Level of the Lake

Rivers into Allatoona Lake

218 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 →

172 cfs3.3 cfs43 cfs175 cfs43 cfs330 cfsout the dam nowEtowah172 cfsShoal Creek3.3 cfsLittle River43 cfsEtowah armEtowah + Shoal CreekLittle River armLittle River91% fullAllatoona storagein 218 · out 330 cfsnet −112 cfs ≈ -0.24 in/day on the lakeEtowah at Allatoona…USGS gauge below the dam
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.

The rivers, gauge by gauge

218cfs combined

79% of the inflow is coming from the Etowah

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

No measurable rain forecast over the next 3 days, averaged across the basin.

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? Down 0.35 ft over the last 7 days (USGS lake level).

Where the water came from and where it went, at today’s rates. Dam releases and withdrawals have no complete public feed, so they land in the leftover line, which is inferred from the other lines.

  • River inflowmeasured
    +433 af/day≈ +0.46 in/day on the lake

    USGS gauges, at current rates

  • Evaporationmodeled
    −141 af/day≈ −0.15 in/day on the lake

    Estimate from long-term averages over ~11,246 acres, estimated from USGS storage

  • Everything leaving that we can’t meter (releases, withdrawals)inferred
    −854 af/day≈ −0.91 in/day on the lake

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

  • =Storage changeinferred
    −562 af/day≈ −0.60 in/day on the lake

    The lake's level change over the last 7 days (−0.35 ft, USGS), as a daily average, × ~11,246 acres, estimated from USGS storage

The lines above add up to the storage change: what the lake gained or lost. Inflow is current; storage is the average over the last 7 days, so the leftover also absorbs any change in pace over that time.

That leftover is about 431 cfs leaving the lake, mostly dam releases and withdrawals, plus whatever the upstream gauges missed.

Where it’s going

  • Etowah at Allatoona Dammeasured

    USGS gauge below the dam

    655 af/day≈ 330 cfs
  • Evaporationmodeled

    estimate from long-term averages

    141 af/day≈ 71 cfs
  • Withdrawals and other unmetered waterinferred

    the leftover from the budget above

    199 af/day≈ 100 cfs

Etowah at Allatoona Dam (USGS gauge below the dam) is measured downstream of the dam and stands in for releases. 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 lake’s level change (USGS) times that surface area, averaged per day over the last day for a once-a-day feed, otherwise over the last seven days. The leftover is what it takes to make the lines add up. It lumps together dam releases, 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 →