Western US enters its worst drought in modern history

Extreme drought in the western US has become just as reliable as a thunderstorm in the summer afternoon in Florida. And news reports about the drought in the West may seem a bit like a broken record, and some scientists say the region is on the brink of permanent drought.

This is because in 2000, the Western United States began what scientists call a mega-drought – the second worst in 1200 years – caused by a combination of a natural dry cycle and caused by humans climate change.

In the last twenty years, the two worst droughts have occurred in 2003 and 2013 – but what is happening now seems to be the initial stages of something even worse. And as we enter the summer dry season, the stage is set for extremely dry conditions, with major water restrictions expected and another dangerous fire season ahead.

The image above is a time series of droughts in the western states from 2000 to 2021. This latest peak from 2020-2021 (on the right) is just as impressive as the others, but with one striking difference – this time the area of ​​” “extraordinary drought” is much greater than any other peak, with an air coverage of more than 20%. As we enter the dry season, there is little chance that conditions will improve – it will probably only get drier.

With that in mind, there is little doubt that the drought in the West, especially in the Southwest, this summer and fall will be the most intense in recent memory. The only real question: will it last as long as the last long period of drought from 2012 to 2017? Only time will tell.

Currently, the U.S. Drought Monitor places 60% of Western states under severe, extreme or exceptional drought. The reason for the extensive drought is twofold; prolonged drought is fueled by man-made climate change, and in the short term a La Niña event in which cool equatorial Pacific waters could not fuel enough moisture.

As a result, last winter’s wet season was not very wet at all. In fact, it only added an insult to injuries, with only 25 to 50% of the normal rainfall that fell over much of the Southwest and California. It follows one of the driest and hottest summers of modern times, with two historic heat waves, a summer monsoon cycle that simply did not even turn up and the worst fire season in modern times.

The image below shows what the precipitation percentage is called from October to March, and compares the past six months with the same period of six months in each of the past 50 years.

The light brown shade shows areas in which the last six months have been the driest 10% of the last 50 years. The dark brown shade indicates the areas that have had the lowest rainfall during the last six months. Almost all the areas are covered by one of the two shades.

Kelsey Satalino, coordinator of digital communications for the National Integrated Drought Information System of NOAA, says that over the past few months several states, including Nevada, Arizona, New Mexico and Utah, have experienced the largest drought period since the drought monitor began in 2000. . As a result, the soil moisture content is at its lowest level in at least 120 years.

However, the Northwest in the Pacific is doing very differently this season. The northern half of the West found normal to even above normal snowfall this winter, in line with what is expected during a typical La Niña event with a further storm surge in the north. Luckily, however, it did not extend further south, but most areas now have only 50 to 75% of the normal snowpack.

As the West depends on the melting snowpack to fill lakes, reservoirs and rivers, such as the Colorado, the availability of water will be limited this summer. The Colorado River and its tributaries provide water for approximately 40 million people and 5 million acres of agricultural land. The amount of water flowing into Lake Powell, on the Arizona-Utah state line, in the coming months is expected to be only about 45% of the typical amount. Lake Meade, on the Arizona-Nevada state line, has only 40% capacity.

But this lack of snow suit is not a one-time problem; it’s a trend. Over the past 40 years, the snowpack has decreased by about 25% in the Western states. Meanwhile, the population is still increasing. Today, therefore, the demand for water is greater than what mother nature can supply.

In general, these water problems are not expected to improve. Although there will be wet years, the overall tendency is to dry out. Scientists say this is due to man-made climate change, leading to less reliable rains and warmer temperatures – both in line with what was predicted by climate computer models. The image below shows a clear trend towards worsening drought since 1900.

New research from the US Department of Agriculture shows that precipitation has become more volatile in recent decades and that dry periods have extended between rainstorms. Even if rain or snow falls heavier, it is less important than stability. Soil moisture and vegetation thrive on precipitates that are more evenly distributed over time, rather than heavy events that tend to run off, leading to wasted moisture.

At the same time, temperatures in the Western United States have risen by a few degrees over the past 50 years. The warmer air provides more heat energy to evaporate moisture from vegetation and soil. As a result, the soil continues to dry out and provides combustible fuel for escalating fire seasons.

In fact, 2020 was the worst fire season in the modern history of the West, with California and Colorado recording their biggest fires. As can be seen in the footage below, the intensity of fires and acres of tracks burned with increasing temperatures. Simply put, the hotter and drier it gets, the bigger the fires get.

Due to a hot climate, the fire season in the West is now two to three months longer than just a few decades ago. With the dry season already underway in the West, it is rapidly preparing for veld fires.