A century ago, the Santa Cruz river ran throughout the year, supporting lush vegetation in its surroundings. Lush, in any case, compared to what had become of it at the end of the 20th century. The increase in consumption due to the growth in population from 7,00 to 500,000 in those hundred years is obviously a factor. But another significant cause for the dry-out is the increase in heat caused by corresponding expanse of impermeable surfaces – pavement, concrete structures and so forth.
The increased heat makes water evaporate faster, of course.
But it also creates a thermal bubble over the city which lifts the rain storms right over it. It is a vicious circle: increased heat causes less rain fall and less rainfall increases the heat.
A lot has been done in past years to amend the situation and get the Santa Cruz and its tributaries running perennially again. For one, the Pima County Wastewater Reclamation Department has returned sections of the river to year-round flow by releasing treated wastewater back into the river. (This information may wrinkle some noses, but there is no need. The department’s facilities are capable of purifying water to such a degree, that it can be used for brewing beer.)
Reclamation, however, is only a partial solution. What is needed is a better way to hold on to the 12 inches of rain we get annually. The way to do this is to slow it down, so that it gets a chance to penetrate into the soil. This can be achieved by building berms to obstruct the flow of water and basins to catch it and let it soak in. There a numerous organizations in our area dedicated to the concept, such as Watershed Management Group, the Nature C0nservancy, Sky Island Alliance and Borderlands Restoration, just to name a few.
Ideally, every property owner in the community would landscape his or her plot so that the water goes where it needs to go instead of straight down the drain. That would mean a big increase plant cover and corresponding cooling effect. The Pima County Agricultural Extension of the University of Arizona provides free classes, sponsored by Tucson Water, on how to do this through its SmartScape program.
The Weekly Green spoke with Michael Ismael, master gardener and instructor with the Extension, about SmartScape, water and growing things.
(Full interview 15:30)
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