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One of the more unfortunate ecosystem side-effects of the floodwaters as they move through the Atchafalaya Basin is they help spread some uninvited guests.

This is the invasive aquatic plant known as giant salvinia (salvinia molesta). It may not look big here, but trust us, it can carpet a lake or bayou.

In late 2015/early 2016 unusually large rainfall in the Upper Mississippi River Valley led to significant flooding in Arkansas, Illinois, Louisiana, Mississippi, Missouri, and Tennessee. USGS crews responded to the flooding by collecting streamflow and water quality information and providing it to emergency responders.

In late 2015/early 2016 unusually large rainfall in the Upper Mississippi River Valley led to significant flooding in Arkansas, Illinois, Louisiana, Mississippi, Missouri, and Tennessee. USGS crews responded to the flooding by collecting streamflow and water quality information and providing it to emergency responders.

USGS Scientists Dan Kroes and Charlie Demas set out into the Atchafalaya Basin to inspect flooding conditions in the Basin.

In late 2015/early 2016 unusually large rainfall in the Upper Mississippi River Valley led to significant flooding in Arkansas, Illinois, Louisiana, Mississippi, Missouri, and Tennessee. USGS crews responded to the flooding by collecting streamflow and water quality information and providing it to emergency responders.

USGS sets out to measure streamflow on the Mississippi River at Baton Rouge, sailing past the USS Kidd, a World War II destroyer.

USGS scientist Dan Kroes checks a subsidence instrument. Normally, this area is either barely under water or completely dry. The instrument is housed at around 7 or 8 feet, and there was just 16 inches between the sensor and water.

A panorama of a flooded stand of cypress trees in the Atchafalaya Basin.

Watch your hands! Here you can see one of the many denizens of the swamp that mistake our sensor and gauge houses for prime real estate. As Dan Kroes, the scientist monitoring subsidence, said, "At least it wasn't wasps this time..."

As the Atchafalaya River spreads out through the Basin, the waters slow down, and the sediment falls to the river and lakebottoms. Over time, that sediment can build up, eventually choking the river or permanently closing the lake. Or, as more and more sediment piles up, it compacts, sinking deeper during a process known as subsidence.

Snow-capped peaks of the La Sal Mountain Range as seen from the Island in the Sky District of Canyonlands National Park. This is one area in the Southwest where biocrust plays an important role. 

USGS scientists Mike Manning (left) and USGS National Flood Coordinator Bob Holmes discuss plans for the day. USGS crews departed from the U.S. Coast Guard's Vicksburg Office on the Yazoo River to measure streamflow on the Mississippi River.

USGS scientist Tammy Caudle demonstrates the acoustic dopplar current profiler onboard that will be used to measure streamflow on the Mississippi River.

Image shows a night-time view of the Natchez-Vidalia Bridge at Natchez, Mississippi.

USGS National Flood Coordinator Bob Holmes stands on one of USGS' boats in Vicksburg, Mississippi. This particular boat came from the USGS Indiana/Kentucky Water Science Center. The boat and its crew joined USGS scientists and boats from Alabama, Louisiana, and Mississippi in Vicksburg for the flood measurements.

This is the Mississippi River at Vicksburg, Mississippi, as the crest from the earlier flooding moves through.

The floodwaters from Arkansas, Illinois and Missouri are making their way downstream now to Mississippi and Louisiana. In preparation, USGS scientist Glen Stevens demonstrates the current meter to Hannah Hamilton, also with USGS. The current meter is one of the two primary ways that USGS measures streamflow discharge.

A panorama of the floodwaters at the Bonnet Carré Spillway. In preparation for the river crests due next week, USGS is out sampling on the Bonnet Carre Spillway, one of two spillways on the Mississippi River operated by the U.S. Army Corps of Engineers.

A staff gage at the Bonnet Carré Spillway, which is managed by the U.S. Army Corps of Engineers.

Mississippi River water flows through the Bonnet Carré Spillway into the channel, where it will flow to Lake Pontchartrain.

Flooded land within the Bonnet Carré Spillway. Normally, this land is dry, but when the U.S. Army Corps of Engineers decides to release Mississippi River water from the Bonnet Carré Spillway, this land will be submerged.