The historic drought in the West, explained through maps

WEATHER NEWS: The historic drought in the West, explained through maps


Historic drought has depleted groundwater, melted the snowpack and dried out lakes — and it will get worse


Groundwater wetness percentile as of

June 6, compared to 1948-2012

Groundwater wetness percentile as of

June 6, compared to 1948-2012

Groundwater wetness percentile as of June 6, compared to 1948-2012

Groundwater wetness percentile as of June 6, compared to 1948-2012

The historic drought in the western United States is about to get worse.

Much of the West is already experiencing severe to exceptional drought, but scorching summer temperatures will dry out the parched landscape even more.

“In the last 1,200 years, we haven’t seen a period as dry as right now,” said Ann Willis, a researcher at the Center for Watershed Sciences at the University of California at Davis. “We’re really hitting new lows in terms of how extreme the conditions are.”

California, which is enduring its third consecutive year of drought, has employed unprecedented measures in some counties to conserve water. For nearly 6 million people in the Los Angeles area, outdoor water use is restricted to one day a week. Overall, the state aims to cut water use by 35 percent.

Southwest drought is the most extreme in 1,200 years, study finds

Several other western states, including Colorado and Utah, also have adopted outdoor water restrictions.

How did the West get to this point?

Drought is not new to desert environments, but recent dry spells have lasted longer and been more intense than in previous decades. Although water management and increased water demand by a growing population affect supplies, a warming atmosphere is drying out the ground, shrinking the reservoirs and reducing mountain snowpack.

Scientists say this could be the new normal if climate change continues unchecked.

“There’s no good news for the foreseeable future, for the next few decades,” Willis said. “Fundamentally addressing climate change is the ultimate answer. … If we don’t, then what we’re really seeing is just preamble to an even more extreme and catastrophic set of conditions.”

Not-so-snowy Sierra Nevada

Sierra Nevada roughly translates to “snowy mountains” in English, but the mountains have frequently been bare in recent years.

Snowpack in the Sierra is an important water resource for California, supplying around one-third of the state’s freshwater supply. Winter storms typically bring generous amounts of snow, which melt as temperatures rise in April. The meltwater runoff helps replenish rivers, reservoirs and groundwater.

Because of a historically dry winter, the statewide snowpack stood at 38 percent of its average at the end of the season on April 1. The little snowpack that accumulated in the southern Sierra had fully melted by May 24, leaving no additional freshwater supply for the hot months ahead.


Water available as snowpack

Snow water equivalent, percent of average

Tule Lake

(see satellite

imagery below)

Anderson

(see satellite

imagery below)

Water available as snowpack

Snow water equivalent, percent of average

Tule Lake

(see satellite

imagery below)

Anderson

(see satellite

imagery below)

Water available as snowpack

Snow water equivalent, percent of average

Tule Lake

(see satellite

imagery below)

Anderson

(see satellite

imagery below)

The map above shows the snow water equivalent for the Sierra Nevada, or how much liquid water was contained in the snowpack on April 1 this year compared to its 20-year average. The data, modeled weekly by the University of Colorado’s Institute of Arctic and Alpine Research, is used by water forecasters, managers, irrigators, public utilities and many other parties.

“What matters most is how much snow is on the ground on April 1st, because that’s really the indicator of the total amount of snow that accumulated for the whole winter,” said Noah Molotch, a hydrologist with the monitoring project and a professor at the University of Colorado in Boulder. This year’s depletion of the snowpack followed lackluster winters in 2020 and 2021, making this the third dry year in a row for California.

Snow may vanish for years at a time in Mountain West with climate warming

Molotch said 2022’s winter snow is likely to rank among the smallest five annual snowpacks since 2000. The lowest snowpack occurred in 2015, when accumulation was less than 10 percent of the average. California has not fully recovered from 2015, Molotch said.

Willis said the past two years of drought have been unique because the region’s atmosphere and soil have become “thirstier.” She explained that rising global temperatures dry out the atmosphere, which increases the amount of water evaporating from the ground. Research has shown that the atmosphere’s drying power has intensified over much of the western United States in recent decades.

“[W]e’re getting less runoff from the same amount of precipitation,” Willis said. “That’s been a really unusual and new phenomenon that’s become much more apparent in the last couple of years.”

And those changes are seen on the ground.

