Level of the Lake

Rivers into Lake Powell

9,020 cfs flowing in right now from 3 gauged rivers. Tap a river for its gauge page.

Where the water is flowing

Swipe sideways to follow the river to the lake →

2,680 cfs4,020 cfs2,320 cfs6,700 cfs2,320 cfs7,440 cfsout the dam nowColorado2,680 cfsGreen4,020 cfsrecedingSan Juan2,320 cfsrecedingColorado armColorado + GreenSan Juan armSan Juan River22% fullPowell storagein 9,020 · out 7,440 cfsnet +1,580 cfs ≈ +0.64 in/day on the lakeColorado at Lees Fer…USGS gauge below Glen C…
SteadyReceding · high water draining downOn the rise · climbing right nowInbound wave · big rise upstreamFlooding · NWS, by river heightNo current readingRising or falling is judged from each gauge’s last 48 hours, scaled to its river. Dot speed follows the flow. NWS flood status comes from river height and outranks direction.

Streamflow at the 3 USGS gauges, plus the current flow out through the dam (USGS). Labels are gauge readings in cfs. Line width isn’t to scale. The lake’s net is worked out from these gauges (flow in minus flow out), so it misses ungauged creeks, evaporation and withdrawals. Reclamation’s daily storage for the lake changed +1,649.36 af ≈ +0.34 in on Sep 28.

The rivers, gauge by gauge

9,020cfs combined

45% of the inflow is coming from the Green

Gauged rivers only. Runoff below these gauges and ungauged arms aren’t counted. Streamflow: USGS (provisional). Flood status: NOAA/NWS, from river height at each gauge rather than flow.

Rain outlook

modeled

About 0.27 in forecast over the next 3 days, averaged across the basin, heaviest in the San Juan basin (0.43 in).

Open-Meteo model forecast for each basin that drains to the lake.

Radar map →River inflow forecast →
How we know thisToday’s water budget: what came in and what went out

Up or down? Up. Reclamation's daily storage for Lake Powell rose 1,649 acre-feet on Sep 28.

Where the water came from and where it went, at today’s rates. Reclamation publishes the dam’s daily release and storage, so both are measured. The leftover line covers water with no meter (withdrawals, seepage, ungauged creeks) and is inferred from the other lines.

  • River inflowmeasured
    +17,891 af/day≈ +3.65 in/day on the lake

    USGS gauges, at current rates

  • Evaporationmodeled
    −1,226 af/day≈ −0.25 in/day on the lake

    Estimate from long-term averages over ~58,841 acres, estimated from Reclamation storage

  • Dam releasemeasured
    −16,307 af/day≈ −3.33 in/day on the lake

    Bureau of Reclamation (hydrodata site 919): total release, daily average for Sep 28

  • Everything arriving that we can’t meter (ungauged creeks, springs)inferred
    +1,291 af/day≈ +0.26 in/day on the lake

    What’s left once the other rows and the storage change are counted

  • =Storage changemeasured
    +1,649 af/day≈ +0.34 in/day on the lake

    Bureau of Reclamation (hydrodata site 919) daily storage, Sep 28 vs. the day before

The lines above add up to the storage change: what the lake gained or lost. Inflow is current; release and storage are Reclamation's daily figures for Sep 28, so the leftover also absorbs the gap between the two days.

For comparison, Reclamation put inflow for Sep 28 at 9,483 cfs, calculated from storage and release.

Where it’s going

  • Glen Canyon Dam releasemeasured

    Reclamation, Sep 28

    16,307 af/day≈ 8,221 cfs
  • Evaporationmodeled

    estimate from long-term averages

    1,226 af/day≈ 618 cfs

The release leg is Reclamation's reported total release through Glen Canyon Dam for Sep 28. The withdrawals line is the budget’s leftover: city intakes, ungauged runoff and estimation error. The lines can overlap, so treat the split as approximate.

How this is computed

Inflow converts current streamflow at the gauged tributaries (USGS) to acre-feet per day (1 cfs ≈ 1.9835 af/day). Evaporation uses long-term monthly averages for the region over today’s lake surface. That surface area is TWDB’s daily survey where published, otherwise estimated from storage. With no storage reading, evaporation isn’t estimated. Inches on the lake divides each volume by that same surface area, so an inch takes less water when the lake is low and narrow than when it’s full and wide. Storage change is the operator’s daily storage, compared with the day before. The leftover is what it takes to make the lines add up. It lumps together withdrawals and ungauged runoff, which can’t be split without data the operator doesn’t publish.

All inputs are provisional. This page is an estimate, not an official accounting.

The water budget on its own page →