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Bays & Estuaries

It Goes with the Flow

Marshland along the San Antonio River
2018 eFlows cover


One important part of the holistic function of waterways is environmental flows.

There is a baseline flow established for the San Antonio River that allows the river to function as it should and to meet habitat needs, particularly for young species.

Click the image to the left to read our statement on Environmental Flows.

What Happens Upstream Matters

A city upstream of a bay and estuary, such as San Antonio, can affect the amount of fresh water flowing from a river into a bay or ocean. The volume can be dramatically affected based on how much water the city is using and its efforts to conserve water. The freshwater inflow not only brings water but also nutrients and sediments that feed plants and animals in the estuary. The flow also affects the salinity and temperature of the water in the bay, as well as the structure of the marsh. The salinity levels change depending on seasons, droughts, tides and floods.

Remember the awesome Whooping Crane?

Learn more about how freshwater inflows are connected to the Crane population and why the San Antonio River Authority continues to support scientific research in the bay to further understand how these changes affect wildlife populations. View a 187-page report linking freshwater inflows and marsh community dynamics in San Antonio Bay to Whooping Cranes.

A Whooping Crane with fish in its mouth


How Ecosystems are Connected Across Great Lengths of River

Many fish species rely on certain conditions of water flow, salinity and temperature to thrive in their habitat. Freshwater inflows can directly affect those conditions. Many of these species drive the commercial fishing industry in communities along the coast. This is a good example of how aquatic ecosystems are connected from headwaters to ocean.   

The River Authority can study and predict what may happen with the marsh vegetation in the San Antonio Bay when certain environmental conditions occur by using the Ecological DYnamics Simulation (EDYS) model. We know bays and estuaries are complex, dynamic areas, and this computer program can help model and simulate how vegetation responds to the varying environmental conditions like salinity and tides.