Where does the State Water Project get its water? How does DWR model Delta water operations? Informational webinar features presentations on State Water Project operations and Delta modeling
The Department of Water Resources (DWR) is hosting four informational webinars between July and September 2021 to provide background information related to preparation of the Draft Environmental Impact Report (EIR) for the Delta Conveyance Project. The first webinar focused on State Water Project and Delta operations, and featured presentations on State Water Project operations and the models the Department will use to analyze the project.
The meeting facilitator, Juliana Birkhoff with Ag Innvoations, noted that this is not a formal California Environmental Quality Act public input opportunity; there will be opportunities for public input once the draft environmental impact report has been released in mid-2022.
Carrie Buckman, the Delta Conveyance Project Environmental Project Program Manager with the Department of Water Resources, began by discussing the proposed project, the overall schedule, the planning processes, and future opportunities for public participation.
Ms. Buckman began by noting that the purpose of this series of informational webinars is intended to provide background on technical topics well in advance of the release of the draft environmental impact report, or EIR. The goal is to share the methodology and the assumptions that will be used when evaluating the environmental effects of the project.
“We understand that the issues around the Delta conveyance project can be very technical and complicated,” she said. “So we’re hoping that these webinars will help clarify these topics and help members of the public and reviewing the draft EIR when it comes out next year.”
Ms. Buckman noted that they are currently developing the draft EIR, so the impact analysis and mitigation have not yet been identified. So they will be focusing on the background of the topics and the methodology of how they will analyze things and will continue to share further details as they move towards a draft EIR.
The fundamental purpose of the Delta Conveyance Project is to modernize the aging State Water Project infrastructure in the Delta and restore and protect the reliability of SWP water deliveries in a cost-effective manner, consistent with the state’s water resilience portfolio. As part of that, there are several specific objectives, including addressing sea level rise and climate change, minimizing water supply disruption due to seismic risk, protecting water supply reliability, and providing operational flexibility to improve aquatic conditions.
The slide shows some of the project facilities that could be included in the different alternatives. The project is considering diverting water on the Sacramento River. The proposed project includes two 3,000 CFS intakes near the town of Hood and a tunnel that would connect from those intakes to the south Delta.
Ms. Buckman pointed out that while the slide shows several routes, they are not looking at several tunnels; it would be a single tunnel from the north to the south, following one of several routes: the Central Corridor in orange and the Eastern Corridor in blue. Both follow routes through the Delta down to a new southern forebay adjacent to Clifton Court Forebay. She noted that the central corridor is similar to what was included in California Water Fix, and the eastern corridor shifts the tunnel closer to I-5 in the hopes of reducing effects associated with the logistics of getting construction materials and people to and from the construction sites. Those tunnels terminate in a pump station that pumps water up into a new Southern forebay that regulates flow before moving to the existing Banks Pumping Plant.
Another alternative is the Bethany Alternative, which follows the eastern corridor to a point, and then it veers south, as shown in green. Rather than going to a new southern forebay, the water would be pumped directly into Bethany Reservoir and therefore eliminate the need for the southern forebay.
“All of these different configurations of facilities would be able to provide some operational flexibility as they would all be operated with the existing diversion facilities in the South Delta,” she said. “So there would be what’s called dual conveyance rather than having this project replace facilities that are already in the south Delta.”
Ms. Buckman presented the project schedule. Currently, the Department is developing a draft EIR under the California Environmental Quality Act (CEQA). The Army Corps of Engineers, the federal lead agency, is preparing a draft environmental impact statement or EIS under the National Environmental Policy Act (or NEPA).
Although they are two separate documents, they are working on coordinating the public review for mid-2022. After the public review, they will finalize the documents and release decision documents later in 2023.
Ms. Buckman noted they are concurrently working on other environmental processes. They are starting the preliminary planning for developing a biological assessment and the incidental take permit application, which are documents needed for compliance with the state and federal Endangered Species Acts; those are also expected in 2023. The Department will also be working toward obtaining a change in point of division for our water rights, certifying consistency with the Delta Plan, and securing other environmental permits in mid-2024.
THE BASICS OF THE CALIFORNIA ENVIRONMENTAL QUALITY ACT (CEQA)
Next, Ken Bogdan, senior staff counsel with the Department of Water Resources, then reviewed the California Environmental Quality Act process.
Mr. Bogdan noted that the California Environmental Quality Act (or CEQA) is complex and can’t fully be explained in a five-minute presentation; however, a separate presentation goes through CEQA in more detail on DWR’s website (and covered on Maven’s Notebook). The purpose of this presentation is to create a foundation for those who are unfamiliar with the CEQA process.
The California Environmental Quality Act or CEQA requires all public agencies subject to the jurisdiction in California to analyze the potential environmental impacts of their action before approving the action. This entails a considerable amount of time evaluating what could happen to the environment in implementing the proposed project.
“The requirement is not to study broader issues related to the needs of the state,” Mr. Bogdan said. “Each public agency has specific directives under the law, and they must focus their project approvals related to that. And as such, they prepare some kind of environmental review document that not only discloses the potential significant environmental effects but then talks about feasible ways to avoid or mitigate those significant impacts. This, in turn, shows the public and decision-makers how they have gone through that process. This is prior to making the final decision on the action.”
For the proposed Delta conveyance project, Mr. Bogdan said the Department is preparing an environmental impact report (or EIR) that will thoroughly analyze the potential impacts of the project on physical resources as required by CEQA, discuss whether those are significant, and discuss feasible mitigation or alternatives that would avoid or reduce the impacts while still meeting the project’s objectives.
“We’ll spend the time and focus on potential impacts associated with the physical environment, both the air, water, its physical environment related to wildlife, aquatics, and the variety of resources that CEQA spells out,” he said. “It will also focus on analyzing a range of alternatives that we’re looking at that could meet the project objectives and would avoid or possibly reduce the significant impacts.”
At the end of the EIR process, if the Department determines it is still appropriate to approve the project or an alternative, CEQA requires they adopt findings related to the potentially significant impacts. If the impact cannot be mitigated and the Department feels it is still appropriate to approve the project, it would then adopt a Statement of Overriding Consideration that addresses the feasibility of the mitigation and alternatives concerning the project’s benefits.
