By doing so, wetlands help keep river levels normal and filter and purify the surface water.
Wetlands accept water during storms and whenever water levels are high.
When water levels are low, wetlands slowly release water. A marsh in Scotland Wetlands also release vegetative matter into rivers, which helps feed fish in the rivers. Wetlands help to counter balance the human effect on rivers by rejuvenating them and surrounding ecosystems. Many animals that live in other habitats use wetlands for migration or reproduction. For example, herons nest in large old trees, but need shallow areas in order to wade for fish and aquatic life.