During the fall and winter, the Mississippi River usually drops, but not as much as in October 2022. In recent weeks, dry weather in the Ohio and Upper Mississippi valleys has caused water to drop to levels not seen in key sections of the river for more than a decade.
In addition to slowing barge traffic, the low water levels have raised concerns that saltwater intrusion into the lower Mississippi River could affect water supplies.
Operational Land Imager (OLI-2) on Landsat 9 captured this natural color image of a depleted river on October 7, 2022 (below). This image shows a barge spilling north of Vicksburg, Mississippi. It was learned that more than 100 tugs and barges were waiting as the river was temporarily closed due to the barge running aground and dredging works. The tugs and barges are tied together and come in a variety of sizes, but they can easily be 1,000 feet long and 100 feet wide.
The map above shows how wet the soil was on the same day the Landsat 8 images were acquired. Using data from the Crop Condition and Soil Moisture Analysis (Crop-CASMA) product, this map shows soil moisture anomalies on October 7, 2022. Among them, the brown area is relatively dry and the blue area is relatively humid. Crop-CASMA integrates measurements from NASA’s Soil Moisture Active Passive (SMAP) satellite and vegetation indices from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Terra and Aqua satellites.
By October 20, the river level in Vicksburg had dropped to 0.66 feet, a low level but still well above the record low of -7.00 feet set in 1940. However, by October 17, 2022, more at upstream of Memphis, the river’s water level dropped to -10.79 feet, the lowest level since the National Weather Service began logging there in 1954.
In New Madrid, Missouri, on October 20, the water level dropped to -5.1 feet, just above the minimum operating level of the water gauge. The water levels do not indicate the depth of the rivers, but are measured with respect to a chosen reference point. This is why some water level gauges have negative height measurements.
Tennessee climatologist Andrew Joyner explained that the lack of rain over a very large area is the main reason why the water level has dropped so low. “Given the lack of rain on such a large scale, it didn’t take long for the water level to drop,” he said.
Downstream from the river, the United States Army Corps of Engineers deals with the intrusion of salt water along the river. Normally, the river’s water flow would prevent the salt water from the Gulf of Mexico from moving much upstream, but the river was so shallow that a wedge of salt water had crept north and threatened freshwater intake. To prevent salt water from moving further upstream, the United States Marine Corps began construction of an underwater propeller in Myrtle Grove, Louisiana on 11 October.
Forecasts from the National Weather Service’s Lower Mississippi River Prediction Center indicate a drop in water levels at several points along the river in the coming weeks. In many cases, they expect water levels to be lower than in 2012, 2000 and 1988, other years when water levels reached unusually low levels.
What will happen in a few weeks is less clear. Joyner said: “Looking at the one-month and three-month forecasts, it seems that the possibility of above or below average rainfall is the same. If we end up with average rainfall, the situation may not get worse, but it won’t because it gets better.” .