“That’s only if, going through the process, the agency determines it should approve the project,” he said. “DWR will, as is required in an EIR, be analyzing the no project alternative, which means what are the environmental consequences if the Department of Water Resources does not approve the proposed project.”
The environmental impact report (EIR) will include a detailed project description; the environmental setting, which is the baseline for determining environmental impacts, and then discuss potential impacts based on modeling, surveying, and the subject matter experts that have been retained to provide the detailed analysis related to supporting the agency’s record for determining whether something is significant. The EIR will also discuss mitigation measures to avoid or reduce those impacts.
Currently, the Department is discussing the environmental setting baseline and what tools will be used to assess the environmental impacts.
“We are literally in the throes of working with our consultants and our experts, and we’re coordinating with the responsible agencies who are also participating in giving input on their particular expertise related to the resource evaluation,” he said. “And we’re going through that process to analyze the impacts.”
Mr. Bogdan pointed out that giving the public background on the foundational information that leads to the impact analysis is somewhat irregular in the CEQA process.
“The lead agencies typically don’t stop mid-impact analysis to give the public and other agencies a presentation on their approach to the impact analysis, so it is a special point in the process that DWR is doing,” he said. “You wouldn’t see this in your normal CEQA processes. And certainly, it’s not required by the law.”
He then closed by noting that the draft EIR will be published mid-next year. After that, the Department will respond to those comments and prepare a final EIR that will discuss whether the agency approves the project or not.
“If the Department decides to approve the project, what mitigation would be appropriate to add as part of the project approval that ends up in findings with a final notice of determination. And that would end the CEQA process.”
STATE WATER PROJECT OPERATIONS
Next, John Leahigh, Water Operations Executive Manager for DWR’s State Water Project, delved into the operations of the State Water Project.
He began the fundamental challenges that the state’s water managers face, beginning with the mismatch between supply and demand from a geographical standpoint, as shown by the map on the left. The vast majority of the rain and snow falls in the northern part of the state, while the larger population centers are in the Bay Area and the southern part of the state, downstream of the Sacramento San Joaquin Delta.
In addition to the geographical mismatch, there is a temporal mismatch, as shown by the chart on the right. Most of the state’s precipitation falls in the winter months, and the snow melts in the spring, while the high-demand period is really during the summer and into the fall.
The other major hydrological challenge is the annual variability; California has the most varied annual precipitation in the nation, as shown by the figure on the right. On the left is a graph showing the Sacramento River runoff for the past 100 years, with wetter years shown in green and the drier years shown in red and orange.
“Most recently, we experienced the wettest year on record 2017,” said Mr. Leahigh. “Currently, we are experiencing one of the driest on record. In fact, the 2020-2021 two-year period has been the second driest, only behind the drought record years of 76-77 throughout the 100-year record.”
Two-thirds of the state’s precipitation originates in the Sierra Nevada; about half of the runoff flows through the Sacramento San Joaquin Delta. State Water Project facilities divert water from the southern portion of the Delta for use in the South Bay Area, Central Coast, San Joaquin Valley, and Southern California. The State Water Project provides at least a portion of the water supply for 27 million Californians and for 750,000 acres of farmland, which in turn supports the state’s trillion-dollar economy, noted Mr. Leahigh.
OVERVIEW OF THE STATE WATER PROJECT
The State Water Project has several components. There are several reservoirs, the largest of which is Lake Oroville in Butte County. The other significant reservoir is San Luis Reservoir, a joint state-federal facility south of the Delta. There are hydroelectric plants and pumping plants. The most significant pumping plant is the Edmondston Pumping Plant near Bakersfield that lifts water close to 2000 feet over the Tehachapi Mountains into Southern California. All these facilities are connected by 700 miles of canals, tunnels, and pipelines.
The State Water Project is the largest state-owned, state-planned, constructed, and operated water supply system in the country. The State Water Project is funded project by the 29 contractors who have contracted for the delivery of up to 4.2 million acre-feet per year.
“It is high-quality, affordable supply that augments the contractors’ local supplies,” said Mr. Leahigh. “The introduction of the surface water source lessens the groundwater overdraft in much of the regions, and it is funded by the public water agencies and not through the state general fund.”
He noted that State Water Project water is just one component of a larger portfolio that each region manages. “It is a critical supply that helps the local regions work with the other parts of their portfolio, which includes major investments in local storage, recycling programs, conservation, and groundwater recharge that is facilitated through the introduction of the State Water Project water and water quality management,” he said.
The table on the upper right shows the percentage of State Water Project water in the portfolios of various regions throughout the state.
In addition to the water supply benefits, the State Water Project provides flood control, hydropower generation, recreation, and fish and wildlife habitat. The most significant flood control benefit is provided by Lake Oroville, which is on the Feather River. For fish and wildlife habitat, the project is operated in a way that’s sensitive to the fishery in the Feather River and the Delta, Mr. Leahigh said, noting that there are facilities built for mitigation, including the Feather River Fish Hatchery; the fish screens at the south Delta export locations; and the creation of habitat in various locations along the Feather River and the Delta.
The State Water Project has contracts for up to 4 million acre-feet but rarely does the project deliver the full amount. Currently, because of the drought conditions, the allocation to the contractors is only 5% of their contracted amount; this matches the all-time low allocation.
Mr. Leahigh explained the process for determining the allocation. The initial allocation is issued on December 1 for the following year. That allocation is based on the amount of storage in Lake Oroville and San Luis Reservoir; the initial allocation also considers a very conservative precipitation estimate for the remainder of the year.
“In other words, we assume it’s going to be very dry every year,” he said. “We also have to consider all of the releases that will be necessary to meet other contractual and regulatory obligations. These allocations are updated monthly through the spring, and typically our final allocation is given somewhere in either May or June.”
STATE WATER PROJECT OPERATIONS AND THE DELTA
Where does the State Water Project water come from? Mr. Leahigh said the answer is twofold:
The primary State Water Project reservoir, Lake Oroville up in Butte County, captures the excess flow and excess runoff in the winter and the spring from snowmelt and runoff from precipitation events for storage and release later in the year.
The precipitation falling on the valley floor below Lake Oroville and Lake Shasta itself produces significant inflows into the Delta that are in excess of other needs. Those excess flows are captured at Banks Pumping Plant in the southern part of the Delta and then stored in the San Luis reservoir south of the Delta for later release to coincide with the high demand period.
