Gage height · USGS gauge 06903880 · updated August 29, 2026
Gage height
905.79ft
feet on the station datum
Gauge 06903880, Rathbun Lake near Rathbun, IA, operated by the U.S. Geological Survey. The value above is the most recent reading on file with its own timestamp. When the gauge answers, it is replaced by the current one — no estimate is ever shown in place of a missing reading.
What this number is
Gage height is the height of the water above a reference point set at Rathbun Lake near Rathbun, IA when the station was installed. It tracks rise and fall at this lake accurately, but the zero point is local: it is not depth, not sea level, and not comparable to another lake's gage height.
- Measured as
- Gage height, ft on the station datum
- Most recent reading on file
- 905.79 ft · August 29, 2026
- Water quality
- Readings on the lake page
The Corps of Engineers reads Rathbun Dam & Reservoir at 905.77 ft, 1.77 ft above its Top of Conservation of 904.00 ft.
The USGS reading above is a gage height — feet above a datum set at that station, not feet above sea level — so it is measuring a different thing and is not a smaller version of this number. Both numbers come from the U.S. Army Corps of Engineers for its Rathbun Dam & Reservoir project, on that project's own vertical datum (OTHER). That figure is a fixed level rather than a seasonal target, so a reservoir drawn down on purpose in autumn can sit well under it and still be exactly where the Corps intends. Because the datum is the project's own, this elevation is comparable to its own reference and to nothing else — not to a gauge reading from another agency, and not to a lake's mapped surface elevation.
Surface elevation is a different number
Mapped surface elevation at Rathbun Lake is about 899 feet above sea level, from the HydroLAKES global lake dataset. That is a fixed cartographic value, not a reading: it does not move when the lake rises, and it is not the gage height above. Keep the two apart.
Water quality at Rathbun Lake
Rathbun Lake's readings for total phosphorus, total nitrogen, chlorophyll-a, and turbidity are shown beside the EPA National Lakes Assessment condition classes for its own ecoregion. Clarity averages 3.0 feet of visibility, shown separately.
The gauge measures how much water is in the lake. The nutrient and algae readings measure what is in the water. A rise or a drawdown does not change those readings until the lake is sampled again.
Common questions
What is the water level at Rathbun Lake right now?
The most recent reading from the USGS gauge at Rathbun Lake near Rathbun, IA is a gage height of 905.79 ft, taken on August 29, 2026. This page reloads that gauge every time it is opened, so the number above is the current one whenever the station is reporting. USGS lake gauges typically post a new value every 15 to 60 minutes.
What does gage height mean?
Gage height is the height of the water above a reference point set at Rathbun Lake near Rathbun, IA when the station was installed. It tracks rise and fall at this lake accurately, but the zero point is local: it is not depth, not sea level, and not comparable to another lake's gage height.
Is Rathbun Lake low?
Rathbun Lake stood at 905.77 ft on September 27, 2026, 1.77 ft above its Top of Conservation of 904.00 ft. The USGS reading above is a gage height — feet above a datum set at that station, not feet above sea level — so it is measuring a different thing and is not a smaller version of this number. Both numbers come from the U.S. Army Corps of Engineers for its Rathbun Dam & Reservoir project, on that project's own vertical datum (OTHER). That figure is a fixed level rather than a seasonal target, so a reservoir drawn down on purpose in autumn can sit well under it and still be exactly where the Corps intends. Because the datum is the project's own, this elevation is comparable to its own reference and to nothing else — not to a gauge reading from another agency, and not to a lake's mapped surface elevation.
Does the water level affect water quality at Rathbun Lake?
Rathbun Lake has nutrient and algae readings on record from state and federal monitoring. Each lake's nutrient and algae readings — total phosphorus, total nitrogen, chlorophyll-a, and turbidity — are shown beside the EPA National Lakes Assessment 2022 condition class for that lake's own ecoregion, so a reading is compared against the lakes it would naturally resemble. LakeQuality publishes no letter grade. None of that comes from the gauge. A drawdown can concentrate nutrients and a heavy inflow can dilute them, but neither shows up in the readings until the water is sampled again. Treat the two numbers as separate measurements of the same lake.
Where these numbers come from
The level and temperature are U.S. Geological Survey instantaneous values from gauge 06903880, a public feed with no licence restriction. The water-quality readings come from EPA Water Quality Portal samples submitted by Iowa DNR Surface Water Monitoring Data. For advisories and standards in Iowa, Iowa DNR is the authority — a gauge reading is neither.