Pan Evaporation to Lake Evaporation Calculator
Calculate pan evaporation lake evaporation with our free science calculator. Uses standard scientific formulas with unit conversions and explanations.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
EL = Kp x Ep
The pan-to-lake conversion formula EL = Kp x Ep estimates actual lake or reservoir evaporation from standardized pan measurements. Ep is the measured evaporation depth (mm/day) recorded from a Class A evaporation pan. Kp is the dimensionless pan coefficient, typically 0.60 to 0.80, that corrects for the difference in heat storage, advection, and boundary-layer effects between the small pan and a large open-water body. The result EL gives the lake evaporation rate in mm/day. Multiplying by lake area and the number of days yields total volumetric water loss for reservoir water-balance calculations.
Worked Examples
Example 1: Temperate Catchment
Problem:P=800mm/yr, C=0.3, ET=450mm/yr, dS=20mm, A=10km2
Solution:R = 800 - 240 - 450 - 20 = 90 mm/yr
Result:Recharge: 90 mm/year | Low Recharge
Example 2: Semi-Arid Region
Problem:P=350mm, C=0.15, ET=310mm, dS=5mm, A=25km2
Solution:R = 350 - 52.5 - 310 - 5 = -17.5 mm/yr
Result:Recharge: -17.5 mm/yr | Deficit
Frequently Asked Questions
What is Pan Evaporation to Lake Evaporation?
Pan Evaporation to Lake Evaporation is a fundamental concept in hydrology used to quantify water movement and distribution in natural and engineered systems. It provides essential data for water resource management, flood prediction, and environmental assessment. Understanding this helps engineers design infrastructure and scientists model hydrological processes. Pan Evaporation to Lake Evaporation Calculator implements standard formulas from published hydrology references.
How is Pan Evaporation to Lake Evaporation calculated?
The calculation uses EL = Kp x Ep relating key physical parameters. Each variable must be measured or estimated from field data or published tables. The formula assumes steady-state or quasi-steady conditions. Units must be consistent and results should be validated against field observations when available.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy