Pond Boss Forums POND CONSTRUCTION Renovating a Pond or Lake? evaporation or leak?

We purchased a property last year with a pond. The pond had been leaking from years of trees on the damn and muskrat damage. I had it repaired last year

My pond filled up nicely over the winter but its now down about 6 inches over a six week period. Its not a sudden drop, its slowly reached this level.

I'm trying to determine if it is leaking or if this is just normal evaoporation. Its been well over a month since we've had any rain. Its been bright sunny days and my pond gets a steady wind of 3~5 mph. I know these can be factors for evaoporation.

This is my first pond so I have no idea what to expect as for water level.

Well, I certainly can't say that it isn't a leak. However, it is not at all unusual for water to wick back into previously dry soil when the water level rises. I have one that, to the best of my knowledge, doesn't leak. The water level dropped about 4 inches in about a month. Recent rains have refilled it.

I was thinking that there must be some easy method to calculate evaporate rate to determine how much it contributed to the reduction in water level. So of course I Googled evaporation rate calculation and came up with the formula below:

There are many factors involved in the calculation of water evaporation rates from ponds or lakes, and one of the most important factors is the wind velocity. I would suggest that you study the model recommended by ASHRAE (the American Society of Heating, Refrigeration and Air-conditioning Engineers): W = [A + (B)(V)](Pw - Pa)/Hv where: W = water evaporation rate, (lb/hr) per sq.ft. of pond surface area A = a constant = 95 (**see note below) B = a constant = 37.4 (**see note below) V = air velocity over the pond surface, miles/hr Pw = vapor pressure of water at the pond water temperature, inches of Hg Pa = vapor pressure of water at the air dewpoint temperature, inches of Hg Hv = heat of vaporization of water at the pond water temperature, Btu/lb A good set of Steam Tables will provide you with the latent heat of vaporization and the vapor pressure of water at the temperatures involved. The vapor pressures may be provided in units other than inches of Hg, and you will need to make the conversion.

So the short answer is that there is no way to calculate evaporation rates unless of course you happen to be Theo.

I have read on the forum that you can place a bucket of water at the pond and see how much evaporates to give you a rough idea.