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Delta diversions
Inflow, exports, outflow, and the floor on one axis.
By water year or month, with the reason the pumps ran below capacity and allocations announced beside exports realized.
Open the chartTwo claims about California's rivers
Two basic narratives exist about Delta outflow. One claim says California wastes water by letting it run to the ocean. The other says the state and federal pumps are draining the Delta. Each is usually stated as a single percentage: the share of the rivers that reached the Bay, or the share that the pumps took.
In a wet year the pumps may run near capacity for months and still take a small share, because most of the river passes through in a few winter weeks that no pump could move or reservoir could hold. In a critical year the same pumps take a larger share of a smaller river, and on most days the reason they take no more is that outflow already sits at the legal floor that keeps salt out of the Delta and its intakes. The same percentage can describe an availability limit in one year and a rule limit in another.
California has always needed to manage water across multiple years, storing water from wet years for use during dry years. The variables constraining California's ability to do so are complex.
The pages here put inflow, exports, in-Delta use, outflow, the floor, and the reason on one axis for every water year since 1996, and month by month, so a reader can see which claim the numbers support in which year.
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of inflow was exported in critical water year 2022, against … in wet 2023. The higher percentage came with … pumped; the lower one with …. The share rises when the river shrinks.
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days in water year … a standing rule, permit term, or biological opinion held exports below capacity while surplus water existed, against … days when there was no surplus above the floor to take.
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left the Delta above the outflow floor in wet water year 2023, most of it in a few winter weeks. What part of that could have been captured, and where it would have gone, is the question the Delta Storage Opportunity dashboard lets you test.
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of average for the date is where precipitation over the Northern Sierra stands in water year …, … since October 1. How wet this water year is so far.
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was the final State Water Project allocation for …; south-of-Delta Central Valley Project farms were told … and south-of-Delta cities …. Exports serve both, and the split is shown wherever allocations appear.
Exports are water pumped at the Banks and Jones plants for cities and farms on both projects. The floor is the minimum outflow the State Water Board requires for the month and kind of year. A binding reason is a screening classification from the record, never an operations log. How these figures are defined .
How water moves through the Delta
The Sacramento and San Joaquin rivers meet in the Delta east of San Francisco Bay. Near Tracy, the State Water Project’s Banks plant lifts water into the California Aqueduct for 27 million people and 750,000 acres of farmland, and the Central Valley Project’s Jones plant feeds the Delta-Mendota Canal, the project’s route to farms, wildlife refuges, and cities on the west side of the San Joaquin Valley. Across the whole project, from Shasta to Friant, the CVP serves about 3 million acres of farmland and more than 2 million people. What the pumps do not take, and what the Delta’s own farms and channels do not use, flows past Chipps Island into Suisun Bay as net Delta outflow. Each spring Reclamation and the Department of Water Resources tell their contractors what share of contract supply to expect, and those allocations move with the snowpack, the reservoirs, and the rules that govern the pumps. The Delta Storage Opportunity dashboard models what more could have been captured; the allocation history shows what each class of contractor was told, year by year.
Look it up for any water year
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Allocation history
What each class of contractor was told, year by year.
SWP Table A and every CVP class since 1996, shaded by the kind of water year it turned out to be.
Open the history3
Constraint calendar
Why the pumps ran below capacity, month by month.
A year-by-month calendar of the binding reason, and the daily Old and Middle River index for any water year since 2007.
Open the calendar4
Reservoir storage position
Where each project reservoir stands against its own record.
This water year against every year since 1995 for Shasta, Oroville, San Luis and six more, with the capacity line.
Open the chart5
Upstream diversions
What right holders reported taking above the Delta, by watershed.
Sacramento and San Joaquin river systems by water year since 2010, screened, kept apart from the Dayflow record.
Open the chart6
Scenario panel
What the models say, kept apart from what happened.
The allocation DWR’s CalSim3 rule set implied from February storage beside what was announced, and how each COEQWAL strategy moves exports and deliveries against current operations.
Open the panel7
Place lookup
Which project and contractor class serves a place.
Pick a county or type a town; see the classes present, where it sits against the Delta, and their allocations year by year.
Look up a place8
This water year
How wet the water year is so far.
Precipitation over the Northern Sierra, San Joaquin and Tulare Basin watersheds since October 1 as a percent of average for the date, with last year, the snowpack, and the range of a century of water years.
See this water yearBriefings
Sites Reservoir and upstream capture
In preparation: the Sites Project Authority’s water right before the State Water Board and what the permit terms mean for Sacramento River diversions in wet years. The briefing is shared with the Water Rights Toolkit. Scope of the briefing.
For authorized users
Daily record
Every Dayflow day with the floor, the surplus, the binding reason, the constraints on record, and DWR’s own daily controlling factor, with a spreadsheet download. Sign in with a toolkit account.