Pond Water Loss: Evaporation Estimate for Large Stream System

Same pond specs as previous article. Second answer estimates ~7 mm/day loss, cites wind, water velocity, vegetation as variables. References engineeringtoolbox.com calculator.

Consolidated Guidance

For a 3,150-gal pond with 35-ft stream and three waterfalls in 90°F+ weather:

• Expected loss: 5–10 mm/day (¼–⅜ inch)
• Primary drivers: Wind speed, stream turbulence, low humidity, full sun
• Measurement: Use a marked bucket or ruler on liner; track daily at same time.

If loss exceeds 15 mm/day, suspect leaks—especially at waterfall liner seams, plumbing, or skimmer. The engineeringtoolbox.com evaporation calculator provides physics-based estimates for your exact conditions.