At the January meeting of the Delta Independent Science Board, the board members heard a series of presentations on water management in the Delta to orient new members to the complexities of science and management issues in the Delta. The presentations were also in response to the recent review of the DISB that suggested the Board become more familiarized with the realities of Delta science and management.
The first presentation was from Kristin White, operations manager for the Bureau of Reclamation’s Central Valley Project (or CVP) covered in this post. She was followed by John Leahigh, the Deputy Division Manager for Water Operations for the State Water Project, which is the subject of this post. The third presentation was from Carrie Buckman, Environmental Program Manager with the Department of Water Resources provided an overview and an update on the Delta Conveyance Project. That presentation will follow tomorrow.
John Leahigh is the Deputy Division Manager for Water Operations for the State Water Project. In his presentation, he provided an overview of the State Water Project and its facilities, the operational challenges focusing on the variable hydrology and Delta constraints, and the allocation process for the State Water Project contractors.
California’s hydrology
Much of the rain and snow falls in the northern part of the state, but most of the state’s population is in the Bay Area and Southern California. Besides the geographic disparity, there is the seasonal disparity: most of the precipitation falls in the winter months, primarily December through March, with the snowpack melting from late spring into the early summer. However, demand is highest during the summer months.
“So the pumps and the canals of both projects are there to remedy this geographic disparity between where the water supply is and where most of the demand is,” said Mr. Leahigh. “In terms of the temporal disparity, the reservoirs remedy that by capturing direct runoff and snowmelt in the winter and spring, and then releasing that later during the higher demand periods.”
State Water Project Facilities
The map shows the major facilities of the State Water Project, which extends from Lake Oroville in Northern California to Lake Perris in Southern California.
The State Water Project’s primary reservoir is Lake Oroville, located on the Feather River, used for water supply and flood control purposes. The water released from Lake Oroville flows down the Feather River, where it joins with the Yuba River, the Sacramento River, and then flows into the Sacramento-San Joaquin Delta.
Clifton Court Forebay, located in the South Delta, is the primary diversion point for most of the State Water Project’s water. There is a smaller diversion point at Barker’s Slough in the north part of the Delta that supplies water to Solano and Napa counties. The South Bay Aqueduct conveys water to Santa Clara and Alameda Counties.
The Banks Pumping Plant pumps water into the California Aqueduct, which flows south to the San Luis Reservoir, a joint state-federal facility. The San Luis Canal, one reach of the California Aqueduct, is part of the joint facility that delivers water to Central Valley Project contractors.
While most of the major facilities were constructed in the 1960s, the project has continued to grow. The Coastal Branch, which services Santa Barbara and San Luis Obispo counties, was built in the 1990s. The East Branch and the West Branch of the California Aqueduct convey water into Southern California; the East Branch was recently completed in the 2000s.
Water supply and flood control are the two biggest purposes for the project, specifically Lake Oroville. There is also fish and wildlife preservation and enhancement, hydropower and California power grid support, and public recreation.
The State Water Project has over 30 storage facilities; Lake Oroville and San Luis Reservoir are the two largest storage facilities. There are 29 pumping and generating plants; some are both pumping plants and power generators. There are over 700 miles of canals and pipelines.
He presented another map of the State Water Project with a graph showing the elevation profile. The elevation profile illustrates one of the big differences between the State Water Project and the Central Valley Project: The Central Valley Project is a net power generator; the State Water Project is a net power consumer.
The State Water Project’s major power facilities are at Lake Oroville, a significant generating facility, and three other power generating plants; however, the elevation and the head differences are not that great. There are a series of pumping plants along the California Aqueduct, a big lift to get over the Coast Range to deliver to San Luis Obispo and Santa Barbara Counties, and an even larger lift over the Tehachapis to deliver water to Southern California.
“It takes an enormous amount of power to lift the volumes of water that are provided to many of our customers down in Southern California,” said Mr. Leahigh. “There are several recovery generating plants that do partially recover some of that energy that took to lift the water over the Tehachapis. Through the use of timing and a lot of regulating reservoirs, it helps provide the opportunity to pump when power is cheaper and generate when power is most in need. So that’s an opportunity to offset some of those costs of lifting that water over the Tehachapis.”
Oroville Complex
Lake Oroville is the main water supply reservoir for the State Water Project. It holds 3.5 MAF, and inflow is a little over 4 MAF on average per year. Oroville is an earth-filled dam with a concrete core; at 770 feet high, it is the tallest dam in the United States – even taller than Hoover Dam.
The gated spillway has a capacity of 290,000 CFS, though releases per flood control rules are around 150,000 CFS. Oroville Dam is the largest hydropower plant in the entire portfolio for the State Water Project, producing about 900 megawatts.
Edmondston Pumping Plant
The Edmonston Pumping Plant is the highest pump lift in the world, lifting water 1926 feet up to cross the Tehachapis. The 14 80,000-horsepower plants have a capacity of 4480 CFS; the load from the plant is 840 megawatts.
“To put that in perspective, that’s almost as high as what Oroville complex can generate in terms of power,” said Mr. Leahigh. “It is the same amount of power that at full load, the Edmundston pump would be utilizing to pump over the Tehachapis. So it is the largest contributor to the pump load for the project.”
State Water Project contractors
When the State Water Project was constructed back in the 1960s, 29 different water supply agencies contracted for the water. The map on the slide shows where those contractors are located.
The State Water Project serves primarily urban water users, with the notable exception of Kern County and a few other smaller contractors.
The largest contractor is the Metropolitan Water District of Southern California, with just under half of the contracted amount. The second-largest user is Kern County Water Agency, an agricultural user, with about a quarter of the contracted amount.
Challenges to project operations
Mr. Leahigh noted that the challenges that Kristin White listed for the Central Valley Project certainly apply to the State Water Project, such as aging infrastructure, subsidence, and those types of issues. However, he will focus on variable hydrology, flood control requirements, and Delta operations challenges.
Variable hydrology
California has a large variability of the annual water supply – in fact, the most varied water supply of any state in the country. The map on the lower right shows the standard deviation over the mean annual precipitation, a measure of the range of variability of precipitation. The eastern part of the country has more or less the same amount of precipitation every year, but as you move out west, Northern California becomes quite variable, and in Southern California, even more so.
California relies on just a few storms each year to provide the bulk of the state’s water supply. Once known as ‘pineapple expresses,’ these storms are now called atmospheric rivers. The map on the upper right shows the number of days per year to receive half of the precipitation; it’s only 10 to 15 days for California.
The chart below shows annual runoff over the last 100 years for both the Sacramento Valley and the San Joaquin Valley. The State Water Board has established classifications for water year type depending on runoff: wet, above normal, below normal, dry, or critically dry.
Mr. Leahigh noted the variability for both the Sacramento and the San Joaquin Valleys. Although there’s usually a good correlation between two basins, there are a few years with some differences.
The chart below shows the variation of runoff by month. Green is the average runoff, blue is the highest inflow (1983), and red is the lowest (1977).
“March is generally our highest runoff month because of a combination of direct rain and melting snow,” said Mr. Leahigh. “But then you can see the orders of magnitude difference between a dry year and a very wet year.”
Challenge: Flood control requirements
One of the effects of a warming climate is the increasing disparity between the already challenging variability. One of those areas where that challenge exists is in the flood control requirements at the reservoirs.
Every major reservoir in the state has a requirement to provide vacant space in the wintertime when atmospheric rivers are likely to occur. This space is needed to absorb a large amount of inflow into the reservoirs and to be able to release the water at a slower rate that fits within the levees and channels downstream.
The graphic below shows the rules for Lake Oroville. The dashed black line is the flood regulation rules for storage boundaries. He noted this can vary through the year. “For Oroville, it’s based on how wet the watershed is; the wetter the watershed, the more space we need to provide, because it assumes that we would see larger inflow into the reservoir given the same amount of precipitation, so we need to provide additional space,” said Mr. Leahigh.
