Pond Boss Forums INTRO New Forum Member Introduction Ground water vs. rain water pond

How do I easily determine if any existing/future pond location is groundwater fed vs. rainwater fed? (Without draining it).

Talk to the previous owner or neighbors and ask if the pond normally drops in level from spring to fall. If you see (or hear about) substantial fluctuations (providing the owner isn't keeping a well flowing into the pond), then most likely it's a groundwater based pond. If they are dumping a lot of water into the pond via well, then it could be a rainwater pond that leaks, or a groundwater pond. If they are dumping water into it via well, ask what the level would be if the well was not turned on for a year.

At least that's what I'd do.....

You also may be able to tell by testing for total dissolved salts. While not true in all cases, a pond with low salts not near the coast is more likely to be a runoff only pond.

While understanding this is interesting, the real impact is the pond level over the season. A ground water pond can create problems if the water table typically drops during the summer. A small connection to the water table in the bottom of the pond may go unnoticed if the water table does not drop considerably during most years, but is undesirable if it does.

Thanks for the responses. I'll try to add a little more info. The previous owners have passed away. No neighbors. Located in Wisconsin, so no salt/ocean water nearby. For 9 out of 10 years, there was a small "wet spot" just big enough to fill a watering can. On the 10th year, there was a drought with very little rainfall and no surface water. So I used a backhoe to dig a test hole approx. 15 feet deep. It was a pocket of clay and a few rocks. I never did hit water that day. However, a week later, it was full of water. The next year it was full of water too, so I used a backhoe to enlarge the test hole and slope the sides, in case someone fell in, they could at least crawl out. It has been full, to within a foot of the original ground level, ever since. No liner, no inlet, no outlet, no pump, no well, etc. The strangest part is that this test pond is over 60 feet higher, in elevation, to the house, on the property, with a well at 20 feet deeper than that. There is also a small, unrelated, creek that always dries up mid to late summer. However, the "test pond" is still full.

What you may have are springs that flow downhill above an impervious layer (probably clay in your case). I take it you live in hilly country. Water flows downhill above the clay layer and fills any depressions lower than the upper elevations where the water drains from, and leaves the depression where it can find a path downhill.

This interesting. If it fills, that seems to indicate an aquifer with high seeping ground water. I think I would pump it dry and watch where the water re enters.

Yes, definitely hilly country. I was always hoping it was some type of spring / ground water. However, the clay pocket and the fact that it is located on the highest part of the hill, including the surrounding property, that I don't own, confused me, along with the dry creek bed. I'm happy, with the "improvements" I've made so far. The wild life seems to enjoy and thrive in it, and no algae, pond scum, or foul smell, yet. I just think it's human's nature to try and make it bigger, but I'm afraid to mess around with Mother Nature too much, until I get a better understanding of the true water source.

I'm with Dave on this one. I would pump it dry, then keep pumping it dry till it let the sides dry up a bit. You might not actually see it "running" in, but you will see if there is an area that is "weeping"(staying wetter for longer than other areas). That would be where its coming from.

Now having said that, does it really matter in your case. Sounds like this is on top of a hill. Is the bottom of that pond still higher than the surrounding area? If that is true, how can it be groundwater fed? I always assumed that when folks talk about groundwater fed ponds, they meant collecting from rainfalls. Have you witnessed water running into it during rain events? That gets us back to an underground vein of some sort. Expanding could be tricky, it might not give you anymore water than it is atready producing, and you have to compare that to evaporation loss and normal seepage (right now it sounds like it is keeping up with those demands). Will it keep up if you expand the surface areas of evaporation? Flip side is you could open it up more and have a real gusher. If you seal it off, like most folks suggest with ponds, you may end up with a dry pond because water can't flow up hill.

If you found this wet vein in the current pond, what is the surrounding area like that may help you. Could you dig a trench from that wet spot to a lower surrounding ground area, and then dig a pond there? That way you the vein comes in at the top of the pond instead of the possibility of it back flowing in dry weather at the bottom of a pond.

Thanks for all of the feedback. I think I now have more questions than answers, at this point. But that is o.k. I would best describe the "test pond" to be located in a clay depression, "near" the top of the hill. So, yes rainwater does flow downhill into the depression. However, the little creek bed, that has always dried up by mid summer, starts a higher elevation and flows to a much lower elevation. Yes, the bottom of the pond is higher in elevation, than most of the surrounding area. If I stand at the pond level, I can see over the top of my two story house, that is 960 ft away. I like the idea of having a deep pond for several reasons. One is to minimize the surface area for evaporation. Two is to limit the amount of shallow water plants. Three is the fact that Wisconsin's winters can be brutal, when it comes to ice/snow/fish. The potential that I see the most is the elevation. I could use the water to flow down toward the house for many things, such as watering crops, a garden or even use it as a small power source. However, I don't really want to drain it. I'd rather have a steady source of water, even if the pond level drops slightly. I just feel strange telling people, "lets walk up the hill to see the pond."

