The sustainability of freshwater supplies is a growing concern worldwide.In order to keep the usage of fresh water at a fair amount, the status of water availability in Canada must be tracked. Water availability refers to the volume of water in our rivers compared with the amount of water we are using. These results are found by calculating the ratio of water demand to water availability on an annual basis. Surface water supply changes based on the weather conditions like temperature, precipitation and humidity. This results in variations in the ratio of water demand to water availability from year to year.
The demand-supply ratio of water in the different provinces of Canada will differ not only based on climate conditions but also due to levels of human activity, industrial and municipal water use, and environmental land patterns. The ratios are divided into 4 categories:
High (more than 40% of available water is used): severe water stress.
Medium (between 20% and 40% of available water is used): both water supply and water demand need to be managed; conflicts among competing uses will need to be resolved.
Moderate (between 10% and 20% of available water is used): water availability becomes a constraint on development; significant investment is needed to provide for adequate water supply.
Low (less than 10% of available water is used): low water stress.
Canada's total annual renewable freshwater supply is about 3,470 cubic kilometres. Unfortunately, renewable water resources have declined in Canada from 1971 to 2004. The water yield in Southern Canada, the area in which 98% of the population lives, fell by an average of 3.5 cubic kilometres a year.
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