“This is the big dynamic play between two purposes: flood control and water supply. So there is a need to understand the dynamics of these atmospheric rivers and be able to forecast them better because this is really where the rubber meets the road in terms of the trade-offs between water supply and flood protection.”
Forecast-informed reservoir operations (or FIRO) is a reservoir-operations strategy that uses enhanced monitoring and improved weather forecasts to inform decision-making to either retain or release water from reservoirs to maximize water supply.
The State Water Project has partnered with Yuba Water Agency as both agencies are responsible for meeting common downstream flood control points on the Feather River, and the Yuba is a major downstream tributary to the Feather River.
The partnership includes the Army Corps of Engineers, NMFS, and Sonoma Water. Sonoma Water is one of the earliest FIRO projects in California at Lake Mendocino, so they are part of the steering committee, helping to provide input and lessons learned from their process. The partnership aims to identify improvements in weather and runoff forecasting and look for ways to leverage increased capabilities and skills to modify the flood control rules for both New Bullards Bar on the Yuba River and Lake Oroville on the Feather River.
Challenge: Delta operations
Another major challenge is the Sacramento-San Joaquin Delta, where the Sacramento and the San Joaquin Rivers join before flowing west into San Francisco Bay and the Golden Gate. It is the hub of California’s water system and the largest estuary on the west coast of both Americas.
“It’s both water supply and fishery habitat, and it’s inherent that there would be challenges in trying to manage both those systems,” said Mr. Leahigh.
Hydrodynamics in the Delta are complex. Up until the water enters the Delta, it’s a riverine system, a river flowing downhill. Once the water flows into the Delta channels, it enters a tidal system, where flows reverse twice a day. The graphic shows the magnitude of the tidal fluxes in the Delta. In Suisun Bay, over 300,000 CFS sloshing back and forth twice per day on the ebb and flood tides. There is still significant tidal variation extending into the Delta’s channel system.
Besides the daily tides, there is also a monthly cycle with the spring and neep tidal cycles. There are six to seven days of building towards a spring tide where the average stage in the Delta increases by a foot or so; that is followed by seven days of the slow draining of the Delta. That cycle repeats twice per month and is overlaid on top of the daily variation.
The tidal variations bring saltier water from the ocean into the Delta channels. So as the tides flow in and out, the salt does as well, which has a large effect on the tidal estuary that is habitat to state and federally listed species.
The figure below shows the salinity intrusion into the Delta pre and post-construction of the upstream reservoirs. In drier years, there would be salinity intrusion far into the Delta.
“For there to be a reliable, continuous supply to both users within the Delta and the major intakes for the Central Valley Project and State Water Project in the South Delta, job one is to provide a hydrologic barrier to provide a freshwater corridor through the cross channel, down through the Central Delta, and then Old and Middle River towards the pumping facilities in the south Delta,” said Mr. Leahigh. “That’s also related to the standards that we have to meet as part of our water rights with the State Water Resources Control Board.”
There are two major types of Delta regulations:
Water Quality Control Plan objectives: There are three: municipal and industrial water supplies, agricultural supplies, and fish and wildlife. These regulations are fairly prescriptive, much like a lookup table; given the water year type and the month, ‘X’ is the amount of outflow required or the amount of salinity level required at certain locations throughout the Delta.
State and federal Endangered Species Act protections: Although certain ecological triggers for actions fall under these regulations, it is based on monitoring much more than a fixed prescriptive reduction. Much of the actions are based on a range of flow targets informed by real-time observations within the Delta of both fishery and non-fishery type data that is constantly monitored.
The graphic shows the telemetered monitoring stations which measure flow and salinity and is publicly available through the California Data Exchange (CDEC). These monitoring stations are maintained by the Department of Water Resources, the Bureau of Reclamation, and the USGS.
There are also fishery monitoring programs such as the Kodiak trawl and other special monitoring efforts to manage to the requirements of the biological opinions and the incidental take permit.
The Bay-Delta standards from the State Water Board are displayed on the slide below. He noted that it is divided into flow standards and water quality standards.
The slide below shows the requirements from the 2019 biological opinions for the long-term operations of both the Central Valley Project and State Water Projects. Mr. Leahigh emphasized that both projects are responsible for meeting the requirements.
