Human-Caused Water Depletion in Lake Mead Equals Colorado River Analysis Reveals
Between 2000 and 2021, the impact of human-induced climate change on the Colorado River Basin led to the loss of over 10 trillion gallons of water. This amount is similar to the capacity of Lake Mead, a significant milestone in understanding the devastating effects of global warming on the region, according to a study published in the journal Water Resources Research. Led by hydrologist Benjamin Bass at UCLA, the study is the first to measure the rate of runoff decrease and prove its cause.
The Colorado River Basin, which spans around 250K square miles in seven states of the Western US and provides water to 40 million people, has experienced a drought that started in 2000, resulting in reduced river flow and shrunk reservoirs. The consequences have raised alarm bells on the increasing scarcity of water and its potential implications as the climate continues to change.
Surprisingly, the researchers discovered that the Colorado River Basin has a higher sensitivity to warming compared to other major western US basins. The findings emphasized that climate change caused by human activities removed as much water from the basin as the size of Lake Mead during the recent megadrought, sending a clear message about the current climate change realities.
Without climate change, the drought in this region would not have led to supply cuts in 2021, as seen through the first federally declared water shortage. In May 2021, Nevada, California, and Arizona agreed to cuts until 2026, which is expected to be sanctioned by the US government by August, with Nevada facing a 4% reduction, California experiencing an 8% cut, and Arizona facing a 10% reduction.
To thoroughly understand the changes in hydrology in the basin, the researchers conducted a comprehensive study using a land surface model capable of analyzing water, vegetation changes, and vegetation response to the increasing level of atmospheric carbon dioxide. They drew from standard atmospheric data, streamflow gauges, and other records to capture the regional hydrology, and utilized ground and satellite data to track changes in vegetation.
By considering all these data types, the authors noted, "we had all the major players in terms of runoff's sensitivity to climate change.”
Temperature Increased by 2.7 Degrees
The study revealed that the temperature in the Colorado River Basin increased by about 2.7 degrees Fahrenheit due to human-induced climate change from 1880 to 2021. This temperature increase has led to a 10.3% reduction in runoff under existing conditions, though the loss would be more significant (13%) if vegetation effects were not considered.
This 10.3% reduction in runoff culminated during the historic drought between 2000 and 2021, during which a massive volume of lost runoff water nearly equaled the full capacity of Lake Mead, the largest reservoir on the Colorado River.
Furthermore, the study found that the areas of the basin that are typically snow-covered in winter are losing water twice as fast as the region without snow. This rapid water loss in these snowpack regions signals a transition to an arid climate rather than just additional drought, as indicated by the lead author of the study.
This study's implications highlight the need to revise the 1922 Colorado River Compact, which governs the allocation of water from the Colorado River among the seven western US states where it flows, as it was written based on the assumption of a stable regional climate. Had the compact been formed today, the expected water flow would need to be adjusted due to the impact of warming. Moreover, the study predicts that if greenhouse gas emissions are not curtailed, the decreasing trend in runoff is expected to persist.
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Source: www.casino.org
