Water Storage Update

I got an opportunity to put out another blog this evening, so I thought I would examine the storage at Oroville again. Remember that this is the main storage component of the California State Water Project, so this provides the fastest check on our water picture.
This week’s update shows that we eclipsed last year’s storage for the first time this year — good news. Look at how last year’s graph changed over the final eight months of the year. The change in storage in the reservoir is due to Inflow minus Outflow. Inflow continues through the year, but declines steadily after the rainy winter months. Right now, stream flows are still pretty high. Snow melt will continue for the next few months, and later in the year, mostly just groundwater flows will be entering the reservoir.
This year, the snow pack is more substantial than last year, so we should expect that the Inflow part of the equation will work to increase storage.
But what about the Outflow? The “Allocation” method is how the Department of Water Resources seeks to control the Outflow of the reservoirs. We reported last week that the allocation this year is planned to be 40%. DWR will be watching the storage in Oroville — along with us — to determine if an increase — or decrease — is warranted. It is extremely rare that DWR will decrease the allocation; that’s why they are so cautious early in the year in setting the allocation level. Typically, the May 1 allocation will hold for the rest of the year.
But some Outflows are beyond the authority of DWR. Environmental regulatory agencies may divert flows out of the reservoirs to assist one species or another. Such diversions could cause Outflows to rise substantially over the rest of the year. Stay tuned!
If environmental diversions are the same as last year, and DWR diversions are about the same, then we should start off next year with a significant improvement over this year. Watch the graph over the next month to see if it flattens out — like last year — or if it continues to show a storage increase.
Again, best of luck to those of you taking the test this Saturday, and see you next week.`

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