Pumping brackish water from the ground could affect freshwater supplies or lead the land to sink in areas along the Gulf.

Groundwater districts have enacted different rules to protect themselves from these possibilities. But the lines that delineate groundwater districts have been drawn on the surface and cannot stop actions outside the districts from affecting underground aquifers, which extend beyond their boundaries.

Think of it like throwing a rope across a lake and making separate rules for water use on either side of the rope, said Kyle Frazier, Texas Desalination Association executive director.

"The line doesn't mean anything to the lake," Frazier said. "That's the unreasonableness of the problem. The line on the ground doesn't make a difference."

A lot of groundwater districts agree developing brackish water is a good move in providing more water supplies, said Gonzales County Underground Water Conservation District general manager Greg Sengelmann.

But before brackish water within a given aquifer can be used, research needs to be done to make sure the use of brackish water doesn't affect the freshwater or slightly brackish zones used to water cattle, he said.

"How far do we have to go away from the freshwater not to affect it? You have to test," Sengelmann said. "But testing is expensive, and developers want a guarantee they will get a permit."

Brackish water tends to underlie freshwater zones. But the level of separation between the zones can vary from one aquifer to another, Sengelmann said.

Studies need to be done in advance of permitting for brackish water to ensure that the interconnectedness of the two resources doesn't cause intermixing of freshwater and brackish water, said Tim Andruss, the general manager of the Calhoun, Victoria, Refugio and Jackson County Groundwater Conservation Districts.

In aquifers with a high clay content, there's also a possibility that pulling brackish water out of the ground could cause subsidence, or sinking of the land surface.

With more questions than answers in brackish water desalination, some water project developers are focusing on seawater desalination instead.

Seawater has an exponentially higher content of salt, which can cost more to filter than brackish water. But there's no question of who has the water rights, said Greg Neal, a project developer with RWL Water, which builds water, wastewater treatment and desalination plants.

"I'm very focused on seawater desal right now," Neal said. "In my opinion inland brackish is just - until the rules are established - it's just too difficult to determine the business model."

Pro: Legislation could define management of brackish water