fish pond loss of water?

Hi there,

The fact that you had to keep mopping up the lowest spots as water continued to seep back into the pond suggests that at least some of the problem might be related to seepage, but evaporation, especially in hot weather, does take more of a toll on small ponds than most people appreciate.

I'm a little puzzled -- you have a plastic liner... under the cement? Do you mean a hard plastic or fiberglass preformed pond reservoir? Is it totally covered by your cement mixture? Could it have cracked? The plastic ones are very prone to cracks, although the fiberglass ones are pretty durable, tolerating our weather extremes we have here quite nicely (freezing winter, 100 degree F [37 C] summers).

The cement mixture sounds like what we in the US call hypertufa and that is definitely very porous. It does indeed make great planters - we've made some - but not great ponds unless it is applied over a heavy rubber liner. It would make a divine pond edging but I can tell you that our hypertufa trough planters drain well without drainage holes.

We have a large pond - 9,000 gallons (almost 35,000 liters). We get quite a bit of evaporation loss and one of the biggest culprits is the waterfall. In the hottest weeks, we can lose as much as 3-5 inches (10-12 cm) of pond water depth over 2-3 days. When you consider that our pond is 22 feet ( 6.7 m) by 11 feet (3.35 m), that represents a minimum of 450 gallons or about 5% water loss in sometimes as little as 2 days and at the height of the summer, we can easily lose over 700 gallons in 2-3 days. I calculated your volume and at the same rate of evaporation, you could easily lose 225 liters to evaporation in a day or a few days.

The water spilling over the sun-heated rocks evaporates at a much higher rate than the water in the pond and is a huge water drain. Our pond is in part shade, part full sun, depending on the season and time of day. On a blistering hot summer day, the water level can drop a full inch between 10 AM and 4 PM in a single day.

Shallow water loses water by evaporation faster because the water is warmer and so it requires less energy. Since the primary source for evaporation is solar radiation, and since it is totally dependent. on the ratio of air temperature gradient to vapor pressure gradient above the surface, if the water is warm and the air is dry, the loss to evaporation can be substantial. That is why sitting a bucket in the pond really didn't give you any answers. My guess is that a good percentage of the loss occurs in the shallower areas and the waterfall.

We have very cold winters here and our pond freezes - we keep one section open with a bubbler to provide an area for air exchange so our hibernating fish get adequate oxygen. The waterfall is shut down for the winter. Despite rain, ice and snow, our net loss over the months from November to April when we reopen the pond is still at least 6-8 inches from simple evaporation even in winter.

In the spring we drain the pond to clean it and to prune, clean up, and repot the bog plants as needed, and our ecosystem readily resets itself. We have a shelf built into the side of the pond on which we set pots of bog plants. When the creepers (pennywort and water mint) cover about 50% of the water surface, we do notice a reduction in evaporation as well as complete control of algae as the creepers compete with the algae for food as well as sun.

Aside from what you have done to date, the only other thing to consider is using a liquid rubber to coat the surfaces that water can leak through if you still think you have a seepage problem or a leak. We successfully repaired a fountain that cracked using Flex Seal.. I think it comes in gray and black. The gray might not be as "obvious". The pond would have to be drained and dry to use it though, the one drawback. Here's a link:

http://www.getflexseal.com/?tag=im|sm|go|tm&a_aid=...

I know you dread the thought but if you do decide to rebuild it, I would line it with a 45 mil EPDM rubber (Ethylene Propylene Diene Monomer) liner. I love your cement idea but if you don't have a good foundation underlying it, it's going to be a consistent water drain.

Our solution to the water problem has been to invest in rain barrels. We, too, have to pay for water use and we have a garden that occupies a full half acre and we manage well with water conservation, using composted leaf mould to mulch, harvesting water from our roof via gutters, and adding Soil Moist to the hole when planting in the beds. We have been very fortunate to be able to capture enough water to meet our needs, but the initial investment for the barrels and a solar pump was not insignificant.

If you have any questions we can help with, feel free to message through Q&A or via our blog. There is a link to a post about our pond in the source section.

Hello Porky, haven't seen you around for a while!

I have a pond that's about 2m x 1m x 600mm deep and it's been losing around 5cm a day to evaporation over the last week or so because of the high temps (up to 40 in Melbourne, but very dry atmosphere too). 20cm sounds like too much. Perhaps you could try covering it with a tarp and see if the evaporation is reduced? Or surround it with a tarp tucked under the concrete to catch any wicking that might be happening.

We once had a problem with ours when one of the fish must have bumped the fountain thingy and it ended up shooting water out of the pond but at the back and down low. We only noticed it when the pond was almost drained dry. Poor fish, they survived it, but only just.

Edit: I in no way condone the theft of fish from public ponds. Shame on you.

Fibreglass Ponds Melbourne

I would say that 20 cm is a little much for evaporation.