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Source: California Data Exchange Center

Tool: Tableau Public

Note: I pulled this data last week. Since then, the water storage has gone up to 4,700 ft.

Is this exceptional? How about a comparison with previous years to see how unusual it is, if at all?

Great feedback, I'll look into doing a year on year comparison for context.

I think percent of capacity would be a better metric. For all I know this could be from 5% of capacity to 12% of capacity which wouldn’t be a big deal. Or is it full?

Not a bad idea, although most sites in California were built (purposefully) to never reach true “capacity”.

I’d recommend doing a trend line from Sep to Mar from 1980 - 2023, graying the middle 66% trend lines, and separate coloring lines for the top 16% and bottom 16% with year identifies

Well the thing with the reservoirs is they measure them differently. They can't hold all the water. If they did then there wouldn't be room to store the runoff from the snow melt later. But trust me I'm in northern California and it's a lot of fricken rain.

It’s full.

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Sweet; now do Lake Cachuma - downriver from Gibraltar and much larger capacity (and more depleted).

All things cycle, we just adapt.

During a twenty-year drought, it might seem that way. The large reservoirs still have room for a lot of water and cracks in the ground, but I am informed that a lot of the smaller ones would chart like that one

And some things cycle faster and disproportionately due to outside influences (here, human activity), and will be beyond our capacity for large-scale adaptation (see, impacts of rising sea levels and increased natural disasters, etc.)

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There are a bunch of relevant numbers. Below the dead pool threshold power stops generating. Above the flood pool threshold water has to be diverted.

Percent capacity can be a bit hard to interpret because what’s fine for one dam may not be fine for another. These ranges will also change for the same dam over seasons. Without more context it’s not possible to know if the percent capacity is ideal, too high or too low.

Historical average for the time period is probably another good line.

The rain is great but this graphic misses the mark on a lot of points in my opinion. First, water storage is in acre feet not just feet (unless you are looking at lake level elevation but I can tell you now the lake level didn't increase 1500 ft). Second, this mosses any and all context. Is the lake level 3 months ago low? Is it low because of drought or was it lowered for downstream water releases or water rights discharges? To add additional context it might be good to show how much rain has fallen, maybe percent to year average rainfall or something. Finally, this is just 4 bars highlighting 4 months. This is the definition of picking and choosing data and imo doesn't really display the data in any beautiful or meaningful way. It's just 4 bars. From the county of Santa Barbara you can get auto generated charts showing the increase in storage with more detail on your x axis (days) and using a line as well, just a better way to represent data and give the reader an idea of how fast or slow reservoirs fill.

Please pardon my ignorance of CA geography but wasn’t it Lake Mead that was so low they were finding old corpses in it? Has that water level risen significantly or is it in an area that hasn’t seen the newsworthy impact? TIA

Yes lake Mead and Powell have been the big names in the news in terms of low resevoir storage. The purpose of the analysis I was doing was just to look at California reservoirs and how atmospheric rivers have been affecting them.

Thank you for the feedback, I'm still a little new to data analysis/visualization so it's definitely not perfect. I'll take that feedback and apply it to the next post I make here.

Lake Mead is in Nevada, on the Colorado River. California simply imports water from there. It won't be getting as much aid from the atmospheric river because the Colorado River is on the far side of the Sierra mountains. California has a lot of its own reservoirs -- apparently, there are even rubber dams making reservoirs now; the smaller ones have really benefited