I have dug (but not yet filled) a 2.5 acre pond with a 0.5 acre island in the middle. I am now digging a 500 foot long stream that will be used to circulate water from one side of the pond back around to the other side. I would appreciate any advice on what type of stone to put in the stream.
The goals of the stream are to 1) help with filtration and circulation, 2) give walleye a place to potentially spawn, and 3) be fun for kids.
I will be using a series of airlift pumps to pull water into the start of the stream. The stream will be roughly 12 feet wide and 1.5 feet deep. There will be no “head”, just high volume horizontal flow. Together the airlift pumps should move about 120,000 GPH resulting in a flow rate of just over 1 ft/second through the stream.
Right now I am thinking of putting a one foot layer of 0.5” to 1” washed round stone along the bottom, which would sit on top of landscaping cloth, which would sit on top of solid clay. My thinking is that this stone will be nicest for kids to walk on barefoot, but I’m wondering if it might not create big enough gaps for walleye eggs to spawn.
What do you all think? Anything I could be doing differently?
I have seen people on Pond Boss propose similar plans to circulate water. However, I cannot grasp how they are going to get the volumetric efficiency that they claim.
Pushing water down a stream with no gradient is not the same as pushing water in a pipe. If you get a chance, could you put up a schematic and calculations so I can learn?
I would build a wall at the "discharge" end of my stream and make the top of the wall about 3" above the water elevation of the pond. I would then place a pump at the base of the wall and lift the water only 3" and over the wall. Your water volume movement through the stream would then be exactly equal to your pumping rate.
(If the wall is ugly, you could cover it with a nice bridge for the kids.)
As to the walleye spawning gravel, I would put down some different sizes and grades in different sections. In theory, an expert could predict exactly what they want. In practice, give the walleye a few choices and they will pick exactly what they want.
Good luck on your pond, it sounds like an awesome project!
I am interested in this, I am currently using an air-lift system to move water through floating plants. The best I can figure I am only pushing, at best, 1800 GPH. What kind of pumps will you be using and how many?
FishinRod, your recommendation with the wall is basically what I’m doing - I have a concrete wall, and am using airlift pumps to effectively raise the water on one side of the wall an inch or two, forcing it to flow through the stream. I’m not sure how much of the theoretical flow of the airlift pumps will convert into flow in the stream, as you’re right that a stream has a lot more “resistance” on the sides compared to a smooth walled pipe. That said the cross section of this “pipe” will effectively be 12 square feet, and the flow rate only 1 ft/s, so I’m hopeful that we will see some good flow. But it is an experiment for sure. What do you think of this plan?
Tony I’m using twenty seven 4” pipes for airlifts, with 3 cfm of air injected into each pipe at a depth of 48” using a regenerative blower. Based on a few research papers I’ve read this should give 71 GPM of water flow per pipe, for 1,917 GPM or 115,00 GPH total flow across all pipes.
Esshup that’s a good point, maybe I just add different sizes and let them choose. Smaller would be nicer to walk on so I wondering if I just go with that but I will do some more research.
Thanks for typing up a response for my benefit! I think I am just being dense, and not correctly envisioning your set up.
I am seeing a column of water in the middle of your "stream" that gets elevated by 1.25" inches to get over the 1" wall to the pond. However, the gradient on the other side of your elevated column of water is still going be right around 0.0" since there is not any wall to push against. Therefore, most of your lifted water is going to flow down the gradient and AWAY from the wall. Your lifted water volume will not translate into the equivalent flow volume down the stream?
I think I can see how it would work by turning your 4" corrugated pipes into a smooth 90-degree bend and having the air-water mixture flow over the other side of the wall. However, I don't know how badly a 90 ell hurts your efficiency.
I am definitely NOT AN EXPERT in this area, but I believe a centrifugal pump would move more water over the wall for fewer kW-h on the electric meter than compressing air to provide the equivalent water flow.
However, a water circulation pump solution would not provide your pond with any significant aeration. Perhaps your solution will be more energy efficient in covering both needs simultaneously.
Hopefully, I am all wet and your system will provide an elegant solution!
I have many fond memories of catching walleye (and SMB) in Canada with my cousins. I hope your 2.5-acre pond creates many happy walleye which tends to create happy kids and grandkids!
Hey FishinRod. Let me try explaining again, as it’s a bit of a different design from anything else I’ve been able to find online.
There is a 500’ foot stream that goes from one end of the pond to the other. Across the stream is a 7’ high 40’ wide concrete wall. This concrete wall separates the two sides of the stream, such that any water pumped from one side of the wall to the other side needs to flow through the stream, into the pond, and back around to the start of the stream.
5 feet below the water there is a 4” pipe that goes horizontally through the concrete wall. This horizontal pipe then connects to a 90 degree elbow pointing towards the surface, which then goes into a 4 foot straight section of pipe that runs vertically, which then goes into a 90 degree bend right near the surface pointing away from wall.
