The mean is based on at least five approximately evenly spaced samples. Wildlife, Livestock, Raw Drinking Water and Irrigation Dissolved oxygen criteria for the protection of wildlife, livestock, raw drinking water supplies and irrigation are not considered necessary at this time. Recreation and Aesthetics Dissolved oxygen criteria for recreation and aesthetics are not deemed necessary for British Columbia, as the criteria for aquatic life can be protective of virtually all waters where aesthetic considerations such as hydrogen sulphide generation could be an issue. It is accepted that industries incorporate conditioning processes to provide the quality levels necessary for the water supply, based on their own needs. Therefore, dissolved oxygen criteria for industrial water uses have not been developed.
Special considerations are necessary when designing a monitoring program and applying criteria.
Oxygen Cycles and Monitoring Frequency Dissolved oxygen cycles in productive waters are common, and site-specific details must be taken into account when designing a sampling strategy. Diurnal oxygen fluctuations typically result in sub-optimal conditions for at least brief periods, therefore the timing of measurements is very important. It is the intent of two-number criteria proposed that these fluctuations do not go lower than the instantaneous minimum criterion. In natural waters influenced by oxygen generation from primary production, daily cycles usually are sinusoidal with a maximum concentration reached late in the day and a minimum concentration in early morning. In addition, maximum dissolved oxygen concentrations used in calculating daily averages should not exceed the known saturation limit.