In the summer and fall, the previously stored water in Lake Oroville is into the Feather River, where it flows south to converge with the Sacramento River and flow into the Sacramento-San Joaquin Delta. Then it is re-diverted at Banks Pumping Plant to meet deliveries during the high demand period. Added to that is the stored water in San Luis Reservoir that also is released during the summer and into the fall to meet the high demand.
The Delta is an inland estuary; it’s a network of islands channels and wetlands located at the confluence of both the Sacramento and the San Joaquin rivers before flows into the San Francisco Bay and the Pacific Ocean. An estuary is where fresh water from rivers intersects with the saline water from the Bay. The Delta is the largest estuary on the west coast of both North and South America.
The Delta is also the hub of California’s water management system. Much of the rain and snowmelt is either diverted directly in the wintertime at the SWP export facilities or is re-diverted during the summer period from previously stored water. Additionally, the federal Central Valley Project’s export facilities are also located in the South Delta.
In terms of hydraulics, the Delta is a complex network of over 700 miles of tidally influenced channels and sloughs, so there is a strong forcing mechanism from the tidal flux and freshwater inflows. There’s a significant amount of in-Delta diversions that support agriculture in the Delta and then both the Central Valley Project and the State Water Project exporting from the south part of the Delta.
For freshwater flows, the largest flows are coming from the Sacramento River and, to a lesser degree, the San Joaquin River. There are other rivers and streams on the east side of the Delta, such as the Cosumnes and Mokelumne Rivers. In addition, there is demand within the Delta to support agriculture and the large water projects exporting water in the south.
Any additional flow goes to Delta outflow, but it’s net Delta outflow, said Mr. Leahigh.
“There is a natural reverse flow that occurs because of the tidal influences in two different time periods,” he explained. “One of those periods is during each day, there are two flood tides and two ebb tides that are coming in and out of the Delta every six hours. Then the other timeframe is on a monthly time step due to the moon’s and sun’s gravitational pull on the tides. There is a spring tide where there’s essentially six to seven days of gradual filling of the Delta, and the water level of the Delta surface elevation increases slightly; that’s followed by six or seven days of a neap tide, where there is a general draining of the Delta, and the water levels start coming down.”
In the Delta, there is a network of monitoring stations for water quality measurements, primarily salinity, and for gauging flows on various channels throughout the Delta. These sampling sites are telemetered so they can be accessed remotely; the data is publically available on the CDEC platform.
The monitoring is performed by the state and federal projects to help them meet their primary responsibility of meeting the Bay-Delta D 1641 Water Quality Control Plan objectives. The other priority is meeting the demands of other senior water rights holders; these includes the settlement contractors, who are senior water rights holders who entered into agreements with both Reclamation and the Department of Water Resources when the State Water Project and Central Valley Project were constructed. There are other regulatory requirements as part of federal and state Endangered Species Act requirements; most recently, the Department received its incidental take permit from the Department of Fish and Wildlife.
“After all of these other requirements are met, at that point, if there is excess water to the system, then the two projects can develop water supply and convey water across the Delta,” said Mr. Leahigh. “Essentially, we’re capturing and storing mountain runoff in the upstream reservoirs and capturing excess Valley runoff in the Delta itself; this is primarily in the winter and the spring period.”
When the Delta is in ‘balanced conditions,’ the water projects actively manage the system to meet those in-basin demands, including the water quality standards. “We’re doing this by making appropriate releases from the upstream reservoirs and throttling the exports as necessary to meet those water quality requirements.”
The slide shows the different sources of water for State Water Project exports and how it differs, depending on the water year type.
The first bar is for 2011, a wet year. The gray represents the excess flows in the system, either unstored flows that came into the system or flow passed through the reservoirs for flood control purposes.
“In wet years, there are generally excess flows for most of the year, if not all of the year in some cases, and that’s the source of the exports,” said Mr. Leahigh. “There’s a small amount there you see in the red and blue that represents a stored water release for export.”
The middle bar is 2012, a below-normal year, which is the typical operation where upstream reservoirs capture winter rains and spring snowmelt and rereleasing that water for re-diversion at Banks in the summertime. But in those years, he noted a substantial amount of unregulated flows are picked up as well in the winter directly.
In the critical years, the bar on the right, the only difference is the lack of water released from reservoirs. “All of the stored water in those types of years goes to meet the Bay-Delta standards,” Mr. Leahigh said. “So there is nothing available to meet the allocations of the State Water Project. It is completely dependent upon the excess flows that were picked up in the wintertime in those particular cases.”
SWP AND THE DELTA CONVEYANCE PROJECT
Mr. Leahigh then turned to how State Water Project operations would change with the new North Delta diversion location.
He first addressed the things that will not change. “One thing that will not change is that we would still be responsible for meeting these Delta water quality requirements. We would assume that the same South Delta operating rules would apply for fishery protections. There would be new operating rules that would apply to the proposed North Delta diversion location for fishery protection. There would be no change to our water rights with the exception of petitioning for a new point of diversion, but we’re still looking at exercising the same water rights for the exports from the south Delta.”
However, the additional North Delta diversion location could provide an opportunity to capture more excess flow for water supply purposes, Mr. Leahigh said. He presented a hydrograph of Delta outflow for 2016. The gray line represents the actual Delta outflow, the blue line is the State Water Project exports that were occurring, and the red line is the additional diversion that could have occurred if the facilities in the North Delta had been in place. The yellow line shows the effect on the Delta outflow.
“So it is skimming off the high flow events from these large inflow events that occur in the Delta in the wintertime,” he said. “But these would only be occurring when the flows are significantly greater than what is needed to meet the Delta standards and other needs.”
This figure shows what happens in the summertime when the previously stored water from Lake Oroville is released into the Feather River and flows down to the Delta to be conveyed across the Delta. Inflow coming down the Sacramento River from Lake Oroville is in light blue. Some of that water flows across the Delta through the Cross Channel and other natural sloughs, Georgiana slough, making its way into the Central Delta and then down Old and Middle River and is diverted towards the export locations in the South Delta.
However, when the pumping is at a high rate, some of that flow does not fit through the capacity of the Delta Cross Channel, and it has to come around through the confluence area near Suisun Bay, shown by the red arrow.
