APALUMA CURRENTS 04 · A FIELD STUDY ON PUBLIC DATA
The Colorado drains 246,000 square miles across seven states and two countries, waters 40 million people and 5.5 million acres of farmland, and in most years no longer reaches the Gulf of California. Run the camera backwards from that dry channel — through Mead, through the Grand Canyon, through Powell — and you arrive at snow falling at 10,000 feet in the Rockies. This is the story of how a river that large runs out, and who is holding the ledger when it does.
BALANCE THE RIVER YOURSELFFRAMING NUMBERSCONGRESSIONAL RESEARCH SERVICEINTERNATIONAL BOUNDARY AND WATER COMMISSION
FOLLOW THE WATER ↓
Four handoffs turn a winter's snowfall into an accounting entry. Follow them in order and the arithmetic at the end is unavoidable.
Winter storage in the Rockies. The Colorado headwaters at La Poudre Pass, the Green in the Wind Rivers, the San Juan in the San Juans. Roughly 85 percent of the river's flow originates in the Upper Basin high country. The snowpack is the reservoir before the reservoirs.
MEASURED · method labelUSDA NATURAL RESOURCES CONSERVATION SERVICEThe April-to-July runoff pulse. One season's snow is the entire year's supply. Warmer springs mean thirstier soils and a thirstier atmosphere take their cut before the river does — which is why a 60 percent snowpack does not produce 60 percent of a normal runoff.
FORECAST · method labelNOAA COLORADO BASIN RIVER FORECAST CENTERPowell and Mead, the two largest reservoirs in the United States, together holding roughly four years of average flow when full. This is the plumbing that made the paper allocations feel real for a century.
MEASURED · method labelU.S. BUREAU OF RECLAMATIONLees Ferry, Arizona. The compact point where one river becomes two basins on paper. The Upper Basin's obligation: not to deplete flows below 75 million acre-feet across any rolling ten years. This is where the accounting happens, and where the two basins do not agree on how to count.
PUBLIC RECORD · method labelLAW OF THE RIVER7.5 million acre-feet to the Upper Basin, 7.5 to the Lower Basin, 1.5 to Mexico under the 1944 treaty. Against a river whose modeled natural flow at Lees Ferry has averaged 12.558 million acre-feet a year since 2000 — 17.5 percent below its own 20th-century mean of 15.224. The ledger promises more water than arrives, and it has for a quarter century.
SOURCELAW OF THE RIVERINTERNATIONAL BOUNDARY AND WATER COMMISSIONU.S. BUREAU OF RECLAMATION
Four readings on the same river, taken four different ways. Each carries the label for how it was produced, because a measurement, a model output, and a tree-ring reconstruction are not the same kind of fact.
Modeled natural flow at Lees Ferry averaged 15.224 MAF/yr from 1906 to 1999 and 12.558 MAF/yr from 2000 to 2020. Both figures come from the same Reclamation dataset, computed the same way. The decline is not a forecast; it already happened.
MODELED · method labelU.S. BUREAU OF RECLAMATIONPublished attribution work finds that a large share of the decline is driven by temperature rather than precipitation shortfall: less reflective snow, more evaporation, thirstier soils. A drought ends when it rains. Aridification does not.
Combined live storage as a share of combined capacity, read daily from Reclamation. When this piece was built the two reservoirs together held well under a third of what they can hold.
12.29 of 50.9 MAF of combined live capacity.
MEASURED · method labelU.S. BUREAU OF RECLAMATIONThe negotiators used the wettest stretch of the gage record available to them. Against a 1,244-year tree-ring reconstruction whose long-term mean is 14.655 MAF/yr, the years the compact was built on were an outlier — not a normal from which to divide a river.
RECONSTRUCTED · method labelNOAA PALEOCLIMATOLOGY / TREEFLOWCard D is the yardstick problem in one number, and Section 05 puts twelve centuries behind it.
Two columns, a hundred years apart, describing the same river. Status verified as of 2026-08-11.
The Colorado River Compact split the basin at Lee Ferry and apportioned 7.5 million acre-feet of beneficial consumptive use to each half, with a further 1.5 million later guaranteed to Mexico by treaty. The gage record they relied on ran from 1906 and happened to cover one of the wettest stretches in twelve centuries.