The chart below shows the requirements on the State Water Project for the Incidental Take Permit issued by the Department of Fish and Wildlife. These are the requirements of the California Endangered Species Act.
He said there is significant overlap with the biological opinions, but there are some differences. “For the most part, we’re protecting the same species during the same life stages and the same months. There are a few additional actions in the Incidental Take Permit. There are some actions for Suisun Gate operations from the biological opinions and additional summer actions for the State Water Project in the ITP. There’s also spring outflow action in the ITP for the State Water Project.”
Another difference is that some species are listed under the California Endangered Species Act but not federally listed, such as the longfin smelt. So there are actions for the longfin smelt in the Incidental Take Permit.
When needing water to meet requirements in the Delta, the Coordinated Operations Agreement outlines under what conditions which project is responsible for what proportion of flows that are required. This could be in the form of releases from upstream reservoirs or a reduction in pumping from either the State Water Project Banks Pumping Plant or the Central Valley Project’s Jones Pumping Plant.
How the State Water Project develops its water supply
Similar to the Central Valley Project, the State Water Project has also entered into contracts with settlement contractors who have senior water rights; the State Water Project must ensure those needs are met before developing water supply.
“The winter-spring period is when there is additional water that is excess to all the other needs, including all other legal diverters of water plus meeting the standards in the Delta,” said Mr. Leahigh. “Anything in excess of that is when the State Water Project would be capturing water in Lake Oroville. For direct runoff in the valley itself, there can be a significant amount which is captured at the Banks Pumping Plant and stored in San Luis Reservoir.” He also noted that typically, there is low demand at that time of the year.
When there is high demand during the summer and fall, the State Water Project releases previously stored water from Lake Oroville. Water in excess of the Delta requirements can be released from Lake Oroville and rediverted at the Banks pumping plant for delivery south of the Delta. Water stored in San Luis Reservoir can also be used to meet demands south of the Delta.
State Water Project allocation process
The slide shows some of the key elements considered when determining the allocation of the State Water Project. These include storage in Oroville from the previous year, forecasted hydrology for inflows into Oroville and the Delta, and unregulated flows into the Delta.
“We need to know the timing of that on a monthly basis, so we get that information from DWR’s Division of Flood Management,” said Mr. Leahigh. “They also coordinate the snow survey process. In cooperation with the Forest Service and other water districts in the various watersheds, they go out and physically measure the snowpack, compile the information, and run it through their models to come up with forecasted inflows to all the major reservoirs on a monthly basis for the coming year at various exceedances.”
“So anything from a dry scenario 90% exceedance, to median conditions for precipitation that’s assumed for the rest of the year, to a wet condition that would only be exceeded 10% of the time; there’s a full range of probability forecasts that we receive. We base our allocations on the more conservative number. We also take into account all of the Delta restrictions, and we come up with Banks pumping capabilities.”
“The timing is really important in terms of how much of that water can be stored in San Luis. And then ultimately, we get our delivery capability estimates for the year.”
The State Water Project contracts require a December 1st initial allocation. Since that date is very early in the season, it’s primarily based on the amount of storage that we have carried over from the previous year and a conservative assumption of the amount of precipitation that will fall for the remainder of the year.
The initial forecast is on December 1st, and there are subsequent updates each month based on the snow survey information and any projected Delta regulations that would come into play. The final allocation is typically made by June.
The graph on the slide below shows the State Water Project allocation since the project came online in the 1960s. The blue line shows the requested water from the contractors, and the green bars show how much the project delivered.
“The requested demand from our 29 contractors has changed over the years,” said Mr. Leahigh. “So you can see that demand got to the full build-out by about the year 2000. Early on, we were, with a few exceptions, such as 1977, we were able to meet the requested demand. We started to come up short in the six-year drought in the late 80s-early 90s. We met it again during the wet late 90s period.”