“Some of it causes reverse flow from the confluence into the central Delta, and so that’s going to be saltier water that is coming into the central Delta as a result of those higher exports,” said Mr. Leahigh. “So to mitigate for that, and to meet the water quality standards, the projects need to release additional flow from their upstream reservoirs in order to prevent that saltwater intrusion.”
With the proposed project, there’s a more direct route to the export pumps, which would put less reliance on the cross channel flow, and significantly reduce the reverse flows, as shown by the purple arrow.
“This would result in a more efficient operation in terms of conveying that water across the Delta,” he said. “There, it would require less of the previously stored water from upstream reservoirs in order to mitigate for saltwater intrusion than if it were exports from South Delta only.”
So to summarize, Mr. Leahigh said that with the new export location, the Department would still be meeting the same Delta water quality flow requirements. There’s no change to the water rights except for the new point of diversion. And it would actually improve our flexibility in meeting some of the standards.
“The new diversion location would be operated in conjunction with the existing South Delta intakes,” he said. “It would augment our ability to capture excess flows in the wintertime and give us more flexibility in meeting the Bay-Delta standards in summer. We would not change any operational criteria for the upstream reservoirs. And we would continue to operate to the existing board standards and federal biological opinions in our state ITP permits.”
“The North Delta diversion intakes operations would remain consistent with the regulatory requirements,” he continued. “The most significant are the Old and Middle River flows, Delta cross channel gate operation criteria, Rio Vista minimum flow requirements, Delta outflow, and the export to inflow ratio would still be needed to be met with the proposed project.”
QUESTION: Geographically, where would the water from the Delta Conveyance Project go? What percentage goes to agriculture and urban uses?
“As it exists today, of the 29 contracts in terms of volume of water, approximately two-thirds to three-fourths of the water is for urban use; the remaining quarter to a third is for agricultural use,” said Mr. Leahigh. “That’s the existing split, in terms of where the allocated State Water project goes. For Delta Conveyance, it depends on which of these contractors are going to participate. Generally, there’s going to be more interest from urban contractors, so we suspect that it will generally be more for urban needs moving forward.”
QUESTION: If the precipitation is so variable, how will the Delta Conveyance Project provide benefits?
“We do have highly variable hydrology, and what studies are telling us for climate change is that variability is only going to increase,” said Mr. Leahigh. “That’s why it becomes all the more important to be able to capture some of these higher flows from storm events during the wintertime. An additional diversion location would allow us to do so while still maintaining the protections that are in existence for the existing diversion location in the South Delta. Of course, there will be fishery protections for the new diversion location, but it does help us adapt more to the changing hydrology that is anticipated with climate change.”
QUESTION: Can you also further define excess Delta flows?
“Excess Delta flows are flows that are greater than are necessary to meet all of the other in-basin uses, which is essentially meeting all of the water quality and flow standards in the Delta itself and meeting all of the contracts for deliveries to senior water contractors and other legal diverters of water,” said Mr. Leahigh. “So there are a substantial number of periods in years where the flows are extremely large and are well above the needs of other users in the system. Those are the flows on which the two projects can develop their water supply.”
METHODS TO MODEL DELTA OPERATIONS
The third presentation was by Andy Draper, principal engineer with Stantec and the lead for the modeling efforts for the draft environmental impact report.
For the draft EIR, the models are used to represent a complex Integrated Water Supply and water use system, the elements of which are illustrated by the figure on the slide. Precipitation over the mountain regions accumulates as snowpack and results in runoff from rainfall or snowmelt, which supplies the rivers and the reservoirs located in the foothills. Many of these reservoirs are multipurpose and operated for flood control, water supply, hydropower, recreation, and environmental purposes.
Irrigated agriculture on the valley floor depends on a mix of stream diversions and groundwater pumping. Similarly, water supplies for municipal and industrial purposes are met from a mix of surface water and groundwater. Some of the diverted water is used consumptively, and some returns to the stream system or percolates downward to the underlying aquifer. Groundwater inflow may sustain summer stream flows, or alternatively, streams may lose water through seepage to groundwater.
Models represent the real world through mathematical relationships based on specific inputs, channel configuration, regulations, and operational policy. Models for water resources may be classified as physical models representing the underlying governing and tech equations of water flow. Or they may be classed as management models, whereby they represent what a manager’s decisions are for a given set of circumstances.
The effects analysis for the draft EIR relies on a suite of models, some of which are illustrated in the figure.
The foundational model to simulate State Water Project and Central Valley project operations and the operation of the proposed North Delta diversion is the Cal Sim 3 model. Inputs to Cal Sim 3 include climate change hydrology, based on projected changes to temperature and precipitation, and Delta flow salinity relationships for a given sea level rise scenario.
Subsequently, output from Cal Sim 3 is used as input to downstream models that include detailed Delta flow and salinity modeling, water temperature modeling, groundwater modeling within the Delta, and salmonid population and mortality modeling.
Cal Sim 3 has been jointly developed by DWR and the Bureau of Reclamation for conducting planning studies relating to State Water Project and Central Valley Project operations. The model domain includes the Delta and the entire upstream watersheds of the Sacramento and San Joaquin rivers and their tributaries.
The flow of water through this domain is represented using a detailed plumbing diagram shown on the left, known as a network schematic. It consists of nodes connected by arcs. Nodes on the schematic represent water management infrastructures, such as dams, diversion structures, or weirs, or they may represent locations on streams and rivers, such as the location of stream gauges, regulatory compliance locations. Arcs represent flow between the nodes during a given time step.
“Though Cal Sim 3 is a simplification of the real world, it is based on one of the most detailed representations of the Central Valley’s water resources,” said Mr. Draper. “The model contains many advances and refinements compared to the Cal SIM II model that was used to support the Bay-Delta conservation plan and the Water Fix.”
The figure on the left illustrates Cal Sim’s representation of Shasta Lake and Dam by a blue triangle labeled SHSTA. The incoming light blue arrow or arc represents the inflow volume during the model’s timestep of one month. The red arc on the right represents direct diversions from the lake by local communities. The green arc on the left represents lake evaporation. The monthly volume of releases from the reservoir is shown by the outflow arc labeled C_SHSTA.
“Each month, the model decides whether to retain water in storage or release water to meet downstream objectives,” said Mr. Draper. “And each month or timestep, Cal Sim 3 performs a flow balance on Lake Shasta and for every other node in the model to determine the resulting end-of-month storage, shown by the rectangle labeled S_SHSTA.”
