World water demand has tripled over the last half-century, and most of it is being used to grow food. About 70 percent of the water we divert from rivers or pump from underground is used for irrigation.
Producing food takes a lot of water. For example, 1000 tonnes of water is required to produce a tonne of grain. Most of the water for agriculture is from precipitation, but irrigation has been used increasingly throughout the past 50 years to boost production of grain and other crops world-wide.
Today, some 40 percent of the world's food is from irrigated cropland, making the security of the world food supply highly dependent on irrigation water. However, after a period of growth, the spread of irrigation is slowing. The amount of irrigated land per person has shrunk by 5 percent since its peak in 1978. At the same time, one in five hectares of irrigated land is damaged by salt.
Although most of Saskatchewan's food production depends on precipitation rather than irrigation, agriculture remains a major water user.
In the Prairie Provinces, almost half of the water used by people goes to food production, and unlike other industries, very little of the water used in agriculture is cycled back to surface and groundwater sources. In Saskatchewan, agriculture uses almost 70% of all water withdrawals.
The Saskatchewan River Basin supports 650,000 hectares of irrigation. Of this amount, 500,000 hectares are in Alberta. Some 90,000 hectares are irrigated intensively in Saskatchewan, about half of it around Lake Diefenbaker. A potential exists to triple the irrigated acres in this area.
With Saskatchewan River flows declining due to climate change, and various municipal and industrial water demands increasing, the amount of water being withdrawn for irrigation is substantial. If irrigated hectares increase in Alberta and around Lake Diefenbaker, agricultural demand could significantly affect supply, especially in drier years.
One way to alleviate this stress is to increase water productivity. Irrigation accounts for two thirds of global water use, but less than half that water used is thought to reach plant roots. Improving the water efficiency of irrigation systems will go a long way toward conserving the resource.
The simplest solution is to eliminate leakage from existing irrigation systems, but much more efficient systems are also being designed. Farmers in India, Israel, Jordan, Spain and the United States have shown that drip irrigation systems that deliver water directly to crop roots can cut water use by 30 to 70 percent and raise crop yields by 20 to 90 percent. Drip irrigation can be applied to some types of agriculture here.
In the Texas High Plains, farmers using highly efficient sprinklers raised their water efficiency more than 90 percent while simultaneously increasing yields by 10-15 percent. Israel is now reusing 65 percent of its domestic wastewater for crop production, freeing up additional freshwater for households and industries.
In Saskatchewan, snow trapping has been found to be effective in maximizing precipitation's potential to recharge soil water. Snow trapping can be increased by the strategic use of shelterbelts and snow fencing, and by adapting harvesting equipment to leave tall strips of standing straw in the field after harvest. Accumulated, trapped snow tends to melt slowly and recharge the soil and ground and surface water.
Intensive livestock operations use up to 15 percent of the water in agriculture. A 5000-sow hog operation, for example, uses more than 500,000 litres of water daily, or around 200 million litres a year. The placement of a large number of intensive cattle or hog operations in Saskatchewan could place a significant new demand on water supply.
The growing interest in urban horticulture and peri-urban agriculture (peri-urban refers to rural area on the periphery of cities) also creates new water demand.
Urban communities like Regina and Saskatoon are experiencing a boom in horticulture. Though production is mainly ornamental inside the city, peri-urban vegetable, small fruit and nursery production is also expanding. Both increase water demand. A number of ways to control water demand in household gardens and urban agriculture include: