Proposed features/Hydropower water supplies

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Hydroelectric water supplies
Status: Proposed (under way)
Proposed by: fanfouer
Tagging: waterway=*
Applies to: Node Way Area
Definition: Propose to map hydropower water adduction systems involving tunnels, canals, ducts and pipes using waterway=pressurized and man_made=pipeline when appropriate
Drafted on: 2017-10-13
RFC start: 2017-12-02
Vote start: 2018
Vote end: 2018
Water feeding system.png

Rationale

With and without waterway=pressurized

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. High pressure pipes leading to generators are necessarily shielded and are called penstocks.
When overground, penstocks are often huge and can be great orientation ways in landmarks.
It's not currently possible to involve facilities which carry water in topological paths 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: a whole overground canal goes into 3 penstocks but water dissapear unless we look for pipelines.

Users have to look into man_made=pipeline which is not a water oriented key and reflect infrastructure. waterway=pressurized means it's a major raw water path in global hydrographic system and will distinguish features from drinking or industrial aqueducts.
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.

Definitions

  • Open-channel flow : The situation when water flows freely with a free surface outdoor or inside a pipe or tunnel.
  • Pipe flow : The situation for a fluid to flow without any free surface in a closed space like pipe or tunnel. The main difference with open-channel flow regime is the pressure the fluid applies on the conduit.
  • Penstock: A conduit taking water from a river, lake or tunnel and leading it to power turbines or mills at a high pressure as to maximize mechanic power transmission.
  • Spillway: A construction related to dams allowing overflow water to go downstream. A spillway operates only in special conditions and shouldn't be walked by humans.
  • Nominal diameter: The nominal size of pipes, as defined in ISO 6708 norm. It often correspond to internal diameter, but at some precise temperature and pressure conditions.

Proposal

Pressurized waterway (pipe flow only)

Waterway flows.png

Usually, waterway=* key refer to free flowing water situations, like rivers and streams, inside tunnels or outdoor. It also needs a value to refer to pipe flowing facilities when raw water from lakes and rivers runs into tunnels and pipelines.
The point is to involve pipe flow water paths into the already big waterway=* hydrographic system without looking in any other key (like man_made=pipeline).

It's not possible to always involve pipelines into river relations since water can be sent miles away in other watershed through tunnels. waterway=pressurized will be available to tag any pipe flow feature like water tunnels, penstocks and siphons where water flows without any air.
Furthermore, it may be useful for speleologists and natural underground rivers/siphons out of this proposal scope. Side illustration shows pressurized waterways aren't always pipelines.

As a side consequence, waterway=canal won't be used any more for underground facilities and waterway=drain may only be used on short distance drains (stream under a road for instance) and it mainly covers free flowing situations.

Penstocks

Outdoor pipeline penstock

Penstocks are tilted pipes taking water from a high elevation to power turbines. Such pipes should be mapped with existing man_made=pipeline + substance=water + usage=penstock.
Those structures are particular and 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.
waterway=pressurized applies here.

Penstocks can be whether overground or underground (location=*). Underground penstocks can be directly dug in bedrock or located inside a human accessible tunnel. tunnel=yes should only be used for human accessible tunnels hosting pipes. If not, don't use tunnel=* key.

Key Value Comment Recommendation
waterway pressurized This is always a pipe flow waterway mandatory
man_made pipeline A penstock is always a pipeline mandatory
substance water A penstock always carries water mandatory
usage penstock No comment mandatory
location <penstock location> Depending of environment and ground shape, penstocks can be overground or underground recommended
diameter <penstock nominal diameter> The nominal diameter (ISO 6708) of the pipe optional
pressure <nominal penstock pressure> The nominal pressure the penstock is designed for optional
material <penstock material> The material used to build the pipes. optional
operator <penstock operator> Name of the company operating the penstock recommended

Penstocks can be part of Relation:waterway with side_stream role.

Water feeding flows

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 unshielded galleries (upstream from penstocks) with pipe or free flow operation.
As said before, it may be possible to involve water feeding infrastructure in Relation:waterway with side_stream role only if all water is took and released in the same river. It's not always the case and waterway=* graph have to be extended with or without waterway relation membership.

Free flow tunnels

Water is freely flowing inside a drain

Free flow tunnels are currently mapped with waterway=drain + tunnel=* and there is no point to refine it at all.
There is no need to add pressure=* key since water always flows at atmospheric pressure.

Pipe flow tunnels

Horizontal water carrying culvert map

Assuming penstocks are different from pipe flow horizontal feeding galleries, the last will be mapped with usage=transmission instead of usage=penstock.

Furthermore, such tunnels can be whether slightly pressurized or operate at atmospheric pressure. Leading intakes are always below water level as to not allow air to get inside. pressure=* can be used to make the difference.

