Pond Boss Forums POND CONSTRUCTION Selecting a site mountains watertables springs & ponds on slopes

I've been reading through the information here, and I have a question about how water tables work on a slope. I am intrigued by underground water, and I'm always trying to figure out what it's doing that I can't see.

I live at the base of a small mountain in the Pacific Northwest where we have very wet winters and dry summers.

During the first week in September, in the driest part of the year, I had a 20 by 20 pond excavated on a gentle slope at the base of this mountain and on the lower side I built a dam of clay on good clay subsoil. The pond will be at most about 6 feet deep.

In the upper corner of the slope where this pond is now located I had already dug a 3 by 5 foot hole that was about 2 feet deep. I have watched this for years and even in the driest part of summer there was always 6 inches of water in this hole and most of the summer there was 1 1/2 to 2 feet. I used it to irrigate a garden downhill and the water always replenished itself.

The top of the newly built dam on the lower part of the slope is slightly below where the top of the water table in the old watering hole usually was, and the old water hole is now incorporated into the upper corner of the new pond.

Although it was excavated at the driest time of year the clay was slick with water and the excavation uncovered a couple spots where small trickles of water ran out of the bank on the side that is backed by the mountain.

I'm not sure if it is correct to call these springs or if they are something else. One is located about 3 feet up from the bottom of the hole and seems to put out about 2 cups of water every 5 minutes and the other is about 4 feet up from the bottom and puts out maybe a cup every 10 minutes.

There may have been other springs lower down that got covered with water before their existence could be noted. The bottom spring at 3 feet seemed very consistent in it's out put during September. It is just a little hole about the size of a drinking straw. The water rose from this like the water in a drinking fountain about 1/4 inch above the hole.

The top spring is much more puzzling as it waxes and wanes for no apparent reason and with no rainfall to influence it. It ran for a week after the initial excavation, dried up, and then started again. As the dry season continued the top spring just maintained a small pool of water at the 4 foot level which never overflowed and would quickly refill if I bailed it out. If I muddied the water in the top spring's pool, I could see a tiny trickle of clear water still flowing into the pool through a crack in the clay but it never overflowed the pool. I wondered how the water could be flowing in and disappearing like that. The bottom spring that was a foot beneath it continued to run clear, even when the top spring was muddied, suggesting if the upper spring was also somehow sucking the water back in, both these little springs were independent of each other.

September was dry with no significant rainfall but by the end of the month the water from this bottom spring had filled up the first 3 feet of the pond and covered the hole with 6 inches of water.

It seems the pond stopped coming up at about the point where the water was trying to rise above the natural undisturbed clay subsoil to where it first met the new clay dam . I'm not sure yet if it is leaking or wicking. When we got a couple inches of rain the pond came up about 4 inches and then slowly went down to that same level. We just had about 6 inches of rain and the pond came up a foot for the first time covering the top spring. Now the heavy rain has stopped the water level is dropping at a rate of an inch a day.

The aquifer hasn't fully recharged yet as a seasonal creek which is not connected to the pond is still not running, so I expect the general water table is going to get quite a bit higher.

If over the next year I continue to loose water down to the level of where the dam begins I will suspect there is a leak in the dam, and if I continue to loose water down to the level of the top spring I will suspect that spring is sucking water and I will try and block it with clay.

About 50 feet and slightly downhill from the lower edge of this pond is a 1 1/2 foot deep drainage trench running along the back of my garden. I need this trench to get rid of excess water, just as much as I need the pond for when it is too dry later in the season. As soon as things get wet in the winter water trickles into this trench from numerous underground seepages. I don't know if this is connected with the water table that feeds my pond, but as I already have 4 feet of water in the pond well above this trench it seems it isn't.

I have been reading in other places here about springs and the water table and how these can give water and take it away, and although I understand the idea that the water in a pond that is connected to a spring or water table will be the same as the level of the groundwater or aquifer, what I can't get my head around is how that works on a slope when the underground water is in aquifers above and below the pond.

