ABSTRACT
Rivers, lakes, reservoirs, and dams provide more than 75% of the water used in the U.S. Surface water systems are also used for recreational purposes and in many cases are important transportation conduits. The importance of surface water in the development of the U.S. is illustrated by looking at a map of the nation. Virtually all cities with populations exceeding 150,000 are located on rivers, and many smaller communities are located on rivers or lakes. There are about 2 million streams and rivers in the U.S., including the mighty Mississippi River, which is the fourth longest river in the world at 3710 mi long. Of the world’s 11 freshwater lakes with the largest surface area, 4 are located in the Great Lakes system (Superior is 1st, Huron is 5th, Michigan is 6th, and Erie is 11th). In addition to the Great Lakes, we have many thousands of smaller lakes, dams, reservoirs, and ponds. These include 25 lakes with surface areas greater than 100 mi
and more than 200 with surface areas larger than 10 mi
. All of these water bodies depend on the phenomena of runoff.
