What is normal evaporation from my koi pond?
Water does evaporate. Plants also use the water in a process called transpiration. Some plants are thirstier than others. So then the question is how much evaporation is normal for my pond? Does my pond have a leak or just evaporation?
Does that wet mark on my rocks about 1″ above water level mean I have a leak?
Nope. It is normal and expected to notice that your koi pond rocks will be wet about an 1″ above the actual water level. This is due to the water wicking up the rock. You can call this capillary action, wave action, etc … this effect has been called many different things. Leonardo da Vinci wrote about it, Einstein studied it, and you can learn more about it by searching for “Fick’s laws of diffusion” … or just relax and enjoy your pond knowing that it’s normal and expected and not a cause for concern.
Is it a leak or evaporation in my pond?
Short answer is that every fish pond is different but on average you can expect to lose 1″ of water per week for an average koi pond with a waterfall. With no pump running you will typically not notice any water loss in 24 hours. Use the chart below to understand how the waterfall gallons per hour flow and the size of your pond affects how many inches you could expect to lose in a day and in a week.
How much water should I expect to add to my pond every week? Well, it depends …
Let’s consider the example of a 150 square foot pond about 10′ long by 15′ wide …
(Here’s the math – looking at the chart we see that there is approx. 93 gallons in the top 1″ of water. If you have a 6,000 gallon per hour pump, it is estimated that you could lose anywhere from 2.25″ up to 4.5″ per week from splash, evaporation, and transpiration (think thirsty plants). That’s 2.25″ x 93 gallons = 209.25 gallons or up to 418.5 gallons per week…)
If your hose flow rate is 10 gallons per minute (which might be a good estimated average if you are on a municipal water supply) then you could expect to add water from your hose 20 – 40 minutes per week to your fish pond… or 1-2 hours per month during hot and dry summer season … probably a bit less in cooler damp weather …
Keep in mind every pond is different… a koi pond in full sun with a bunch of tall splashy waterfalls is going to lose more water than a shady goldfish pond with short waterfalls …