How much is the recent onslaught of rain storms helping the California drought? Some, but it’s not erasing it. At least from the vantage point of reservoir capacity.

I stumbled upon California’s Department of Water Resources / CDEC website as part of a larger analysis. It has a lot of great data. Particularly, up-to-date sensor data for the major reservoirs in the currently green but trending golden state.

Of the 12 reservoirs listed on the CDEC website all of them are trending well below average capacity for the year despite the extremely wet weather.

This is Lake Shasta’s data as of today. It’s the largest reservoir with CDEC data by a healthy margin. All of these graphs come from the CDED site. You can generate your own if you like.

I actually had to modify the graph to remove one blue line, they seem really excited about blue lines.

The historical average reservoir storage level is the hard-to-see aqua in the background, and the thick blue line that stops around today’s date is the current storage level. All values are in acre feet which is such an absurd unit of measurement. The straight blue line is total capacity, which I believe is included for spite. The top curved blue line is a particularly wet year and the red line is a particularly dry year. We’re averaging somewhere in the same vicinity of a really dry year.

Think about how little it rained last year. If this year is something like a traditionally dry year then what was last year?

Unfortunately the CDEC doesn’t seem to have data on the Hetch Hetchy reservoir where most of the San Francisco bay area’s water comes from, but we can look at more reservoirs throughout the state to get a broader picture.

Things are much worse in the central valley. The New Melones Reservoir, just into the Sierras from Modesto and Stockton, is in pretty bad shape.

Granted the dry year looks demonically grim, but this year is still just a quarter of the historical average.

Things are a little better in southern California at Castaic Lake, but we’re still trending at less than 50% of the average, well below the reference dry year.

Rainfall is only one piece of the drought puzzle. You also have to consider snowpack and water usage across various sectors (urban, agriculture, ecological, etc) and more.

I wanted to share the little slice that I’ve learned. There’s plenty more to uncover.

We’re lucky to live in a time where you can look at the pissing rain and wonder to yourself how much it’s affecting the drought and after a couple hours of fighting with a very bad government website you can have some kind of blob that resembles the shadow of an answer.

There’s a bunch more on the CDEC website.