As I watch the pond fill I worry that it might not fill enough due to getting drained by a lower water table downslope from the pond, and then I worry that I may have uncorked the bottom of the mountain and find myself contending with a lot more water than I want.

Is it possible to uncork the bottom of a mountain full of water?

I'm also not sure what happens in a pond where the usual water table at the high end of a slope where a pond has been excavated, would be about 4 feet higher than at the low end?

Which end of the ponds water table usually decides the level of the pond?

Hello, and welcome!

Well, where to start?

You can take much of the mystery out of springs and seeps by knowing that water always seeks its own level. The best way to visualize this is to get a clear piece of tubing about 3' long, bend it into a "U" shape, and fill it with water. No matter how you raise or lower the ends or bend the tubing, the water level on both ends are always the same distance from the earth. (level)Knowing that principle and taking gravity into account, you can visualize any water situation.

Theoretically, you can build a little circular dam ever higher around a tiny spring. The level to which it fills is the same level of the source of the spring, or another outlet upstream.

welcome fellow pondmeister, i too had this happen during building my pond in iowa, there we call this a side hill seep. water soaks into the ground hits clay and has to work sideways to the path of least resintance
i too had a small hole 10 feet arounmd 2-3 feet deep that always had water in it we opened up the side with a hoe during pond construction and this thing ran all the time, it is now under 15 feet of water my land is sloping on two sides and the pond built in the middle of old crick bed i think most of my seep was coming off the cornfield and seeping into this crick
nice topic though interesting keep us posted

WELCOMB

Good to have you abord, You are gong to love this place.

You have done a lot of looking and thinking. Just remember that water is not magical it is very powerful.
It moves down all the time, even if it looks like it is filling up a water hole. Somewhere the water is higher that the pond level.

You said you have been studing other information, Where and what?

Thanks for the welcome. I have been enjoying reading everyones pond stories and I'm glad some folks here find mine interesting. If I ever get around to getting a few fish things will get really exciting.

When I said I had been reading information here on springs and the water table I was referring to what comes up in many of the pond stories here. The links below are a good example of some of the information I've found.

Groundwater; signpost to disaster?
http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=3871#Post3871

Spring??? Yes or no.
http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=3547#Post3547

Water table ( very informative )
http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=3524#Post3524

Spring Fed
http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=3475#Post3475

Springs? Asset or Liability
http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=3119#Post3119

My main reason for wanting a pond is so I have enough water for my large vegetable garden.

I would also enjoy a pond for it's ornamental value, and the idea of being able to have a dip and a float in even a small pond when it is hot and I've been in the garden is very appealing. For both of these other uses I would appreciate deeper water. Once I figure out what sort of pond I have, I will probably want to get a few fish. Something edible would be nice, but I suspect in such a small pond that might not be too realistic.

When I only had the little watering hole everything in the garden was on extreme water rationing. Although I would love it if this new larger version of the old watering hole maintained the same water level as the old hole, the extra water provided by the springs is really valuable even if it only rises to 3 1/2 feet before it finds a back door route to run downhill.

I am kind of confused because over the last 20 years my old little watering hole allowed me to keep an eye on what the water table was doing and now I don't have that I'm not sure what is going on. It seems water is draining out of the pond from somewhere. I gain water after a rainfall and slowly loose about an inch a day. With the amount of rain we have had the little watering hole would be close to full. If the new pond had this much water in it, the outlet pipe in the dam would be overflowing. The water is still 2 feet down from that. I see lots of water seeping in off the back clay edge of the pond and where it is coming in is a bit higher than the clay dam and outlet pipe, but the water level doesn't seem to come up and is instead going down.

This is surprising because there is so much water here that in the winter everything runs and oozes and though it is just beginning to get really soggy, I would have expected more water in this pond by now.

