It's Never Been Like This Before

Every so often I'll get in a conversation with someone about our droughts here in the mountains of California. The snow pack in the Sierra Nevada mountains is the major source of fresh water in the state so knowledge about it is vital. Fortunately there is data to be had that I can use to inform myself. I get the snow pack data for the two watersheds I am interested in from the California Data Exchange Center.

I update my files every year at the end of the snow season. This is usually April 1st. It's always surprising to me when people talk about the Sierra snowpack from news reports they hear or see, but don't actually look at the numbers. In fact some of the things I hear from people is so far from what the data implies it's troubling. Let me be clear from the outset, this is not about the overall water situation in California. It is about the two watersheds that directly impact my life. They are the Kern River Watershed and the Owens River Watershed.

Both of these watersheds are immense. The Kern River is fed by the area running from just west of Mt. Whitney in the north to the Breckenridge Mountains in the south near Bakersfield. The western boundary is along the ridgeline of the Greenhorn Mountains. Here is a map of it. The Owens River is fed by the area from up near Mono Lake and south to Lone Pine. It is bordered by the Inyo Mountains on the eastern side of the Owens Valley and the Sierra Nevada Mountains on the west. This is its map.

Los Angeles gets the vast majority of the Owens River water due to Mulholland's efforts when he built the first aqueduct, "Forget it Jake. It's Chinatown." The water content of the snow pack for the two systems is shown in the first graph. You can see that the data goes back quite some time. California has always been intensely monitoring the water situation in the state for obvious reasons.

Kern and Owens River Water Content by Year.

From a previous post I wrote about knowing where the data comes from and what's been done to it. The measurements methods themselves are well documented by the state of California at the website I gave. The next question is how did I treat the data? I approached it in as much of a hands off manner as I could. From all of the individual sensor stations I took the water measurements and summed them for that year for each river system. I then checked each station's data against the sum to look for discrepancies. Here's one station versus the sum. Where there were large gaps I filled it the years with the previous year's measurement. It didn't affect the overall picture to any significant degree 

CSV Station Versus Total Water Content

The first thing to note is the rough cycle that is apparent. This is the classic feast or famine for the California water situation. Approximately 5 to 6 years of dry conditions followed by 2 to 3 years of very wet conditions. It becomes a little more apparent when you look at the graphs for each river system with a running average which are shown below.

Kern River Water Content with 7 Year Moving Average.

Owens River Water Content with 7 Year Moving Average.

Let me discuss the last drought season. It was bad, which is why information is so important to help me understand where I stand. One measure that people tend to use is the bark beetle infestation and the associated tree kills from it. It was one of the worst seasons I've seen, but then so was the one in the late 80's. The beetles are always present and the trees are in a constant battle with them. With a slightly prolonged drought the trees struggle more and the beetles win out and are able to infest and kill the trees. This is now more readily apparent to humans and we tend to think how much worse it is.

Looking at the snowpack measurements though tells a somewhat different story. The drought was slightly dryer and slightly longer but the subsequent years have seen a return to near normal conditions. In fact, it looks very much like some of the previous years. At least in the timescale where we actually have measurements. Of course one can always extrapolate along some sort of model, but that always brings forth more than a few questions in my mind. "Those two are going to have 13 children. Just look at the data, they've had two kids already in their first four years of marriage. My fit predicts they'll have 13." 

Perhaps we are not as aware of what the future might bring as we like to think.

I'll be writing more about this in the future, including about some of the new laws that have been passed that may have some profound consequences in the state.