I am interested in building a pond near my home in Maine. Unfortunately, water supply is limited, so I was curious to see if it would be possible to maintain a pond without having to manually refill it using well water. I found some resources suggesting the possibility of using rooftop collected rainwater for topping off a pond, but I wasn't sure if this would be sufficient, so I created a spreadsheet to determine feasibility.

The spreadsheet can be found here.

The results of this spreadsheet appear too optimistic for me to believe. Using average rainfall/evaporation data for my area, an assumption of 1 gallon leak per hour, and inputs for the dimensions of the roof and prospective pond, the water level seems to stay completely full without any intervention all year round.

Is this possible? Have I missed anything in my calculations? I'm thinking of using a rubber liner, but mostly I'm investigating if this is possible in any way first before looking at specifics.

  • Is your pond really just going to be 30x30? I'd say some of the optimism is because your roof that gathers rainwater is larger than the pond itself so that more than doubles the normal effect rainwater has. How reliable is that leakage number? I guess you plan on it having a waterproof liner?
    – JPhi1618
    Jun 3 '19 at 19:54

How did you determine a leak rate ? Will it be concrete or rubber , or ? Will there be high edges to keep out roots and prevent capillary action of soil. My small pond in TX ( 800 gal) , rubber liner , leaks over a gallon an hour which I can't find. But one data point ; swimming pool in northern IL essentially stayed full from precipitation Oct to May ( no swimming/splashing ) ; being frozen significantly reduces evaporation which I think will work even better in Maine. Depending on the location and size , wildlife like deer may be a factor. Deer drink out of mine but it leaks so much I have no idea.

  • you could post a question about your pond leak
    – jsotola
    Jun 4 '19 at 3:34
  • An engineer family friend suggested the leak rate. In retrospect, I realize that this might not be the best good source. Thanks for the info! I just plugged your number of 1 gallon per hour (or 975 drops per second) and it the pond remains full. Was planning on using a pond liner. Updated question, thanks! Jun 4 '19 at 3:47

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