A former scientist and opponent of Dam removal in the Northwest has recently reversed his stance and now believes dam removal is the only way to help endangered salmon. He has stated that his position has changed because of Global warming. If water temperatures increase from 20ºC to 25ºC in the Columbia River,
a. What is the change in the saturated dissolved oxygen levels (in mg/L) which would be expected in the river?
b. In what way does impounding (damming) a river reduce the dissolved oxygen? Please state the specific variable that might be affected.
What will be an ideal response?
a. From nomograph Figure 4.23
b. The reaeration constant can be estimated from:
???? is reduced for an impoundment
???? is increased for an impoundment
Thus both terms decrease the reaeration constant for an impounded river compared to a freeflowing river.
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