The Colorado River basin has lost 27.8m acre-feet of groundwater in the past 20 years, an amount of water nearly equivalent to the full capacity of Lake Mead, the largest reservoir in the United States, a new study has found. The research findings, based on Nasa satellite imagery from across the south-west, highlight the scale of the ongoing water crisis in the region, as both groundwater and surface water are being severely depleted. … With less visibility has come less regulation: California only instituted statewide management of its groundwater in 2014, and before that, groundwater use was largely unregulated. Arizona, which has seen big groundwater decreases, still does not regulate groundwater usage in the majority of the state. … Since 2015, the basin has been losing freshwater at a rate three times faster than in the decade before, driven mostly by groundwater depletion in Arizona.

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• E&E News by Politico: Groundwater drying up in Colorado River Basin, study finds
• The Arizona Daily Star (Tucson): Study: Groundwater loss across Colorado River Basin threatens economic security
• The Washington Post: The Colorado River is running low. The picture looks even worse underground, study says.
• The Hill: Groundwater supplies are plunging across the Colorado River Basin: Study