If the water has an alternative downhill route through a spring by going 3 feet up a hole the size of a drinking straw, I would think it would be pretty easy to plug it by pounding in a slightly larger dry cedar stake and packing the small pool it comes into with clay. But I'm not sure I want to do that as that spring water may be my best bet for a continuous source or irrigation water. On the other hand the little watering hole did seem to have a higher water table and if this was coming from water running downhill through the topsoil over top of the clay and not the deeper springs we uncovered, and if the springs suck water after 3 and 1/2 feet, I might get more water by plugging the springs.

I guess it's too soon to conclude the springs are acting as a siphon and I will just have to watch it over the next year to see what it does. But it sure does get me wondering what is going on down there.

For gardeners water is both magical and powerful !

welcome to PB littlefish. thanks for finding those older threads, i had not seen those before. that steve young guy was pretty smart.

mods - whatever happened to steve young? come to think of it, i saw him doing a toyota commercial recently.

edit...littlefish, you know if you could figure it out, it might be really helpful to see a topo and/or satellite image of the property and pond, and some pictures. aquifer systems in hill country can be tough to figure out. MOST of the time, subsurface water follows topography, but in mountainous areas with confined aquifers and fractured bedrock anything can happen.

Early this morning I went out and the water was really still. There is a lot of clay suspended in the water which in this situation is helpful as when there is clear water running in, it can be seen in clear clouds mixing with the clay colored water.

I noticed that directly over the springs I know of, on the surface I could see blooms of clear water. So it appears the springs are still giving not sucking. But something is draining water and lots of it. Today was sunny and there is lots of water trickling in from the backside plus the springs going full tilt, but the water level seems to be staying pretty much the same or even slowly going down.

I am now thinking there maybe a few feet between the natural clay backside of the pond that produces water and the dam, that were not sufficiently stripped down to clay subsoil and damed or sealed.

If the water continues to disappear I may try to make a tool to see where exactly all the water is going.

I am thinking once the pond over winters and settles and reaches a level just over where it seems to loose water, I could take two pieces of Plexiglas or even plywood that were about 1 foot long and 6 inches wide and attach them together along their long sides in an L shape. Then I could attach ends shaped like the bottom 1/2 of a D. This could then be pushed into the clay 5 inches below the water line creating a protected pocket of water. If I then added something like non toxic kids paint or white pastry flour it seems like I would probably be able to see signs of a current going out. That way I would have a better idea of what needs to be fixed and I wouldn't be fixing somewhere that isn't leaking. Might this work?

Before I saw my springs are still giving water to the pond and aren't removing it, and while I was wondering how I might keep what they gave, without loosing what they might remove, I wondered if it would be possible to stick a hollowed out round cedar peg into a spring and pack around it with clay. The hollow cedar peg could have a long tube attached to it. A valve could be put on the end of the tube and this on the end of the tube could be attached to a float. This would solve the problem of water pressure making a hole in the clay used to seal up the spring. When the tube on the float reached a level where the spring stopped producing water the valve could be turned off before the spring could start to suck. Would this be worth trying in some situations?

I'm glad I only have a small pond. It would be a lot harder to do troubleshooting on a big one. But what I have read here helps as I have a better idea of what clues to watch for and make note of. Thanks for the input.

littlestfish


You are my kind of pondmister. Not really sure if your plan will work but it sounds like a lot of fun.
The ideas you have are great let us know what you learn, so we can tell our friends.

Otto

Well... I am still trying to get my pond to hold water.

It filled up a couple times with natural run off in the heavy winter rains, but as soon as we had a few dry days it drops. At first it dropped about 4 inches a day, and then after loosing about a foot it slowed down to about an inch a day. It seems to stabilize at about 3 feet deep, but at this time of year, with visible water trickling in from the back side with the mountain behind it, this doesn't seem like good news.

