Megadrought

A megadrought is an exceptionally severe drought, lasting for many years and covering a wide area. There is no exact definition of a megadrought.[2] The term was first used by Connie Woodhouse and Jonathan Overpeck in their 1998 paper, 2000 Years of Drought Variability in the Central United States.[2][3] In this, it referred to two periods of severe drought in the US – one at the end of the 13th century and the other in the middle of the 16th century.[3] The term was then popularised as a similar severe drought affected the Southwestern US from the year 2000. https://en.wikipedia.org/wiki/Megadrought

Southwestern North American megadrought

Southwestern North American megadrought - Wikipedia

Ongoing megadrought in southwestern North America that began in 2000

the drought is the driest multi-decade period the region has seen since at least 800 CE

Climate change models project drier conditions in the region through the end of the 21st century

Furthermore, global La Niña (see El Nino) meteorological events are generally associated with drier and hotter conditions and further exacerbation of droughts in California and the Southwestern United States and to some extent Southeastern United States. Meteorological scientists have observed that La Niñas have become more frequent over time.

Further information: 2020–2023 North American drought

Megadroughts, a term used to describe periods of multidecadal drought, are a recurring feature of the North American Southwest over the past millennium. For example, droughts lasting at least a decade occurred in Texas in each century of the past millennium.

40 SWNA drought events of at least 19-years duration

Of these, four megadroughts were 0.25 standard deviations drier than any experienced in the 20th century: 863–884, 1130–1151, 1276–1297, and 1571–1592. The droughts of the twelfth and thirteenth centuries bracketed the Ancestral Puebloans' Pueblo III Period, with the thirteenth century drought coinciding with the abandonment of Mesa Verde, Chaco Canyon, and other settlements in the Four Corners region

The megadrought that began in 2000 was preceded by the wettest period in at least 1200 years

Models indicate that the years 2000–2018 would have trended towards megadrought conditions regardless of climate change, with a predicted severity of the 11th worst period of drought since 800. However, anthropogenic warming pushed conditions into a severe megadrought. From 2000 to 2021, mean annual precipitation in the region was 8.3% below the 1950–1999 average and the temperature was 0.91 °C above average

Both 2002 and 2021 were drier than any of the previous nearly 300 years and were, respectively, the 11th and 12th driest years between 800 and 2021.

The drought is largely driven by temperature, which increases the rate of evaporation, with some contribution from the lack of precipitation

While monsoon rains in the desert Southwest in mid-2021 and heavy rain and snow in California in late 2021 had raised hope of ending the drought, January 2022 was characterized by record dry conditions across much of the West.

Recovery to pre-2012 soil moisture levels in the most affected areas was predicted to require several decades of average rainfall. Even without increasing temperatures, predicted low precipitation would be sufficient to produce unprecedented dry conditions, but with higher temperatures could create megadroughts as not seen since medieval times.

The reduced water supplies along the Mexican-American border area have caused tensions. The 1944 water treaty that is administered by the International Boundary and Water Commission (IBWC) divides the waters of 450,000 square miles (1,200,000 km2) the Colorado River and Rio Grande basins between the two countries

On 8 September 2020, thousands of Mexican farmers in Chihuahua, fearing for their own livelihoods, took control of the La Boquilla Dam to stop Mexican Federal authorities from releasing reservoir waters to the Rio Grande. Later that month, Texas Gov. Greg Abbott asked the Federal government to intervene to force the release of Mexican waters from the Rio Conchos that would be used by farmers in South Texas.

In March 2021, the New Mexico Interstate Stream Commission took the unprecedented step of asking farmers along the Rio Grande and Rio Chama not to farm; while agriculture uses 76% of water withdrawals in the state, it makes up 3% of the state GDP.

Peer-reviewed studies indicate that storing water in Lake Mead rather than in Lake Powell would yield a savings of 300,000 acre feet of water or more per year, leading to calls by environmentalists to drain Lake Powell and restore Glen Canyon to its natural, free-flowing state.