SHERMAN, Texas (KTEN) -- The City of Sherman is working with the North Texas Municipal Water District to repair the "catastrophic failure" of a massive six-foot wide pipeline that supplies half the city's water supply.

Utility customers are urged to reduce water use until the fissure is fixed.

The NTMWD first noticed the leak Tuesday near Davy Lane and FM 1417 in Denison.

The pipeline supplies water from Lake Texoma. As the break is being fixed, Sherman is relying on its groundwater wells.  Sherman utility customers may be seeing a drop in water pressure as a result. 

"During the summer months, the groundwater system by itself is not enough to supply the entire city," explained Sherman city spokesperson Nate Strauch. "So really what we're doing right now is on reserves and our tanks.  That's why we are asking for people to conserve water as much as they can. Please, no watering of lawns;  if you can avoid doing laundry, washing dishes with the dishwasher, that kind of thing."

The NTMWD released a statement saying the restoration work may not be complete until Thursday. It added that the cause of the leak is unknown and remains under investigation.

The City of Sherman said if the water reserves run low, they will issue a boil water notice to residents.

Work is underway to repair a leak in a 6-foot pipeline supplying water to the City of Sherman.