I have a seasonal creek up above the pond which doesn't actually flow into the pond and I rigged up a hose and completely filled it a couple times, and it still looses all that water fast. The dam has firmed up over the winter and although it may allowing a bit of water to seep out somewhere, there is no visible leak and if that much water was coming through the dam, I am sure I would see some sign of it. So I am thinking I am probably loosing it through the bottom or the sides which are in the natural clay sub soil into the water table. When the pond was dug at the end of the summer, the excavator began fluffing up some clay in the bottom to compact it, but there was too much water coming in from a couple tiny springs. It quickly turned into a sloppy mess, and never got properly compacted. So I am using an electric pump to drain it, in the hopes I might be able to fix it.

What I am hoping is that I can attach a rubber tube onto either a hollow cedar peg or a hollow metal tube and insert this in the main springs, packing clay in around this,(as I mentioned above) Then hopefully I can send most of the water into a bucket or if there is enough water pressure out of the pond basin entirely. The run off from the back I hope to channel into a low spot, or possible into a bucket. Then I can siphon or pump it out, which I hope might give me a dry enough space to do some compacting. I guess if I am lucky I will find one obvious hole but I suspect I will have to try to compact the whole inner basin of the pond.

As this is a small space (about 18 by 20 at the rim) it isn't going to work to get a machine in to do this, never mind a sheep's foot roller on a tractor, and I am hoping I may be able to do this with hand tools, like a base ball bat, my own body weight walking around on the bottom, and maybe a sledge hammer.

This isn't the best time of year to try and do this as things are still very wet, but I don't have any source of water to refill the pond besides the seasonal creek so I would like to try and make a repair with plenty of time to work the pond over with hand tools and refill the pond from the creek. When conditions get drier the creek will also dry out and I don't want to be left with a compacted pond and no way to completely fill it later in the season.

What I am wondering is, will my best bet be to try to remove the soft clay muck which resulted from the bottom being fluffed up but not compacted, and then work the undisturbed clay beneath that with the base ball bat and sledge hammer, or should I remove the muck, then fluff the undisturbed clay with a shovel and then try and compact that?

If the base ball bat and sledge hammer doesn't work, is there any way to compact clay in tight spaces other than those huge sheep foot rollers? I don't have access to a herd of cattle.

And if the water can be mostly pumped out, is it possible to compact a pond bottom that exists below the natural water table?

LittleFish, Thanks for the update!

You didn't mention them, but are your springs still visibly flowing? If so, let the water drain to it's low point and that will be the level of your leak source. Mark the level and siphon/pump off another 2 feet or more of water and if you're very lucky, I'm not, there will be holes were the leak(s) occur. Even if they are not visible you can compact that area very well and possibly seal the seapage.

You can use PVC tubing to isolate the springs by driving adequate sized pipe into the openings and pumping the water away. If the water pressure is high enough on the springs and will push the water above the dam height no pump is needed. If however the pressure does NOT lift over the dam, THIS IS A LEAK and will need to be adequatly sealed using the same method as isolating it.

Thanks for the advice Rainman. I think you are right and I suspect my tiny springs have begun to suck.

They are still flowing and even kept an area free of ice for a while when it got cold a month ago, but now I drained the pond and took a look, I see the springs are just as tiny as they were last summer. I really doubt they have enough pressure to continue after they have more than a foot of water on top of them.

What I saw when I drained the pond was interesting.

Most of the the water running in from the back seems to be coming through the topsoil over top of the clay subsoil. I was surprised to see that except for the three small springs or seeps, no water seems to be coming in through the clay subsoil at all.

I expected water to be pouring in from a hundred places in the clay basin which is several feet below the present water table but the 2 tiny springs and seep are the only place this is happening. From what I have read here, this is probably good thing, as it seems maybe the main leaks are the aforementioned springs and not the whole clay basin.

With the amount of water coming in off the back it's impossible to get anything dry enough to really pack any of the seeps with clay. I could only manage to cover two of the seeps / springs with a foot of squishy clay, and I put some big rocks around this and on top of it. If they are going to suck between now and when it gets dry enough to get in there, they will have to suck through a lot of goop.

