ditch the pond, or pond the ditch?

I had this idea or dream about ponds on a hillside (on my parents' old dairy farm... and no, I haven't brought it up yet because I don't have a fully formed idea). Just thinking about the shape of a typical man made pond, it's kind of a circle or rectangle. Putting that on a hillside sounds really expensive and/or unsafe. Could I make something more like a ditch or swale instead, still sealed like a pond, but following the contour of the hillside and much longer than it is wide?
The place has a slope of 1/10 or so, and I know soil around here is a silt loam of glacial origin (I don't really know how hard it is to seal this kind of soil... there is an old pond there, but for all I know it was sealed by the cows). We get about 40" of total precipitation. The elevation of the land is about 1400' to 1600'.
It seems like it might have benefits that outweigh drawbacks, but I figured it's a good question to ask the forum.
First off, am I already making any type 1 errors? Does it make sense to do this at all, given climate, terrain, etc.? Is it dangerous in any way?
If not, here are the benefits I imagine:

The dam wouldn't have to be eleventy feet high and contain a massive amount of dirt... (I've seen ponds like this nearby) it would really just be a berm.

The pond would have a lot of edge. Say instead of ~100' on a side for about a 1/4 acre pond, it could be only 10' wide, and 1000' feet long. So about 5 times the edge.

Which also means there could be a lot more natural food sources for any fish that might be stocked in the pond, if there are lots of bushes and trees on that edge that produce food for the pond food web.

I was thinking of growing a hedge on the downhill side of the pond, so this long pond could have a long hedge that benefits from the humidity and water availability of the pond.

If the hedge is made stock proof and used as a paddock fence, then the pond could offer a water source for (theoretical) livestock on the pond side of the hedge.

The hedge, plus the pond itself, would provide quite a bit of biodiversity that the current hayfields can't.

A really long pond on contour would have a lot of watershed, correct? If the bottom of the pond is sealed, but not the uphill side, could it still let ground water feed into it?

Please feel free to correct me on any of the above... I am pretty new to the idea of permaculture in general, and I've never done anything like making a pond, and while I grew up on this farm, I got out of it as soon as I got out of school.

Another thing I was wondering... could a pond/ditch that's only 4 or 5 feet deep be dug with farm equipment, rather than earth movers? I'm thinking like repeated plowing in one direction, and using the front loader on the tractor to push the loosened soil into a berm. This was a farm, and still has equipment. If so, that would obviously be way cheaper than hiring both the heavy equipment and a trained operator. But then, earthworks are forever, so I wouldn't want to do something rash just to save a buck, and cause a disaster.

Your thought and approach sound pretty reasonable. The one caution is that earthworks design takes a lot of practice and experience.

What I would do:
1. Buy a backhoe - this isn't something to mess around with the wrong equipment. And make sure it's sized right for your tractor -- and prefer one that attaches to the underframe over a 3-point unless you need to change it out a lot.
2. Read up some advice on ponds and sealing -- then read twice more!
3. take a small area and try it out -- make a pond like this that is 10 or 20 feet long and see how it does through a few seasons. Take your time here, study the soil, and maybe read a little more depending on what you find. And be ultra-paranoid about rolling the tractor!!

Don't think about fish until you see the stability and clarity through a year..

Good luck! Report back soon!!

Thanks for the response. I probably won't be reporting soon... I have to ask if I can even rent a bit of the land first (I suppose it's possible they might say no... my Dad was a dairy farmer, so it was corn oats and hay in rotation for him. Catfish and hedgerows were not in the mix).
1. I have to admit I didn't even know there was such a thing as a backhoe attachment, 3 point or otherwise. I'd looked at ditch plows a bit online, but not backhoes. I agree about not wanting to mess around, although I do know that plows loosen and move an awful lot of dirt very quickly, even if it doesn't go very far. I still think it might be worth plowing the spot with a mind to scooping the topsoil for reuse on the top of the berm. I don't think I can afford even a used backhoe at the moment. One of the reasons for the farm equipment idea was that I don't have a lot of money to spend. But I could save.
2. Before I even try this, I have to ask about the existing pond (my Dad would probably know how it was sealed) and other ponds in the area (I'm guessing the golf course lines theirs...).
3. That's probably the most obvious thing I hadn't thought of! Ha... A tiny pond that would be no big matter to just fill back if it was not worthwhile. I'm in no hurry... despite being really into the idea, I inherited my Dad's caution. Hmm... especially about rolling tractors! We used to rent some land that had slopes that frightened me when I would rake hay... luckily my parents' land is pretty gentle that way, outside of one spot where I wouldn't even consider going anyway.

