Climate change is disrupting the nation’s water cycle

The water cycle, which circulates Earth’s most important resource in a never-ending loop that nurtures life, is in trouble. Climate change is upsetting the delicate balance of that cycle, disrupting how water circulates between the ground, ocean, and atmosphere.

The events of 2023 show how significant these disruptions have become. From extreme precipitation and flooding to drought and contaminated water supplies, nearly every region of the United States has faced some kind of impact from climate change and changes in water availability.

The water cycle controls all aspects of Earth’s climate system. In other words, as the climate changes, nearly every phase of water movement on Earth changes as well. Water availability is becoming increasingly scarce in some regions, and climate change is increasing rainfall, flooding, and other extreme weather events in others.

As the planet warms, this cycle is expected to become increasingly stretched, distorted, and broken.

water cycle — A staple of elementary school science classes — It describes the constant movement of water in all its phases (solid, liquid, and gas) above ground, underground, and in the air. The water cycle, powered by the sun and energized by temperature changes, forms an invisible link between Earth’s glaciers, snowpack, oceans, lakes, rivers, plants, trees, clouds, and rain .

Liquid water flows over land as runoff, and some of it percolates deep underground and is stored as groundwater. Some of the water flows into streams, rivers, and other bodies of water. And in some parts of the world, water is also stored in a frozen state, as is the case with glaciers and snowpack. Water on the ground or in a body of water turns back into water vapor through a process known as evaporation. Some water is absorbed by plants before it evaporates into the atmosphere, a process known as transpiration.

Water vapor eventually condenses into clouds. Precipitation falls in the form of rain or snow, transporting water from the atmosphere back to the land and starting the cycle again.

Human activities have a major impact on the water cycle, as water is needed for drinking, agriculture, industrial activities, electricity, etc. While each of these uses impacts water availability and supply, climate change is likely to place further stress on the movement of water between land, ocean, and atmosphere.

Below, we’ll walk you through the critical steps of precipitation, evaporation, transpiration, runoff, and storage to understand how climate change is already changing our environment and impacting millions of people across the United States. I’ll explain what’s going on.

In 2023, extreme precipitation, likely accelerated by climate change, hit nearly every corner of the United States.

For every Fahrenheit increase in temperature, atmospheric moisture increases by about 3% to 4%. Earth’s temperature in 2023 was 2.43 degrees warmer than before the industrial revolution, so today’s storm could hit harder.

In Vermont, July’s torrential rains caused flash flooding that nearly caused a dam in Montpelier to burst and flooded roads. A similar situation occurred in New York City in September, when some areas received 7 inches of rain in 24 hours, submerging cars and city buses and disrupting rail service.

In cities like New York, the effects of storms are even more severe. There, storm drains and subway tunnels have fallen into disrepair or simply been built for milder climates.

Climate change is also changing the behavior of hurricanes, producing more extreme rainfall amounts. Today’s hurricanes are likely to intensify quickly, quickly increasing wind speeds as they feed on warmer water near the coast. And when these storms make landfall, climate change is increasing the likelihood that hurricanes will stall and dump incredible amounts of rain as they move across the landscape.

When Hurricane Idalia approached the Florida coastline in late August, wind speeds increased by 55 miles per hour in just 24 hours, increasing from a Category 1 to a Category 4 storm. The storm dumped more than 13 inches of rain on Holly Hill, South Carolina, the heaviest location.

Rising temperatures are increasing evaporation and transpiration in some regions, making them more prone to drought and stressing plants, which was evident in the hot summer of 2023.

Climate change will make droughts more frequent, more severe, and longer lasting.

A prolonged drought has caused water levels in the Mississippi River to drop to historic lows in 2023, allowing salt water from the Gulf of Mexico to flood upstream and contaminate drinking water supplies in urban areas.

Meanwhile, Hawaii’s drought has dried out vegetation and turned Maui’s invasive grasses into a “ticking time bomb,” in the words of one researcher, further increasing the risk of wildfires. In August 2023, a devastating wildfire caused by hurricane-force winds swept through the historic town of Lahaina, killing 101 people.

The Midwest and South were hit by a spring-to-fall drought, making it the costliest natural disaster in 2023, costing $14.5 billion.

Climate change is changing the patterns and timing of runoff, particularly in the mountainous regions of the United States, which can lead to extremely high or low river levels.

In Alaska, where temperatures are rising at about twice the global average, a glacier dam burst, sending massive amounts of flood water downstream, tearing through trees and inundating areas near Juneau.

According to the National Oceanic and Atmospheric Administration, this event would not have happened without climate change and glacier retreat.

Warm spring and summer temperatures in the Pacific Northwest caused snow to melt earlier in the region, leading to water shortages in the fall and straining the region’s hydropower capacity.

Water supplies are decreasing in Western states, the Great Plains, and parts of the Midwest.

Years of overexploitation, driven in part by rising temperatures and drought, have led to farmers consuming unsustainable amounts of stored groundwater, pushing some aquifers to the brink.

In 2023, California experienced more than a dozen atmospheric river storms and unusually heavy rainfall. The storm, which appears to have been exacerbated by climate change, eased a drought and blanketed the state with two to three times the normal amount of snow.

But the California Department of Water Resources says all that rainfall will only alleviate groundwater shortages across the state after another drought, with groundwater levels now lower than they were after the last four-year drought ended in 2016. It also remains low.

Last year, several states reached an agreement to reduce usage of the Colorado River, but despite a year of heavy snow, only 43% of the water was in reservoirs at year’s end.