By piping air into the bottom of the pipe it lifts the water, causing water to get pulled from one side of the wall to the other, where the only way to balance the pressure is to flow through the stream, into the pond, and back around.
Everything I’ve read suggests that using air will be the most energy efficient way to move high volumes of water at low head. It will also aerate the water (at least a bit), and should be easier to maintain (just an air filter to keep clean, and only one moving part in the blower).
Does that make more sense? What do you think of this approach?
Your description in paragraph #3 is essentially the same way I was trying to picture to make it work with an air lift system.
I agree with you that an airlift system is an elegant solution since you do not have any moving parts in your working medium.
However, I am concerned that the process will not scale and you will get interference once you have twenty-seven pipes running in the same spot.
I am also concerned about your efficiency losses. Compressing a gas creates lots of waste heat which represents lost work. The second efficiency loss will be when your air stones (or other bubbler system) start developing an algal coating. Once you are not operating at the optimal bubble size, then some water will be partially lifted up your air-water mixture column and work its way back down through the rising mixture streams. This will also be an energy loss.
You are working way above my pay grade on this project! I hope your project works well because it would be another great tool to add to our pond management tool boxes!
My advice at this point would be to run the experiment as "proof of concept". Set up two 4" pipes and measure your water flow at the outlet end of the stream. If that works as designed, then experiment on scaling up your design.
[I don't think you require the cement wall at this stage. A lightly-compacted earthen berm across the stream should be sufficient. With the water level roughly the same on both sides, then water transmission flow through the berm would be effectively zero. You can then modify the berm as needed to develop the flow rate required for successful walleye spawning. Once you have that perfected, you could then finalize your system in cement.]
Your stream is essentially a raceway system. These are actually fairly common in freshwater aquaculture. However, (in my very limited knowledge) I have never heard of the raceway waterflow being developed by the type of system you are designing.
We do have lots of aeration experts in the forum. We also have some pump experts. We even have a few people that operate raceway systems. Hopefully some of them will reply in this thread and correct the errors in my WAG speculation.
This is over my head.the only thing I did know about airlift systems was from reading and watching utube. I have a few months of experimenting now and I can share this, with a 60 watt air pump and 3" pipe, 5-6' seems to be the best depth. I have tried air stones and manifolds, but I get more flow with air piped straight in at the bottom of the pipe. You can put an elbow at the bottom and draw water from any depth, even an inch below the surface, as long as the main vertical pipe stays at 5-6,.
The air lift powered stream flow idea will move water through the stream channel. However for natural streams to stay relatively "clean" or healthy they absolutely need periodic flushing or spates from flooding events to discharge lots of the accumulated materials that will want to collect in a rocky bottom areas of a stream including FA, plants, dead stuff, and lots of incoming terrestrial produced materials including silt, muck. Without periodic spates or scouring from strong flows and some needed good maintenance, even with some air lift powered flows, I foresee this long 500ft stream after several several years trending towards vegetation clogged, slower flowing and moving towards conditions in an oxbow. The shorter length of stream the better the flow from air lifts would help scour the stream sides and bottom areas especially any of those with depressions. Observe what happens in good quality trout streams when even small flooding events occur that flush excess materials out of the channel. It takes good strong flow to do that flushing.
In lakes successful walleye spawning occurs on windswept shorelines with 5"-12" cobble sized rocks. WE eggs are adhesive and fall into rock crevices where good oxygenated clean conditions occur and eggs survive to hatching and fry swim up. Crayfish and small fish among the rocky habitat eat a lot of the walleye eggs. Siltation keeps a lot of the eggs from surviving until hatch. Walleye can have egg hatching in streams with good water flow. I think that promoting successful walleye spawning in ponds can easily result in way too many stunted starving walleye just as it does with LMB and many other fish species. Successful reproduction and lots of recruitment are not always beneficial.
Last edited by Bill Cody; 09/06/2111:06 AM. Reason: edited improvements
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Thank you for the good comments everyone. It will be interesting to see how much flow the airlifts actually produce - maybe the resistance will be too much.
I think for now I’ll do 0.5” to 1” gravel, as I think that will be best for kids to play in. I’ll then see if Walleye spawn or not, and if not, as Bill points out, maybe that will be a good thing. I’ll also have access all along the stream, so we can clean it out if necessary, but maybe a slow flowing “wetland”, if that’s what it becomes, won’t be the worst either.
what about a large paddle wheel. it would keep water moving and only have 1 motor. Could be set on a floating frame.
Similarly the highly efficient water wheel in reverse, could build one yourself out of treated lumber and power in any number of ways. Solar to DC motor allowing variable speed depending on available power, if any. Direct wind, etc.
