Stormwater Drain

When precipitation occurs, several things can happen to the water. Through the hydrologic cycle, natural landscapes, such as forests and wetlands, trap rainwater and snowmelt, and filter it as it percolates into the ground. In contrast, an urban environment consisting of paved surfaces such as roads, buildings, bridges and parking lots, and other impermeable areas such as airports and building sites, interrupt the natural hydrologic cycle by preventing percolation and thereby decreasing the water available to recharge groundwater. Instead of seeping slowly into the ground, water remains on the surface, accumulates and runs off in large amounts, creating the potential for flooding and erosion. This runoff is referred to as stormwater.

Adapted from Pollution Probe's Source Water Protection Primer