The monthly inflow hydrograph to Lake Shasta, shown on the top left, consists of a rising limb fed by winter runoff and a falling limb as inflows recede in the summer months. Storage in Shasta follows a similar pattern of refill and drawdown.
Historically, annual inflows to Lake Shasta, shown by the chart center-right, vary significantly from 2.5 million acre-feet per year to 10.8 MAF. Therefore, to represent the full range of possible water supply conditions, Cal SIM III considers a 94-year long time series of monthly inflows to Lake Shasta and inflows to the rest of the model domain. These inflows are based on the historically observed flows, and for each month in the 94 years, the model made its reservoir release decisions to meet downstream objectives.
This portion of the Cal Sim 3 schematic represents what is known as the Feather River service area. The Feather River is represented by the vertical blue line on the right. Two of these are non-discretionary actions and so are assigned some of the highest priorities in the model.
First, as shown in the bottom right-hand box, the model must release water from Lake Oroville to meet in-stream flow requirements specified in settlement agreements and agreements with fishery agencies. The model may release additional water to meet downstream obligations in the Delta.
Second, shown in the top right-hand box, the model makes water deliveries from Thermolito After Bay to senior water rights holders in the Feather River service area to meet the State Water Project obligations under a series of water rights settlement agreements. The simulated water demands for these senior water rights holders are based on assumptions of irrigated crop acreage and weather conditions for the particular month, precipitation, and crop evapotranspiration.
The slide on the lower left shows Cal Sim 3’s representation of the western Delta. The State Water Project and Central Valley Project have water supply obligations to their respective contractors, but the annual allocations and the amount and timing of exports from the south Delta are discretionary decisions made by Cal Sim as it balances competing water demands and tries to manage system operations in an efficient manner that mimics real-world operators’ decisions. In model simulations, exports are made after all the non-discretionary obligations have been met.
Prior versions of Cal Sim were limited to simulating the surface water system. However, Cal Sim 3 includes the simulation of the Central Valley’s groundwater aquifer for a holistic representation of the Valley’s water resources. Cal Sim 3 is linked to a distributed groundwater module known as a dynamic link library or DLL that simulates groundwater flows and storage for approximately 1400 elements shown on the figure on the left. Cal Sim 3 determines stream flows, groundwater pumping, and vertical recharge from precipitation and irrigation. The groundwater module simulates groundwater elevations under these stresses and determines the resulting stream seepage losses.
Cal Sim 3 Delta operations conform to the regulatory requirements under which the projects must operate. These include, amongst others, the Coordinated Operations Agreement that defines the sharing of water and responsibilities between the State Water Project and Central Valley Project, the decision D 1641 water quality standards that were established by the State Water Board in 1995, the 2019 biological opinions for the long term operations of the two projects, and the 2020 incidental take permit for operation of the State Water Project.
Much of the analytical studies focus is the area downstream from the proposed North Delta diversion, i.e., the Sacramento San Joaquin Delta. Cal SIM modeling provides information on Delta boundary conditions; these include inflows from the Sacramento and San Joaquin rivers, exports by the two projects in the south Delta, and net Delta outflow. However, Cal SIM’s coarse monthly timestep, simple Delta channel network, and flow balanced accounting precludes simulation of tidal flows that dominate the Delta and resulting channel salinity. Cal Sim 3 is a monthly model that cannot resolve issues occurring on a shorter timescale, such as the flood and ebb tidal cycles.
Therefore, an additional model known as DSM 2 is used to simulate Delta conditions in detail. DSM 2 uses a 15 minute time step. The figure on the right shows the grid or node-arc network for DSM 2 model. There are several 100 nodes compared to the approximately 40 in Cal Sim 3’s Delta representation. DSM 2 modeling tiers off the Cal Sim 3 modeling using Cal Sim 3 output to define boundary conditions.
DWR developed the DSM 2 model in the late 1990s to support planning studies related to the Delta. It is a hydrodynamic model, meaning that the physics or governing equations of channel flow drive the simulation, rather than simple flow balance accounting used in Cal SIM. DSM 2 is also a one-dimensional model, meaning that flow through a channel of varying shapes and cross-section is represented by a single velocity parallel to the channel with no transfers or vertical float components. One-dimensional models are best suited for planning studies because of their software runtime, which allows the simulation of a full 94 years of varying Delta conditions and varying boundary conditions.
The hydro component to DSM II calculates channel velocities, stage, and resulting channel flow. Subsequently, the flow component of DSM II calculates water quality based on saline intrusion and channel mixing. Lastly, a particle tracking module can simulate the transport of particles released or injected into the model at different locations.
Two model scenarios or simulations in Cal Sim 3 and DSM 2 represent what we consider baseline conditions: existing conditions as of 2020 and the no project alternative that represents projected conditions as of 2040 in the absence of the proposed project. The no-project alternative includes the effects of climate change and sea level rise; these aspects will be discussed in greater detail and presented in webinar number three.
In the first set of model simulations, five in total, the proposed project, and project alternatives are layered on top of existing conditions. This is a construct required by the California Environmental Quality Act or CEQA that looks at the potential effects of a project if it was implemented today. In the second set of model simulations, again five in total, the proposed project and project alternatives are layered on top of the 2040 no project alternatives. These model simulations are used to identify the potential effects of a project if it was implemented in 2040 under an environmental change by population growth, global warming, and sea level rise.
All models have limitations, and understanding the input data, model assumptions, and solution algorithms lead to recommendations on the appropriate use of model results. Firstly, Cal Sim 3 is not a predictive tool and does not simulate what will happen next year or in 20 years. Instead, the model provides information on a range of river, reservoir, and Delta water conditions that result from sequences of different weather conditions.
Cal Sim 3 can be used in two ways. The first is in a comparative mode, and the second is in a standalone mode. The comparative mode consists of comparing two model runs or simulations: one that contains the proposed project and one that does not. Differences in model results such as streamflows are analyzed to determine the effects of the proposed project. The model assumptions are less significant in a comparative study than a standalone study because all of the assumptions and data are the same for both the with-project and no project model runs, except the project itself, and the focus in the analysis is the difference in model results.
