New "Green Streets" Policy on the way for Tucson

Image borrowed from HydroGeoWorks.com

Last week the Tucson City Council considered and approved a new policy that will direct the Transportation Dept. to implement passive water harvesting features on most future road projects within the city.  This policy was largely developed by Watershed Management Group (I'm biased as a former board member of WMG) who put in a lot of effort to build consensus and support for this sensible change in a desert city.  The policy calls for incorporating curb cuts and depressed basins adjacent to roads to collect, filter, and utilize storm runoff for fostering roadside vegetation that will provide shading (heat island reduction) and pollution mitigation (both air and water).  These are remarkably simple modifications that should save water, previously used for irrigation, in addition to reducing the strain on stormwater infrastructure.

Major kudos to the city and to WMG for making this happen.  And I should also mention James MacAdam, formerly with WMG but now working in the mayor's office, who I know was a major impetus in getting this done.

Well ... maybe

I found a link to this story on Aquafornia this morning and was intrigued enough to read the article - even though I was skeptical.  Obviously the first thing that jumps out at you is the title - "Watering fields in California boosts rainfall in Southwest".  Makes you think that someone has possibly confirmed a link between the two.  But then you read the first line in the story and that claim is qualified with "a new computer simulation suggests."  So it turns out that using an appropriately scaled atmospheric circulation model and making some assumptions about excess evaporation occurring in the Central Valley of California in the summer it appears it just might be possible that some of the summer thunderstorms over the southwest could be modestly enhanced by said excess evaporation.

Can Reclamation Change its Ways?

There has been lots of chatter in the blogosphere and elsewhere about the recently released Colorado River Basin Water Supply and Demand Study from the Bureau of Reclamation (BOR).  This really is a ground-breaking study in many ways: it enshrines the likelihood that climate change is likely to have an impact on water supplies in the basin in the future; it acknowledges that the lower basin is already out of kilter in the supply vs. demand equation, and is highly dependent on deliveries of excess water from the upper basin to continue meeting that demand; and probably biggest of all, it largely acknowledges that the era of large public works projects to address water needs is probably over.

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.