Water Supply Update

As I reported to you a couple of weeks ago, I was pretty worried about our water supply in California this year. Things were good on the storage side, but we had very little precipitation over what are usually our wettest six or seven weeks of the year. The late February storms — and apparently a couple more on the way in early March — have relieved my anxiety — at least a little bit.

Looking at today’s graph, we see that water levels in our most important reservoir — Lake Oroville — are nearing the highest levels that we have seen in the past five years. We have matched last year’s storage maximum, and we’re within about 300,000 acre-feet of matching the numbers of 2006-7. And the trend is decidely upward.

In fact, we might be forced to “waste” some water to the ocean over the next few weeks, so that Oroville has enough empty space left in the reservoir to handle Spring floods. On today’s graph, the dashed lines are the limits for flood control purposes. Oroville’s storage is supposed to stay below the dashed lines.

But reservoirs are only part of the story. Another extremely important factor is the frozen reservoir that is the accumulated snow pack in the Sierra Nevadas. According to the March 1 snow survey, we might be in even better shape in this category. See:


With snow levels at 124% of normal for this date, things are looking good. The Department of Water Resources still has a conservative allocation percentage of 60% for this year. That means if you are entitled to 100 gallons of water from DWR, they are currently promising to deliver 60 gallons. So water agencies are not entirely content with the water supply situation yet.

What will it take to get an increase in the allocation from DWR? Mostly we need a cool Spring so that the frozen reservoir can thaw slowly. If it all thaws at once, much of the snow will wind up as Spring floods instead of being our water supply for later in the Summer and Fall.

And of course, worry-warts like me would still like to see a few more productive, cold storms come in over the remainder of our rainy season — prior to May 1 — so that we can put a little more water in the bank — snow bank, that is.

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