Estuaries & Watersheds… What are They?

Estuaries are places where freshwater from rivers meets saltwater from the ocean. Estuaries are usually partly closed areas that slow down the river water, giving it time to mix with saltwater. Salmon River Estuary, Oregon

This mix of salt and fresh water creates a rich and complex environment that can support thousands of varieties of plant and marine life. Sand Lake Estuary, Oregon

Why do animals live in an estuary? An estuary is a safe and protected environment for young animals, so many fish and animals come to estuaries to lay eggs or give birth. The waters of an estuary are usually nutrient rich, bringing many species to the area to feed in safety. Beaver Creek, Oregon

What are the different types of estuaries? Beaver Creek, Oregon

Salt Wedge Estuary Salt wedge estuaries occur when the mouth of a river flows directly into salt water. The circulation is controlled by the river that pushes back the seawater. This creates a sharp boundary that separates an upper less salty layer from an intruding wedge-shaped salty bottom layer. The mouths of the Mississippi, Columbia and Hudson rivers are examples of salt wedge estuaries.

Partially Mixed Estuary Partially mixed estuaries have a tidal flow that provides a means of erasing the salt wedge. The salt water is mixed upward and fresh water is mixed downward. Deeper estuaries such as Puget Sound and San Francisco Bay are examples of partially mixed estuaries.

Well Mixed Estuary Well-mixed estuaries have strong tidal mixing and low river flow that mix the sea water throughout the shallow estuary. The mixing is so complete that the salinity is the same top to bottom and decreases from the ocean to the river. Shallow estuaries such as the Delaware Bay are well-mixed estuaries.

Now you know what an estuary is… So… What is a watershed?

Eventually, all water drains into the world’s oceans. Because of gravity, water always runs downhill from high points like mountains and hills to lower points in lakes, rivers, wetlands, and estuaries. Eventually, all water drains into the world’s oceans.

In every area, the water flows into what is called a “watershed” because the water “sheds” from high areas and travels into the low areas. How could you use this information to write a definition of “Watershed”?

How are Watersheds and Estuaries related? And WHY do we care? Stop and discuss…

Passing through the estuary is the final step. The watershed is all the water traveling through the land towards the ocean. Passing through the estuary is the final step. As water runs through a forest, it picks up leaves, dirt or pine needles. If it runs through a city or neighborhood, it will pick up things people us, such as garbage and fertilizer. Past factories, the water can pick up dangerous chemicals.

It can tell the health of our watersheds. An estuary is a perfect location to test water and “tell the story” of what the water picked up throughout the watershed. It can tell the health of our watersheds. Make a prediction… How healthy will we find the watershed that leads into the Beaver Creek estuary? Why?