Runoff water carries pollutants as it flows downhill from where rain and snow fall. Rainwater harvesting helps save water and protect it by capturing runoff in rain barrels or rain gardens before it reaches streams or groundwater. Rain barrels and rain gardens redirect runoff water from downspouts and other sources to be used for watering plants or allowing water to slowly seep into the ground, reducing pollution and flooding while conserving water supplies. Permits are generally not required for simple rainwater catchment systems using rain barrels, but more complex systems may need permits.