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That's a heck of a long way to bring water to a small community.

What about rainwater harvesting, wells, well-jetting, rivers and infiltration galleries? What about using existing sources but improving the water quality through biosand filters or other means (settling, filtration, chlorination)?

If you really want to pipe water over 6kms then it would be good to know the volume available, the needs of the population and institutions.

Would extracting the volume of water required cause problems to farmers, habitat or other downstream users?

I was closely involved with a project in the DRC where we initially ran a 25mm dia, mdpe (alkathene type) pipeline buried where possible in a shallow channel through a forest but over a much shorter distance and with only around 75m head. We kept it flowing downhill and where we couldn't bury it we encased it in concrete. People set fires in forests for all sorts of reasons - including getting rid of snakes - so you have to protect plastic pipe. Even when buried, the pipeline and break pressure boxes will need to be inspected daily. Break pressure points are needed if you expect to need to stop the flow but these provide means of public access to a community water source - do the water source points and break presssure points present potential security risks?

One year later we installed 125mm dia. HDPE SDR11 piping in 6m lengths butt welded via a hot-plate trimmer, welder and clamping machine and installed a pico-hydro system that is still running after over 20 years (with one rehabilitation) providing power for lighting, fridges and surgery to hospital buildings and worker's houses. You could make power at each break pressure point but it is useless unless there is a local demand.

Local distribution was performed using the previously installed 25mm mdpe piping and Talbot Talflo taps at several tapstands. We used several pressure regulators to reduce the pressure at some of the tapstands.

If only water is required it is tempting to examine what could be done with an open pipe design - how far could the pipe run with only friction creating the pressure before a break point would be needed? This may allow a much cheaper pipe to be selected. It would however be susceptible to blockages causing bursts higher up....

Don't forget to mark where the pipe is - undergrowth will cover it up, small trees need to be discouraged from taking hold and damaging the pipe and any break tanks need to be examined on a very regular basis.

Water from resurgent high mountain sources tends to also have entrained particle which over years prove to be quite abrasive. The hdpe and mdpe pipes we used have survived well but the brass/bronze valves and bronze Pelton wheel suffered.