A mediocre Colorado River Basin forecast

The Climate Prediction Center’s seasonal outlook, published this morning, is another “meh” for the Colorado River Basin. The good news is that odds favor wet for the southerly part of the basin, especially Arizona and New Mexico. The “meh” part is that the low country doesn’t contribute much of the river’s overall supply. Most of that falls in the Rockies to the north, where the current forecast could be worse – slight tilt in the odds toward wet for a portion of the basin. But only slight:


Nov-Jan forecast, courtesy Climate Prediction Center

It’ll be a while before we can say much that is actually useful about the impact on the Colorado River Basin’s reservoirs, but this is just a blog and no one reads it, right? So I’ll just find a vague thread of evidence and then improvise, and y’all won’t hold me to it, OK? The vague thread of evidence is this month’s Bureau of Reclamation 24-Month Study (pdf), which projects a bit of bonus water to be released from Lake Powell down to Lake Mead. But even with the extra water, Mead’s still projected to drop another 5 feet. This is the “structural deficit“, which Arizona’s so exercised about, in action:
Total storage in Lakes Mead and Powell. Data by USBR, graph by Fleck

Total storage in Lakes Mead and Powell. Data by USBR, graph by Fleck

For those squinting at the graph and trying to keep score at home, that’s the lowest total storage in Mead and Powell combined since 1967.