More to irrigation than meets the eye

Over the last few years, residents in the city of Williams Lake have shown tremendous response to the Water Wise program and made substantial efforts to conserve water and protect the integrity and sustainability of the City aquifer.

Over the last few years, residents in the city of Williams Lake have shown tremendous response to the Water Wise program and made substantial efforts to conserve water and protect the integrity and sustainability of the City aquifer.

However, we often receive questions at Water Wise about what is happening outside the city.

People trying to save water at home can wonder at the significance of their efforts when they see the massive quantities of water being used to irrigate the farmland in the area. So here are some of the more common questions we have received:

How often does a producer have to irrigate? How do they know when to stop?

This will depend on the crop being grown, the type of soil and the weather. Producers can test the soil to assess how dry it is and calculate the volume of irrigation needed knowing this as well as local evapotranspiration data. Over-irrigating is detrimental to the crop as well as to the environment, affecting productivity, stream flows and adding to run-off issues. It also adds unnecessary expense for producers with significantly increased electricity costs as well as wear and tear to equipment.

I am only supposed to water my lawn in the mornings and evenings to reduce water loss from evaporation — so why are producers irrigating all day, even in hot sun?

Crops need a specific volume of water to be productive. In our area, watering only at night would mean less time to get that water on the field, with a higher flow rate. Since most irrigation water comes from local rivers, this would mean pulling a higher volume of water out of the river in a shorter time, so to maintain steady stream flows, it is better to pull out water at a lower rate over more time. But, yes, depending on the irrigation system used, then considerable water is being lost to evaporation.

Isn’t it wasting water to irrigate when it is raining?

Most summer rains are half an inch or less. The standard crops in our area need significantly more water to survive and grow, with crop grass requiring 1.5 inches and alfalfa requiring as much as three inches of water. Watering in the rain will supplement the rainfall while increasing the irrigation efficiency, as evaporation losses are lower.

What is the most efficient form of irrigation?

There are many systems available, and efficiency rates vary, depending on factors such as whether a system moves, how the water is dispersed and how close the water is released to the ground. The least efficient system (at 58 per cent) is a “stationary handgun” system, where the water is shot into the air in one direction. The most efficient (80 per cent) being a pivot system with drop tubes to get the water close to the ground.

So there is much more to the irrigation story than meets the eye. The science of irrigation is becoming increasingly important as we start to face more common water shortages in our area and the need to protect summer stream flows and stressed aquatic life is becoming evident. The type of crops we grow and where we grow them will be just one more of the many challenges facing those involved with food production in our area, as changing snowpack and rainfall patterns affect the predictability of our water supply.

Producers — find ways to save water and reduce power costs in an upcoming irrigation workshop presented by Water Wise in partnership with Ministry of Agriculture, Department of Fisheries, Ducks Unlimited, Fisheries Riparian Interface Stewardship program. Details to be publicized shortly, or contact the Cariboo Chilcotin Conservation Society at 250-398-7929.

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