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Colorado River losing water

Svein-Magne Tunli / Wikimedia Commons

Water availability for ecosystems and human use is under threat in the Colorado River basin in the southwestern USA, a region that has been facing the worst drought in 500 years since the early 2000s. About half of the water volume of the river, which runs through Colorado, Utah, Wyoming, New Mexico, and Arizona, comes from the groundwater; the other half is provided by precipitation. Groundwater is essential for feeding the streams and creeks that lead to the river, on which some 40 million people now depend, and maintaining its flow outside the rainy season. A group led by Olivia Miller, a hydrologist working for the US Geological Survey (USGS), used a mathematical model to predict what might happen to Colorado River’s groundwater over the course of this century in three different climate change scenarios. In the best-case scenario, if the weather is warm and rainfall high, groundwater could increase by 6% by 2030, but then decline to 3% below its current level by 2080. In the worst-case scenario, with warm weather and low rainfall, groundwater could decrease by 23% by 2030 and up to 33% by 2080 (Geophysical Research Letters, October 25).