If contaminated, it could be weeks or months before freshwater returns, unless there is significant rainfall, leaders say.
Catch up quick: A drought across the Mississippi River Valley means salt water from the Gulf of Mexico is coming upriver, threatening drinking water supplies in New Orleans and two nearby parishes.
Many municipalities in southeast Louisiana, including New Orleans, pull their drinking water from the river.
Communities further south have had salt in their water since June.
Driving the news: A massive reverse osmosis machine that desalinates water is being installed in Plaquemines Parish, just southeast of New Orleans, and two more machines are on the way.
But these units won't be able to produce enough water to meet the demand in metro New Orleans.
Plans to protect the drinking water include building 10- to 15-mile-long pipelines to draw water from further upriver.
Gov. John Bel Edwards approved plans Friday for Jefferson Parish, which includes suburbs west and south of New Orleans, to build multiple pipelines. Construction could start this week.