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California Water Update

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It is mid-February, and I promised that I would catch up with the water conditions in California. Over the summer of 2015 I ran a 13-post series on the drought in California, in which I attempted to estimate whether California would be able to cover its future water deficit, and if not, what it would do to California’s economy.

I concluded that California faced not only a severe current drought, but a future in which they would lose a significant fraction of their water supply, resulting in a severe water deficit. Various remedies would cover only part of the deficit. The combined consequences of the shortage and the remedies would throw the state into a recession, possibly even a depression. The series of posts starts here.

I’m neither a hydrologist nor an economist, and I learned a lot as I wrote the series. I still know of no other analysis that attempts such a comprehensive assessment of California’s water future.

About the time I finished the series, signs were increasing that a large El Niño event was starting. Large El Niños typically bring above average precipitation to California. The most important form of precipitation for California is the snowpack in the Sierra Nevada and Cascades. This forms a “reservoir” that melts slowly during the spring and summer, providing water during months when much of California receives virtually no precipitation at all.

The water content of the snowpack on April 1 is the most important, but measurements at the end of January can give some indication of how things are going. California measures two ways. First, they conduct “media oriented” events in which they physically go to specific locations and measure the water content of the snowpack at that location. Last April 1 when they did this, there was no snow on the ground at all. This year, on February 2 there was a snow water equivalent of 25.4 inches, which is 130% of the average for that date.

Source: California Data Exchange Center 2016.

Source: California Data Exchange Center 2016.

A second way they measure is via continuous electronic measurements at a couple of dozen locations around the state. Figure 1 at right shows the results for this year through February 12. The charts show the water content of the snowpack as percentages of the average amount on April 1. The top chart is for Northern California, the middle one is for Central California, and the bottom one is for Southern California. The blue line represents this year. The green line represents 1982-1983, the year with the biggest snowpack. The brown line shows 2014-2015, the year with the lowest snowpack on record. The light blue area represents average.

You can see that the average snow water content builds during the winter and reaches its maximum right around April 1 – that’s one reason the April 1 measurement is the most important. This year, in all 3 regions, the snowpack has built towards its April 1 average much better than it did last year. However, the data do not suggest that, statewide, it is an exceptional snow year. In this data, it looks like a pretty average snow year so far.

Somewhat worrying is the fact that since about February 1, the line for this year has leveled off. Might the snow season peter out and end up below average? I hope not.

Source: Mammoth Mountain Resort 2016.

Source: Mammoth Mountain Resort 2016.

Finally, I located one other source of data, this one more hopeful: the snow report at Mammoth Mountain, a large ski resort in the Central Sierra Nevadas. The resort tracks snowfall at the resort by year and by months, and it is available on the Web. Figure 2 shows total snowfall by year, and the different colors in the columns represent the amount for each month. The data suggest that at Mammoth Mountain it has been an above average snow year, 11th highest out of 47 years. February is, on average, the biggest snow month, however, and data for the first half of the month this year show the same tapering-off that the other data did (not shown on the chart).

I’m not sure how to reconcile these three contrasting data sources. Could above average snowfall have occurred, but above average temperatures melted more than usual, leaving about an average amount on the ground? Possibly, as January was 2.4°F warmer than average in California. That explanation would not, however, reconcile the difference between the electronic measurements and the media oriented measurement.

Now, one final word of caution: none of this changes my projection for California’s water future. It is surely good news that they are not having as dry a year as last year. However, my analysis was based on projected 30-year average precipitation levels. During any 30-year period, there are bound to be wetter years and drier years. If my analysis is correct, then while it is good news for right now, the real issue will be the average size of the snowpack over many years.

So, for the future, we’ll have to wait and see. For right now, it looks like a better snowpack year than last year: at least average, and perhaps above average.

In my next post, I will look at an analysis of water scarcity around the globe.

Sources:

California Data Exchange Center. 2016. California Statewide Water Conditions: Current Year Regional Snow Sensor Water Content Chart (PDF). Downloaded 2/13/16 from http://cdec.water.ca.gov/water_cond.html.

National Centers for Environmental Information. 2016. Climate at a Glance. Data retrieved 2/13/16 from http://www.ncdc.noaa.gov/cag/time-series/us.

Mammoth Mountain Resort. 2016. Extended Snow History. Data downloaded from http://www.mammothmountain.com/winter/mountain-information/mountain-information/snow-conditions-and-weather.

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