Impacts from grazing practices include increased
sediment and nutrient loading due to erosion of stream bank areas
destabilized by animal impacts and waste deposition. (The impacts of
grazing practices are discussed in greater detail in the Agricultural
Management Sources section.) As grazing animals tend to frequent stream
bank areas due to easy access to water, wastes are often deposited
directly in the stream channel. Grazing within these areas results in
decreased stubble height and damage to riparian areas due to removal of
vegetation and hoof action on stream bank sediments.
Pollutants from forest management(sediment), grazing activities
(sediment and animal waste) and natural processes (sediment) deposited in
streams during low flow can be rapidly resuspended and transported to the
reservoir during high flow events.
Forested land, as identified by the land-use designations
discussed earlier,is present in all subwatersheds within the Cascade
Reservoir Watershed. While forested land represents the major land use in
all but Cascade, Mud Creek and the North Fork Payette River subwatersheds;
only Gold Fork and West Mountain subwatersheds represent areas where forested
land is the major contributor to total phosphorus load. These two subwatersheds,
along with the NFPR subwatershed also contain the vast majority of the
grazed acres of forested land and have a large proportion of steeply-sloped,
forested land which grades rapidly toward the valley floor. Because of this,
transport of both dissolved and sediment-bound phosphorus is highly efficient
in these areas.
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