The satellite imagery below, provided by Planet, highlights changes in the past year in northern California. The first image pair shows Tule Lake near the Upper Klamath Watershed, which is one of the prime migratory destinations for birds as they travel between the Northern and Southern hemispheres.


Tule Lake National

 

Wildlife Refuge

Tule Lake National

 

Wildlife Refuge

Tule Lake National

 

Wildlife Refuge

Tule Lake National

 

Wildlife Refuge

Tule Lake National

 

Wildlife Refuge

Tule Lake National

 

Wildlife Refuge

Tule Lake National

 

Wildlife Refuge

Tule Lake National

 

Wildlife Refuge

Over the past year, much of the lake has dried out. Willis also pointed out the poor water quality in 2021, as less water was available to flush the system.

“Because there’s so much less runoff than we would normally expect out of these watersheds … we’re seeing exactly the effects of what you’re showing here,” Willis said.

The next pair of images shows communities in Shasta County. Notice how much of the lush vegetation and agricultural fields visible in 2021 has browned by 2022, probably because of a combination of drought and recent cuts in water supply to the Sacramento Valley.

Kyra Kim, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory, said that during such times of drought, many areas can pump water out of the ground to compensate for the lack of surface water. Much of this groundwater supports agricultural industries in California.

However, drought also affects groundwater levels. Groundwater data from NASA, shown in the map at the top of this page, indicate that some areas in the Southwest contain only around 2 percent of their average groundwater for this time of the year.

“California has experienced about 100 years of groundwater depletion, much of which occurs during drought periods,” said Jay Famiglietti, the executive director of the Global Institute for Water Security at the University of Saskatchewan. “Research in review from our team indicates that the rate of depletion may actually be accelerating since 2019, relative to the previous droughts of 2006-2010 and 2011-2016.”

Climate change also slows the replenishment of groundwater. A warmer atmosphere increases evaporation over land and affects the amount of water that penetrates into the soil. Groundwater takes a long time to recover from drought and requires moisture slowly and steadily seeping through soil and rock layers.

In California, the majority of pumped groundwater is also ancient groundwater from the last glacial maximum, when ice and snow covered the terrain. “It’s really old groundwater, and we were essentially not getting that with one year’s worth of rain or one year’s worth of snow,” Kim said.

Variable snowpack in the Rocky Mountains

The Rocky Mountains are another important source of water for many western states. Winter snowpack accumulates on the western slopes of the mountains and melts during the spring, with the runoff funneling into the Colorado River, which feeds into some of the largest artificial reservoirs in the country, Lakes Mead and Powell.

The Colorado River is in crisis, and it’s getting worse every day

For winter 2022, Rocky Mountain snowpack tracked close to the long-term average until March, then April was “horribly dry,” said Leanne Lestak, who works with Molotch on modeling snow water equivalent across the Sierra and the Rockies.

As of April 1, snow water equivalent over most areas ranged from 46 to 95 percent of the long-term average, as shown in the modeled data below. By June 1, snow water equivalent had decreased, ranging from 2 to 64 percent.


Water available as snowpack

Snow water equivalent, percent of average

Lake Powell

(see satellite

imagery below)

Water available as snowpack

Snow water equivalent, percent of average

Lake Powell

(see satellite

imagery below)

Water available as snowpack

Snow water equivalent, percent of average

Lake Powell

(see satellite

imagery below)

Lakes Powell and Mead have dropped to historically low levels in the past year. Lake Mead has dropped so low that previously sunken boats and human remains have been recovered.

Depleted by drought, Lakes Powell and Mead were doomed from the beginning

Lake levels have been decreasing for the past two decades because of poor recovery from past droughts, water management practices and increased demand from booming populations. The U.S. Bureau of Reclamation has declared water shortages and reduced operations on the lakes for 2022.


Glen Canyon

National

Recreation

Area

Glen Canyon

National

Recreation

Area

Glen Canyon

National

Recreation

Area

Glen Canyon

National

Recreation

Area

Glen Canyon

National

Recreation

Area

Glen Canyon

National

Recreation

Area

Glen Canyon

National

Recreation

Area

Glen Canyon

National

Recreation

Area

Some researchers say the lakes may never recover to healthy water levels again — especially with the added stress of climate change.

“Climate change makes things more challenging because it makes things more extreme,” said Willis. “Our droughts are drier than they’ve ever been in the past. … Some of our flood seasons will be bigger than they’ve ever been in the past. What we’re really losing is the kind of moderate, manageable middle ground.”



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