Wednesday, January 20, 2016

The Rains Come and the Snow Falls: Normal in California Doesn't Feel Normal

Normal just doesn't feel normal.

In 2014, researchers were declaring the California drought the worst in 1,000 years. And then we had a year, 2015, that was in many ways much worse. We actually had near normal rainfall on the valley floor that year, but it was so warm that the snowpack ended up at 10% of normal, a value never recorded previously. It has been a horrific time. Not only are the reservoirs low and agricultural fields dying away, groundwater has been overdrafted at catastrophic rates, and the worst wildfires in living memory have destroyed vast swaths of forests in the Sierra Nevada and Southern California.
Dry Creek, January 20, 2016
It's not going to get all that much better. Climate models are suggesting that megadroughts, lasting decades, will be the norm starting in about 30-40 years. So this year has been one of hope, in California anyway. El Nino, the climate phenomena that causes all kinds of chaos across the world, tends to bring lots of rain to California (it also unfortunately brings drought elsewhere).

The storms so far have actually not been directly related to El Nino. They have been cold arctic storms that have been dropping prodigious amounts of snow in the Sierra Nevada. For the first time in five years, the snowfall has been above normal. Not far above normal, around 110-115%, but it feels unprecedented after such a long period of paltry precipitation.

The climate of the floor of the Great Valley is semi-arid to desert. The winter rains don't contribute much to the agricultural yields, but wet years are important, as they allow for some recharge of the groundwater. It's never been enough, so our groundwater "savings account" is always shrinking overall.

So I've been watching the precipitation pretty carefully of late. Well, actually I've been tracking rainfall amounts in my backyard rain gauge since 1991, and this year has been interesting. At 2.82 inches, the November rain was the second highest I've recorded. December didn't set records, but 2.60 inches fell that month. But once January arrived, the spigots opened up, and we've four good storms already, dropping 4.21 inches. We've already reached 10.01 inches for the year, where 12 inches is average for an entire season.
Dry Creek on January 7, 2016
Two weeks ago, I noted that Dry Creek, a minor tributary to the Tuolumne River, was "flooding". The earlier storms had only been percolating into the dry soils upstream, but the first heavy storm in January ran off, producing a flow in excess of 1,000 cubic feet per second. We got two more inches of rain in the last three days, and Dry Creek was flowing at nearly 3,000 cubic feet per second this morning. It was a delightful sight.
Dry Creek in March 2011, at more than 3,000 cfs
The future is hard to predict. Last year, we had a wet autumn, but there wasn't a single drop of rain in January, and what little snow had fallen quickly melted away. According to the climate models, the El Nino storms will be starting to affect California in a matter of weeks, bring intense warm storms, primarily to Central or Southern California. There can be no doubt that we need to fill our depleted reservoirs, if for no other reason than to stop depending on groundwater during the irrigation season.
Merced National Wildlife Refuge, January 2014
But I also worry about the health of our regional wild habitats. The wildlife refuges of the Great Valley are critical roosting places for millions of migratory birds, and they tend to be at the low end of priority for water allocations. The rivers that I love, the Merced, the Tuolumne, and the Stanislaus, have been running low and warm, killing tremendous numbers of native fish, and allowing the spread of invasive Water Hyacinth. We've taken over 95% of the natural habitats of our valley, and have a responsibility for taking care of what little remains.

It's been normal, but it doesn't feel normal.
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