“But for the last 20 years, requested demand has been at its full Table A amount, which is a little over 4 million acre-feet. But we’ve also seen what some would call a 20-year drought. We also had some of the more restrictive regulations kick in since 2008 2009. So the combination of drought and more regulation has put us in this essentially chronic shortage condition on the State Water Project that we haven’t been able to meet 100% delivery since 2006. And so that’s how we got where we sit today.”
QUESTIONS AND ANSWERS
QUESTION: I was intrigued by the long history of flow, or maybe it was precipitation that John presented. Have you ever looked at whether the variability of flow has changed, or is the management challenge really that demand is so close to supply at this point?
“We’re definitely looking very closely at any changes to not only precipitation patterns, but more fundamentally, the runoff patterns because that’s really where the rubber meets the road in terms of what we’re actually managing,” said John Leahigh. “So a lot of the forecast for climate change as it relates to Northern California is a mixed bag in terms of the total amount of precipitation.”
“But the very strong signal is the warming,” he continued. “We’re seeing things that were not even anticipated to be observed until mid-century. The lack of any significant snowpack in 2015, for example, was a huge change that we hadn’t seen anything like it historically. What we saw last year, for example, in terms of the low efficiency on the snowmelt, both in terms of evaporation and very parched soils, caused very large losses to that snowpack. As a result, we saw very little runoff.”
“What we see already in the observed record, really pronounced since about the year 2000, is the warming trend. We don’t need models to indicate a change there; we are observing it. That’s having some profound effects in terms of the actual timing of runoff and the amount of runoff that we would expect to see from a given amount of precipitation. So precipitation itself – unfortunately, it will continue to be a challenge in terms of variability from year to year. But one thing we do know, though, is that the warming that we have experienced is going to change those runoff patterns.”
QUESTION: You seemed a little frustrated that you have to do these initial allocations in December. Has anyone ever looked at how your final allocations relate to your December allocations, and how accurate are they? And then, given that, has there been any discussion of changing when you do your initial allocations?
“For the initial allocations done in December, typically we use a conservative estimate for precipitation for the remainder of the year or the runoff for the remainder of the year,” said Mr. Leahigh. “Typically, we use the 90% exceedance as a rough guide. So this is based on historical trends. We look at the 100-year history, we take a look at 100 different traces for the remainder of the year, and we look at the runoff that would be achieved from that precipitation that exceeds that amount by 90% of the time. So it’s, it’s the lowest and the driest ten percent.”
“What we would expect is that since we’re making a fairly conservative estimate on their future runoff, the allocation level that we set will be good 90% of the time, though 10% of the time that the water doesn’t show up, we would have to reduce that allocation. That’s pretty close to what we’re observing. So there are instances where we have to make reductions in the allocation. Last year was a good example; we started with a 10% allocation for the State Water Project, and we had to cut it in early spring to 5%. So, last year was a really good example of the hydrology turning dry very dry on us. It was a dry year to begin with, but we ended up seeing the driest April through June, well, really April through September period on record, the warmest and driest, and so it had an effect. But that’s the management decision; the policy decision right now is to make allocation decisions based on 90%.”
QUESTION: Assuming that conveyance structures are built, what will be the biggest changes in the operation of the water system in the Delta? How will it impact your operations?
“In the winter-spring period, we’re essentially capturing those excess flows coming into the system,” said Mr. Leahigh. “We are capturing some of them upstream into Lake Oroville, but also a significant amount of runoff occurring from the rain hitting the valley floor or unregulated rivers that are coming into the system. So this is an opportunity to capture some of that supply and put it in San Luis Reservoir.”
“Unfortunately, this is also the habitat for listed species, so we have a lot of restrictions on when we can actually pick up excess flow. The idea behind the new conveyance is by locating the intake structures on the northern part of the Delta, it would improve at least some of that conflict with the Old and Middle River corridors; those are thought to be significant in terms of trying to limit how net negative those flows go. If we can capture the water more upstream, it would eliminate some of that conflict. It could allow the capture of additional excess flows coming from the Sacramento Valley into the export locations here in the South Delta because it’d be bypassing the Delta. So that’s the primary change that would affect the State Water Project operations.”
