Atmospheric Rivers: the Danger of Too Much Water

This past December, California was inundated with rain storms, causing severe flooding and damage across the state. The state of California often experiences rain around this time of the year, combatting the dry season, but the storms this year produced rainfall out of the ordinary for the state’s generally mild winters.

These storms are classified as atmospheric rivers and deliver 30 to 50 percent of California’s average rainfall annually, while also resulting in over one billion dollars in damages per year in the West Coast.

An atmospheric river is a long narrow band of exceptionally wet air that has the ability to flow for thousands of miles over the ocean and carries with it two to three times the amount of water the Amazon River holds. This system, known as IVT or vertically integrated water vapor transport, provides both pros and cons for states such as California suffering from severe drought.

Atmospheric rivers carry with them such immense quantities of water that they possess the ability to resolve droughts, while at the same time posing a devastating threat to the residents of areas they affect. The set of atmospheric rivers that passed through California this December left over a dozen people dead, hundreds of thousands without power, and many Californians forced to evacuate their homes. This led Governor Gavin Newsom to declare a state of emergency on January 4th, with the White House following suit with a presidential emergency declaration on January 8th. 

Climate change has resulted in increasingly severe, frequent storm systems of various types and atmospheric rivers are no exception to this pattern. Typically, mountain ranges such as the Sierra Nevada suck all the moisture out of atmospheric rivers, resulting in great blankets of snow, but more recent storms have trekked across the mountains and into the states beyond. This is due to an alarmingly rapid increase in the volume of water contained in these storms.

As greenhouse gas emissions continue to wreak havoc on our environment, we can only expect more severe atmospheric rivers and heavier rainfall, with simulations predicting 71% of annual rainfall to be packed into a 30 day period in the future. 

Due to the severity of these storms, one can only wonder if they have the ability to put an end to California’s three year drought. Unfortunately, while these weather systems carry such high quantities of water and replenish California’s groundwater supply in reservoirs, lakes, and snow, it will require a longer duration of time to aid our aquifers and underground water supply. Additionally, as rainfall increases, drought conditions become more severe in tandem, meaning that the chances of atmospheric rivers drowning out the California drought are slim.