Monday, June 01, 2009

Watering When It Is Wet

The neighbors think I am strange. When it rains, I run out and turn on the sprinklers.

My actions actually make sense.

Utah is in the high mountain desert. The air is arid. When it does rain, the rain is often light.

Most of the time, Utah rains are not substantial enough to wet the ground. Our rain often does little more than moisten the leaves, then evaporates.

When we have a light rain with no winds, I turn on the sprinklers to enhance the rain.

What really matters is the amount of rain that gets to the roots. Watering during a light summer rain increases the amount of water that gets to the roots.

On the conservation side of the equation, what matters is the amount of water lost due to evaporation. Watering during the rain reduces evaporation loss.

A few years ago, I had advised the physical plant of a school to water during the rain. This decreased the water bill. A small number of loud voices complained and my experiment was ended. I found the incident sad because I was able to demonstrate that the school was able to keep a green campus while cutting its water consumption.

Utah is currently running a major Slow The Flow campaign that advises turning off water during times of rain. I think a much better approach would involve looking several inches below the surface and watering in ways that get the most water to the roots with the least amount of evaporation.

Light rains fail to get water to the roots. The first several minutes of any watering cycle is lost to evaporation. Watering during the rain enhances the natural cycle and gets more water to the roots.

Watering during the rain not only makes sense from an individual perspective. It makes sense on a system wide basis.

The interesting thing about the Wasatch Front is that there is a big salty lake in the center of things. There is a large fresh water aquifer under all towns surrounding the lake. There are several municipalities and farms that draw their water from the aquifer.

The water that seeps into the ground that is not sucked up by the roots simply drops into the aquifer that is then available for towns drawing from the aquifer.

Were I to design a conservancy plan for the Wasatch Front, I would design a system with the health of the aquifer in mind.

Prior to human settlement, water from the Spring run off would flood into the valley where it would be spread by alluvial fans and seep into the aquifer. Humans put the streams in pipes. Some of the Spring Run off is captured in reservoirs, the rest is piped underground into the salty lake.

Were I in charge I would design things with the aquifer in mind. I would water during the rain and even water in the Spring (knowing that water would be going into the aquifer.

I would then promptly be run out on a rail by all the people saying: "It's common sense: you don't water during the rain!"

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