDFW Agreement on pulse flow decision making
- DWR/Partner Contractor agreement to accept WSIP Project in-lieu of SWP water
- DWR/WSIP Project agreement for exchange operations and reimbursement of SWP costs
- DWR/USBR MOU for Efficiency Credits (Carriage Water savings)
An environmental impact report for the pulse flows has been finalized, and an agreement between DWR and CDFW has been drafted. DWR is drafting the agreements with the WSIP projects, and DWR has an MOU with Reclamation for the carriage water (called efficiency credits). DWR is working with all three WSIP projects on how to reimburse the State Water Project for costs associated with the exchange.
DISCUSSION
Commissioner Makler asked, given there won’t be pulse flows every year, how do you determine the project can achieve the benefit the program is funding?
“IEUA recently did a tabletop exercise where we looked at the probability of being able to call on a pulse flow over the 25-year life of the project, and they were able to demonstrate that we could meet that obligation,” said Ms. Davis-Fatdke. “Under adaptive management, we’d have the ability to provide a pulse flow in a different water year type for that exact reason. So maybe over that 25-year term, we don’t have enough dry and below normal years, but there’s going to be years we could have an above normal water year, but yet we have a really dry period in April, so it would be beneficial to have a pulse flow. There still will be those opportunities outside of the drier years that if the conditions are right, we can take advantage of. And we believe there will be enough of those opportunities to achieve these total volumes over the life of the projects.”
Commissioner Gallagher noted it’s a big difference, going from 600 CFS to a pulse flow of 100,000 acre-feet.
“Currently, the required minimum flows in the low flow channel are 600 CFS,” said Ms. Fatdke. “An example that we did with DWR recently looked at if we were to release 50,000 acre feet this year, what would it look like? And we designed it to peak at 4000 CFS for a couple of days in the low-flow channel. And I think it lasted for about 12 days. We do know that’s going to increase survival. We work collaboratively with DWR this year, our scientists do some additional work looking at survival studies. And we know that when you hit at least 2500 CFS in the Feather River, you’re going to see an increase in survival. So we have very high confidence that these pulse flows will make a meaningful contribution.”
Commissioner Sandi Matsumoto asked how far downstream those pulse flows would be protected.
“In their application, the projects had proposed to have these flows protected by a Section 1707,” said Ms. Davis-Fatdke. “After many conversations between our department, DWR, and the State Water Resources Control Board, it became apparent that because these pulse flows are being released under DWR water’s right, it would be a very complicated analysis and process to protect those under 1707. So, we collectively determined that it would be better to use an existing framework and protect those flows under the Bay Delta Plan update, so the Healthy Rivers and Landscapes program is working on an accounting methodology to demonstrate that the flows being provided and those VA assets are occurring. We think that would be the most effective methodology to demonstrate that these flows are being protected and contributing to Delta outflow.”
“As part of the Bay Delta Plan update, there’s an accounting framework that it’s being committed to, and then there would be an agreement that we could utilize that accounting framework. So these wouldn’t be part of the Healthy Rivers landscapes, but we would utilize the same framework that they’re developing for that process, and through the accounting framework, it would demonstrate the flows made it out.”
