Water Stewardship Information Sources
| ID | 992 |
|---|---|
| Citation | Jensen, V. n.d. Water quality trends in Okanagan, Skaha and Osoyoos Lakes in response to nutrient reductions and hydrologic variation. BC Ministry of Environment. |
| Organization | Ministry of Environment |
| URL | http://www.env.gov.bc.ca/wat/wq/trendsWQS/WatTrendOkanaganSkahaOsoyoos.pdf |
| Abstract/Description or Keywords | The population of the Canadian Okanagan basin is approximately 300,000, tripling every 30- 40 years since 1940, and presently exhibits one of the fastest growth rates in the province of British Columbia. To guard Okanagan, Skaha, and Osyooos lakes from excessive eutrophication, phosphorus (P) reduction from municipal sewage treatment plants was implemented in various stages since 1971. Oligotrophication is now evident in Skaha Lake. Spring phosphorus, and autumnal phytoplankton chlorophyll a values are decreasing and hypolimnetic dissolved oxygen readings have increased in Skaha. Similar trends but to a lesser extent have occurred in Osoyoos Lake but with considerable year to year variability. Reductions in municipal point source phosphorus loading to Okanagan Lake improved water quality near two points of discharge. Two recent multi-year periods of increased water discharge from Okanagan Lake (1981-84 and 1996,1997 1999) are closely associated with increased spring and fall P, reduced water clarity and elevated phytoplankton chlorophyll a in Okanagan Lake. Despite a long residence time, changes in hydrology clearly affect nutrient loading, and aquatic ecosystem processes in Okanagan Lake. Hydrologic variation and nonpoint source nutrient pollution account for the majority of the nutrient variation observed in these lakes. Management efforts to reduce NPS nutrient loading are described and multiple benefits to non-point source pollution control noted. Further study is needed to more accurately apportion and effectively manage non-point source nutrient loading from agriculture, urban run-off, and forestry. Setting more comprehensive water quality objectives for the Okanagan lakes is recommended as a key component of ecosystem based management of the Okanagan basin. water quality, chemical water quality |
| Information Type | article |
| Regional Watershed | Okanagan |
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| Project status | complete |
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