Boulder County irrigation water should not sit long enough for mosquitoes

Irrigation water does useful work, then becomes a problem the moment it stops moving. Moving water rarely breeds mosquitoes; water that pools and sits for days does. So the simplest prevention on farm and pasture land is to keep irrigation ditches free flowing and to reduce standing water in fields and low spots before it lingers.

The reason is West Nile virus. Standing water can turn into mosquito breeding habitat, and some of those mosquitoes carry the virus. None of this is a reason to fear irrigating, which feeds crops and pasture across the Front Range every season. It is a reason to keep an eye on where the water goes once you have used it.

On a small acreage, pasture, or horse property, the trouble spots are easy to overlook. Tire ruts, hoofprints pressed into wet ground, clogged or weed-choked ditches, water troughs, and the low corners of a field can all hold water far longer than you would guess, and a few days is enough. Walking the property a day or two after irrigating or a rain shows you exactly where to dig out a rut, clear a ditch, or tip out a trough.

Boulder County Public Health’s West Nile guidance lays out the specific prevention steps for the area. One caution before you start moving water around: if it is tied to a ditch or irrigation right, talk to the ditch company before you change how it is delivered or drained, since those rights come with rules of their own.