I wrote a short post the other day about our late wet season this year. As some of you know I have this tendency to follow single facts down the rabbit hole that is the internet. I like research, I wrote my Ph.D. dissertation on the topic. Yes, the snowpack interested me, so I looked a bit deeper as it were.
Yesterday and today it was been wet and grey outside my windows and I read an article by a water management district representative who said that we should not be worried about flooding just yet because this "usually wet late season storm would keep the temperatures cold in the mountains." He went on to say that this system was also going to add even more snow to the already above average snowpack, so the flood watch would continue much later than usual, probably until the end of July.
Off I went looking for data on average snowpack and runoff. The first good source I found was a chart based on the average snowpack as of April 1st. It seems that is an excellent date to measure from because late March and early April is statistically the height of the snowpack throughout California. The melt begins around then followed by the streams and rivers beginning to rise.
First stat I found was that as of June 1st we were at 109% of the average April 1st snowpack up here in northern California. Not a worrisome total at all, but you gotta be careful with statistics. If we are at 109% of normal that would be one thing, but the numbers say we are at 109% of normal for April 1st that arbitrary measured date. So I had to ask: On June 1st, how are we compared to average for June 1st? I mean shouldn't we already have had about two months of melting?
It took some searching but I found the numbers. Before this big storm came through, the one I am looking at outside my window right now; before this drenching we were at 559% of normal snowpack for June 1st. No typo there - Over five times normal. Its a double whammy of a big snow season and a wet spring that has delayed the spring melt.
Donner Summit at the top of the pass between Sacramento and Reno has seen a staggering 740 inches of snow this winter/spring (so far). Only four years since 1900 have seen snowfall in excess of 700 inches. The average is just over 400 inches. In 1982-83, Donner got 880 inches of snow; that summer in many higher elevations the snowpack did not completely melt, not until the following spring after a more normal winter in 83-84.
What does this all mean for the 2011 fire season and for potential flooding? Well short term predictions are generally unpredictable. But as far as global warming or climate change as is the current PC label - this year's wet winter adds nearly nothing to that conversation. Annual or decade long variations do not preclude the scientific evidence on the long term effects of greenhouse gas emissions. The only piece of evidence I can verify is that it is very wet outside at that moment and snowing up in the Sierras.
Meanwhile, could someone please locate two wolverines and a pair of pythons.