Richard J. Cannings and Eva Durance. 1998. Human use of natural resources in the South Okanagan and Lower Similkameen valleys in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

HUMAN USE OF NATURAL RESOURCES IN THE SOUTH OKANAGAN AND LOWER SIMILKAMEEN VALLEYS

Richard J. Cannings and Eva Durance

HISTORICAL WATER USE

MAIN IMPACTS OF HISTORICAL WATER USE ON WILDLIFE AND HABITAT

1. Damming and channelizing of central Valley lakes and river and subsequent control of water levels

inability of salmon to migrate for spawning beyond Vaseux Lake Dam
destruction of some lakeshore vegetation and associated wildlife habitat if water levels low even for a year; more severe effects for longer periods of time, but probably reversible even up to five years or so; generally beneficial effects of high water levels as during periodic flood, however, not present after 1955 and effects seen in decrease in shoreline thickets, organic matter along the shore, and wildlife associated with these conditions such as muskrat and dabbling ducks and other waterfowl
general lack of consideration for wildlife needs in water level controls
destruction of marshes, wetlands, and riparian vegetation associated with the wetlands
overgrazing of marshland vegetation such as bulrushes by cattle when water levels low

2. introduction of non-native species of plants and fish

decrease and in some places virtual annihilation of pondweed and other aquatic plants in mainstem lakes by carp, introduced to Okanagan Lake about 1917 and the subsequent decrease in waterfowl; decrease in muskrat populations partly from depletion of food sources by carp
displacement of native fish species by introduced lake whitefish, and largemouth and smallmouth bass
decline in kokanee salmon from introduction of mysid shrimp in 1970's
displacement of native waterside vegetation by purple loosestrife
choking out of native aquatic vegetation and destruction of habitat for native fish and other aquatic species by Eurasian millefoil which has invaded seven mainstem lakes and one upper elevation lake in the Okanagan Valley and affects about 1,000 ha of shoreline (BC State of the Environment Report, p. 83) ; masses of millefoil prevent light and thus photsynthesis in native vegetation and spawning areas may be affected

3. filling and draining of marshlands and wetlands for agriculture and urban development

destruction of water habitat, riparian vegetation and other brush and thickets critical to many species of birds, small mammals, amphibians, and reptiles
destruction of watering places for mammals and birds

4. increased urban development and shoreline housing

increased need for water and water storage at the expense of upland source ecosystems: degraded upland lake/reservoirs, altered spring runoff regimes
further destruction of shoreline vegetation, especially cottonwood stands and riparian thickets, disturbance of wildlife with power boats, increased danger for wildlife from domestic cats and dogs
cutting off of access for wildlife to water sources

5. pollution of water

from poorly maintained home septic systems
runoff from agricultural operations and residential areas of fertilizers and pesticides and of industrial pollutants from industry
runoff from roads and highways of petroleum derivatives, anti-freeze, salt, and other such substances
increased sedimentation from land clearing to edge of waterways in forestry, residential development, or agriculture