Model output is considered the most accurate when two or more simulations are compared, and results are expressed using statistical measures such as monthly averages for different water year types. The draft EIR will present Cal Sim 3’s simulated results for State Water Project and CVP operations, including storage Delta exports, including a North Delta diversion and State Water project deliveries. The draft EIR will also present streamflows at key compliance locations. And lastly, it will include simulated Delta channel flows, net Delta outflow, and the location of X2.
The draft EIR will also present DSM II simulated results for delta water quality. This includes electrical conductivity at D 1641 compliance locations, bromide and fluoride concentrations at municipal takes, dissolved organic carbon, delta water temperature, and other constituents of concern.
QUESTION: Do you use AI to make decisions with Cal SIM?
“No, we do not,” said Mr. Draper. “We talk to the operators of the Central Valley Project and State Water Project and formulate operating criteria and the basis used for making State Water Project allocations. And we code that using simple (sometimes detailed) linear equations. There are two types of equations we use in the model. One is a hard constraint; the model must do this to meet the regulatory requirement. And the second one is what we call a soft constraint in which we try to persuade the model to perform a certain action by assigning it a very high priority or a lower priority, but we do not use AI.”
QUESTION: How can a 94-year water average in Shasta happen when the dam wasn’t completed until 1945, which is only 76 years ago?
“Cal Sim 3 is not a predictive model,” said Mr. Draper. “It’s not a historical model. We are not simulating what happened in 1922 or what happened in 1924, which was an extremely dry year. What we’re doing in the Cal Sim 3 model is representing the existing world – the existing water resources of Central Valley, the existing infrastructure, all of those regulations that John Leahigh explained in his presentation. And then we use the historical weather sequence beginning in 1922 to represent varying conditions. So, in effect, we are saying that if a repeat of the 1922 temperature, precipitation, snow accumulation, and snowmelt runoff occurred today, how would the projects operate? So we are considering two sequences. We are considering one for existing conditions based on the historical precipitation, temperature, and flow available. And then, we are considering a second sequence for 2040 whereby the precipitation and temperature that has occurred historically has been transformed through the effects of climate change.”
QUESTION: Have the Cal Sim 3 and DSM 2 models been tested to understand accuracy and what conditions they best model? Have they been compared to historical information, or how have they been validated?
“I’ll address the Cal Sim III portion first,” said Mr. Draper. “The two models work in conjunction. I explained that Cal Sim III was unable to simulate Delta salinity, yet at the same time, we need to meet water quality standards. So there is a contradiction there. So we use a device called an artificial neural network, which is a statistical model that translates a water quality standard that we can’t directly model in Cal Sim III into a flow equivalent. There has been extensive work done or studies undertaken by DWR to validate that the flows provided in Cal Sim III to meet the water quality standards do in fact meet those lending standards by running DSM II studies using the Cal Sim flows.”
“In terms of validating Cal Sim III, I said it’s not a historical model; it is representing today’s regulations,” he continued. “So it is representing the 2019 biological opinions, and it’s representing the incidental take permits and those requirements. However, we have compared simulated data with recent historical data. So we’ve made detailed comparisons particularly focused on either a 20 year period from 1996 to 2015 or 10 year period from 2006 to 2015 where we look at simulated flows throughout the model domain and compare it with historical data and compare diversions, return flows, and stream gains along river reaches. So there have been very significant efforts to validate the model.”
QUESTION: Have similar models looking like either of these models been used for other river systems or projects?
“The Cal Sim 3 model is built on a generalized modeling platform called RIMS,” said Mr. Draper. “Cal Sim 3 is a particular application of RIMS to the Central Valley. The RIMS platform has also been used to model other systems, for example, the Klamath irrigation project, which straddles the border between California and Oregon. A RIMS model was built out of that system to look at the issues that they’re facing with climate change, similar to State Water Project in Central Valley Project: less water available for agricultural applications. So the answer is yes. But most of the focus has been on applying the RIMS platform for modeling the Central Valley.”
QUESTION: Is the Department going to make the Cal Sim 3 model and model results available?
“Yes, the state of California is working on releasing the Cal Sim 3 model,” said Mr. Draper. “That will be released certainly before the draft EIR, but I’m not sure of the exact timing. When we release the draft EIR, we will also make publicly available the results of the model that we are using within the draft EIR. In addition to releasing the Cal Sim III model and the simulations, I believe DWR and Reclamation are planning to release documentation, model schematic, and as much information about the model that has been developed by the two agencies.”
GENERAL Q&A
QUESTION: The State Water Board has not completed the Bay Delta Water Quality Control Plan which will determine flows in the Delta, so why is DWR planning for a project when it’s increasingly unclear how much water will flow through the project, especially given the project effects of climate change? Why is DWR more focused on putting billions of dollars towards a potentially unused and wasteful project when what the state agency needs is to worry about the seismic and climate resiliency of the existing State Water Project infrastructure?
“The purpose of this project is to work on the piece of the State Water Project that is within the Delta, so the Delta diversion and conveyance facilities,” said Ms. Buckman. “DWR is also working on other efforts that are parts of separate projects on resiliency for both seismic and climate issues. So there are other efforts, but this effort is focused on the Delta component of the State Water Project.”
QUESTION: How the facility would be operated is critical, especially in years such as this one. As an example of the state’s stewardship in the way that they operate the State Water Project, could you tell me what has the state done this year during this drought to ensure that there will be cold water for salmon this fall and winter?
“Largely what we’ve been thinking about as part of the Delta conveyance project is how the Delta Conveyance Project would be operated to be protective of sensitive fisheries resources and other terrestrial biological resources and comply with the Endangered Species Act and the California Endangered Species Act,” said Ms. Buckman. “Our focus has really been on future planning with the Delta Conveyance Project. And so, as we work through this process, and I will say we don’t have answers yet, a lot of that is related to the analysis of impacts. Our next meeting on August 3 is going to be focused on fisheries. And during that meeting, we will talk about some of the operational constraints that we’ve been considering specific to protecting fish. But a lot of the questions that you’re asking are more related to what the impact analysis shows and the mitigation measures that we incorporate so that we can be protective and operate during dry conditions in a way that is protective of fish. But again, our operations are focused on the Delta conveyance project and not the other upstream operations that are a bit separate.”
