|January 2016, one year ago|
But the storms haven't exactly arrived yet! There has been a lot of snow and rain in the last few days, but nothing that can explain the river this morning. In the picture above, the nearest channel isn't normally a channel at all. It's a dead-end slough, a spot that collects River Hyacinth and garbage. But right now it is a raging torrent. The hated invasive hyacinth is being flushed downstream. That's a very good thing.
So what's going on? Why is there a flood going on today a few days before some serious stuff starts happening across California? The explanation is pretty simple, really. The authorities are clearing space in Don Pedro Reservoir in preparation for the expected runoff from the storm this coming weekend.
There are three main water storage reservoirs in my immediate area, the New Melones Dam on the Stanislaus River (capacity 2.4 million acre feet), Don Pedro Reservoir on the Tuolumne River (2.03 million acre feet), and McClure Reservoir on the Merced River (1.02 million acre feet). The story of today is told by the present levels of each: McClure is at 47% of capacity, and New Melones is at 27%. There is little danger of these two filling during the coming storms. But Don Pedro is sitting at 74%. And two smaller reservoirs upstream, Hetch Hetchy and Cherry Lake are at 89% and 88% capacity respectively. The level at Don Pedro is not dangerously high necessarily, but if the storm plays out as expected, things could get a little too much like conditions in 1997 when the reservoir filled unexpectedly and for a short time was flowing uncontrolled through the emergency floodgates and over the adjacent weir. Downstream towns like Modesto were hit with the highest flood levels ever recorded (just imagine 60,000 cfs instead of today's 8,000; I don't have to imagine: I saw it, and it was astounding).
So, Mrs. Geotripper and I had a treat today, the chance to see a "good" flood, a flood on a sunny day that is probably not going to cause too many problems (although fast cold running water is always dangerous; we saw kids at the town park getting too close to the river). I gave up on my plans to clean up the geology lab in preparation for the new semester, and we took off up the river to see what else was happening out there.
Our second stop was the Old Basso Bridge near the Gold Rush town of LaGrange. The 1912 vintage bridge is a tough one. It survived the 1997 floods, but is today only used for pedestrian traffic. A newer concrete structure crosses the river just upstream. The river had inundated an adjacent pasture.
The tone in this post has been pretty upbeat, but please, if you live in the path of the storm, take the coming flooding very seriously. It has the potential to be the biggest such event in several decades. Even if it doesn't set records, high water is always dangerous. Don't ever try to cross flooded bridges or waterways. Find out if your home is in a potential flooding zone. Keep up with local news reports and take official announcements seriously. If word comes to evacuate, do so without hesitation. If there are things you think you can't live without, then have them packed and ready to go beforehand. Today was a good practice flood. Be ready for the real thing!