ted,
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.
Good luck!
