Live updates: Salt water tracker shows latest location of intrusion near New Orleans - NOLA.com

Live updates: Salt water tracker for New Orleans, Louisiana | Environment | nola.com

An intrusion of salt water moving up the Mississippi River from the Gulf of Mexico is threatening local drinking water supplies.

A federal emergency has been declared in Orleans, Jefferson, Plaquemines and St. Bernard parishes.

Effects could last as long as three months, officials said Wednesday.

Here's a live look at the latest locations being affected by the salt water:

Map shows a timeline animation of salt water creeping up the Mississippi River threatening area water supplies, according to the Army Corps of Engineers. The Mississippi River is the primary source for drinking water for the New Orleans metro area, since nearly every other body of water surrounding the region is salty or brackish.

NO.sillwork

Where is it?

As shown above, the salt water's location is river mile 69.4, or about six miles south of Belle Chasse.

When will it arrive?

It is forecast to reach St. Bernard on Oct. 19, New Orleans' Carrolton plant on Oct. 28 and East Jefferson on Oct. 29.

Rain anytime soon?

Significant rainfall is needed further north to increase the amount of water flowing down the river and flush out the salt. But the forecast is not looking good for now.

"We're not seeing any relief to the low water conditions through the middle portions of October rom what we're seeing upstream," said Jeffrey Graschel, a hydrologist with the Lower Mississippi River Forecast Center, based at the Slidell office of the National Weather Service.

"And beyond that, it's just too far out to predict whether enough rainfall would fall in the Mississippi, Missouri or Ohio river basins — and make the two-week journey downstream — to give any relief to the salt water problem, he said.

"At the same time, forecasters with the National Weather Service's Climate Prediction Center believe that there's a chance of rainfall returning to those areas in November, but, again, how much and when the relief would arrive downstream is not known."

See the latest on drought conditions at the U.S. Drought Monitor website

What is being done?

The Army Corps of Engineers is heightening a sill, or underwater levee, it built in July to partially block the salt water. It will however include a notch to continue to allow shipping along the river, and it will only slow the salt water's progress.

Separately, the Corps is preparing to barge in 36 million gallons of water per day from further upriver to mix with supplies at local plants and dilute the salt.

It is also looking at locating reverse-osmosis machines to filter water in some areas.

Barges won't be enough for plants supplying the east bank of New Orleans and Jefferson Parish. Those parishes are instead hoping to build a pipeline from around Kenner to pump water downriver that would be used to dilute the salt at New Orleans' Carrollton Plant and the plant for East Jefferson.

-Updated at 11 am on Thursday