“It depends a little bit about how the final project comes together and what kind of operating approach is used on it,” said Kristin White, Central Valley Project Operations Manager. “There’s a big difference between the Central Valley Project and the State Water Project; the Central Valley Project is called ‘storage rich and pumping poor.’ And the State Water Project is the opposite. We have numerous upstream reservoirs, and although our pumping plant is very large, it’s much smaller compared to the State Water Project’s facility. I think we’re less than half of the total capacity that they have, so whereas the state can capture a significant amount more excess flows in the systems, we’re quite limited by our facility. So I think there will be opportunities when those fishery regulations are limiting how much we can move, and those tunnels can help move water without impacting those fishery impacts; that’s certainly something that can benefit both projects. But in general, it’s challenging to see exactly how it’s going to affect the CVP. It depends on what kind of operating rules and how we work with the state on that project.”
QUESTION: I heard from both of you that you emphasize the importance of monthly and seasonal planning, especially given regulatory constraints. How are you thinking about long-term planning? Are you taking into account climate change or changes in demand? Also, how does that work for the coordinated operations agreement? Is there some long-term mechanism where that gets updated regularly?
“In terms of the update of the coordinated operations agreement, that agreement does call for periodic review,” said John Leahigh. “In fact, there was a recent addendum to that agreement at the end of 2018. So, yes, this is something that we take a look at periodically, especially if there are significant changes to the regulations we’re operating to. Or any other observed changes that we see in the system.”
“One of those changes has been the more extreme conditions that we’d seen of late … the wettest year on record 2017 was shortly followed a year with no snowpack, 2014-15, what we thought was a once in a generation type event, and yet 2021 was in some respects, drier than what we saw in 2014-15,” he said.
“There are a number of efforts in terms of responding to this in the long term. For the State Water Project, San Luis Reservoir is operated on an annual cycle. We attempt to fill as much as possible in the winter and then release it in the summertime. So that’s looked at it on an annual basis. Lake Oroville is looked at more long-term. But it’s really a trade-off between water supply reliability one year versus long-term yield. But in light of 2014-15, we decided to make some changes to our carryover storage; for example, at Lake Oroville, we’re relying on carrying over more to protect against these kinds of 14-15 types of bands. And in fact, that’s something we put in play, just before the last two-year period, and it was still a struggle.”
“The other thing that we’re looking at is forecast informed reservoir operations,” continued Mr. Leahigh. “So we’re looking at new ways to store water when it is available because there are still many periods when there’s ample amount of water in the system. In fact, we’ll see more extreme cases where there are large amounts of flows, so how do you capture that flow when it’s available? So you can look at physical infrastructure. And we’re partnering with a lot of WISP projects under Prop 1, managed by the California Water Commission. A lot of those projects depend on the State Water Project and Central Valley Project to help implement these projects and make them work. So that’s an effort that’s underway. We want to be supportive of new storage opportunities where it makes sense.”
“The FIRO process up at Lake Oroville and New Bullards Bar is looking at ways that; part of it is digging a deeper hole in advance of a large and more extreme atmospheric river event on the flood side of the scenario. But on the flip side of that, it’s just as important to be able to forecast when we’re going to hit a prolonged dry period. One of the things we’re seeing with climate change is that we get stuck in these patterns for longer periods of time. So it’s either wet for a longer period or dry for a longer period than we have seen historically. And so if we’re able to predict those dry periods better as well, if we’re in the part of the year – late winter, early spring, where we can start filling that reservoir sooner than we do today, there’s a potential increase in additional supply that could be used for multiple purposes. So that’s a way to increase storage capabilities without physically building any new infrastructure. That’s just changing the operating rules at the reservoir, a software change rather than a hardware change. But that’s a way to help improve the ability to capture these more episodic events.”
“Groundwater storage is certainly another one,” he said. “A lot of Water Storage Investment Program projects are groundwater storage facilities that will interact directly with some of our state water contractors and will be partnering with these groundwater storage proposals up and down the California Aqueduct. So we will help facilitate the recharge of those facilities and the extraction during the drier periods. So those are all activities directly related to the increased struggles that we see in pairing up that supply with demand. And this is where all of our attention is now.”
