Nearly half of the lakes (46.5 percent) were artificial, mostly impoundments that were smaller, shallower and in watersheds with more human activity than natural lakes.
(Nearly half of the lakes; were; artificial) (mostly impoundments; were; smaller, shallower and in watersheds with more human activity than natural lakes)
Nearly half of the lakes mostly impoundments
were were
artificial
smaller, shallower and in watersheds with more human activity than natural lakes