In the most substantial "spring" I managed to install 2 pieces of hollow metal pipe. Both with a piece of 10'long flexible plastic tubing attached. This spring is very small, but it had enough water pressure to make a new hole every time I tried to block off the old one. ( why I installed 2 tubes instead of just one. ) The pipe allowed me remove the water pressure by siphoning water from underground to a lower area and hand packing about 8 inches of clay into the basin where it emerged. Then I put a large heavy flat rock on top of that. Having two tubes has an advantage in that I can blow through one and get the other one flowing, so if they ever get plugged this might be useful. I tied the tubes to a rock near where they emerge from the spring and tied the far ends of the tubes to a string.

I didn't want to try lifting the tubes to see how high the water would climb as I didn't want to tempt the springs to find an easier route and bust through the 8 inches of goopy clay on top.

For now I will leave them to run downhill into the pond but once the pond is full I will pull the ends of the tubing above the surface and hopefully the combination if water pressure, 6 inches of goopy clay to have to suck through, and the heavy flat rock on top of the whole mess will at least slow down the leak till things get dry enough to do a better job.

Even with a tiny temporary dam to try and divert the water flowing in off the back, it was a constantly trickling mucky yucky mess....

My idea of trying to compact things better, at this time of year was one of the dumbest ideas I ever had .... Like trying to compact 3 to 6 inches of chocolate pudding onto a barn door. The sides of my pond are quite steep and every wack of the baseball bat sents the surface 3 inches of ice cold muck flying into my face and everywhere else. The dam under the 3 inches of slimly jelly clay seems to be nice and firm though.

I won't be able to really fix anything till the run off dries out at the end of next summer, but I'm glad I drained it and got to see what is going on down there at this time of year, as now I have a better idea of the most likely trouble spots.

I've seen enough mud to keep me from wondering what is going on down there for at least a few months.

Now I'm filling it back up with water.

So much for that theory...

I was so sure the spring I put the tubes on was too wimpy to rise above itself. Surprise surprise ...

My pond is now about 6 inches from being full and I pulled up my clear plastic tubes. ( both connected to the same spring ) One is still dribbling when I hold it 6 inches above the water, and I can see little particles of clay getting pushed along in the water still moving through the tube when it is above water level. It isn't much but it is still giving not taking. I guess that fits with how I noticed the water over this spring not freezing and the clear water plume I saw when the water was a bit shallower. I guess I should be glad as this means my pond will probably be self filling even in the summer, and even if I am using water for irrigation, but that is only if I can stop the leak or leaks.

My next guess is my leak may be the quirky spring which is located a foot and a half above and about 6 feet back from the good spring. ( Now also located under a pile of gloppy clay and boulders ) I couldn't get a tube attached to it because it is right beside an area where a lot of water is trickling in through the topsoil at the back of the pond. The quirky spring spent a month last September in a little pool that quickly refilled if I bailed it out but never over flowed. Which seems suspicious.

The quirky spring doesn't seem like a big hole. It's about the size of a pencil. Am I right in guessing with water pressure on top of it, it could remove substantially more water than it seems to give?

I'm also wondering if I am probably correct in assuming that if there was no water coming in through the clay basin ( except these 3 springs / seeps ) at this time of year when everything is saturated, that it's unlikely any substantial amount of water is leaving through the clay basin, except through the visible springs and seeps?

Sorry to ask so many dumb questions.

My pond sure looks pretty now it is full of water again.

