She provided an overview of the State Water Project facilities, project purposes, key agreements and requirements under which the State Water Project must operate, Delta operations, how the water allocation to our contractors is determined, and the challenges they face in operating the State Water Project.
There are several key agreements and requirements under which the State Water Project operates.
There are also State Water Resources Control Board permit and conditions: Water Rights Decision 1641 has water quality and outflow standards that both the Central Valley Project and the State Water Project have to meet; there is also a water quality certification for Lake Oroville as part of the hydropower relicensing.
“One thing in managing for fish, we’re seeing more of increasing requirements for fish protection and enhancement, but we’re also seeing actions upstream and in the Delta,” Ms. Petitt-Polhemus said.
The Sacramento River flows in from the north; three-quarters of the water in an average year is from the reservoirs; in drier years, up to 90% of the inflow coming into the Delta is from reservoir releases, Ms. Petitt-Polhemus said.
“We use forecasts to help with our inflows or flows, and that helps with planning and how we operate in the Delta.
There is also the Delta consumptive use and return flow from the over 1800 agricultural diversions in the Delta; they are taking water out, and then you have their return flow coming from their irrigated lands, and so that has an effect on water quality and flow and the hydrodynamics within the Delta.” There are also the tidal conditions.
“What happens is, when you think of the exceedance probabilities, you have 50 and a 90, and eventually the 50 is going to go the 90 or the 90 is going to up to the 50, and we’ve seen that this year in our allocations, we had a lower allocation and our final allocation is 100% for north of Delta and 85% for south of Delta, and that’s because the 90 moves up to the 50%.” Storage conditions are also considered, not only what’s in State Water Project reservoirs, but also the reservoirs within the Central Valley Project.
There are a lot of operational challenges for the State Water Project.
“There are times where we’ve operated to one of the State Water Resources Control Board objective versus a biological opinion, and we’ve seen that conflict, or a trade-off in the sense that if you take an action now for Delta smelt, how is that going to affect the fall salmonids, so you can have conflicting standards on species.” There are also changing in-basin demands, the timeliness of real-time monitoring, Delta uncertainty and variability, power scheduling, and facility outages, as well.