Runoff is the excess liquid that flows across the surface of the land and into nearby creeks, streams, and lakes when there is more water than the land can absorb. A runoff lake is a lake that is formed by the accumulation of surface runoff water. Runoff water can contain pollutants, debris, and harmful chemicals, which can make their way directly into nearby streams, lakes, or wetlands if the runoff is not properly captured in a stormwater basin. Runoff can also have significant economic effects, such as reducing crop yields and causing erosion.

In summary, a runoff lake is a lake that is formed by the accumulation of surface runoff water.