Key Value Comment Recommendation
waterway pressurized This is pipe flow waterway mandatory
man_made pipeline A pipe flow water stream is always in a pipeline (while we differentiate the water and the pipe) mandatory
substance water Such infrastructure always carry water mandatory
usage transmission Horizontal ducts are intended for water transmission mandatory
location underground A tunnel is underground, don't you ? mandatory
diameter <pipe nominal diameter> The nominal diameter (ISO 6708) of the pipe optional
pressure <nominal waterway pressure> The nominal pressure the waterway is designed for optional
operator <pipeline operator> Name of the company operating the pipeline optional

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.
Please only use tunnel=yes when the pipeline is human accessible in operation.

Even if tunnel=culvert is recommended to render such underground facilities, a pipeline is not a culvert and a specific rendering solution will have to be found for waterway=pressurized

Canals

When overground, water flows in free surface canals, then waterway=canal is appropriate and doesn't need to be refined at all.


Surge tanks

Isawa II power station surge tank and penstock.jpg

Surge tanks are useful to dissipate the power water is applying to pipes and tunnels when a valve is closed (sometimes brutally).
Depending of upstream (only, not downstream penstocks) tunnels length and diameter, they can be pretty huge shafts like 200m of depth and 20m of diameter - often found in the middle of nowhere.
Overground building can be found sometimes where it may be useful to add name=Valve chamber on it.
Surge tanks is a concept related to fluid flows, not specific to penstocks.

As part of a pipeline system, often at the start point of penstocks, we can map them in OSM with pipeline=surge_tank on a node.
Even if such tanks can be huge shafts or chimneys, pipeline=surge_tank should be used on a pipeline node placed at the position of the tank. Visible infrastructure can be tagged with man_made=shaft or man_made=chimney since it can be complex buildings or construction.

Key Value Comment Recommendation
pipeline surge_tank It's a pipeline surge tank mandatory
location <tank location> Location of the surge tank. Can be outdoor, underground recommanded
diameter <tank diameter> The internal diameter of the tank optional
operator <surge tank operator> Name of the company operating the surge tank optional

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.

Such connection flows have to be added to Relation:waterway relations with side_stream role.
Usually a waterway=dam is built to direct water inside tunnel or pipes instead of natural riverbed.

Spillways

Spillways need to be distinguished from actual streams or river due to very occasional streams going along it. There is additionally a potential danger for persons crossing or located downstream of such ways.

Spillways don't allow to preserve rivers flow rate and are only active when special situations occurs upstream of dams. Then it's proposed to map them with waterway=spillway and add it to waterway relation with side_stream role.

Pages to be edited

Examples

Tunnels and canals

Photo Aerial view Tagging Note
Horizontal water carrying culvert map
--

waterway=pressurized
man_made=pipeline
substance=water
usage=transmission
operator=...
location=underground
diameter=4900

Horizontal galleries carrying water from intakes to penstocks. A duct always have a pipe flow regime, its inlet is always below the water level and no air can get inside.
Water drain outlet
--

waterway=drain
operator=...
location=underground

Horizontal drains work at atmospheric pressure and water have a free surface while flowing inside. Its inlet is designed to be above water level and air can get inside too.
Water siphon
--

On all parts, use:

waterway=pressurized
man_made=pipeline
substance=water
usage=transmission


operator=...

On the bridge part, use:
bridge=aqueduct

On the underground part, use:
location=underground

A big siphon allowing water to cross a valley. Only half side is visible on the picture, drains are connecting each side at equivalent altitudes. The siphon is a pipe flow waterway.

Penstocks

Photo Aerial view Tagging Note
Pipeline penstocks
--

waterway=pressurized
man_made=pipeline
substance=water
usage=penstock
operator=...
location=overground
diameter=1200
pressure=70 bar

Metallic penstocks feeding a power plant down the mountain. No air can get inside and water goes pipe flow
Lack of free illustration --

waterway=pressurized
operator=...
man_made=pipeline
substance=water
usage=penstock
location=underground
diameter=4900

Vertical shafts are shielded as pipeline without tubes. Pipes are connected upstream and downstream.

See the two vertical shafts on the power plant digital model and some pics of how it was built with a raise drill machine

Water intakes

Photo Aerial view Tagging Note
Man made water intake dam
--

On the dam, draw a Way and: waterway=dam
operator=...
material=concrete

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.


Note that air can get inside intake. This will necessarily leads to a drain and not a pressurized

Surge tanks

Photo Aerial view Tagging Note
Isawa II power station surge tank and penstock.jpg
--

At the center of the shaft or chimney, add a node and use :
pipeline=surge_tank
operator=...
location=outdoor

A chimney is installed above the pipeline it is supposed to protect
Pipeline underground surgeTank.JPG
--

At the center of the shaft, add a node and use :
pipeline=surge_tank
operator=...
location=underground

Here is an underground shaft acting as a surge tank for a penstock located 170 metres below. The shaft outlet is about 18 metres wide

Spillways

Photo Aerial view Tagging Note
Dam spillway.jpg
-- Draw a Way along the spillway and use tags :
waterway=spillway
The spillway on the picture is active but it's not always true.
Llyn Brianne spillway.jpg

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