SOURCELAW OF THE RIVERINTERNATIONAL BOUNDARY AND WATER COMMISSION
Since 2000 the basin has run a sustained deficit against its own allocations. The tree-ring record shows the deep past held droughts as severe — the driest 25-year window in the reconstruction, 1130 to 1154 CE, averaged 12.621 MAF/yr. That is the point: the gage era the compact was built on was the anomaly, and a drier river is the normal the basin never planned for.
SOURCEU.S. BUREAU OF RECLAMATIONNOAA PALEOCLIMATOLOGY / TREEFLOWU.S. BUREAU OF RECLAMATION
The 2007 Interim Guidelines, the 2019 Drought Contingency Plans, and the related Minute agreements with Mexico all expire. Everything that has governed shortage on this river for two decades runs out at once.
PUBLIC RECORD · method labelU.S. BUREAU OF RECLAMATIONThe seven basin states miss the consensus deadline for a state-negotiated replacement. The decision reverts to the federal process.
PUBLIC RECORD · method labelU.S. BUREAU OF RECLAMATIONThe Lower Division States submit a shortage-distribution proposal. Reclamation's modeling assumptions for 2027-2028 reflect it.
PUBLIC RECORD · method labelU.S. BUREAU OF RECLAMATIONReclamation publishes the Post-2026 Final EIS. The Preferred Alternative is not a fixed rulebook but an adaptive decision framework for operating years 2027 through 2036, implemented in two-year intervals within defined operational sideboards: Powell releases between 5.0 and 12.0 MAF, and Lower Basin shortages up to 3.6 MAF including assumed reductions to Mexico.
PUBLIC RECORD · method labelU.S. BUREAU OF RECLAMATIONShortages up to 1.5 MAF are distributed under the Lower Division States' proposal; anything beyond that is distributed by priority. Consultation is triggered if projected Mead elevation falls below 1,000 feet, or projected Powell elevation below 3,500 feet.
PUBLIC RECORD · method labelU.S. BUREAU OF RECLAMATIONThe distance between the promise and the river is no longer a projection. It is a published federal decision with a two-year clock on it. What remains genuinely open is who absorbs the reduction — and whether the states agree before the priority system decides for them.
VERIFY BEFORE PUBLISH: as of this build no interstate Compact suit had been filed. An original-jurisdiction action between states would go directly to the U.S. Supreme Court. Do not sharpen this line beyond the filed record.
Four readings that update on their own schedules, each shown against the threshold that makes it mean something. One place at one time is not the season.
Elevation is how the Lower Basin's shortage tiers are written, so this one number sets deliveries for Arizona, California, and Nevada.
Below 3,490 feet the turbines stop, and Glen Canyon Dam may be unable to deliver its specified annual release through the river outlet works alone.
The compact gage. This is regulated release from Glen Canyon Dam — what the dam let out today — not the river's natural flow.
Regulated release from Glen Canyon Dam, not natural flow.
MEASURED · method labelU.S. GEOLOGICAL SURVEYMeaningful roughly November through June. Outside that window this card shows the last season's peak and says so, because summer snowpack is not a signal.
Out of season (meaningful roughly November-June). Showing the water year 2026 peak from 114 reporting sites.
MEASURED · method labelUSDA NATURAL RESOURCES CONSERVATION SERVICEHOW THIS UPDATES · Regenerated on every production build. Reservoir values update daily at the source; USGS discharge every 15 minutes; NRCS SWE daily. A snapshot older than its source cadence is labeled stale on the page. Reservoir elevation and storage and the Lees Ferry gage are re-read in your browser on load with an eight-second budget each; a feed that misses it leaves that one card on its dated snapshot and changes nothing else. Snowpack is a build-time reading because the authoritative basin index takes far longer than that budget allows.
A wet week does not repay a twenty-year overdraft. Today's elevation is weather; the direction across a decade is the story. Both numbers are real, they answer different questions, and only one of them is being negotiated.
