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| High quality site characteristics |
Impacted site characteristics |
| Non-forested headwater streams can be characterized as being steep
step-pool streams with abundant riparian shrub cover or be low gradient
meandering streams reaches through meadows with little woody vegetation
shading. Steep shaded streams operate similar to forested headwater
streams in that they are hetertrophic, i.e., their energy base is primarily
derived from outside the stream's banks (a.k.a., allocthonous material).
Unshaded meadow streams are typically autotrophic, i.e., their energy base
is primarily derived from material originating within the stream's banks,
e.g., algae (a.k.a., autochthonous material). The type of aquatic
invertebrates found in the stream will vary depending on whether the stream
is heterotrophic or autotrophic. Shredder-type invertebrates will
be most abundant in hetertrophic streams, whereas, scraper-type invertebrates
will be more prevalent in autotrophic streams. |
River reaches impacted by concentrated livestock grazing are characterized
by higher width to depth ratios, less overstream riparian cover and higher
sediment and nutrient loads than ungrazed or lightly grazed streams.
Overgrazed stream reaches generally lack instream habitat, such as deep
pools for fishes and crevice space among gravels and cobbles for invertebrates
and young fish. Primary indicators of stress will include stressed
riparian vegetation characteristics, such as no young shrubs or lots of
bare ground, increased deposition of fine sediment in pools and later in
riffles, warmer summer water temperatures, lower dissolved oxygen concentrations
and higher fecal coliform counts. |
| Potential impacts |
|
| Livestock grazing in riparian areas, mining, and road crossings. |
| Hydrology |
|
| Discharge regime- variable depending on the size of the watershed and
the input from groundwater. Spring snowmelt and summer rain events
can drastically increase flows even in pristine watersheds.
Temperature- variable depending on distance from source, shading, and
groundwater inputs. Annual and seasonal variations are typically
higher than in forested headwater streams. |
Discharge regime - Snowmelt and precipitation induced flows are generally
higher and late summer low flows are generally lower than in comparable
unimpacted stream reaches.
Temperature - Daily, seasonal, and annual variations can be much greater
than in less impacted streams. Daily variations can exceed 15 degrees
C, and annual variations can approach 30 degrees C. |
| Instream habitat |
|
| Coarse substrate interspersed with aquatic vascular plants and mosses.
Pools and riffle/run habitats occur in similar numbers. Substrate
is often covered with algae assemblages. Large woody debris dams
create pools which trap partially processed coarse particulate organic
matter from upper forested reaches. Beaver dams and pools may be
present. |
Riffle/run habitats dominate with pools occurring less frequently.
Algae populations may explode during mid to late summer which may lower
dissolved oxygen concentrations at night. Riffle gravel and cobble
substrates may become embedded with fine sediment. |
Sampling
equipment
kicknets and Surber
nets |
|
| Dominant functional feeding groups |
|
| Scrapers, filterers, collector gathers, shredders, and predators. |
Collector gatherers, filterers, scrapers and predators. |
| Invertebrate assemblage members |
|
Coleoptera: Elmidae
Diptera: Chironomidae, Blephaceridae, Tipulidae
Ephemeroptera: Heptageniidae, Ephemerellidae
Megaloptera: Corydalidae
Plecoptera: Nemouridae, Perlodidae, Chloroperlidae, Pteronarcyidae
Trichoptera: Glossosomatidae, Limnephilidae, Philopotamidae, Rhyacophilidae |
Diptera: Chironomidae, Simuliidae
Ephemeroptera: Baetidae, Tricorythidae
Trichoptera: Brachycentridae, Hydropsychidae |
