There are a couple of mysteries unfolding at the pond.

Number one showed up sometime during the two weeks I was away in Wyoming. Babies.

Our pond is host to one large Koi (whitey) and five orange fish, of which I can never quite remember the species. Four are orange and the other is a pink-yellow shade we haven't been able to agree on. At one point only three of them were orange, the fourth was smaller and sporting a dusky brown shade, almost invisible in the pond. One week it went from dusky to orange.

We have had these six fish for over four years now. No babies. Yet this summer finds not one, but two (and maybe more) baby fish. These are good sized, the biggest is a couple inches long already. You'd think they would have been visible for quite some time.

I've also caught fleeting glimpses of little, and I mean dinky, minnows in the shallows of the pond. Just a few, here and there, no idea if they are part of the same gang or not. It's a mystery.

Rare Baby Fish Sighting: far right blur

A couple months ago I decommissioned our indoor tank and tossed the four remaining fish into the pond. I didn't want to flush them and living in the pond seemed like a great upgrade from the indoors tank. Two of them died after few weeks and yet the smaller two, another species, are still going strong to this day. So maybe the dinky fishlets are from them?

All in all the pond is really teaming with life. It's fun to just kneel by the edge and try to spot new things. There's a new crop of frogs, big and small. A beautiful snake was swimming around the other day. Water spiders, little diving beetles, and a few things I can't identify.

No toads. After having a pond filled with thousands of toad eggs, which turned into thousands of toad-poles, there isn't a single toad in the pond.

That's not to say they aren't around. I run into them by the side of the house, in front of the house, at the wood's edge. For little pencil eraser sized hoppers they sure do get around.

The big mystery this Summer is where is the water going? There's a leak, you see. A sneaky leak. After a day or two the water level will go down by a half inch to an inch, which is quite a bit for a surface area of roughly eight by thirteen feet. Finding a leak is one of the bigger challenges in pond care.

Turn off the pump and the leak seems to stop. The pump moves water through a pipe to the waterfall, which cascades down a rock stream back to the pond. Seems like a simple process of elimination. Yet it has been an elusive and tricky bit of investigation.

If the waterfall was to blame, then it would lose water when the pump is off. Doesn't happen. If the rock run between waterfall and pond were to blame, then bypassing it would stop the leak. Doesn't happen. If the pipe were to blame then water wouldn't stay at the same level overnight. It does.

My first thought was evaporation. We are in a windy spot and there's a lot of surface area and water moving about. Surely that is responsible for some evaporation? Here's a website with lots of evaporation information: G.R.O.W. Arizona.

The map shows average evaporation rates across the US (click for detailed version) as calculated by the weather service. We are in the 30-40 inch zone, or about .09 inches per day. Translated to gallons (they have a calculator on the page to help you compute your swimming pool or lake loss) that's 2,275 gallons a year or a little over six gallons per day.

Which seems like quite a bit. The formula for calculating pond volume is:

Length (ft.) x Width (ft.) x Average Depth (ft.) x 7.5 = volume of water

Roughly estimating our pond surface area I come up with 65 gallons of water lost for a drop of one inch. If that is the case then it would take a week and a half to lose that much to evaporation.

While researching evaporation I ran across a couple of links on evaporative refrigeration. Here's a Q&A on the process and info from this year's Rolex Award to Mohammed Bah Abba for his design.

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