Climate Change Daily Earth Science Hydrosphere Repost

Dry Missouri River headwaters

The time was late in the 13th century before Europeans happened upon the shores of North America. The place was Montana, and drought was ravaging parts of western North America. Snow and ice became sparse, and then the Missouri River headwaters ran dry as spring meltwaters disappeared. Mountain snowpack no longer accumulated during the winters, thus depriving the river of vital water supplies. Interestingly, this event did not repeat itself until the first decade of the 21st century. 

From 2000 to 2010, the Upper Missouri River Basin was more parched than during the great Dust Bowl in the 1930s. The driest of these ten years saw conditions unmatched for 1,200 years, except for the 13th-century drought.

But the upper Missouri basin is not alone. The American West from California to Oregon and Idaho have been in drought conditions for two decades. Researchers believe this region is in the early stages of a megadrought that could go on for decades. The current dry conditions are the latest in a string of megadroughts starting in the 800’s. The key to unraveling this long history of water in western America lies in tree rings.

Tree ring data takes us back 1200 years to the first recorded megadrought in the 800’s during the Medieval Era. This long period of severe drought was a harbinger to repeated dry spells in the mid-1100s, the 1200s, and the late 1500s. These historic droughts also tie into the collapse of the native North American Anasazi culture, and the downfall of civilizations in Mexico.

Climate change and megadroughts

While it is true that natural causes led to historic megadroughts, that does not mean human influences are not also at work today. Natural climatic cycles are contributing to the current dry conditions. However, Anthropocene climate change and global warming bring human-induced changes that amplify the severity of this current megadrought. 

Global warming produces a hotter atmosphere that sucks more water from the land. Combine this with changes that reduce precipitation, and you have the ingredients for a megadrought. Researchers estimate that human-induced climate change has increased the severity of the current drought by 50 percent.

Historical meteorological records show that in many areas of the American West, the dry seasons are longer, hotter and dryer than 50 years ago.  These changes have also brought with them an increase in snow droughts, where sparse snowfall results in thinner or non-existent winter snowpack in the high mountains. Meltwater from the mountain snow is the lifeblood of the Missouri River headwaters. So drought at the start of the river translates to lower flows downstream, affecting farming and municipalities dependent on the Missouri River.


The Missouri River flows for 2300 miles traversing the USA mid-continent. It is the longest river in America. Its headwaters lie in Montana, and it runs east and south, eventually joining the Mississippi River. Along its journey, this river provides essential water to the basin’s farmers and ranchers, who raise 46% of the wheat, 22% of the corn, and 34% of the cattle in the United States.

In July of 2012, the State of Missouri was declared a disaster area due to a crippling drought. Crops failed, and municipal drinking water supplies dropped to critical levels in some areas. Drought in the upper Missouri basin also hit farmers in 2018 when poor grass growth and hay production reduced the feed available for cattle. 

The past two decades have seen records set for thin snowpack and low flow in the Missouri River headwaters. This is a disappointing way to start the growing season since the knock-on effect from this low flow then moves downstream for another 2300 miles. Fortunately the spring of 2020 looks more promising with above average snowpack. 


Hot and dry in the Western USA, a megadrought in progress (Source: ArcheanWeb) –   Also:

The Colorado River is running dry (Source: ArcheanWeb) –       Also:

Wildfires and Mudslides (Source: ArcheanWeb) –  Also:

Climate change and surface water (Source: ArcheanWeb) –  Also: 


America’s longest river was recently drier than during the Dust Bowl. And it’s bound to happen again. (By Darryl Fears; Washington Post) –  Also:

Missouri River Flood Drama Likely Took Direction from La Niña (Source: NOAA) –ña   Also:

Drought Starting to Affect Missouri Livestock (Source: Missouri Farm Bureau) –   Also:

From drinking water to farms, drought’s effect creeping across Missouri (By Kurt Erickson; St. Louis Post-Dispatch) –  Also:

Missouri River Basin Water Supply Statement (Source: National Weather Service) –  Also:

Feature Image: The confluence of the Missouri River and the Niobara River. Near Yankton, S.D (Modified) – By Chris Light – Own work, CC BY-SA 4.0,

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.