Saltwater has been flowing from the Gulf increase the Mississippi River, and that"s as much of a trouble as you could think.

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Due to the historical drought still searing the Midwest and taxing the heart of our agricultural economy, the Mississippi river is in ~ its lowest circulation rate in years. In Memphis, for instance, the flow is 8.9 feet listed below baseline. When the low flow has been ground connection barges and creating pockets the quicksand, the is also enabling the Gulf that Mexico to flow nearly 90 mile upstream from the mouth of the Mississippi.

Why? Salt water is denser than fresh water, which means if friend mix the two, the salt water sinks. The Gulf is salt water. The bottom of the Mississippi is reduced than the surface ar of the Gulf. Complying with that gradient, the thick gulf waters actually flow up the Mississippi, crawling along the riverbed. Theoretically, the salt water can circulation 350 mile from the mouth that the Mississippi, the suggest where the bottom the the river reaches an elevation greater than the surface ar of the Gulf. Yet the braided waters never makes the this far, as the downward flow of the Mississippi holds lock back.

A diagram from an army Corps report displayed the salt-fresh water interface crawls follow me the riverbed.


During a normal year, National Geographic reports, the saltwater wedge just makes it to 50 mile upstream. As of respectable 24, the army Corps reports the top edge that the Gulf waters to be 89.8 miles upstream. At 95 mile upstream, there is one intake pipe that supplies fresh water to new Orleans. This is a problem.

The intake pipe is not on the bottom the the river; the saltwater wedge would have to progress 20 or therefore miles beyond it prior to salinity i do not care an issue. Yet saltwater could flow upwards at a rate of 2-3 miles every day under the ideal conditions. Come ensure the doesn"t happen, the army Corps is building an $8.1 million underwater sill (shown in the diagram below) to stop the flow of the salt water, in ~ a ar 64 mile north the the mouth of the Mississippi.


Although the chart doesn"t quite present it, the corps has reported it can need as much as 2.7 million cubic yards that dredged sediment to develop the sill. You can fill more than fifty percent of the new Orleans Superdome through that quantity of sludge. As soon as in place, it would certainly halt the upward flow of the Gulf in two weeks. Once the river output increases again, the sill will normally degrade.

But there is another factor to compete with: Hurricane Isaac. The oncoming storm could impact the procedure in two ways. One would alleviate the problem; the other would make it worse.

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"There is no one size fits every answer come what impacts a hurricane might have top top the saltwater issue," Rachel Rodi, an army Corps spokesperson said me via email. "Every storm is different and also there are too numerous variables to pen down. For example: when the storm surge may temporarily advanced salinity levels in the area, the rain associated with a floor falling storm would make its method up the Mississippi flow Valley, end up draining earlier into the river, and raise operation upstream that would help push the saltwater wedge ago down river."

The Mississippi is much more human-engineered than a herbal river in ~ this point. Together Alexis Madrigal placed it: "The Mississippi no longer fits the meaning a river as "a organic watercourse flowing in the direction of an ocean, a lake, a sea, or an additional river." Rather, the waterway has been shaped in countless ways, large and small, to suit person needs."

But weather tho matters, and also effects the daily operations of the river. While that is a greatly engineered and also meticulously preserved piece of transportation technology, in ~ the end of the day, the mighty Mississippi is still beholden to floods, droughts, and also hurricanes.