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Water: Wadeable Streams Assessment

WSA Glossary of Terms

  • Benthic macroinvertebrates: Aquatic larval stages of insects, such as dragonfly larvae and aquatic beetles; crustaceans such as crayfish; worms; and mollusks. These small creatures live throughout the stream bed attached to rocks, vegetation, and logs and sticks or burrowed into stream bottoms.

  • Biological assemblages: Key groups of animals and plants -- such as benthic macroinvertebrates, fish, or algae -- that are studied to learn more about the condition of water resources.

  • Ecoregions: Ecological regions that are similar in climate, vegetation, soil type, and geology; water resources within a particular ecoregion have similar natural characteristics and similar responses to stressors.

  • In-stream fish habitat: Areas fish need for concealment and feeding, such as large wood within the stream banks, boulders, undercut banks, and tree roots.

  • Macroinvertebrate Index of Biotic Condition: The sum of a number of individual measures of biological condition, such as the number of taxa in a sample, the number of taxa with different habits and feeding strategies, etc.

  • National Hydrography Dataset: Comprehensive set of digital spatial data -- based on U.S. Geological Survey 1:100,000 scale topographic maps -- that contains information on surface water features such as streams, rivers, lakes and ponds.

  • Nutrients: Substances such as nitrogen and phosphorus that can over-stimulate the growth of algae and other plants in water. Nutrients in streams and lakes can come from agricultural and urban runoff, leaking septic systems, sewage discharges and similar sources.

  • O/E (Observed/Expected) Ratio of Taxa Loss: A ratio comparing the number of taxa expected (E) to exist at a site to the number that are actually observed (O). The taxa expected at individual sites are based on models developed from data collected at reference sites.

  • Perennial streams: Flowing throughout the year.

  • Probability-based design: A type of random sampling technique in which every element of the population has a known probability of being selected for sampling.

  • Reach: Stream segment.

  • Reference condition: The least-disturbed condition available in an ecological region, determined based on specific criteria, used as a benchmark for comparison with sampled sites in the region.

  • Riparian disturbance: A measure of the evidence of human activities in and alongside streams, such as dams, roadways, pastureland, and trash.

  • Riparian vegetative cover: Vegetation corridor alongside streams and rivers. Intact riparian vegetative cover reduces pollution runoff, prevents streambank erosion, and provides shade, lower temperatures, food, and habitat for fish and other aquatic organisms.

  • Stream order: Stream size, based on the confluence of one stream with another. 1st order streams are the origin or headwaters. The confluence or joining of two 1st order streams forms a second order stream, the confluence of two 2nd order streams forms a 3rd order stream, and so on.

  • Streambed sediments: Fine sediments and silt on the streambed. In excess quantities, they can fill in the habitat spaces between stream cobbles and boulders, and suffocate macroinvertebrates and fish eggs.

  • Stressors: Effects or substances that are stressful to -- and therefore degrade -- aquatic ecosystems. Stressors may be chemical (e.g., nutrients), physical (e.g. excess sediments on the streambed), or biological (e.g., competing invasive species).

  • Taxa: Plural of taxon; groupings of living organisms, such as phylum, order, family, genus, or species. Scientists organize organisms into taxa in order to better identify and understand them.

  • Wadeable streams: Streams that are small and shallow enough to adequately sample by wading, without a boat.

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