100 Years of California Water Reservoir Data

I find it neat that we can publish data that is 100 years old online.

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The California Department of Water Resources (CDEC) provides an API serving data on California’s water resources. This month marks 100 years of published California water reservoir data! Lying on the Lagunitas Creek in the Mount Tamalpais (colloquially Mt. Tam) Watershed are Alpine Lake (APN) and Lake Lagunitas (LGT). Take a look at the recorded data:

LGT,M,1924-12-31,434
APN,M,1925-01-01,4033
APN,M,1925-01-31,3566
LGT,M,1925-01-31,429

This data above shows the amount of water in acrefeet for each lake. Lagunitas can hold about 430 acrefeet and Alpine can hold about 9000 acrefeet today. Here is an interactive historical chart of water Lake Lagunitas and Alpine Lake here:

Why did we start collecting water storage data? I don’t have an exact answer! Today the reservoirs are operated by the Marin Water District. I contacted the Marin Water District for comment but they did not respond to my inquiry. But here are a few things we know:

1. Alpine Lake was first constructed in 1919 and enlarged twice, once in 1924 and again in 1941. Perhaps in 1924 they added a way to measure the amount of water that was stored in the lake and added the ability Lagunitas as well.
2. The 1919 Marshall Plan² (not to be confused with the post-WWII 1948 Marshall Plan) gained popularity throughout the state and by 1924 became the basis of what would become California’s State Water Plan.
3. What likely led to the popularity of the 1919 Marshall Plan was what happened in the water year of 1923-24. That water year was the driest year of rainfall in California’s recorded history which led to a dust bowl.

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What lies ahead in the next 100 years?

I don’t have a crystal ball but there are two easy things to expect:

1. CDEC will continue on publishing this data!
2. California is slated to obtain a new water reservoir, the Sites Reservoir adding a potential 1.8 million acre-feet of water storage capacity that will sit in Northern California, just above the Sacramento-San Joaquin Delta area, near Red Bluff. As I understand, it will act as a water bank that could be used to maintain water levels in Sacramento River during dry years via the Tehama-Colusa Canal and the Colusa Basin Drain. This will help some to address climate change.

The unpredictable part of the next 100 years will be how we as a society manage our water under the advent of climate change. Water is a very political topic, and it’s taken for granted until you don’t have it! Climate change is unfolding and our ability to manage water will become ever more important as time goes by, in the next 100 years. Over the next 100 years, I think the biggest fight will be our water rights and usage. Agriculture is our heaviest water consumer and I think we will come to a point in time where society will have no choice but to forfeit the way water rights and usage are done today.

Above is the cumulative total amount of water stored in our reservoirs inside the state of California (i.e. excluding Lake Mead and Lake Powell).

With climate change, the variability of drier years and wetter years will be ever more pronounced and so we should become more resilient in: (1) managing and capturing more water in wetter years and (2) managing our utilization of water in drier years. Please see my blog series on water management in California to read more on what I think ought to be done!

So here’s to 100 years of California water reservoir data!

References

A special thanks to the Homestead Museum for permission to use their picture and Scott for hacking on rust with me to make these charts!