Letter: Reduce irrigation water use
The current drought in Western Colorado is more severe than normal due to lower than normal snow melt feeding the river system, and has predictably led to more calls for water conservation. Here are some relevant facts about hydrology and landscape maintenance that everyone should understand before embarking on either voluntary or mandated water conservation measures.
First, for the bluegrass lawns that are central part of most residential landscapes to grow continuously without turning brown, the water that they receive must equal the water lost by evaporation from the soil and transpiration from the leaf surfaces. In the absence of significant rainfall — which often occurs for weeks at a time in this area — the water must be supplied by irrigation. During the months of June through August, evaporation typically averages about 8 inches per month. Although grass that is watered deeply every few days can grow with somewhat less water, various inefficiencies in irrigation systems make it necessary to apply about as much to a lawn as evaporates from an uncovered water surface.
Now, consider the water used by a typical family of four, living on a 10,000 square foot lot (about a quarter of an acre), with half of it in lawn. With 8 inches of water applied to it in a month, that would be about 25,000 gallons, which is five times the typical non-consumptive household use by four people.
It stands to reason that efforts to conserve water by reducing non-consumptive uses like showering will not accomplish much, and that serious conservation efforts need to focus on reducing irrigation. This applies not only to homeowners, but even more importantly to agricultural irrigators, whose irrigated pastures cover 10s of times the area of residential lawns.
Carl Ted Stude
Professional Engineer, retired