Simplify the following text for a Grade 4 native English-speaking person.
Original: Today the main stem of the Columbia River has 14 dams , of which three are in Canada and 11 in the U.S. Four mainstem dams and four lower Snake River dams contain navigation locks to allow ship and barge passage from the ocean as far as Lewiston , Idaho . The river system as a whole has more than 400 dams for hydroelectricity and irrigation .
Simplified: There are 14 dams on the Columbia River .