On my property I have a creek that flows non-stop. Sure, during the mid summer it slow down to around 100 gpm. When it ran, it can become 30 fee,t wide 6 deep and raging. At normal it usual runs pretty good, guessing 2,000 gpm.

Our property is mostly sand and gravel. They have tested many areas with trackhoe and holes. Apparently, this creek is lined with enough clay that it doesn't bleed over into the test holes next to it. otherwise, it would probably just flow into the area and be wet and the creek would come to its end. Secondly, this creek flows into a large swamp area. Up the hill from there, they dug a test hole. They hit an underground vein that was running water more than the creek usually does and is hundreds of feet away from it. It was strange seeing this water flowing from one edge of the hole and going out the other side.

Perhaps this may shed a little light onto your situation in similarity, or just confuse you more.

I'm also in Wisconsin. The neighboring property to me has the same situation. On top of the hill there is a Spring/seep. That runs/seeps down hill into a small very shallow pond area that would be full in wet season and just damp in the dry seasons. This area for the most part is still on the top of the hill. The old property owner dug out the pond/damp area and made a nice pond. Then between the start of the spring/seep he dug a new smaller pond. Both ponds hold their water pretty good may fluctuate a couple of inches from a wet season to time of drought. Funny thing is between our properties is a deep kettle that would make an awesome lake. This kettle area is approx 10 acres and if filled with water it would be close to 100 ft deep. We always laugh at the oddity that there is water on top of the hill and at the bottom of the kettle its dry. I guess the soil types can really make a difference.

Ground-water fed usually means fed from ground water, not rainfall or run-off. Think of a spring like a hose hooked to a bucket held in the air (perhaps a pond at a high elevation miles away). If water trapped at a higher elevation has an underground channel to your pond, and this is the path of less resistance, then it will fill the pond up to the elevation of the source or the ponds overflow/exit. Springs form on hills when the water is held down on surrounding lower-elevation ground. This is like an artesian well where a hole is poked through an water-tight strata fed by water at a higher elevation. See last line drawing at the following link. http://geology.com/articles/bottled-water.shtml

Rah- wouldn't a spring and artesian well actually be and act the same thing, except that an artesian well is created from the pipe being driven in by man.

Seems like "ground water" is used interchangeably here on the forum. I can see what you are saying in that it soaks in and seeps thru the ground into an empty low spot. However, if that's the case into a pond, it could leave the same way too, just like a spring? Thus a bad thing. Most here on the forum building a pond seal there basin with clay, thus making a seal. Then wouldn't it stand to reason that most groundwater entering a pond is from the top surface, or runoff?

Edit- Perhaps my term "empty low spot" should be "top of water table that can fluctuate".

Well again, thanks for all the helpful input. Obviously, the snow melt, surface water run off, rain water & natural clay lining are all contributing to the "test pond's" success. And my gut feeling is, because there is little to no change in the surface level of the pond water, there must be some type of below ground contribution to the water. Although I have no easy sure way to prove this, yet. This is all good news to me. So, back to the original question. How can I easily determine if there is a below ground contribution to the pond water? (Without draining, it.) Should I try pumping / syphoning a small amount, to see if the water level can "keep-up"? Or any other easy suggestions? I'm not complaining or confused, I just feel like a giddy hillbilly (no offence) that just shot into the ground and found oil. Or better yet, a free, fresh water source at a higher elevation. Any other suggestions, as far as how to improve / proceed will be greatly appreciated. Thanks again, I'm going to "walk up the hill, again, to see the pond."

Your idea of siphoning would work(I think). You would be able to gauge how much "extra" you could pull off without hurting. Even if it was a mere 1/4" dia tube, if it kept up with that, keep increasing sizes till you see the water level dropping. You will need to consider normal evaporation for your area. If it was me, I would prefer my pond to stay at a constant level with evap., but hey, if you can pull some out of the "water bank" without that happening that's great!

I am sure there are charts/calculations available that will give you volumes of water for siphoning if you know tube size.

If you start a siphon with a larger hose, you can put a valve at the bottom to regulate the flow. By timing how fast a 5 gallon bucket fills, you could estimate the rate when the pond stays just full.