Statistical Characterization Of High Flow Volumes Across The Conterminous United States Supporting Managed Aquifer Recharge
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https://doi.org/10.1029/2025WR041955 <-- shared paper
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https://www.latimes.com/environment/story/2025-06-24/california-2024-groundwater-report <-- shared media article
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H/T @Robert Shibatani
“Many areas in the U.S. rely on groundwater, which has been significantly depleted over the last decades.
One emerging means of permanently restoring groundwater is by using excess floodwater, a strategy known as flood-managed aquifer recharge (Flood-MAR).
While it’s effective implementation depends on reliable information on the availability and frequency of high flows, outside of California, the U.S. lacks a nationwide assessment of high-flow volumes suitable for Flood-MAR planning, particularly at ungaged locations.
A recent study [link above] undertook a nationwide characterization of “over-threshold” high flow frequency to support Flood-MAR siting across the country. An approach was developed that relied on daily flow time series estimated with four widely-accepted PUB methods and standard GEV distribution.
High-flow volume frequency at the outlets of 2,115 subbasins across the U.S. were characterized with high-flow volumes defined as the volume exceeding the 80th, 90th, and 95th quantiles of daily streamflow, thresholds commonly adopted to satisfy environmental flow requirements.
Not surprisingly, results indicated that high-flow volume availability was highest and uncertainty is lowest in wetter regions, including northern California, the Pacific Northwest, and portions of the Lower Mississippi Basin, reflecting greater potential for Flood-MAR.
In contrast, arid and semiarid basins across the central and southwestern U.S. exhibited lower high-flow volume availability and higher uncertainty.
While these results are not surprising, they do provide an additional database of statistical hydrologic frequencies across the nation that can certainly help assist in first-level Flood-MAR siting and screening.
Nevertheless, they represent only one portion of the total available water within waterbodies, waterways, and terrestrial storage that when viewed against demands ... can identify an untapped supply source for MAR operations.
Flood-MAR, as an “use-approach”, can capitalize on ANY water supplies integrated into its operational yield; it need not necessarily be high-flow volumes, as defined. But ANY instream flows either above regulatory minimums OR above that required to meet downstream abstraction needs or environmental baselines.
For it goes without saying that, in a water-efficient use era, ANY instream flows above required minimums should be retained either in above- or below-ground storage rather than be wasted out to sea…”
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“Managed aquifer recharge using floodwater (Flood‐MAR) is a promising strategy to mitigate groundwater depletion. Its effective implementation depends on reliable information on the availability and frequency of high flows. However, outside of California, the United States lacks a nationwide assessment of high‐flow volumes (HFV) suitable for Flood‐MAR planning, particularly at ungaged locations. Here, [the authors] present a continental‐scale statistical characterization of HFV frequency at the outlets of 2,115 subbasins across the conterminous United States (CONUS). HFV is defined as the volume exceeding the 80th, 90th, and 95th quantiles of daily streamflow, thresholds commonly adopted to satisfy environmental flow requirements. [They] estimate daily streamflow time series, Q(t), using four methods for prediction in ungaged basins (PUB), extract independent HFV events, and model their frequency using the generalized extreme value distribution. Leave‐one‐out cross‐validation at 701 stream gages shows that the accuracy of estimated HFV depends on the ability of the PUB methods to capture over‐threshold flows and the serial correlation structure of Q(t). HFV quantiles for Flood‐MAR‐relevant return periods are estimated as weighted averages of the PUB methods, along with their associated uncertainties. Results indicate that HFV availability is highest and uncertainty is lowest in wetter regions, including northern California, the Pacific Northwest, and portions of the Lower Mississippi Basin, reflecting greater potential for Flood‐MAR. In contrast, arid and semiarid basins across the central and southwestern United States exhibit lower HFV availability and higher uncertainty. These results provide a consistent, CONUS‐wide foundation for first‐level Flood‐MAR siting and screening…”
#water #hydrology #groundwater #watersecurity #waterresources #watersupply #watermanagement #USA #CONUS #aquifer #ManagedAquiferRecharge #MAR #FloodMAR #depletion #overpumping #flood #flooding #recharge #planning #policy #streamflow #extremes #hydrography #highflowvolumes #HFV #model #modeling #uncertainly #siting #screening #usecase #spatialanalysis #geostatics #spatiotemporal #mapping #hydrogeomorphology