Deltas are wetlands that form where rivers empty their water and sediment into another body of water, such as an ocean, lake or another river.
Deltas are important to humans, fish and other wildlife because they hold very fertile soil and support a variety of vegetation.
Many animals are indigenous to the shallow waters of a delta. Fish, crustaceans, birds and even predators such as tigers and bears can be part of a delta's ecosystem. A variety of plants and herbs—such as lilies and hibiscus—also thrive in this unique ecosystem.
Deltas absorb runoff from both floods and storms, and filter water as it makes its way through the delta's distributary network. This can reduce the impact of pollution flowing from upstream.
The term delta comes from the Greek letter delta, which is shaped like a triangle. Deltas with this triangular shape are called arcuate “arc-like” deltas. One example is the Nile River, which forms an arcuate delta as it empties into the Mediterranean Sea.
You can help protect river deltas wherever you are!