A summary of water temperature guidelines for beneficial uses (domestic, recreational, agricultural and industrial) is provided in Appendix 1. The summary borrows from a recently completed compendium of environmental quality benchmarks (MacDonald et al.. 1999) and includes updates from the present literature search. The summary provides guideline, standard and criterion information for Canadian, American and European jurisdictions at the federal, provincial or state level. Certain jurisdictions have identified surface water uses (water supply, aquatic life, recreation, etc.) that apply to specific surface water classifications. Classification standards include water quality characteristics that are arranged from the highest to the lowest (e.g., Class AA to Class C) within individual jurisdictions and include designated uses applicable to the water quality standard. The number of beneficial or designated uses usually decreases with declining water temperature quality. Within some jurisdictions, sub-classes may be designated (e.g., B1, B2, or B3). Surface water quality temperature criteria or narrative statements are assigned to specific classifications for protective purposes. In certain instances, exceedance levels due to human activities are specified by formulae that allow incremental increases beyond ambient conditions. In regard to point-source activities, maximum permissible temperature increases are calculated using the highest ambient water temperature at a point or points unaffected by the discharge for a given period. In some instances, the amount of change above background or allowable rate of change in temperature is also specified. A list of acronyms and classification details for individual jurisdictions associated with guideline summaries are appended in a glossary at the end of the document.
With respect to characteristic uses, water supply designations are sub-divided into domestic, agricultural or industrial uses, while recreation designations are sub-divided into primary contact (i.e., ingestion possible) or secondary contact (i.e., ingestion not possible) uses. Aquatic life designations may include a sub-division between cold water (i.e., <18 degrees C) and warm water (i.e., >18 degrees C) biota or specify temperature criteria for fish life history activities that include migration, spawning, incubation and rearing. Similarly, specific water temperature criteria may be provided for the protection of threatened and endangered species.
5.1 Drinking water
Of eleven jurisdictions reported in North America and Europe, guideline values range from 12-15 degrees C and water quality standards range from 16-28.3 degrees C, depending on geographic location. The upper values are associated with the eastern seaboard states of the continental United States (refer to Appendix 1-1). Temperature guideline recommendations in the Pacific Northwest (PNW) range from less than or equal to 15-18 degrees C. Maximum temperature change, above ambient conditions, range from 0.3-2.8 degrees C across four surface water classifications. Temperature changes in the PNW range from 0.3-0.6 degrees C. Criteria have been established for aesthetic purposes or to accommodate thermal requirements of cold water or warm water fisheries. Narrative statements are provided to limit temperature change in lakes from background conditions.
5.2 Recreation and aesthetics
Of twelve jurisdictions reported in North America, water quality standards for primary contact use range from 13-32.2 degrees C and from 19-32.2 degrees C for secondary contact use in fresh, salt or estuarine waters (refer to Appendix 1-2). Maximum temperature criteria for secondary use such as angling include numeric values up to 23.9 degrees C for cold water fisheries and up to 28.3 degrees C for warm water fisheries. Maximum allowable increases over ambient conditions extend from 0.3-3.0 degrees C for all uses. Within the PNW, Washington and Montana have the most stringent permissible increases within individual classifications when natural conditions are exceeded (0.3-0.6 degrees C). Narrative statements are provided to minimize temperature change from background levels for lake classifications or provide guidelines for swimmers and bathers.
5.3 Aquatic life and wildlife
Of 20 jurisdictions reported, freshwater temperature guidelines are defined for general or specific life history activities or species within classifications or individual basins that distinguish cold water and warm water fisheries (refer to Appendix 1-3). For cold water designations, temperature criteria range from 8-24 degrees C with specific designations defined for salmonid spawning, incubation, rearing and migration. Listed species with special restrictions include bull trout and white sturgeon. Adopted protocols to establish numeric values are based on mean weekly average temperatures, maximum daily average temperatures or maximum daily temperatures. Maximum allowable temperature increases above ambient conditions range from 0.3-1.7 degrees C. The numeric values and allowances established by Washington, Oregon, Idaho, Montana, Alaska, Virginia, Massachusetts and Europe provide a level of protection that fit the range of environmental conditions observed for cold water fisheries in British Columbia. Temperature criteria for warm water designations range from 10-29.4 degrees C with allowable increases up to 3 degrees C. In a few cases, narrative statements are provided to limit alterations to natural thermal regimes or identify conditions under which further temperature increases are unacceptable.
Water quality standards for the protection of aquatic life in marine or estuarine waters are generally specified for water quality classifications (refer to Appendix 1-4). The standards show wide variation over geographical areas ranging from 13-39.4 degrees C. Temperature changes above ambient conditions are also variable within applicable beneficial use designations (0.3-2.8 degrees C). Narrative statements are provided within certain jurisdictions to address maximum rates of temperature change or alterations in amplitude or frequency of daily temperature cycles. The standards are generally expressed as maximum values or maximum daily means. Standards with the greatest applicability to cold water biota in British Columbia are derived from Washington State guidelines where numeric values range from 13-22 degrees C.
Of nine jurisdictions reported, water quality standards or criteria for wildlife use are specified within water use classifications that range from 13.0-32.2 degrees C (refer to Appendix 1-5). Water quality standards or criteria are provided as maximum or maximum daily mean temperature values. Maximum allowable increases above ambient water temperature range from 0.3-3.0 degrees C. Narrative statements include allowable changes from natural conditions for lakes, the amount of allowable weekly average increases, and the maximum hourly rate of change. Allowable alterations to daily temperature cycles are also included for some jurisdictions. Standards with the greatest applicability to wildlife in British Columbia are again likely derived from numeric values provided from Washington State guidelines (13-21 degrees C).
5.4 Irrigation and livestock watering
Of six jurisdictions reported, water quality standards for irrigation uses identified within classifications range from 16-30 degrees C (refer to Appendix 1-6). Water quality standards are provided as maximum temperature values. Maximum allowable increases above ambient water temperature range from 0.3-2.8 degrees C. Narrative statements reflect allowable changes from natural conditions for lakes.
Of five jurisdictions reported, water quality standards for the protection of livestock within water use classifications range from 16-30 degrees C (refer to Appendix 1-7). Water quality standards are listed as maximum temperatures for all categories. Maximum allowable increases above ambient water temperature range from 0.3-2.8 degrees C. Narrative statements include allowable changes from natural conditions for lakes.
5.5 Industrial use
Of seven jurisdictions reported, water quality standards for the protection of industrial uses within water use classifications range from 13-29.4 degrees C (refer to Appendix 1-8). Water quality standards or criteria reflect maximum temperatures for all categories. Maximum allowable increases above ambient temperature range from 0.3-2.8 degrees C. Narrative statements include allowable changes from natural conditions for lakes.