Tree rings put the instrumental record in its place. The reconstruction below runs from 762 CE to 2005, overlaid with the modeled natural-flow record from 1906. Two things become obvious at this scale: the years the compact was built on were unusually wet, and the deep past was drier than the gage era ever showed.
One year is weather. A century is the yardstick. The compact used two decades, and they were the wrong two.
Water changes custody nine times between a Rocky Mountain snowfield and the Gulf of California. At every handoff something is measured, something is inferred, and something is invisible.
Roughly 200 SNOTEL sites weigh the Upper Basin snowpack all winter.
MEASURED · method labelUSDA NATURAL RESOURCES CONSERVATION SERVICESnow water equivalent at automated sites, daily through the accumulation season.
How much water is standing in the mountains before any of it moves.
Dust-on-snow events, which darken the surface and accelerate melt weeks early. The gauge sees the water, not the dust.
The forecast centre converts snow into an expected April-July runoff volume.
FORECAST · method labelNOAA COLORADO BASIN RIVER FORECAST CENTERSeasonal water-supply forecasts against climatology, updated monthly.
That the snow-to-runoff conversion is not fixed — it depends on how thirsty the ground is.
The soil-moisture deficit that consumes runoff before it reaches any gage. In 2021 a snowpack near 80 percent of median produced roughly 30 percent of median runoff.
The Colorado, the Green, and the San Juan gather the high country.
MEASURED · method labelU.S. GEOLOGICAL SURVEYMainstem and tributary gages across the Upper Basin.
That roughly 85 percent of the entire river's supply originates above the compact point.
Transbasin diversions that leave the basin before any gage counts them toward the river's own ledger.
Upper Basin consumptive use — and the New Mexico chapter. The San Juan-Chama Project moves Colorado River basin water under the Continental Divide into the Rio Grande. That is the water Albuquerque and Santa Fe drink. If you live in northern New Mexico, this river is your tap too.
MODELED · method labelU.S. BUREAU OF RECLAMATIONModeled consumptive use by state, reconciled annually.
Where the Upper Basin's half of the compact actually goes.
Metered field-level use. Upper Basin consumptive use is estimated from crop and climate data, not measured — and the two basins do not agree on the method.
Glen Canyon storage, and the plumbing problem underneath it.
MEASURED · method labelU.S. BUREAU OF RECLAMATIONDaily storage and pool elevation from Reclamation.
That below 3,490 feet the turbines stop, and the river outlet works were never designed to carry a full annual release indefinitely.
Sediment. The 2017 survey found the reservoir had lost storage capacity since it was built, and the losses continue every year.
The compact gage, seventeen miles below Glen Canyon Dam.
MEASURED · method labelU.S. GEOLOGICAL SURVEYDischarge every 15 minutes, provisional until reviewed.
Where the ten-year rolling accounting between the basins is settled.
Natural flow. What the gage measures is a dam release. The natural-flow number the compact turns on is computed, not observed.
Hoover Dam, the shortage tiers, and the straws Las Vegas drilled deeper as the lake fell.
MEASURED · method labelU.S. BUREAU OF RECLAMATIONDaily elevation, which is the trigger variable for Lower Basin delivery cuts.
That a single elevation reading determines how much water three states receive next year.
Groundwater. When surface deliveries are cut, pumping often backfills them, and none of that appears on this gage.
Imperial Valley, the Central Arizona Project, Las Vegas, Los Angeles, Phoenix, Tucson.
PUBLIC RECORD · method labelCONGRESSIONAL RESEARCH SERVICEAnnual deliveries by contractor, published in the water accounting reports.
That the great majority of consumptive use is agricultural, and a large share of that grows alfalfa and other forage.
The priority system's human consequences. Seniority decides who is cut first, and seniority is not distributed by need.
Mexico's 1.5 million acre-feet, the Minutes, and the estuary the river built and then abandoned.
PUBLIC RECORD · method labelINTERNATIONAL BOUNDARY AND WATER COMMISSIONTreaty deliveries at the border and the results of engineered pulse flows.
That the delta only receives water when someone deliberately sends it, and that the treaty framework governing it expires into the same post-2026 renegotiation.
An ecological baseline. Nobody measured the delta before it was dewatered, so recovery is being judged against an estimate.
