Detective 3

The graphs below shows the relationship between IBI and the residue captured in a filter.  The amount of residue is a measure of the amount of sediment that was found in the water sample.   Study the graphs and answer the questions.  Be prepared to explain the correct answers to your group.


Watershed Glossary

  1. Describe the relationship between Maximum Residue and IBI - as Residue goes down, the IBI ??.  Is there a consistent relationship?
  2. Where are the places/times where the relationship does not seem to be consistent on the line graph?  Write those down.
  3. Does the scatterplot show any kind of consistent trend in the relationship?
  4. What we would expect in the relationship between residue and BOD is

    - As the residue goes up, the IBI would go down

    A is correct!

    - As the residue goes up, the IBI would go up

    B is incorrect - We would expect that more sediment would mean it would be harder for fish to find food and to breed.
  1. The two main sources of sediment loads in Ohio streams are:

    - Older city areas and farms

    A is only partly right - Older cities have pavement and planted grass so that soil does not get loose very often.

    - Forest areas and older city areas

    B is incorrect - Forest areas trap sediment in the tree roots and leaf litter; older cities have stable grass areas.

    - Construction areas and farms where the soil is uncovered for long periods of time

    C is correct -

    - Construction areas covered with hay and farms with mature crops

    D is incorrect - Construction areas that are covered with hay or other cover will not erode so much nor will farms with mature crops.
  1. How does a good riparian zone relate to sediments that reach the stream?

    - It has no effect

    A is incorrect - Won't the forest or grass in the riparian zone have some filtering effect?

    - It will filter out many of the sediments before they reach the stream

    B is correct -

    - It will filter only a few of the sediments

    C is incorrect - A good riparian zone will filter out many of the sediments.