How do you think workers dug the canal in 1900?

Workers dug the canal in 1900 is explained below in details.

Explanation:

The Panama Canal was created by constructing gates on the Chagres River to build Lake Madden and Gatun Lake, following the Gaillard Cut from the river within the two lakes and across the Continental Divide.

The canal was formerly a French scheme, and Panama was originally a portion of Colombia. Foundation started in January 1882. By 1888 the work crew estimated about 21,000, There were French engineers and others.

answer; i believe that the correct answer is ( rivers);

what is the answer