QUESTION: Is DWR going to present its operation plan for the SWP and CVP reservoirs as part of its operations plan for Delta conveyance, in particular, both in the EIR and in the hearings before the State Water Board? Will DWR be stating in numeric terms its initial operations criteria for bypass flow for the North Delta diversions on an upfront basis? To what degree is DWR planning to rely on real-time operations and adaptive management in stating its proposed operations for the North Delta diversions? And how is that quantifiable and understandable both for water rights purposes and process?
“I really want to be clear that at this point that the Bureau of Reclamation and the Central Valley Project are not a part of the Delta Conveyance Project,” said Ms. Buckman. “We are considering an alternative where it does include a connection to the Central Valley Project, but the Bureau of Reclamation has not expressed any interest. We’re only including that for comparison purposes just to understand how that would potentially change the impacts and benefits. But the CVP is not involved. So talking about an operations plan for the CVP – that certainly would not be part of this project because they are not engaged.”
“In terms of operating the Delta conveyance project, yes, we will outline our plan to operate the Delta Conveyance Project as part of the environmental impact report,” Ms. Buckman continued. “And right now, a lot of the more detailed questions that you were asking about the specific bypass flows and real-time management and adaptive management, we are planning to incorporate all of those, but to the extent and how I think is still a part of the discussion, because we’re working on the impact analysis and mitigation. We will be talking at the next meeting about the potential use of bypass flows as part of the operational criteria on August 3. But really, we won’t know where we come out until the impact analysis is done, and we see how our proposed operational criteria affect fish, and then we revise and reconsider based on those effects.”
QUESTION: “How do you justify spending the 16 to $40 billion of ratepayer of funds without putting this to a public vote? There’s no referendum; there’s no opportunity for the public to vote on this. It’s really just the agencies. I think you can tell from the huge amount of comments and questions, the public is very interested in this project.”
“Before a Delta Conveyance Project would move forward, the state would need to decide that it should move forward, as well as the agencies that would fund it,” said Ms. Buckman. “This is tied to a number of questions that we received in the Q&A about funding. John mentioned during his presentation that the project could be funded by contractors and people asked a number of questions about that. So just to tie that in for a minute, since we’re here, this project would not be paid by state taxes or by the state general fund but would be funded by the water purveyors that receive the water through the effort. So this is, at this point, a State Water Project-only project, and the water contractors that are part of the State Water Project could elect whether or not to participate. In the process of electing whether or not to participate, they will engage the public, they will follow their own processes in terms of understanding their ratepayers’ desires, and there will be plenty of chances for ratepayers to weigh in on those decisions. So there is an opportunity as part of the process that will move forward in decision making for all of that to happen, as well as the CEQA public process. So as when we release the draft EIR, we will have a pretty extensive comment effort where we will be collecting information and hearing public feedback.”
QUESTION: During the presentation that talked about CEQA and a lot of the environmental impacts that would be covered in the EIR, there was no reference that I saw of to cultural resource protection. What measures have been taken to work with tribal governments, such as a government-to-government consultation, on the protection of cultural resources throughout this project?
“When we first issued the notice of preparation to initiate the CEQA process, we did send letters to 121 tribes asking if they wanted to consult either under an AB 52 or under the DWR’s tribal engagement policy,” said Ms. Buckman. “We received letters back, and about 15 tribes have engaged in consultation, and out of that, I think about eight to 10 are really in very active consultation. So we are working with those tribes to understand tribal feedback and engage them in analyzing impacts and identifying mitigation.”
QUESTION: What do you think are the most significant limitations to the systems in determining whether the Delta Conveyance Project will impact water quality in the future? And are there any ways that we can improve upon that, or that you’re pursuing to improve that?
“I’m not sure whether the question addresses the limitations of the model or the uncertainties that we have in projecting conditions for 2040,” said Mr. Draper. “But I think those uncertainties are the biggest obstacle in determining what a 2040 environment could look like both in terms of climate change and sea level rise. The Department has considered a range of scenarios that are produced by global circulation models and uses what’s called an ensemble approach where all of those projections are considered. Those projections of sea level rise are changing every day or every year. So I think our biggest obstacle is coming up with a reasonable quantification of what the environment would look like in 2040 and to identify potential effects of the project.”
QUESTION: Why did you pick 2040? It seems like fairly soon in the future and may not represent the operational lifetime of the project. Are you going to do any other operational simulations for other future years?
“Let me start a little bit with CEQA requirements,” said Ms. Buckman. “So CEQA requires the comparison of an alternative to the baseline at the time of the publishing of the notice of preparation, which was in 2020. So much of the analysis to comply with CEQA looks at that 2020 baseline. And so it does compare under existing conditions, what the conditions would be with the project to the conditions without the project at that time. We are trying to provide more information and the EIR to be sort of good planners. And so that is one of the reasons that we are looking at 2040. Also, that’s a future period that the modeling is available for.”
“I’ve already mentioned the climate change piece and sea level rise piece,” said Mr. Draper. “Mostly, sea level rise is going to affect the amount of Delta outflow or net Delta outflow to meet water quality standards. But we’re also modeling all of the water resources of the Central Valley. So that includes looking at land use and coming up with land use projections. What is the urban footprint going to look like in 2040? What’s the agricultural footprint going to look like? What crops are going to be grown? We’ve used information from the 2015 urban water management plans to characterize urban water demands. The 2020 urban water management plans weren’t available when we started the modeling. So there is a land use base calculation of water demands on the agricultural side and estimates of urban demands coming from the urban water management plans. So those are just a couple of the inputs to 2040. And the land use data was developed by DWR as part of their California Water plan update. And they develop projections of land use through 2050.”
QUESTION: My first question is, is DWR going to present its operations plan for the State Water project reservoir as part of its operating plan for the Delta conveyance? Leaving aside the issue of the Central Valley project, is the SWP reservoir going to be part of your operations plan this time around? It was not during Water Fix.
“For the Delta conveyance project, we are not proposing reservoir reoperation upstream as part of the project,” said Ms. Buckman. “We recognize that there may be some small auxiliary changes to operations that occur because we’re changing things in the Delta. And we will analyze that in the EIR. But we are not proposing changes to the existing operations of Lake Oroville upstream. And the San Luis reservoir, we are not proposing changes there either.”
QUESTION: Is DWR planning to state its initial bypass flow requirements for the North Delta diversion in numeric terms? I’m not asking whether or not you’ve decided what those terms would be. Last time, we had a problem with the complete project definition under CEQA in stating what the initial proposed operations would be. Are you prepared to offer an initial numeric bypass flow proposal?
