By Cara Drury, PAg, Irrigation Agrologist, Outlook
If you’re considering setting up an irrigation project, one of the very first questions you need to ask is, “What will be my water source?” This in itself can be the most limiting factor. Long distances to the source, low quantity, and poor quality can all stop a project before it even begins.
How far is too far? There is no simple answer to this question; it depends on land control to the source and how much money you are willing to invest. Pipelines to a water source require permission from landowners and, potentially, rural municipalities or utilities if you need to cross roads or existing infrastructure. You also need to consider the cost of bringing in power (preferably three phase) to the pumpsite at the water source, as well as a power line to run the pivot.
The cost range for the infrastructure needed to develop an irrigation project, not including power, is roughly $1,300 to $1,500 per acre; this is in situations that have minimal lift requirements, the vertical distance travelled from the water source to the pivot. Projects requiring a significant amount of lift can cost in the range of $1,800 to $2,200 per acre to develop, due to the power required to pump water.
Water quantity is a very important aspect of irrigation development. In Saskatchewan, irrigation projects are certified by the Ministry of Agriculture when they are considered sustainable. One of the requirements for sustainability is a water source that can provide 12 inches of water per acre, in seven out of 10 years. An average quarter section irrigation pivot covers 130 acres; this would require a water source that holds 42.3 million gal (US), or 160,352 m3. The water source’s inflow is also an important consideration. Large shallow sloughs, with no incoming flow, lose large volumes of water to evaporation, making poor sources of irrigation water due to unsustainability.
The Canadian Environmental Quality Guidelines, along with more specific guidelines developed by Agriculture and Agri-Food Canada in Swift Current, are followed for irrigation certification in Saskatchewan. There are many parameters listed in the guidelines, but the two parameters of most concern are the Electrical Conductivity (EC) and the Sodium Adsorption Ratio (SAR) of the water source.
The EC of water is a measure of the amount of salts dissolved in the water. The amount that can be tolerated depends on the soil textures on which it is being applied. Fine-textured soils, like clays, are more susceptible to salt accumulation than coarse-textured soils, like sands; therefore, determining suitability is done on a case-by-case basis. That being said, a water source with an EC above 2.5 mS/cm (2,500 µS/cm) is not a desirable source for irrigation.
The SAR of a water source is the ratio of sodium compared to the calcium and magnesium. Irrigating with highly sodic water sources has the potential to lead to a breakdown in soil structure. In turn, this can lead to soil crusting, reduced permeability and infiltration rates, and cause the soil to develop a massive structure that feels similar to cement. Water sources with an SAR above 5 start to become a concern; but, like dissolved salts, the amount of sodium in irrigation water that can be tolerated depends on the soil textures on which it is being applied. Fine-textured soils are more susceptible to damage than coarse-textured soils, and determining suitability is done on a case–by-case basis.
Irrigation enables producers to achieve higher yields, grow higher valued crops, secure feed sources for livestock, and diversify their operations. This can be achieved when the water source is found to be suitable for the land on which it will be applied. With highly suitable water sources like Lake Diefenbaker and the North and South Saskatchewan Rivers, there is a great potential to expand irrigation in much of Saskatchewan. If you are considering developing a project or need help in determining the suitability of your water source, please contact the Ministry of Agriculture’s Crops and Irrigation Branch at 306-867-5500 or visit the Ministry’s irrigation information pages.