Sediment Flows into Galveston Bay Studied to Help Understand Health of Watershed

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A better understanding of sediment and freshwater flow into Galveston Bay is now available from a new U.S. Geological Survey report, done in cooperation with the Texas Water Development Board, and the Galveston Bay Estuary Program.

Photo of USGS streamgage measures flooding in the lower Trinity River
A USGS streamgage measures flooding in the lower Trinity River, Texas. Credit: Zulimar Lucena, USGS. 

Galveston Bay is an important watershed that provides the public with food and economic security, as well as a place for recreational activities. The health of this ecosystem is reliant on the quality and quantity of freshwater streamflow and sediment from the land. Flows can be influenced by alterations in the river course, such as withdrawals and diversions. With population and water demand projected to increase, the ability to provide adequate flows to coastal ecosystems presents a resource management challenge that requires improving the current understanding of freshwater flows.

For the first time, USGS scientists are now collecting real-time sediment and water-quality information on water traveling into Galveston Bay. Researchers examined streamflow and water-quality data in the lower Trinity River watershed from May 2014 to December 2015 to improve understanding of freshwater inflows. This study is part of a larger USGS project, done in cooperation with the TWDB, to monitor the nutrient and sediment concentrations entering Texas bays and coastal wetlands in four major river systems, to include Trinity River, Colorado River, Guadalupe-San Antonio River and Nueces River.

“This study is the first step in understanding how water and sediment flows into the bays and coastal wetlands of Texas,” said Zulimar Lucena, USGS scientist and lead author of the study. “This will help decision makers make informed choices about these important resources.”

At high flows, a large part of the volume released from Lake Livingston did not reach Galveston Bay through the main channel of the Trinity River. Streamflow and the amount of sediment and nutrients that are seen in the lower basin are different that what’s seen upstream.

“Water is diverting from the river and being held in the wetlands, which might be acting as a filter for nutrients and sediments,” said Lucena. “While more studies are needed, it has become clear that wetlands are playing a large role in how much streamflow, sediment and nutrients are being delivered to the bay.”

Coastal ecosystems depend on freshwater flows from land to maintain adequate levels of salinity, nutrients, and sediment to support diverse biological communities. Reduced sediment supply can result in changes in coastline, particularly when coupled with erosion, sea level rise and subsidence. Increased sediment and nutrient levels can also cause detrimental effects, such as algal blooms.

 

Map of Lower Trinity River Watershed
Map of Lower Trinity River Watershed.
A USGS streamflow gauge station in the lower Trinity River, Texas. 
A USGS streamflow gauge station in the lower Trinity River, Texas. Credit: Niccolas Piano, USGS. 
A USGS streamflow gauge station in the lower Trinity River, Texas. 
A USGS streamflow gauge station in the lower Trinity River, Texas. Credit: Niccolas Piano, USGS.