More bad news on climate change effects on surface water flows

The Christian Science Monitor has a blog on their website called Discoveries, that had a post yesterday summing up the recent Scripps study on the possibly dire future of the Colorado River watershed (discussed in my previous post here).

If you have followed the news this week the story has been pretty inescapable. The gist of it is that with or without the effects of climate change, the Bureau of Reclamation will be unable to meet the existing water delivery obligations in the lower basin almost half the time by the middle of this century because of overallocation of the river. This is primarily due to the fact that the amount of water divided up by the Colorado River compact was based on anomalous weather during the 20th century according to records reconstructed from tree-ring data. If average flows on the river over the past 1300 years or so are an accurate indication of reality, the river is currently over-allocated by as much as 4 to 5 million acre-feet per year.

These reports are on top of the recent announcement by the Bureau that the level of Lake Mead is expected to drop below 1,100 feet at some point this summer. That is a level not seen since Lake Powell was being filled upstream in the 60s and would be perilously close to the level that would initiative provisions of the recently completed shortage-sharing agreement(pdf) under which the basin states agreed to divvy up any shortfalls on the river during prolonged shortages.

The Discoveries post also mentions a recently completed study that shows declining flows in 2/3 of the large river basins in the world over the second half of the 20th century. The only places where flow is increasing is in rivers fed primarily by melting glaciers in places like the Arctic. That's some really ominous data there.

Keep an eye on developments on the Colorado and watch what is occurring in Australia with the Murray-Darling River Basin. If these predictions come true for the Colorado, what is currently occurring in Australia will be an important lesson for planners and policy-makers here.