How much water does California have left?

The California Data Exchange Site has lots data and some nice graphs that show how much water is in the California reservoirs, however there was one particular view that I was interested in that I never found.  So, I went ahead and made the graph myself using the historical data downloaded from the CDEC query tools.

how much water does california have left reservoir levels


This is a stacked bar graph that shows the amount of water in each of the 12 major California reservoirs.  For a reference, I plotted the historical average data as well (it is repeated), and the total reservoir capacity as well. The reservoir data is daily data taken from Jan. 1, 2009 to Jan 1, 2015, and the historical average data is monthly.

What does this graph tell us? For one thing, it is obvious that as of Jan. 1, 2015, we are well below our historical average, and this dry spell in January is not helping.  You can also see how the major rainstorms in mid-December helped us quite a bit, pulling us out of the lowpoint on the graph and actually made it so that the total amount of water in our reservoirs as of Jan 1, 2015 is close to the level in Jan. 2009.

I am working on something to automatically update this graph on a daily basis, so stay tuned. This data was downloaded and processed using Python/Numpy, and then graphed in Matlab.

Folsom Lake Before and After Drought

folsom before after2

One of the more stunning photo comparisons that I’ve come across is this one above which shows Folsom Lake, one of California’s Reservoir’s, before and after the drought.

The photos were posted on Reddit and Imgur, and the original may have come from NASA. The photo comparison is pretty stunning, and the lower lake levels even revealed the ruins of an old town that was submerged when the lake was constructed.

However, how much do these photos really say about our drought conditions?  It’s hard to tell without a little context. Using data from the California Data Exchange Center, I created the graph which shows the lake levels and a comparison to historical levels.

Clearly the photos were taken at points during the year at which the difference in water levels was exaggerated by the normal yearly cycle.  The January 16, 2014 photo was clearly exacerbated by the very dry November and December in 2013.

Another thing to consider is that Folsom is one of the smaller California reservoirs as measured by total capacity.  Lake Shasta and Lake Oroville are both more than 4 times larger. So the Folsom Lake levels may not be the strongest indicator of the overall California drought situation.

There is no denying that there is a serious drought, but there is a lot more context to the situation than what is apparent in those two photos.

Did the massive rains of the week of Dec. 9 make a difference to California’s drought?

Well, it didn’t fix the drought, but it definitely made a difference. You can visually see how a lot less of the California map is dark red which means it went from “exceptional drought” to “extreme drought.” The impact on the northern part of the state was also noticeably larger than down south. Of course it should be apparent that virtually the entire state is still in a drought, but the difference the storm made is pretty apparent.

ca comparison

This comparison was made on the US Drought Monitor site.