Proposed features/Hydropower water supplies

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Hydroelectric water supplies
Status: Draft (under way)
Proposed by: fanfouer
Tagging: waterway=*
Applies to: Node Way Area
Definition: Propose to map hydropower water adduction systems involving tunnels, canals, culverts and pipes using waterway=penstock and man_made=pipeline when appropriate
Drafted on: 2017-10-13
Water feeding system.png


Water intake diverting main part of a stream

Hydropower systems are intended to convert energy from moving or pressurized water into electricity or mechanical rotating energy. There are many kind of such power plants and sometimes, pretty big infrastructure is needed to carry water from intakes to turbine generators.
When overground, penstocks are often huge and can be great orientation ways in landmarks.
It's not currently possible to involve those facilities in water topological routes using waterway=*. It's an issue since such plants need plenty of water and use to divert a large part of rivers inside penstocks, as seen on picture beside: Only the small stream on the bottom right corner remains in its natural environment. Users may look into man_made=pipeline which is not a water oriented key. This proposal will try to associate waterway=* and man_made=* structures for sake of consistency and accuracy.

It's not necessary to know how a hydroelectric power generator works to understand this proposal. It's all about tunnels, canals and pipes.



Let's introduce waterway=penstock to map tilted pipelines going down mountains to feed power turbines. It can be used in association with man_made=pipeline + substance=water and gives indication of design and usage. Those pipes are usually shielded to handle large amount of water flowing at a high pressure. The most the elevation difference is high, the most will be the pressure.
A penstock is not properly a drain or even a tunnel. Furthermore, man_made=pipeline + substance=water can mean the way is a drinking water aqueduct. waterway=penstock means it's a major water path in global hydrographic system and will distinguish features from drinking aqueduct.

Penstocks can be whether overground or underground. Underground penstocks can be directly digged in bedrock or located inside a human accessible tunnel. tunnel=yes should only be used for human accessible tunnels hosting pipes.

Water feeding tunnels

Horizontal water carrying culvert map

Penstocks can be really short, leading water from a lake behind a dam to turbines, or kilometres long. Water can go through complex systems of horizontal galleries prior to go inside a penstock.
Assuming penstocks are not actual drains, such water carrying tunnels can be mapped as waterway=drain + tunnel=culvert + location=underground without introducing any new tag.

Furthermore, such tunnels can be whether slightly pressurized or operate at atmospheric pressure. pressure=* can be used to make the difference.

Human accessibility

It's not unusual to find actual pipelines installed in dry tunnels where technician can walk along the pipe. Otherwise, tunnels are full of water and are never human accessible when in operation.
tunnel=* key may be adjusted like :

  • tunnel=yes : Human accessible, because it's a pipeline inside a dry tunnel
  • tunnel=culvert : Don't even think you can swim

This part will both ease mapping and render. tunnel=culvert is recommended to render such underground facilities.

Water intakes / release points

For topological accuracy, penstocks, tunnels, or any waterway=* feature should be connected to natural input rivers, streams or canals. The same waterway=* values should be used on additional connections than on source water feature.


Pages to be edited


Tunnels and canals

Photo Aerial view Tagging Note
Horizontal water carrying culvert map


Horizontal tunnels carrying water from intakes to penstocks


Photo Aerial view Tagging Note
Pipeline penstocks


Metallic penstocks feeding a power plant down the mountain

Water intakes

Photo Aerial view Tagging Note
Man made water intake dam

On the dam, draw a Way and: waterway=dam

Such a dam is intended to divert part of a river into a tunnel leading to power plant turbines. About 3.5 m3 per seconds go into the intake while only 0.6 remain in the natural environment.

See also