Buried Irrigation Pipe Bottom Branch

Have a filled trap and maintainable strainer at the entry to to underground system, arrange the buried main pipe to stay full and have accessible filled traps at all exit points?

Hi, bit more info would help.
1: is the main pipe filled with constanstly flowing water or is it closed and simply filled as required ?
2: What is the source of the water used, pumped up ground water or river bed, etc. ? Reason for asking is to see if the water is relatively clean or muddy with silt depositing.
3: Are the retaining ponds open or also buried below ground?
4: Why is there a need for the retaining ponds ?

4: is the system pressurised ?
5: Without the relative dimensions of the Main / Pipe Outlets but my suggestion would be locate your "branches" on the side / upper half of the main pipe so you avoid the need for Access traps to clear any sediment build-up, especially if the water is not constantly flowing!

1. I believe the main pipe will be filled as required in an open channel flow, but the flow rate will vary on demand and season. We are designing it to have a flow capacity of 30 cfs. The outlets range from a 2 to 4 cfs requirement.

2. The source of the water is from a nearby reservoir. They also have some water rights to a river that will contribute occasionally.

3. The retaining ponds are open.

4. I believe the retaining ponds provide the individual shareholders with a way to "pressurize" their irrigation lines without actually pumping the water. The pipe we're designing will be open channel flow.

5. The main pipe will be 42" in diameter to eventually 30". I don't know the size of the outlets (maybe 8"?). The main pipe will be about 4 miles long, and the maximum length of the outlets is 750 ft, another travels 415 ft, and another travels 150 ft. The remaining outlets travel less than 50 ft to their pond.

Thank you for your comments.

I also have some questions first.

What is the scale of the system – dimensions and flow of channel ?

How much water is allocated to each user ?

What is done when the retaining dam is already full or when a specific customer does not require water ?

What is the rules when there is a shortage of water (pipe not full) – first come first served ?

What type of irrigation systems are used ?

One of the advantages of a pipe reticulation system is that the customer may avoid or reduce pumping costs by utilizing the pressure in the pipe for direct irrigation – what is the strategy ?

1. I believe the main pipe will be filled as required in an open channel flow, but the flow rate will vary on demand and season. We are designing it to have a flow capacity of 30 cfs. The outlets range from a 2 to 4 cfs requirement. The main pipe will be 42" in diameter then funnel down to 30". I don't know the size of the outlets (maybe 8"?). The main pipe will be about 4 miles long, and the maximum length of the outlets is 750 ft, another travels 415 ft, and another travels 150 ft. The remaining outlets travel less than 50 ft to their pond.

2. I am unsure, but outlets require 2 to 4 cfs. Each outlet will have an isolation valve to open or close the flow of water.

3. The respective isolation valve will shut the flow through the outlet.

4. I believe it is first come, first serve. However, I do understand that each shareholder has a certain allotment that they cannot exceed.

5. There are pipes running from each shareholder's retaining pond out to their orchards. I believe the pond "pressurizes" the flow through these pipes.

6. Since the pipe will be open channel flow (initially, anyway), I believe that the retaining ponds each outlet leads to provide the pressure for each shareholder's irrigation system. When the main pipe is eventually pressurized, perhaps the retaining ponds won't be necessary anymore.

Thank you for your comments.

Since a closed pipe will be difficult to clean, a trash rack and screen is often included in such installations.

Perhaps the lateral exit pipes should exit at a slight angle back from the main pipe, so that a stick or object transported by the main flow would have to turn slightly upstream to travel down the lateral. I think that distribution pipes near the bottom of the main pipe should be adequate to ensure distribution during low flow. This would imply that your main pipe was level over the entire 4 mile length.

Of course, the first pipes will accept all of very low flows, leaving the downstream pipes & reservoirs wanting. If the reservoirs are all constructed to have matching bottom elevations, then the distribution should equalize reasonably well, proving the upstream consumers don’t consume their delivery in a short time.

The conversion to a closed system should make it easier to keep clean, especially from outside sources.

The sizes you mention seem reasonable for most any common materials of construction. (concrete?)

Having reservoirs at the ends of your distribution will provide another settling point for debris, and provide a buffer for periodic irrigation demands, smoothing delivery of water to the crops.

Irrigation on an orchard may already have filters and some sedimentation will also occur in the pond and the water in the pipe will also be cleaner than the water in the canal.

My concerns would be

The flowrate of the outlet - it should also be limited to what the pond can handle. In a canal system the flowrate is restricted by a weir or something.

It is not ideal to at some stage require the full flow to go all the way.

The second concern is that if the big pipe is trenched at 6 ft an 8" bend may add another 2ft and it will be deeper than the existing outlet pipe.