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Watershed Watch Community Science

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  1. Watershed Watch Community Science
  2. Watershed Watch Methods
    Introduction & What is a Watershed?
    1 Quiz
  3. How Do I Collect Watershed Health Data?
    How to Measure Stream Chemistry?
    4 Topics
    |
    1 Quiz
  4. What is an Benthic Macroinvertebrate, How to Sample, What do they tell us about Watershed Health?
    4 Topics
    |
    1 Quiz
  5. How do we Measure the Health of Riparian Areas
    7 Topics
    |
    1 Quiz
  6. How to Measure Streamflow?
    5 Topics
    |
    1 Quiz
  7. How to I Turn My Data Into Action?
    How to organize and interpret my data and develop findings?
  8. How to make a community presentation with my findings?
  9. How write a watershed management plan?
  10. We Calibrate Because We Care! ~ How to maintain and calibrate equipment
  11. How can I find work in the field of watershed science?
  12. How can I influence policymakers and turn my data into action?
Lesson 5, Topic 6
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Are there many pools and riffles?

August 31, 2020
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Pool to riffle ratio (riffle frequency). Undisturbed streams typically have alternating pool and riffle areas which tends to support the highest species diversity and food sources for fish. Fish wait for benthic insects to float by at the head of a pool or at the tail of a riffle.

Pool RiffleIf the ratio of distance between riffles to stream width is between 5:1 and 7:1, heterogeneity for aquatic insects and fish is optimal, while a ratio of more than 25:1 is considered a poor habitat. Since benthic communities thrive as a result of integrated environmental factors (substrate, food availability, current etc.), and species have preferences for alternative substrate types, it follows that maximum variability in streambed morphology should support higher species diversity (Barbour and Stribling 1991). Riffles are places that support high-quality habitat and a diverse fauna of aquatic insects and fish. Upstream land use activities can profoundly change pool/ riffle relationships, as well as human-caused changes in flood and low-flow discharge (Frissell et al. 1986). The evaluator uses a tape to measure the average distance between riffles and the width of the bankfull channel.

For high gradient streams, calculate the ratio by dividing the average distance between riffles by the average stream width. Measure this for a distance of approximately 150 to 300 feet. For low gradient streams, calculate the ratio by dividing the average distance between river bends by the average river width. You may want to determine this ratio on a map rather than in the field if your river is large and the distance between bends is great. If a stream contains riffles and bends, the dominant feature with the best habitat should be used (Barbour and Stribling).