Study Reveals Colorado River Basin Groundwater Levels Dropping Faster than Surface Water

July 2025

California Water Law & Policy Reporter, Volume 35, Number 10

With Colorado River Basin (Basin) operating guidelines set to expire in October 2026 and negotiations still underway, the seven Basin States, federally recognized tribes, and Mexico have seen a twenty percent decrease in Colorado River flows over the past century. Surface water shortages in the Basin have been well-documented and widely publicized, while groundwater conditions have historically been less visible. A recent study from researchers at Arizona State University, however, reveals that groundwater underlying the Basin is depleting at a faster rate than surface water supplies in the Colorado River, Lake Mead, and Lake Powell.

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