The more narrow the stream the faster the flow would be using the same powered source - flow. I think a channelized stream no wider than 3ft-4ft would be best to optimize flow. For experimentation test I would use a rubber liner, maybe rubber roofing material, for a section of the stream. If it works add more, if unsatisfactory remove it.
Last edited by Bill Cody; 09/07/2108:45 AM.
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I imagine a long rubber liner or roofing material might be pricey.
Another thought, in an old thread folks were getting used billboard 'tarps' on ebay for cheap. I think they are 35-50' long. They can be glued together with PVC cement per my recall of that thread. Folks used them for a liner in their pond and they were pretty tough. I would think for a narrow chute you could either fold the billboard tarp in half to make it stronger or cut in half to make it go further. A couple large billboard tarps and it should be fairly slippery for flow. Carefully putting rocks on that material should not harm it at all.
I don't completely understand the air lift design or implementation but maybe someone shares a youtube video or diagram and I'll understand. It sounds like a great idea and trying it at a smaller scale and then scaling it up later would be the way to go.
I'm curious how you got to the unusual number of 27 PVC pipes (since that isn't a multiple of any number)?
Another link...about 60 gpm lifted several feet...for twenty watts power. My pumped "creek," 2 1/2 hp, over 1,800 watts, about twenty foot lift through a 3" pipe, flows (my rough estimate) about 7 gallons per second or about 400 gpm. It has seven pools cascading about 100 feet. Six useable pools makes a drop from one to another of about three feet. So I see that these airlifts can be staged, first, from the pond to a pool, and second, that feeds the next stage to a higher pool, and so on. My pond bottom aerator runs about 50 watts to drive two diffusers...we should all know that the uprising volume of water spilling over the surface is impressive! But yeah, for maybe four lifts to the top pool (about fifteen feet), it seems that 80 watts would make another 60 gpm! The real problem is how to fit this in to the existing system and make it look good in the landscape. Okay, what if I want 600 gpm additional!? Ten parallel systems! 800 watts. Well, my dream was always to get a diesel powered pump (say ten to twenty hp), plumbed with six inch pipe, to enable a kayak run. Ha ha!
I will say that Mr. Bill Cody is right! A stream is like the riffles in a sluice box to catch gold...but it plugs up with sediment. Cleaning out my pumped "creek" is a b#tch, but on the other hand, it's easier than cleaning the sediment from the pond.
Nehunter, I did think about a paddle wheel and/or propellers in a wall. I thought the airlifts would be less maintenance and more aesthetically pleasing, but if they don’t work maybe I will try something like a paddle wheel next.
Bill my thought on the width is that a wider stream would give a slower flow, which would result in less friction between the water and the stream sides, which would result in more water movement. What do you think that? Also the stream is cut into clay and holds water perfectly, so I don’t think a liner is needed, but maybe you see something that I am missing.
Canyoncreek the video DannyMac shared is a good intro. A bunch of studies have been done on the optimal efficiency of airlifts in terms of diameter, injection depth, and volume of air. It was found that the most efficient design was to use a bunch of airlifts in parallel. Despite lots of searching I’ve never seen this tried in practice, so perhaps this will be a first. If so we will see how well it works.
DannyMac your creek sounds impressive. I would love to see a picture. From what I understand airlifts aren’t good in high head scenarios. That’s why my stream design has no slope, it is just flat all the way around. I’m not sure what you mean about starting the creek with a deeper area. Unlike a natural creek where the water comes from run off, I am hopeful that the water being pumped into this stream will already be relatively “clean” and relatively sediment free already. That said I will have a grate in front of the bubble wall to catch big stuff like algae and leaves, which is a big part of the goal of having it. What do you think of this plan?
Thanks ted for that link, this pic is similar to the one I am using http:// You right about low head, I can raise this up about 6" and it will greatly reduce flow, but when I reduce the 3" outlet to 2" it will gain some head.I only use it at water level anyway to push water through a plant island. I have used a troll motor (your propellers in wall idea) that also worked well, just takes more energy. If your creek fills with plants, it might not be a bad thing, they do a good job of cleaning up the water. This might not help you, Just relaying my experiences . Good luck and keep this updated.
That’s a good point Tony. I am interested to see how it all works out.
As a quick update, we are going to go with 4-6” stones on the bottom of the stream to give it some “staying power”, especially on the banks where kids will be climbing in and out, and then add some 0.5” pea gravel after to soften it for walking on. We are going to put landscape cloth underneath, and have the stone come up to 3 to 6” above water level, and then have the topsoil come down and butt into / bleed into the stone, and then erosion seed the topsoil. Our hope is that this design helps lock everything together.
A thought pooped in my head of being able to "backflush" the streambed at times by installing some plumbing underneath your gravel/stones in which you can temporarily pump high volumes of water to kick out sediment and keep things clean. Otherwise without a fairly strong water flow, the gaps between rocks will clog up with gunk.