The problem with this method is that not all crops can be irrigated this way. Surface water supplies most Canadian cities, and only 10 % of the population is served by municipal systems that rely on groundwater (Draper 1998). Many sources of contamination may affect surface water and groundwater supplies, drainage or seepage from industrial, commercial, residential, and recreational land use, including waste disposal sites and agriculture. To be safe for human consumption, water affected by such contamination must be filtered and treated chemically prior to entering a city's distribution system. Cities are linked to larger ecosystems, and therefore have a responsibility to them. For example the relationship of cities to the hydrological cycle, cities withdraw water from a water source and treat the water to make it potable. As the water is used the water receives pollutants, such as human waste and it needs to be treated again prior to its return to the hydrologic system. Downstream other communities may depend on the same water and some users may discharge untreated water, which then continues through the cycle (Draper). Water regulations are rules of conduct, which the minister is empowered to make and to facilitate the carrying out of an act of Parliament. Regulations exist under some federal water- related legislation, for example the Fisheries Act, and the International River Improvements Act. Water quality regulations, should call for polluting contaminates to be stopped all together from entering water sources, but for the most part they are allowed in low concentrations. Canada has pollution control regulations in place, an example of a successfully regulated substance is the phosphate found in laundry detergent. The Canadian Environmental Protection Act will regulate substances that are harmful to the environment. .
Some questions to ask about what to control or limit.
- What are the sources, amounts and effects of substances?.
