Question about evaporation

[michey1st]

Hi folks!

This is my first Spring with my new pond. It's actually 3 bodies of water - a bog that waterfalls about 12 inches into a middle pond, and then another short waterfall (about 10 inches) into the lower pond. The entire setup is around 650 or so gallons and of that, the lower pond is about 125 gallons.

Over winter, the level of the gravel in the bog (which is about a 4' by 3' semicircle) dropped slightly so that more than half of it has about an inch of water on top of the gravel.

I'm noticing that I'm losing about 1/2" of water in the lower pond every 2 days (keep in mind that the lower pond is the smallest of the three, so 1/2" isn't really all that much... a few gallons maybe?). The pond gets direct morning sun (until the forest behind my house leafs out) and afternoon shade. I've checked my waterfalls and my edges religiously (especially since we had some edge issues late last year) and have found no wicking and no leaks. So now I'm wondering, since the pond has a comparatively large surface area compared to depth and the water is pretty swiftly moving (my pump is 2900 GPH as I am planning to expand the lower pond within the next year), could this loss simply be due to evaporation?

I haven't had a moment to get more gravel to fill the bog back up (but I plan to). I suspect this doesn't help with the whole evaporation thing.

What do y'all think?

Kindest regards,
Michele

 

[RobAmy]

It sounds normal to me. I feel it is just evaporation.

 

[sissy]

I know here we have had lots of wind and if you are getting the same it is evaporation .

 

[michey1st]

Thanks RobAmy and Sissy! It hasn't been too terribly windy around here (save for brief bouts in the evening) but after putting the water loss in writing and doing a quick calculation, I guess the water loss isn't too much to be alarmed about -- I just have to keep my eyes on it. It helps to hear that you all aren't alarmed! I'm sick of worrying about this dang water level and checking my edges, lol!

This almost makes me want to take the tiny lower pond out of rotation and just keep the fish in the middle pond until my upgrade...

 

[sissy]

you can mark your liner but to me the gravel sinking is just settling as the ground under the liner settles .Plants in your bog may be taking up more water also .Do you have critters that come in your yard .My deer drink from my pond

 

[JBtheExplorer]

I agree with them. Likely evaporation. When it was 90+ degrees in the summer I was losing almost an inch a day. I was also worried about a leak but once the days got cooler I was losing less.

 

[addy1]

I am losing water right now, dry air, windy, cool at night, water warming a lot of water starts to evaporate. In the summer I lose an inch a day, usually, the bog and plants suck down that water.

 

[dieselplower]

Splashing 2900 gph of water between 3 ponds is definitely going to cause noticable evaporation.

 

[taherrmann4]

I lost about and 1" of water today, very windy and I also have lots of surface area for evaporation to really take a toll.

 

[Dave 54]

Evaporation can be quite a scary thing especially when you dont know if it is or not .
Check all the edges of your liner that are out of the water or just below for any holes if you feel your loosing too much for this time of year
Just to put your mind at rest wind evaporation and evaporation by sun do take alot of water between them at the height of summer last year we lost half an inch daily from a pond that cant leak unless its from either the bottom drain and inlet pipe.
"I know for certain that the bottom drain isnt leaking "as I would have seen water outside of the pond in the soil however I did check the inlet pipe situated 2ft down in the pond just to be on the safe side and that wasnt leaking either.
My conclusion evaporation ....


Dave

Dave

 

[michey1st]

Thanks everyone for your reassurances and sharing in my pain! This whole waterfall thing is uncharted territory to me... my last pond was just a preform with a fountain spitter -- the need to top off is rather new, lol!

Yesterday was much better in terms of evaporation - at least for me - even though it was a bit warmer than the day before. Weird stuff!

Unrelatedly, Mourning Doves are dumb! They have a nice, shallow bog area to drink from not three feet away, yet they consistently try to balance precariously on the edge of the lower pond. The robins, cardinals and goldfinches got the idea rather quickly, but not these guys!

 

[michey1st]

Torrential downpours today. The pond is filled up again... hooray!!!

 

[sissy]

We had bad rains last night and guessing you are getting them now .It has not gotten to my over flow yet but barely touching it and I took 20 gallons of water out yesterday because they said the rains were going to be heavy .Was going to take more out but i didn't .

 

[Waterbug]

What you're seeing is a bit more than just simple evaporation. In a single pool the water level goes down due to evaporation, pretty simple. However your pond has 3 pools. Does the water level in the upper 2 pools ever go down at all due to evaporation? Nope. Because you're always pumping water from the lower pond into those upper pools. The lower pool acts a reservoir for those upper pools. All the evaporation for all the pools appears only in the lowest pool, which also the smallest so the amount of loss is magnified.

So say your bog is 4x3 and your pond is 10x10 and the lowest is 3x3. That's a total of 121 sq ft of surface where evaporation can take place (plants would suck up even more). Say on a normal day you lose 1/4" to evaporation. For the 121 sq ft that would be about 19 gals of water. Spread out over a single 121 sq ft pond that 19 gal would be just 1/4". Hardly noticeable.

However, in your case the entire 19 gal will appear to be lost in just the lowest 3x3 pool (the upper pools remain full). That would appear as 3.37" loss in that lowest pool.

Prepare yourself for this summer. You could see the water level in that lower pond drop scary amounts. Many people think this is caused by a leak when you see your pond 6" lower in one day. Tear their pond apart, and hair out, looking for a leak that doesn't exist. First time I saw this it scared the heck out of me.

If you want to add an auto fill the lower pool is where it should go.

You can test for leak by testing evaporation. A straight sided container fill to the top with water placed in or near the pond will show the evaporation rate for whatever time period you the test. Week is good. Because you have multiple pools you have to do a bunch of calculations. Not super hard but it takes a little noodling.

Or you have to shutdown the pump and measure the drop each pond. You can keep a pump running in each pond but you can't pump water from one pond into another or you're back to the calculating method.

You may also notice that when you first turn your pump on the water level in the lowest pool drops, maybe a lot. This is because it has to first fill the upper pools before any water starts flowing back into the lower pool. There is a time lag. And if you then top up that lower pool and then turn the pump off the lower pool may overflow because even though the pump is off water will continue to flow out of the upper pools for a short time.