I found an artesian spring on a place I once owned. It had an outlet about 1.5 inches in diameter. folowing the hole with a backhoe about 12 feet led to a large reserve/cavern that held about 30,000 gallons of water and an outlet around 2' in diameter. I was able to get to solid rock and clean away all the clay, then placed 4" pvc and capped the "cavern" wth concrete, then installed a water pump to supply my home. If you dig out your "spring" holes to find the SINGLE source pathway, you can dig a deep enough hole to place PVC with an anti-seep collar (farm discs are good for small pipe) and compact at least 4' X 4' area of clay around the pipe. Extend the pvc above your water line and determine the "Height " it will push the water to. For low pressure areas try to pump water from the pipes until the pond level rises higher than spring pressure to eliminate a blow out. If it is above the ponds waterline, support the pipe and trim it to stay just above the water's surface. If it does NOT raise above the waterline, determine the height it will rise and again, trim it to be above the waterline. Once the pond has filled, the pressure of your pond's water will not overcome the compacted clay in the low pressure areas and drain, plus you will always have a clean water source from the higher pressure springs.
You'll need to dig out and find the main spring feeds if possible. Vent all the springs you can find when there is good ground moisture to make them appear. Vent them ALL. Some low pressure ones will become HIHG pressure during/after a rain and the goal here is to make the PIPE the path os least resistance and NOT a new hole.

Make sense?

Is there a difference between a spring and an artesian well? If so what?

Bing

Spring water originates in an underground formation from which it flows naturally to the earth’s surface. Spring water must be collected only at the spring or through a borehole tapping the formation feeding the spring.

Artesian well water comes from a well that taps an aquifer—layers of porous rock, sand and earth that contain water—which is under pressure from surrounding upper layers of rock or clay. When tapped, artesian pressure pushes the water above the level of the aquifer. According to the EPA, there is no guarantee that artesian waters are any cleaner than ground water from an unconfined aquifer.

LL: Thanks, I don't want to simplify too much but it sounds like an Artesian can just be a spring under pressure.

There isn't any guarantee that a spring is any cleaner than an Artisian well is there.

Bing

Right I think that a Artesian well is man made by poking a hole in an impermeable layer and the pressure bring the water up. I think with the spring it is just natually occuring.

Artesian as I have ever known it is a spring that is from very deep, is very pure and flows under it's own pressure at a constant, unchanging rate regardless of area rainfall.

Thanks once again for all the information and well informed suggestions. I may have to adapt them a bit to my specific situation, but once it is drier, I am going to try and cap the springs so I can release outflow into the pond and prevent inflow from the pond.

From my own limited past experience, ( .. as in having dug a lot of holes in the past 30 years here for fruit trees, foundations, drainage trenches, outhouses etc ) the water seems to be traveling downhill in numerous veins through the clay, and if I follow it back up the mountain, it is more likely to break up into many small seeps. ( Think of tiny underground rivers running to the ocean which tend to get larger as you go downhill and smaller heading uphill )

The clay here usually seems to have many small veins of water running through it. This is why I was surprised there wasn't a hundred tiny seeps coming into the pond basin at this time of year. Perhaps this lack of porosity is why there seems to be an unusual amount of water coming in from one spot from on top of the clay.

My pond is shaped like a coma, with the tail going up the hill a bit to connect with where I noticed incoming water. The tail is only 2 feet deep at the tip and as it goes down to the main round body of the pond it gradually gets deeper to be about 6 feet at most.

The main source of incoming water for most the year is right at the place the topsoil meets the clay at the tip of the tail of the coma. I've already dug there over the years trying to follow back the water as it dried up in the summer, which is why my pond is shaped like a coma in the first place. Today I went out and dug some more and once I uncovered it I see it is also a very energetic seep or "spring" up about 2 feet from the water level when the pond is full, though in the summer this seems to dry up or go a lot deeper.

I'm thinking my situation might be like a hose that is siphoning water downhill that has some small leaks on the way. Except in this situation it is probably several different "hoses" or water veins involved, each with it's own unique properties of water source, capacity for flow and drainage.

I'm afraid that if I go digging after water any further than I have, I may break into another vein which has better drainage down slope and be in a situation of loosing even more water than I am now.

Rather than messing with something that may not be broken, I think I would rather try to fix my leak in stages, starting with the most likely problem and if that doesn't work going on to the next.

