I don't think depth matters that much, except that with a deeper pond you have less risk of it drying out completely in a dry season.
More important is: how much rain do you get, how warm is your climate, what is the average humidity, is the pond well sealed, and does the pond collect runoff from the surrounding area?
I'm in Oregon. I made a pond during the pandemic that's probably about 1500 gallons, and about 3 1/2 feet deep at the deepest. When it gets hot and dry in the summer I have to add a couple inches of water maybe every couple weeks, but for the rest of the year I don't add anything at all.
(I tend to get a fair bit of silt runoff in the pond during the winter, because some of the ground nearby drains into the pond.)
I’m in the Rockies. The vast majority of our annual rainfall comes in the form of snow and then a short melt that leads to a late spring to late fall that is quite dry and warm. I’ve got 5 acres and would love to dig a pond to attract wildlife.
Based on what you say, I think the keys for me would be
1) digging it at the bottom of the property and building a berm
On the low side to collect as much snowmelt as possible
2) digging it deep enough to hit clay to ensure it is well sealed
3) adding some shade plantings to minimize evaporation
Did you find any good resources before you dug yours?
I've built ponds before, so I was already familiar with the process.
I don't know how much water you'd lose from soil percolation; I've always just used a liner. EPDM rubber is what most people use. It's not terribly expensive and can be purchased in surprisingly large continuous sheets, or multiple sheets can be glued together if you want to go even bigger.
I keep koi in my pond. Koi have particular requirements with respect to aeration and filtration and depth. If you're just building a general purpose pond those aren't as much of an issue. Be aware that if you use herbicides or pesticides that you don't want to end up in the pond, then you probably shouldn't design the pond to capture the maximum amount of runoff.
You'll probably want to at least get some mosquito fish to keep mosquitoes under control. Mosquito dunks are another solution -- they're these floating things you toss in the pond that contain a bacteria that's specifically harmful to mosquito larvae.
Some pond plants can survive a freeze (cattail, azolla, lily pads, horse tail) whereas others don't (water lettuce, water hyacinth, taro). I'll usually buy a clump or two of water lettuce and water hyacinth in the spring, and then by the end of summer I have so much I have to fish it out of the pond to keep it from taking over completely.
>>> I'll usually buy a clump or two of water lettuce and water hyacinth in the spring, and then by the end of summer I have so much I have to fish it out of the pond to keep it from taking over completely.
To expand on this, if anyone is interested in water hyacinth: it is beautiful, but if you want it in your ponds, you _will_ have to clear it out by hand at some point. It grows unbelievably quickly, and if left unattended it will happily suffocate everything else in the pond.
It's kind of interesting how the plants compete. In spring and early summer, azolla usually dominates. Once the water lettuce and water hyacinth get going, the azolla starts to die off and is largely replaced by duckweed. Eventually even the duckweed starts clearing out, and the water lettuce starts looking kind of malnourished even as it (along with the water hyacinth) takes over every available surface.
I'm not sure what resource the plants are competing for. Phosphorous maybe?
When you design deep you must take in mind first: safety.
Ponds with too vertical sides can be very dangerous for toddlers and pets.
Evaporation depends on climate, shadow location, covering of the surface by plants, rains and extra income of new water. In very dry places with minimum work, you could desire a temporal pond, and let it dry naturally each year. If you want fishes and live in an arid place use killies, specially the native species. Take in mind that fishes in a pond are totally optional.
Carps are normally too big and behave as a bunch of piglets so better not in very small ponds. If your water is cold and from snow take a look to the (non american) Tanichthys albonubes. If you live in UK use crucians and Gasterosteus
Note that the water table in that case would only fill the pond to the depth of the water table. Otherwise the surface of your pond will flow out into the water table.
The other strategy (as used in this video) is to instead cut off flow with ground water. In that case, what matters is whether more water flows in on the surface (rain, creeks, what have you) verses evaporation and any leakage.
Yeah just check your water level. If you have an area where the water level is already really high, you can get away with just digging
Otherwise you'll have to add clay or use techniques like gleying.
Or you can do it the easy way and use plastic like in the video. Just make sure it's not biodegradable plastic. That'd be the fastest route to a microplastic polluted pond you can take
Sepp Holzer uses pigs to "waterproof" his ponds. They roam around and eventually compress the earth. And he famously said, if you don't have pigs, you will have to do the pigs' work!