Kristin White agreed with John Leahigh and noted that storing wet year water as a buffer is important. “When we think about reclamation projects across the state, the Central Valley Project provides a very critical water supply for a critical food source. Sometimes it gets lumped in with some of our other projects, such as the Colorado Basin, where we have Hoover and Glen Canyon dams, but our storage is nothing compared to what kind of storage they have there. For example, Shasta Reservoir, our largest reservoir, is only 4.5 MAF, whereas Hoover and Glen Canyon are over 50 million acre-feet. They’re just significantly larger amounts of storage, which affords them the ability to look more long-term and make those software adjustments to account for things that are changing. Our reservoirs are much smaller; they all work together, but they each have their unique characteristics, and so our operating window is significantly smaller.”
“We used to say that Shasta is a three-year reservoir, meaning it can be relied upon to get to get through a three-year drought; Folsom is a one-year reservoir, meaning it can be relied on for one dry year, but there’s not enough storage to go much beyond that,” she continued. “However, over the past 30 years or so with winter-run endangered species, there’s been a significant focus on temperature management. In Shasta, we had a temperature control device constructed in the 90s. So that really limits our ability to pull that reservoir down too low. So, for example, in 1977, which was the drought most similar to last year, the reservoir was pulled down to about 500,000 acre-feet. So, of course, we’d like to keep it higher than it ended last year. But there’s a big difference in how it was managed prior to those species being listed versus today.”
“What that’s done has limited the operating window at Shasta; going much higher than that bumps you into that flood risk, so we find that if we end the reservoir too high, all we’re doing is increasing that risk and increasing the impact of storms that could be coming in the winter,” Ms. White continued. “And what we’re seeing with climate change is that we can expect to see more extreme events, meaning that those very large warm storms could be coming in more frequently, which means we need to prepare for them. So there’s a huge risk to end the year with very high storage in case the next year is dry.”
“So it’s certainly a balancing act. And given the tools we have right now, it’s a major challenge just to do software updates. I think it is looking at how can we get better at moving water from those wet years into dry years because our current capacity and our current facilities are quite limited.”
QUESTION: I noticed in one of John’s slides, he used the term ecological triggers. What do you mean by that? What kind of an ecological trigger feeds into this?
“A couple of triggers would be flipped,” said Mr. Leahigh. “One would be flow. For example, one of our actions can be triggered by a certain flow threshold coming into the Delta on the Sacramento River. But another significant one that’s been around now for quite a while is turbidity. If we observed a certain turbidity level at key stations within the central Delta, that also is an indication of Delta smelt habitat; they typically follow the turbidity during their lifecycle. When the adults move upstream, they will follow the turbidity. And if the turbidity moves into a location, that could put their larva at risk later in the season. So the reason for the moderation of the exports is to prevent that turbidity condition from getting too close to the project pumps, so that there would be that increased risk later in the year to the offspring of the adults.”
“The Delta cross channel gate is a significant piece of our salinity operation, but it certainly can have major impacts to fish when they’re moving past those cross channel gates,” said Ms. White. “So we do have certain time periods where closures are required based on fish that are caught in certain areas.”
QUESTION: The water system here is pretty complex and extends to the thousands of retail water systems and many other wholesale systems. The large projects often supply wholesalers that provide water to other wholesalers and retailers. How important are the operations of all of those other customers and their ability to manage and store water and their independent sources to the system’s overall success?
“I can speak to some of the State Water Project customers and wholesalers,” said Mr. Leahigh. “The Metropolitan Water District of Southern California has their experts, and they monitor the project operations very closely. And I think a lot of their decisions regarding their investments are based on the limitations that they see on the State Water Project operations. So, for example, Metropolitan has invested heavily in local storage; Diamond Valley reservoir is a good example of that. … In the past, we were always able to meet 100% of their requests, but it became pretty clear that that’s not going to continue to be the case; it’s going to be feast or famine. So they wanted to be prepared; they wanted to invest in ways to capture the feast years. And so that’s the reason that they’ve invested in both groundwater storage, the Hayfield groundwater basin is a good example, and Diamond Valley is a good example of surface storage.”