“I think that I might have to go back and better understand the concerns from the last time to be able to fully answer that, unfortunately,” said Ms. Buckman. “I think that we are planning to propose a set of bypass criteria for analysis. I’m not sure, though, what that is in terms of how that differs from California Water Fix. I wasn’t part of that project. But I can look into that. We can include that in the Q&A responses after the meeting.”
QUESTION: My question concerns Miss Buckman’s answer regarding a young lady who asked whether or not there was going to be any vote on this project. Her answer was pretty disturbing. She said that the conveyance project would be paid for by the South of Delta water districts that wanted to participate. So what I hear is that no matter how the people in the Delta feel or the negative consequences of this project, the people in the Delta don’t have any voice on something that could affect their entire lifestyle.
“I will say that I know I am a little bit of a CEQA purist, and I might be a little idealistic on this, but, in my mind, this is the main purpose of the environmental impact report, which is to really be able to characterize the potential effects of the project,” said Ms. Buckman. “So that is why we are out in public a lot trying to get feedback, and we’re working to include all of those potential effects within the EIR. So while there is not a vote opportunity, there is a lot of opportunities to make sure that those effects are characterized for the decision-makers, that they are taken into consideration, and that we evaluate them as part of the environmental process.”
QUESTION: What is the threshold when you say excess water? And who defines that?
“In terms of who decides what are required flows in the Delta, that’s the State Water Board through its water quality control plan review process that will determine what the appropriate amount of flows are in the Delta,” said Mr. Leahigh. “So that is the metric on which this is gauged in terms of what is considered excess to those required flows.”
QUESTION: Models should be reviewed by an independent board and validated in some way. How will this be validated? And who will be the independent reviewer?
“I’ll break down the Cal Sim model into various pieces to work through this question and answer,” said Mr. Draper. “I showed a plumbing diagram that Cal Sim uses to route water through the network, including Delta outflow and exports from the south Delta. It’s using simple flow balance or mass balance to do that. So that’s not part of the validation. The validation would consist of, do we have boundary inflows correct in terms of unimpaired flows from those mountain watersheds into the valley floor? Do we have a reasonable representation of agricultural and urban water use? And then lastly, are we representing the water manager’s decisions correctly?”
“There was a peer review of the Cal Sim model that was conducted in 2003, under the auspices of Cal Fed; that review is available on the internet,” Mr. Draper continued. “There was a response to DWR, and the development of Cal Sim 3 grew out partly from that review process. A lot of the simulation in Cal Sim 3 is driven by our characterizing of Central Valley Project and State Water Project operations. So the modelers have regular weekly meetings with the water managers to make sure that we fully understand what the managers of the State Water project would do under a particular set of circumstances, whether they’re wet years or dry years. That’s a difficult thing to validate because we’re trying to mimic operating criteria and policy. And we do that by talking to those managers and looking to see how well the model replicates operations in the last ten years. Is there going to be a further formal review of Cal Sim 3? I don’t think such a review is planned at the moment. You have to understand that Cal Sim’s been in use for 20 years; it’s been reviewed by DWR technical staff, Reclamation technical staff, fishery agencies, and consultants, such as Stantec. So it’s had a lot of scrutiny.”
QUESTION: About the occurrences of backflow coming into the Delta from the ocean system. So the proposed tunnel would decrease the occurrences of Delta backflow bringing saltier water back into the system. How often does this occur, especially in recent years? And what is the range of salinity increases seen historically?
“I think the question is referencing one of the diagrams that I presented in my presentation,” said Mr. Leahigh. “Another word for that is Q-West; it’s a metric that is an estimate of what that kind of reverse flow from the ocean into the internal Delta is. So that particular parameter becomes negative when there’s a high rate of pumping in the south Delta. So a rate that is significantly larger than the cross-Delta flow can handle, essentially. In drier years, such as this one, where there are extremely low export rates, those reverse flows tend to be lessened. And so you’ll see less of that kind of salinity intrusion. And one of the overall benefits from the additional diversion directly off the Sacramento River is that even in years where there would be a little bit higher overall exports because less of it would be coming from the south Delta, there would be less of a negative impact on that to Q-West flow. So, therefore, there would be less salinity moving into the Central Delta.”
QUESTION: Are the basis and facts for all of these calculations made public? I’m in Discovery Bay. And I’m looking at absolutely horrendous water qualities earlier and earlier on every year. Part of your project doesn’t seem to include all of the necessary components, which include the runoff from farmlands and what that’s doing to the water quality. So are there fundamental statistics of how these reports are created and made public?
“We mentioned earlier that the purpose of our project is fairly narrow; we are looking at the Delta diversion and conveyance facility,” said Ms. Buckman. “So I recognize that there are many, many other issues in California Water that are being addressed through other efforts, and we are somewhat narrowly focused. Andy, could you talk a little bit about how we’re documenting the work within the model to develop the model and release it as we move forward?”
“Documenting the model has been a huge, huge task,” said Mr. Draper. “We developed the seven model documentation in 2013. I believe there are over 500 pages describing different aspects of model data input, whether it was land use, whether it was unimpaired runoff, whether it was urban demands, the way we represent individual water rights holders and their water rights, the way that they’ve been grouped together. That report was updated in 2017 and will be updated again to include the latest information that’s been incorporated into the Cal Sim 3 model for the Delta conveyance project. So, all of that documentation will be available.”
“Just a note on how we simulate and characterize the Delta,” continued Mr. Draper. “I appreciate the Delta water quality can be poor. The simulation does include Contra Costa Water District Los Vaqueros Project, and so we will be looking at potential changes in water quality and delivered water quality as part of that water district as part of the effects analysis. I showed a network schematic of Cal Sim 3, and I called it a plumbing diagram. It was so detailed and complex, it looked like a mess of spaghetti over on the left-hand side of the slide. But we have tried to have a physically-based model that represents all the major flow components of the Delta and the upstream watersheds.”
“I did want just to mention that part of the point of the draft environmental impact report is to document a lot of the work that we’re putting into this,” said Ms. Buckman. “So we will be documenting our assumptions and our analysis and really quite a bit of detail in that document. So that will be available next year when we release that for review.”