The spring I think may be a leak is located right at the very back tip of the coma, about 2 feet into the clay below where the topsoil ends. Once it is drier, it would be relatively easy to create a small concrete box with an outlet pipe and to compact a couple feet of clay ( maybe including some bentonite ) over that spring, and see if that fixes the problem.

The good spring (at this time of year anyways) is about half way down the tail of the coma and about 3 feet below the surface of the ground level. It probably has even better water pressure than my very unprofessional plastic pipes in a pile of goo revealed, as I doubt 8 inches of wet goop created a complete seal. As I don't think that spring is my most likely leak it seems to make sense to leave it be for now and first try and plug up / box in other more likely leaks.

I am most suspicious of the spring at the tip of the coma being a substantial leak because late last summer it quickly filled it's bowl if I bailed it out, but it usually wouldn't over flow suggesting it had only marginal water pressure. The other spring I just tested for water pressure is a foot and a half below this and it always over flowed the same amount ( about the same as it is now ) Muddying the water with clay in the spring that wouldn't overflow that is located above did not result in the water coming out the nearby good spring looking at all cloudy, which makes me think they are separate water veins with different qualities.

There is also a seep located a couple feet below the good spring that began running as soon as the pond was dug in September. The pond filled with 3 feet of water from this and the other spring before the fall rains, so I am assuming this seep has at least 3 feet of pressure behind it in the driest part of the year. I suspect this seep is connected with the same water vein that feeds the good spring, but if the pond still leaks after I seal up that quirky spring, my next guess would be to try and seal up that seep. At least that is in an area where someone with an excavator can get in to compact the clay .

The idea of 4 by 4 feet of compacted clay over both springs would probably work very well, but it would also more than fill in the tail of the coma where the springs are located.

If I can't hold a satisfactory amount of water using a couple feet of compacted clay I may have to do this and just pipe the water into the pond from the covered springs, but if I don't have to do this I would prefer not to. As the bigger and more professional solution would require all the smaller attempts at containment to be done anyways, it isn't like I would be wasting my time by doing something stupid I'd have to redo later. ( something I excel at BTW )

But wanting to approach this in stages is why it's important to have an idea of the most likely source of the problem. I am loosing about an inch every 5 hours from roughly a 20 by 20 foot circle when the pond is full, but this slows down to only an inch a day when the pond goes down 8 inches from full and looses water pressure. I really don't think the dam is leaking in a substantial way as that much water would leave some trace of itself. At this time of year it is impossible to see where the water level stops going down as our frequent heavy rains never give it a chance to really fall to it's lowest level. So far, I haven't noticed any particular level. What I do notice is the fuller the pond is the faster it looses water.

This is why I was wondering if I am right in assuming that since everything is saturated at this time of year and I only saw water coming in 3 places inside the clay basin, that the general clay basin is probably not the source of loosing that much water, and it is most probably the springs or seeps with the least water pressure?

wow, your description matches my situation very well LF ! Also in the NW, built on a slope at about 900' elevation. Great surface flow and seepage through the clay during the winter. pond is just under 1/4 acre.

however, once the flow stops there is maybe a week of stasis and then the dropping begins. Like the water table plugs the drain and fills...then unplugs when it drops.

Bentonite worked to keep the deepest section filled last summer...now the rest has been packed with bentonite and we haven't seen the results yet.

The other thing we did was french drain the uphill side of the pond to get rid of the pressure variation. (i.e. break the suction when the water table goes down) The captured water is funneled into the pond through a backflow valve.

I don't see the small water vents and air bubbling that I've seen in the past two winters so the trench may have helped that. however, without the bentonite, the clay is just too porous and it was packed by a sheep's foot. You may find the same situation. (if you're going to drain and pack it anyway, might as well add the bentonite.)

best of luck !
Brad

Sounds like you did a lot of homework. It can be hard to find the right combination when you are working with a water table.
The french drain is an outstanding idea. Keep us posted.