# Evaporation from a fish pond.

**URL:** <https://boards.straightdope.com/t/evaporation-from-a-fish-pond/665592>\
**Category:** Factual Questions\
**Created:** [August 7, 2013, 3:24pm UTC](https://boards.straightdope.com/t/evaporation-from-a-fish-pond/665592 "2013-08-07T15:24:12Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![janeslogin](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@janeslogin](https://boards.straightdope.com/u/janeslogin)\
**Post date:** [August 7, 2013, 3:24pm UTC](https://boards.straightdope.com/t/evaporation-from-a-fish-pond/665592/1 "2013-08-07T15:24:12Z")

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I studied the Wikipedia formulas and they are beyond my knowledge. Can one figure evaporation from a fish pond with just this information? Copy paste of Historical for August:

```
High: Low: Average:

```

Temperature: 93.1 °F 38.3 °F 69.5 °F  
Dew Point: 47.1 °F 25.8 °F 36.0 °F  
Humidity: 71.0% 12.0% 33.0%

Pressure: 29.91in 29.66in -  
Precipitation: 0.00in

Lat: N 39 ° 11 ’ 36 ‘’ ( 39.194 ° )  
Lon: W 119 ° 45 ’ 53 ‘’ ( -119.765 ° )  
Elevation (ft): 4723

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**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\
**Post date:** [August 7, 2013, 4:57pm UTC](https://boards.straightdope.com/t/evaporation-from-a-fish-pond/665592/2 "2013-08-07T16:57:17Z")

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I’m sure someone else can come up with the right equation, but I’m also sure they’re going to need at least two more bits of information: 1) water temperature and 2) surface area.

Pond plants and muddy shores can also contribute to evaporation. So can waterfalls or other water features that create spray.

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**Author:** ![janeslogin](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@janeslogin](https://boards.straightdope.com/u/janeslogin)\
**Post date:** [August 8, 2013, 12:04am UTC](https://boards.straightdope.com/t/evaporation-from-a-fish-pond/665592/3 "2013-08-08T00:04:28Z")

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At noon today the water temperature was 69F and the air was 81F. The area is 129 square feet.

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**Author:** ![Baracus](https://avatars.discourse-cdn.com/v4/letter/b/2bfe46/32.png) [@Baracus](https://boards.straightdope.com/u/Baracus)\
**Post date:** [August 8, 2013, 12:33am UTC](https://boards.straightdope.com/t/evaporation-from-a-fish-pond/665592/4 "2013-08-08T00:33:46Z")

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I don’t know how to figure it out but you will certainly need to know the wind speed as well.

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**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\
**Post date:** [August 8, 2013, 1:14am UTC](https://boards.straightdope.com/t/evaporation-from-a-fish-pond/665592/5 "2013-08-08T01:14:14Z")

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[Here](https://www.google.cl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CDUQFjAC&url=https%3A%2F%2Fwww.dri.edu%2Fimages%2Fstories%2Fdivisions%2Fdhs%2Fdhsfaculty%2FJustin-Huntington%2FHuntington_and_McEvoy_2011.pdf&ei=2u0CUpbfCaTmiwK5uIDIDw&usg=AFQjCNH0Y0PYGDd1-pqM735S4fDs1vG5kw&sig2=FlrjUBMKZoHxFuySdayo3w&bvm=bv.50500085,d.cGE&cad=rja) you go.

That’s a Desert Research Institute report on evaporation from open water surfaces in northern Nevada, including Carson City. Page 21 of that pdf file gives estimates of monthly evaporation from a number of local reservoirs, and Figure 5 shows the different reservoirs over the course of the year. A fish pond will mix pretty well and doesn’t have a lot of thermal inertia, so you’re going to be closer to the Boca pan evaporation rate (the heavy black line in Fig. 5) than any of the reservoirs. In a typical August, you’re probably losing about 7 in/month (5-6 mm/day) of water due to surface evaporation.

There are references in the back of the report if you really want to dig into the equations, but if you’re just looking for a number that should get you going.