Rio Grande Flooding Recharges San Luis Valley Aquifer
Historic October storms lifted Rio Grande flows and added an estimated 50,000 acre-feet to a depleted Colorado aquifer.
Updated on Nov. 1, 2026 in Current Conditions
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Historic rains from October 22 to 25 increased the Rio Grande's annual flow by nearly 100,000 acre-feet, peaking at 11,000 cubic feet per second, the fastest flow in nearly 80 years. The state estimates the flooding recharged about 50,000 acre-feet to the San Luis Valley's unconfined aquifer.
Why it matters
The aquifer lost an estimated 72,000 acre-feet over the past year, so the recharge offsets part of that deficit for farms and wells in the San Luis Valley. The storms also extended the Rio Grande and Conejos River irrigation season to November 6.
The state estimates the October flooding added about 50,000 acre-feet of recharge to the closed basin area, while the unconfined aquifer lost roughly 72,000 acre-feet over the past year. Forecasts put Rio Grande flow at 68 percent of average, and it remains unclear whether November storms will change those totals.
The details
Rio Grande and Conejos River flows rose sharply during the October 22 to 25 storms and are now receding quickly, with recharge to the aquifers occurring during the high-flow week. The 14ers surrounding the Valley are beginning to form snow caps.
Timeline
October 22-25, 2026: Historic rains increase Rio Grande and Conejos River flows.
November 1, 2026: Clocks are set back an hour, returning to standard time.
November 6, 2026: The extended irrigation season on the Rio Grande and Conejos River ends.
December through February: The National Weather Service forecasts above-normal moisture for the Upper Rio Grande Basin.
Seasonal Patterns
The October storms improved a water year that the Rio Grande Compact's 109,000 acre-foot delivery obligation to New Mexico and Texas makes closely watched. The recharge helps the San Luis Valley's aquifer recover from a deficit that is running well below average flow.
Irrigators on the Rio Grande and Conejos River should plan around the November 6 season end. Residents relying on wells in the San Luis Valley should note that the recharge is an estimate and the aquifer remains well below its earlier levels.
The takeaway
The October storms gave the San Luis Valley a meaningful but partial water boost, and winter moisture will determine whether the aquifer gains hold. Water users should watch the forecast closely rather than assume the flooding solved the year's deficit.
What happens next
The National Weather Service's December through February moisture outlook for the Upper Rio Grande Basin will show whether the recharge holds through winter.
Further reading
For more on river and reservoir levels across the state, see Current Conditions in Colorado.
Source note: This article includes information reported by Alamosa Citizen.
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