“Same for Kern County Water Agency; they’ve invested heavily there,” continued Mr. Leahigh. “They have a high capacity turnouts off of the California Aqueduct, so they can capture more supplies to recharge their groundwater basins during the very wet years. That will help the sustainability of that groundwater program down there. So they’ve reacted to what they see as a limitation of the project’s ability to reliably deliver water on a year-to-year basis. So that’s a couple of examples of how some of our largest wholesaler customers have responded.”
“When we get into these drier years there, it’s critical how they manage their water supply,” said Kristin White. “I’ll give a couple of examples. How some of our agricultural areas are managing their groundwater is very important because it dictates how much groundwater can be used for meeting some of those supplies, which then affects how they would look at and how they would prioritize surface water supplies, especially when it comes to senior water rights or riparian water rights that are not under our allocation structure from the project. So the more that they can be relying on those groundwater supplies, the less pressure it is on the surface water.”
“Last year, we had a 25% municipal and industrial allocation, which is right around the public health and safety limit for some districts,” she continued. “The way that we define public health and safety demand is it’s the amount that’s necessary to meet certain minimum demands after accounting for all the other water that they have. So how much they’d been able to store in their other facilities, or how much they’ve been able to put into a groundwater bank or, or any other tools, or how much they’ve been able to lower their demands all play a critical role in what we’re delivering for public health and safety. So if we have a district asking for public health and safety, and their surface water reservoir has a challenge where they can’t store water there. Now, that’s a huge impact on what we’re doing because now it changes how much we need to supply them just to meet some minimum public health and safety. So it can certainly matter quite a bit when we get into these dry year and drought years.”
QUESTION: There’s been a huge change in the electricity prices over the last decade, with solar power providing a lot of relatively cheap electricity during the daytime. It has turned the daily pattern of energy prices on its head. Does that change your operations much?
“For the CVP, it doesn’t change operations on a daily or a weekly basis, but it certainly changes we’re releasing from major facilities such as Shasta that’s going into a regulating reservoir such as Keswick reservoir,” said Kristin White. “So the water to the river is maintained by Keswick so that it stays constant. But we’re fluctuating Shasta based on the power prices throughout the day. I think we used to have a little bit more stability. Now with solar, there’s a huge amount of solar in the market, but it pretty much goes offline at three o’clock, so then there’s a massive demand at three o’clock. So that’s been a big challenge, especially when we get into these extremely high demand situations that we were in this past summer and the year before that as well, where we’re trying to constantly adjust and backfill where that solar is, which is certainly a different situation than when we were in producing power ten years ago.”
“From the State Water Projects perspective, it’s recognized that there’s been a very significant change in our pattern,” said John Leahigh. “Prior to all the renewables coming online, it was much more predictable, in terms of high prices during the middle of the day and low prices during the night. And so, like clockwork, pretty much the same schedule, maximize that pumping at night and maximize generation during the day. It’s made it much more variable because solar has pushed down the peak during the middle of the day. But as Kristin said, then that price goes sky high once the solar goes offline in the evening. So it’s a much different pattern than we used to see.”
“One of the things that hydropower really represents is it works very well with other renewables in that it’s quick on and off in terms of responding to, say, a change in the wind,” said Mr. Leahigh. “That’s the weak point with the wind and solar is you can’t control when the fuel is being provided; you’re at the mercy of Mother Nature there. And so the other parts of the system have to respond to that unmanageable time period that the renewables present, so it’s had pretty significant impacts on the scheduling on the State Water Project, as well.”
QUESTION: Has it affected your operation at Clifton Court Forebay much, particularly as it interacts with the Old and Middle River flows and things like that?
“Not Clifton Court necessarily that much, but Banks Pumping Plant, yes,” said Mr. Leahigh. “We’re fairly restricted on when we can divert water in Clifton Court based on the high tides, so it’s the tidal cycle that’s going to drive the Clifton Court diversions; that part is fixed, but Banks is going to be variable. So that’s what Clifton Court provides us is that ability.”