Run the Powell and Mead system forward ten years on your own assumptions. The model is an annual mass balance built from Reclamation's own area-capacity tables, natural-flow record, and published operating thresholds. Play with it long enough and it will teach you something the totals hide.
One good winter buys months, not years. Only demand bends the curve.
| SCENARIO | SNOWPACK | DEMAND MAF/YR | POWELL RELEASE | COMBINED STORAGE NOW | AFTER 10 YEARS | CHANGE | POWELL FT | MEAD FT | UNMET DEMAND |
|---|---|---|---|---|---|---|---|---|---|
| BIG WINTER | 140% then 100% | 13.5 | 8.23 | 12.29 MAF | 12.74 MAF | +0.45 MAF | 3515 | 1051 | 0.00 MAF |
| THE GRIND | 100% | 13.5 | 8.23 | 12.29 MAF | 6.79 MAF | -5.49 MAF | 3472 | 988 | 0.00 MAF |
| WORST ON RECORD | 45% | 13.5 | 7.48 | 12.29 MAF | 0.00 MAF | -12.29 MAF | 3370 | 895 | 38.57 MAF |
Initial conditions observed 2026-08-10. U.S. Bureau of Reclamation, Natural Flow and Salt Database, NaturalFlows1906-2020_20221215.xlsx, gage 09380000.
READ THE PROFESSIONAL-GRADE COUNTERPART · CRSS →MODEL INPUTSU.S. BUREAU OF RECLAMATIONU.S. BUREAU OF RECLAMATIONU.S. BUREAU OF RECLAMATIONU.S. BUREAU OF RECLAMATION
A reduction is a single number until you ask whose water it was. Five sectors absorb this river's shortfall, and the priority system — not need, not population — decides the order.
Municipal use is the most visible share and one of the smallest. Las Vegas is the standard case study: return-flow credits mean water sent back to Mead is not charged against the allocation, and a third intake was drilled below the old ones so the city can keep drawing as the lake falls.
5.5 million irrigated acres take the large majority of consumptive use, much of it for alfalfa and forage. The priority system decides the order: Imperial Valley holds some of the most senior rights on the river, so junior Central Arizona Project agriculture absorbs reductions first.
Thirty federally recognized nations hold rights to a substantial share of the river's flow, much of it senior to every state compact under a doctrine the Supreme Court confirmed in 1908. Some of those rights remain unquantified; some are quantified but undeveloped. The 2026 negotiations again proceeded largely without tribes at the primary table.
REVIEW BEFORE PUBLISH · accuracy and tone pass required
The 1944 treaty guarantees Mexico 1.5 MAF a year. Minute 323 and its successors added shortage sharing, storage rights in Mead, and the pulse-flow experiments that briefly reconnected the river to the sea. That framework expires into the post-2026 process alongside everything else.
Below Glen Canyon the river runs cold and clear where it once ran warm and red. Sediment is trapped behind the dam, beaches erode, and native fish like the humpback chub hold on in tributaries. Experimental high-flow releases rebuild sandbars deliberately, on a schedule, because the river no longer does it itself.
Shortages up to 1.5 MAF distributed under the Lower Division States' May 2026 proposal, with volumes beyond that assigned by priority. This is the reduction the basin has broadly agreed to absorb.
PUBLIC RECORD · method labelU.S. BUREAU OF RECLAMATIONThe Preferred Alternative's outer bound reaches 3.6 MAF of Lower Basin shortage including assumed reductions to Mexico, distributed by priority. Same river, same total, a very different map of who pays.
PUBLIC RECORD · method labelU.S. BUREAU OF RECLAMATIONDistribution is the stronger result. The total tells you how much water disappears; only the distribution tells you whose water it was.
Five things this accounting system structurally cannot observe. The last one implicates every number on this page, including the headline.
Upper Basin consumptive use is modeled from crop and climate data, not metered at the headgate. The two basins do not agree on the accounting method for the compact's own core number — and that disagreement is not academic, because it determines whether the Upper Basin is in compliance.
