Evaporation Pan To Lake Coefficient
Infer a pan-to-lake coefficient from a matched fixed-area observed lake water budget; negative inferred evaporation/coefficient exposes condensation or missing fluxes rather than being forced to an empirical default.
Description
A matched lake water budget can infer evaporation, then compare it with an evaporation-pan observation.
A matched lake water budget can infer evaporation, then compare it with an evaporation-pan observation. A fixed lake area converts net volume exchanges into equivalent depth.1
The tool returns inferredLakeEvaporationDepthMm, panToLakeCoefficient. The computation uses supplied observations and parameters rather than acquiring measurements.
When to use Evaporation Pan To Lake Coefficient
Use this for the following task: Infer a pan-to-lake coefficient from a matched fixed-area observed lake water budget; negative inferred evaporation/coefficient exposes condensation or missing fluxes rather than being forced to an empirical default. Prepare observations and calibration parameters on the same unit and reporting basis.
How to use Evaporation Pan To Lake Coefficient and understand its results
- Prepare the measured quantities and supplied model parameters. Match the units and align paired lists before calculating.
- Enter lakeAreaM2, precipitationDepthMm, inflowVolumeM3, outflowVolumeM3, observedLakeStorageChangeM3, panEvaporationDepthMm according to the field table, then run the tool.
- Read inferredLakeEvaporationDepthMm, panToLakeCoefficient. Use the calculation below to interpret the selected mean or the model’s signs, units and comparison flags.
- Review the supplied assumptions and calibration before comparing or reporting the result.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| lakeAreaM2 | Lake area m2 | number | Required |
| precipitationDepthMm | Precipitation depth mm | number | Required |
| inflowVolumeM3 | Inflow volume m3 | number | Required |
| outflowVolumeM3 | Outflow volume m3 | number | Required |
| observedLakeStorageChangeM3 | Observed lake storage change m3 | number | Required |
| panEvaporationDepthMm | Pan evaporation depth mm | number | Required |
Supply positive lake area and pan evaporation, nonnegative precipitation and exchange volumes, and signed storage change over the same period. Return the inferred depth and ratio.
lakeEvaporation mm=precipitation+1000×(inflow−outflow−storageChange)/area; coefficient=lakeEvaporation/panDepth The symbols and boundary conditions refer to the supplied fields and the implementation described above.
| Output field | Meaning | Value type |
|---|---|---|
| inferredLakeEvaporationDepthMm | Inferred lake evaporation depth mm | number |
| panToLakeCoefficient | Pan to lake coefficient | number |
{
"input": {
"lakeAreaM2": 1000,
"precipitationDepthMm": 2,
"inflowVolumeM3": 1,
"outflowVolumeM3": 0,
"observedLakeStorageChangeM3": -2,
"panEvaporationDepthMm": 10
},
"output": {
"inferredLakeEvaporationDepthMm": 5,
"panToLakeCoefficient": 0.5
}
}Limitations and assumptions
Negative inferred evaporation or coefficient is preserved. Missing groundwater, varying area and mismatched periods are not corrected, and no empirical default coefficient is substituted.
Numerical inputs must be finite. Input-shape and calculation checks do not establish measurement quality or the validity of a supplied calibration.
Alternative or Complementary methods
Choose Lake Evaporation Energy Balance Method when you need its operation: Estimate signed evaporation by a caller Bowen-ratio available-energy budget including storage/advected heat; negative results indicate condensation-model potential and missing fluxes are not diagnosed. Choose Stage Storage Volume Interpolation for the complementary operation: Interpolate storage for measured monotone stage/storage calibration within its observed bounds; no extrapolation, contour integration or invented lake geometry.
Background reference: Evaporation from the Interior of Lake Okeechobee, 2013–16.
References
-
Evaporation from the Interior of Lake Okeechobee, 2013–16 — Shoemaker and Wu, U.S. Geological Survey
Similar or alternative tools
- Lake Evaporation Energy Balance Method
Estimate signed evaporation by a caller Bowen-ratio available-energy budget including storage/advected heat; negative results indicate condensation-model potential and missing fluxes are not diagnosed.
- Stage Storage Volume Interpolation
Interpolate storage for measured monotone stage/storage calibration within its observed bounds; no extrapolation, contour integration or invented lake geometry.