And again, not in a rush to get fish, despite thinking it would be really great, considering I recently stopped eating other meats. Gotta learn about fish more first.

ponds will always go to the lowest level..so ponds won't work like a creek over a slope as the water will not stay on the uphill side, it will go to the lowest level..which also could saturate your berm and give you a landslide down hill..which could be very dangerous to those areas downhill from your pond

I agree with Brenda, I think having a permanent water holding terrace or giant swale on the side of a hill is just asking for a landslide. Unless it is a very gentle hill, there's no way to make a proper dam with a "key" on the side of a hill. You can't just pile up dirt on the downhill side and expect it to hold water, and if the dam isn't keyed into the subsoil or bedrock, the dam will leak or slide.

See "Water for Every Farm" by PA Yeomans for lots of information about making dams and other water managing strategies.

I'm watching this thread with anticipation. My family has a farm with a south facing slope (pretty significant slope) and I've always dreamed of terracing it or swaling. Most of the topsoil washed off long ago and I've always dreamed of remediating it.

we found the lowest spot on our property near the house (about 50 ' away) and dug that out for a pond, then it overflows to a lower swampy area farther away..into a ditch that runs the length of the property.

The family farm has the same setup below the two hills, the upper pond stays full while the lower droughts out. The slope that I hypothesize terracing/swailing is above this wet season pond and I hypothesize that water catchment above it would allow it to stay filled longer.

Tyler Ludens wrote:I agree with Brenda, I think having a permanent water holding terrace or giant swale on the side of a hill is just asking for a landslide. Unless it is a very gentle hill, there's no way to make a proper dam with a "key" on the side of a hill. You can't just pile up dirt on the downhill side and expect it to hold water, and if the dam isn't keyed into the subsoil or bedrock, the dam will leak or slide.

See "Water for Every Farm" by PA Yeomans for lots of information about making dams and other water managing strategies.

Well, I admit I don't know too much about Keyline yet, but I've attached a topo pic of the land, and from what I can tell with my completely untrained eye, there isn't really a spot on the property that would be a good place for a keyline pond. But as I read this by Bill Mollison it occurs to me that what I was thinking of is something called a contour dam.

A couple quotes from Bill:

The contour dam is a shallow dam with a large surface area. It will be a
very, very cheap dam. For the amount of Earth moved, we are going to get a lot
more water.

Contour dams are very cheap, no-fuss dams. They are dams in which the
actual dam follows the contour and then swings back to ground level.
Basically, the construction is the same as for other dams, but usually you
put contour dams on pretty flat land, and you grade them up pretty quickly.
They may be six feet high. It doesn’t matter if you get a bit of grass or rock in
them sometimes. They can be a little rougher. Just roll them down tightly and
they will hold.

He says pretty flat, but I haven't yet found a definition of that. Obviously the slope isn't uniform, maybe I just need to find the flatter spots.
Also is there any particular reason that a very long dam like this couldn't have a core trench the entire length of it, if necessary?

In casual conversation with my Dad he told me that my Grandpa put in the pond that's already there. He used a bulldozer, and it's always held water without being sealed in any formal way. So that's a good sign.

tim rew wrote:
is there any particular reason that a very long dam like this couldn't have a core trench the entire length of it, if necessary?

I think it might be possible if the slope is gentle enough ("pretty flat"), but I'm not an engineer!

i would think that there is some way that one could build a pond on a slope, as sepp has 72 ponds on his place and they're not in the valley by any means

but there is a challenge with this to be sure, if there isn't a properly built dam and included swal/spillways, as well as a culvert then it would be way to risky i would think, you wouldn't want this to happen: http://www.youtube.com/watch?v=bWEWVw7TGk4

so what does one do if for some damn reason the house is the lowest point on the property?