Soil moisture

Rivers are critical corridors that connect cities and ecosystems alike. When drought develops, water levels fall, making river navigation harder and more expensive. In 2022, water levels in some of the world’s largest rivers, including the Rhine in Europe and the Yangtze in China, fell to historically low levels. The Mississippi River fell so low in Memphis, Tennessee, in mid-October that barges were unable to float, requiring dredging and special water releases from upstream reservoirs to keep channels navigable. Conditions on the lower Mississippi may be easing somewhat, thanks to early winter rains. But as Earth scientists at the University of Memphis, we see this year’s dramatic plunge in water levels as a preview of a climate-altered future. River barges are an efficient way to transport bulk commodities, such as grain shipments, and heavy equipment over long distances. But that’s true only for normal water conditions. Increased swings between extreme low...

Many people are familiar with flash floods – torrents that develop quickly after heavy rainfall. But there’s also such a thing as a flash drought, and these sudden, extreme dry spells are becoming a big concern for farmers and water utilities. Flash droughts start and intensify quickly, over periods of weeks to months, compared to years or decades for conventional droughts. Still, they can cause substantial economic damage, since communities have less time to prepare for the impacts of a rapidly evolving drought. In 2017, a flash drought in Montana and the Dakotas damaged crops and grasses that served as forage for cattle, causing US$2.6 billion in agricultural losses. Flash droughts also can increase wildfire risks, cause public water supply shortages and reduce stream flow, which harms fish and other aquatic life. A developing flash drought in the central U.S. covered 64% of corn territory and 57% of soybean territory in la...