Upper Colorado Basin lost 4.6 trillion gallons of groundwater in drought
A Virginia Tech-led study estimates that the Upper Colorado River Basin lost 4.6 trillion gallons of groundwater during the severe drought of 2020–2022, nearly twice the Lower Basin’s estimated 2.5 trillion gallons. Published in Water Resources Research, the study found groundwater losses accelerated after 2019 and researchers say water managers need to account for supplies both above and below ground.
Bottom line — The study warns that continued groundwater depletion could reduce river flows and deepen surface-water shortages across a basin serving about 40 million people.
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Virginia Tech researchers used satellite measurements and estimates of surface water, soil moisture and snow-water storage to track changes from 2004 to 2023.
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Lead author Esther Oyedele said the Upper Basin’s snowmelt-driven recharge had led researchers to expect it to be more resilient.
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Co-author Susanna Werth said groundwater losses in the Upper Basin tracked surface-water shortages more closely than in the Lower Basin.
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KUNR reports that groundwater losses in the Lower Basin appeared less coupled to surface water, with human-driven demand potentially the dominant stressor there.
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The study did not assess recent federal cuts to Lower Basin water deliveries, KUNR notes.