MODELED · method labelU.S. BUREAU OF RECLAMATIONEvaporation and system losses in the Lower Basin run to roughly 1.5 million acre-feet a year — an entire Nevada-plus of water — and for most of a century they were assigned to no user's ledger at all. The post-2026 framework begins to charge them.
PUBLIC RECORD · method labelU.S. BUREAU OF RECLAMATIONWhen surface deliveries are cut, groundwater pumping frequently backfills them. That water appears nowhere in the surface ledger, is largely unregulated in rural Arizona, and is being drawn from aquifers that recharge on geological timescales.
PUBLIC RECORD · method labelCONGRESSIONAL RESEARCH SERVICEQuantified but undeveloped tribal rights sit in the system as water simultaneously owed to nations and consumed by others. Every settlement that develops those rights makes the paper river smaller for everyone currently using them.
PUBLIC RECORD · method labelCONGRESSIONAL RESEARCH SERVICENatural flow at Lees Ferry — the number this entire piece turns on, the number in our own headline — is a model output. It is observed flow back-corrected for upstream depletion and storage. Every allocation argument on this river rests on an estimate, including the ones we just made.
MODELED · method labelU.S. BUREAU OF RECLAMATIONEvery number in sections 00 through 09 resolves to a card below. All of it is public; none of it is paywalled. That constraint is the product thesis, not a limitation.
The decision document that replaces the 2007 Interim Guidelines: a 10-year adaptive framework for operating years 2027 through 2036.
PUBLIC RECORDOperational sideboards for the Preferred Alternative: Powell releases 5.0-12.0 MAF, Lower Basin shortages up to 3.6 MAF, and the 2007 shortage volumes of 400/500/600 KAF at Mead 1,075/1,050/1,025 ft.
PUBLIC RECORDLake Mead and Lake Powell operating history, shortage declarations 2022-2025, the 1,090 ft DCP contribution line, and the lowering of Mead's minimum power pool from 1,050 ft to 950 ft.
PUBLIC RECORDObserved flow back-corrected for upstream depletion and storage. The number this whole piece turns on is itself a model output.
MODELEDDaily storage and pool elevation for Lake Powell (site 919) and Lake Mead (site 921). Supplies the model's initial conditions.
MEASUREDDaily pool elevation and storage for Lake Powell (catalog items 508 and 509) and Lake Mead (6123 and 6124). This is the feed the live cards read in your browser; it cross-validates against the hydrodata service to the reported precision.
MEASUREDElevation-area-capacity relationships from the reservoir floor at 3,130 ft to 3,712 ft. Rebased to live storage above dead pool for this model.
MEASUREDTotal capacity of 27,620 KAF between 895 ft and 1,229 ft; surface area 162,916 acres at full pool.
MEASUREDDischarge at the compact point. This is regulated release from Glen Canyon Dam, not natural flow.
MEASUREDSnow water equivalent as percent of median across roughly 200 Upper Basin sites. The reservoir before the reservoirs.
MEASUREDApril-July unregulated inflow forecasts for Lake Powell, the number the basin watches each spring.
FORECASTTree-ring reconstruction of annual water-year flow at Lees Ferry from 11 chronologies including remnant preserved wood. Geophysical Research Letters 34, L10705.
RECONSTRUCTEDApportions 7.5 MAF/yr of beneficial consumptive use to each basin and sets the Lee Ferry accounting obligation of 75 MAF per rolling 10 years.
PUBLIC RECORDGuarantees Mexico 1.5 MAF/yr and, through the Minutes, sets shortage sharing and the delta pulse-flow experiments.
PUBLIC RECORDStanding congressional reference on the allocation framework, the priority system, and the federal role in shortage.
PUBLIC RECORDAttributes roughly a third of the 2000-2014 flow deficit to higher temperatures and projects continued temperature-driven loss.
MODELEDFinds a sensitivity of roughly 9.3 percent flow loss per degree C of warming, driven by snow-albedo feedback.
MODELEDThe professional-grade monthly model this annual mass balance deliberately is not. Read this to see everything the lab omits.
MODELEDThe river ends before the sea. Whether that stays true is being decided right now, in two-year intervals, under a framework published in July 2026 and running through 2036. Every number on this page came from a public record. So can the next one.
This ran on public data. Imagine it on yours.