How to calculate a pond's evaporation rate

Written by andrew leahey
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How to calculate a pond's evaporation rate
Leaks put the health of your fish at risk; establishing an evaporation rate is key to proper upkeep of your pond. (Art Wolfe/Digital Vision/Getty Images)

Outdoor ponds are wonderful additions to any garden landscape, yet they can be high maintenance. With a few proactive steps, however, repairs can be mitigated. Calculating a pond's evaporation rate is the key to determining if a falling waterline is due to a leak or just evaporation. Establish a baseline for your pond's evaporation rate when it is first installed. This will give you an accurate gauge of how long it takes the pond's water level to fall 1 inch through ordinary evaporation.

Skill level:
Moderately Easy

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Things you need

  • Wooden yardstick

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  1. 1

    Measure the depth of the pond using a yardstick. After your pond is installed, place the yardstick in the water at a location you can use again in the future to track your evaporation rate. Determine the depth and record the measurement. Turn off any auto-fill mechanism you may have installed for the duration of the experiment.

  2. 2

    Return to the pond each day and measure the depth in the same location you used for the initial measurement. Continue returning and measuring until the water level has fallen 1 inch. If the pond is exposed to heavy rainfall during this period, start again, since you will not be getting an accurate reading of the evaporation rate.

  3. 3

    Determine the number of days it takes for the water level to fall 1 inch. Divide 1 inch by the number of days, and this is your baseline number for future measurements.

Tips and warnings

  • If you find your pond's waterline to be falling at a rate greater than the baseline, you may have a leak.
  • A small leak can become a large leak quickly. Do not leave fish in a pond that you believe is leaking.

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