One of my main jobs is to dive into piles of data and somehow distill them into something usable. What will river flows look like in 2-3 months? What will reservoirs look like at the end of the year? How much water can we expect to get from the current snowpack? Etc etc. I have been studying that last question for several years now. It's the duty of the Natural Resources Conservation Service to come up with a number as to how much water there is in the snow, but it is up to me to figure out how that water will eventually arrive and what to do with that water once we get it. So I'm constantly checking snow levels and comparing that to river flows. A while back I discovered a very nice linear relationship between snow and runoff. We're talking r-squares of >0.95. I could predict how much water we could expect while there was snow still up in the mountains. Unfortunately that was only a small piece of the puzzle. It was that period of time AFTER the snow had melted which was difficult to predict. I tried a few different methods but usually ended up with a shotgun-blast graph. Last week, however, I stumbled onto something that was very interesting but also quite disturbing. I looked at the volumes of water that came down the rivers while there was snow in the mountains and afterward. The initial graph looked like the all-too-familiar shotgun blast, but a pattern DID emerge. When I separated the data into pre-2007 and post-2007, nice linear relationships popped out. Prior to 2007 20-30% of the runoff happened while there was still snow in the mountains. After 2007, however, the numbers jumped to 70-90%.
What does that mean? It simply means that the snowpack is melting much more quickly and earlier in the season. Is it a climate change signal? Possibly. Is it a signal shift due to continued drought? Possibly. Is it related to the phenomenon of dust-on-snow? Possibly. Are all of those things related? Yes. The dust-on-snow phenomenon has been studied intensively over the past several years. The hypothesis is that dust storms are becoming more frequent and severe due to increasingly warm springs which lead to higher winds. The ground becomes drier as well due to the increased temperatures and diminished soil moisture which cause particles to become more easily entrained. That dust then lands on the snow which reduces albedo. More energy is absorbed into the snow which then causes rapid warming and melting.
So perhaps my little finding is just one more piece of the puzzle. I'll put my hypothesis to the test right here on LJ. The NRCS has a forecast number of 66,000 ac-ft for one of our reservoir's inflow. My prediction is closer to 42,000 to 53,000. I'll post the final number on August 1st or 2nd. Let's see who's closer! SCIENCE!