Pond Evaporation & Splash Loss: What's Normal?

Owner of 3,150-gal oval pond (14.5×19.5 ft, 2.7–3.7 ft deep) with 35-ft stream, three 16-inch waterfalls, 6,000 gph pump asks expected evaporation/splash loss in 90°F+ weather.

Estimating Loss

No universal formula—depends on wind, humidity, sun exposure, splash, stream surface area. Rough guideline: 5–10 mm/day (¼–⅜ inch) in hot, dry, windy conditions with active waterfalls.

Waterfalls and streams increase loss significantly—turbulence and expanded surface area accelerate evaporation.

Leak vs. Evaporation Test

1. Fill pond to a marked level.
2. Run pump 24 hrs. Measure drop.
3. Turn pump off 24 hrs. Measure drop.
4. If loss is similar, it's a leak. If much higher with pump on, it's splash/evaporation.

Common Leak Spots

• Waterfall/stream liner edges (capillary wicking)
• Plumbing connections
• Skimmer faceplate seal

If loss exceeds 1 inch/day with pump off, investigate leaks. Use the engineeringtoolbox.com evaporation calculator for site-specific estimates.