Surface Water

Nearly one third of the United States is covered by the Mississippi River _____.

A lake can form when a river is blocked by mud and lava from _____.

When a lake is created by the building of a dam, the lake is called a _____.

Compared to lakes, ponds are usually _____.

The streams and smaller rivers that feed into a main river are its ____.

Lakes can disappear due to _____.

A stream that flows into two different rivers is part of two _____.

The process of nutrients building up in a lake over time is _____.

A river and all the streams and smaller rivers that flow into it together make up a _____.

Though it occurs naturally, human activities can increase _____ in a lake or pond.