The large rise in the lake level that is seen here is due to a
reduction in the flow of the Iowa River
from 6000 to 1000
cubic feet per second for 3 days. This was done to reduce the crest of a Cedar River flood
where it joins the Iowa. Combine
this with Coralville Lake inflows up to 15,000 cubic feet per second and
one can see why the
lake filled so rapidly.