In Utah, we seem to be strangely comforted by pavement. At the present time we are witnessing many instances where grass and planted areas are being converted to cement, asphalt, gravel or artificial turf, which in sunlight gets as hot as pavement.
These projects seem to be inspired by the mistaken belief that pavement and other hard-scapes conserve water while plants “waste” it. Nothing could be further from the truth.
A great paradox of our current drought situation is that there may be more water in the skies above Utah than at any time in our history. The melting of polar ice makes more of Earth’s water available in liquid and vapor form, to precipitate as rains and to fill our streams and aquifers.
A frustrating problem relative to Utah’s drought is that in the hot summer, rain can evaporate before hitting the ground (a phenomenon called virga) Heat radiation from pavement promotes this and hastens drying. Hard, hot ground cover repels surface water more than it “saves” it. This is true at any scale, whether paving over acres of vegetation, adding a patio or simply widening the driveway of a suburban home.
Our drought is not one of too little water falling from the sky. Our drought is caused by too much heat. Satellite and surface measurements confirm more surface superheating than ever before, according to findings recently presented at the Utah Museum of Natural History by a panel that included Utah climate scientists. The same satellite images also reveal Salt Lake City to be one of the most over-paved cities in America.
Few among us would recommend Kentucky bluegrass as a mainstay of climate-wise landscaping. But in fact, on a sunny summer day, a surface of mixed planting and grass is 30-50 (F) degrees cooler than a paved surface — something readily noticed by anyone attempting simply to walk on our sidewalks.
The bottom line is that pavement and hard city surfaces are what we need less of. Instead, we need more plants, grass and trees. A current, unfortunate example of getting this wrong is the reworking of the Central 9th neighborhood, where five lanes of new pavement and hard-scape have made those streets and sidewalks too hot to walk or even visit during summer daylight hours.
We would do well to consider more water-wise pavement options as described by the EPA, or even to restrict new paving and encourage removal of pavement to permit re-vegetation.
The most water-wise landscape approach to any sized property is to cover as much of that property as possible with plants — even the roofs of buildings. Hot, hard surface installations may cause more water loss than the amount of water to maintain the same ground as planted surface.
Perhaps we could go a little easier on destroying grass, plants and trees and choose to be more sparing with pavement, which is no friend to our urban climate.
If more pavement had the potential to save our city and our Great Salt Lake, we could just keep doing what we’re doing and watch the lake fill up.
Thomas Weed
Thomas Weed, MD, is a long-time local resident and physician and a supporter of Utah Physicians for a Healthy Environment.
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