I am in the planning stage of building a 2.5 acre pond in southern Kansas. The pond has a stream that flows year-round for a water source. However, I want to avoid wild fish from the stream entering the pond and ruining any pond management plans.

I would appreciate any help or advice from the usual "free-thinkers" on the forum.

Background:
The pond will be constructed by expanding a long, narrow oxbow that is currently cut-off from the existing stream except for flood situations. The stream is full of sand bars and sand riffles, but it appears to be perched on a good solid bed of clay. [I will dig a lot of test trenches in the pond site after I refine the plan.]

If I can construct an effective core trench, then my lake level will be 2.77 feet above the stream level at the most downstream portion of the lake. This drop will allow me to pass a significant amount of clean, aerated water through the pond every day.

My initial design is an 18" inflow pipe trenched over to the stream at the closest point of approach. The pipe will be set with the bottom just above the base of the stream. (The bottom of the pipe will set the surface water level of my pond.) I intend to put a 15" drop-pipe into a 12" pipe through the dam. This would pass 3118 GPM for a 2.50' drop.

The source stream gets most of its water from ground flow through sand, rather than direct surface run-off. Most streams and rivers in Kansas turn a mocha color after a big rain. I am amazed at how clear this stream runs after most rain events.

The main objective for my pond is clear water for kid recreation and keeping the boss lady happy. The secondary objective is good fishing, because they all love to catch and eat fish.

This pond will be quite expensive to construct because most of the pond area will have to be excavated, and I will have a very long core trench to keep water above the stream level at the downstream end of the pond.

The pond will be long and narrow so I will not have to move the excavated dirt very far. I intend to spoil the dirt as a large berm just beyond the boundary of the pond.

The stream-plain is very wide on my property compared to the land both upstream and downstream. I believe it will be possible to get my berm above floodstage for everything except a 100 year flood. I think I can exclude wild fish entering by coming in over the top of the berm.

Questions for the experts:

Do you like my "high-bypass" system for developing an attractive pond with clear water? Any recommended improvements?

I would like to avoid BG and GSF nipping at swimmers. Would any type of screen on the inflow pipe stop undesirable fish from entering the pond? Would I be constantly fighting a clogged screen? (The pond is 45 minutes from my house.)

Instead of a screen, I have considered a gravel bar across the entire width of the pond at the point where the inlet pipe enters the pond. This would be more expensive, but it would screen large fish, fish fry, silt, and whatever other crap the stream is trying to bring in. However, it would dramatically cut the rate of water flow through my pond. To keep water flowing into the pond, I would probably have to lower the level of the outlet pipe. As more water "drained" from the pond, more water would be drawn through the gravel. However, I have very little drop to work with, and precious little to "give away".

How would the "gravel bar" screen (with less water flow-through compared to an unobstructed 18" inflow pipe) affect the water quality in terms of clarity? Can the Pond Boss experts even predict water quality in an unusual situation like this? The pond will fill with the very first rainfall (assuming I don't have a design failure). Should I build the pond and observe it for a while, and then tweak the design as needed? I can only drain the top 2.5' of the pond's water, and then only when the stream is at low stage. I will have to pump out all of the deep spots to clear any accumulated undesirables.

Even if we achieved perfect fish exclusion on the inlet end of the pond, could fish enter at the outlet end? When the stream got low, would small fish swim upstream through 100' of 12" outlet pipe to enter? Would the bar guard on the 15" drop-pipe keep out any fish large enough to make this trek?

Finally, would it even be possible to keep an unnatural (for southern KS) pond population of YP-SMB-WE even with perfect protection from water-borne fish contamination? Many PB threads talk about wild fish almost always getting into a managed BOW. Will wild fish manage to enter through "magical means" - eggs on heron legs, frog regurgitation, Kansas tornadoes, or biblical plagues?

I would appreciate any advice or recommendations from the PB experts. I would consider any "trade-offs" that would be a net benefit. (These are much less painful during the "planning" stage.)

Thanks,
FishinRod