GBRA puts in saltwater barrier on Guadalupe
By BY DIANNA WRAY - DWRAY@VICAD.COM
June 28, 2012 at 1:28 a.m.
Updated June 29, 2012 at 1:29 a.m.
As the long hot summer continues, the water levels of the Guadalupe River have dropped, allowing salt water to creep upstream.
On Wednesday, the Guadalupe-Blanco River Authority stepped in to make sure the salt water doesn't contaminate the fresh water flowing down the river.
The Guadalupe River is usually at a higher water level than the San Antonio Bay, but that changes in dry conditions. As the river flow decreases, the river level drops, said Herb Wittliff, manager of GBRA's Port Lavaca operations. When it is equal or less than the levels in the bay, salt water begins moving upstream, contaminating the fresh water that flows out of faucets and is used by those in industry and agriculture.
After measuring that the river's level dropped to 3 feet above mean sea level near the town of Tivoli, about 10 miles from the mouth of the Guadalupe, GBRA crews activated the Guadalupe diversion dam and saltwater barrier on Wednesday, according to a news release issued by the GBRA.
The barrier raises the upstream level of water to 4 feet above mean sea level, the desired operating level, with most of the water flowing over the bags and downstream to San Antonio Bay, according to the release.
The saltwater barrier was built as a way to control water diversion and to protect the water supply, Wittliff said. In the wake of a record drought that gripped Texas in the 1950s, the GBRA put in two 50-foot-long inflatable barriers to span the river in 1965.
"The long-range plan for guarding against a drought, and allowing the firm supply of water to be delivered to customers, required some sort of protection against saltwater intrusion and the dam was the result," Wittliff said.
The barrier has been used when the Guadalupe River gets too low since then.
Hooked to concrete pillars, the barrier fills with water when in use, raising the water level of the river and blocking salt water from traveling upstream. The barrier is emptied of water and lies at the bottom of the river when not in use.
When the barrier is in place, a 2- to 4-feet drop in water level is possible from the upstream to the downstream side of the saltwater barrier. The GBRA is issuing a boating caution for anyone who uses the lower Guadalupe River near Tivoli for water recreation or commercial fishing, according to the release. Warning signs will be posted and lights illuminated for nighttime conditions.
The barrier is also used to make it easier to divert water to the canal that supplies GBRA customers with fresh water for agriculture, industry and consumption. The water that is routinely diverted by the GBRA goes through a gravity-based canal system. When the river level drops, water doesn't move through the canal system as easily. Raising the water level by raising the barrier increases the pressure of flow, allowing the water to move through the system more efficiently, Wittliff said. He said this does not decrease the amount of freshwater flowing downstream.