Talk:Tag:water=reservoir

Usage

Would it not be an idea to add usage values for this? Like usage=hydroelectric and usage=drinking. Gazer75 (talk) 04:16, 21 March 2020 (UTC)

See reservoir_type=*? According to taginfo 3 uses of hidro_power, 2 uses of hydropower. Drinking water can be tagged with drinking_water=* Warin61 (talk) 07:34, 21 March 2020 (UTC)

Service and bankside reservoirs might actually be water=basin

This text was just added:

"Bank-side reservoirs, where water is pumped or siphoned from a river to store the water. Such reservoirs are usually formed partly by excavation and partly by building a complete encircling bund or embankment on Wikipedia. The water stored in such reservoirs may stay there for several months, during which time normal biological processes may substantially reduce many contaminants and almost eliminate any turbidity. The use of bank-side reservoirs also allows water extraction to be stopped for some time, when the river is unacceptably polluted or when flow conditions are very low due to drought. "Service reservoirs are used for storage of potable drinking water close to the point of distribution. While technically reservoirs, these are usually not open bodies of water, but rather a cistern or a water tower, and thus should be tagged instead as man_made=cistern or man_made=water_tower."

Based on the prior definition on this page and on water=basin + landuse=basin, I believe both those kinds of water storage facility are probably landuse=basin / water=basin, since they are not usually formed by a dam across the mouth of a topographic depression, but rather are usually dug out or built up with dykes (levees) on all sides like a basin. The service reservoir type does not seem to describe the physical characteristics so they might be a reservoir formed by a dam across a valley, but as mentioned they could also be a cistern, or storage tank, or a basin, so in this case the idea of "reservoir" is a different term which means "water storage facility" rather than "artificial lake". --Jeisenbe (talk) 16:44, 17 December 2020 (UTC)

I agree with your characterization of service reservoirs, and the point of even mentioning them in this article is to make sure that anything that might be called "reservoir" is somehow listed on this page, with a recommendation on how to tag.

I don't agree with basin as the tag for bank-side reservoirs. The specific example I found,  Queen Mary Reservoir, tagged 147189989 147189989 is clearly a reservoir (for drinking water) and tagged as such. However, I only looked at this one example and maybe it is not reflective of the entire class of bank-side reservoirs.

I understand basin to specifically refer to:  Retention_basin, that is how I've seen that tag used in my area, and based on the name "basin" and picture attached to water=basin.

It's also used for https://en.wikipedia.org/wiki/Detention_basin and https://en.wikipedia.org/wiki/Infiltration_basin at least: See basin=* --Jeisenbe (talk) 21:56, 17 December 2020 (UTC)

What do you think about service reservoirs that are man_made=reservoir_covered? ---- Kovposch (talk) 04:21, 18 December 2020 (UTC)

I just added it to the list -- unless you were thinking differently? --ZeLonewolf (talk) 04:34, 18 December 2020 (UTC)

Reservoir repurposed as a basin

Hi, thanks for the cleanup edit in water=reservoir. However, are you sure that reservoirs can't become basins? It is somewhat common in my area for old agricultural reservoirs to see new development around the reservoir. During this process they decommission the reservoir from the original use of storing water for agricultural use (perhaps even building up and regrading the sides), but keep the depression in place for use as an infiltration or detention basin for stormwater. I'd suggest that the recommendation should remain, though perhaps with more specificity on when that would happen. --Phidauex (talk) 16:20, 29 December 2020 (UTC)

Could you point out an example of one of these? Usually the difference between water=basin and water=reservoir is that the latter is made by a dam across a watercourse or valley, while a basin is created by regrading the land to make a depression (or to raise up a dyke around the basin, rarely). Repurposing a reservoir from agricultural use to flood control wouldn't change this. --Jeisenbe (talk) 06:09, 30 December 2020 (UTC)

Hi, the definition between reservoir and basin can get a bit blurry, particularly in the plains where pushing dirt up to form a short dam is not that different than pushing up from the sides to form the walls of a basin. I do agree that an existing watercourse is usually a prerequisite for a reservoir, though in some cases that existing waterway might be removed at a later date, especially if it was a ditch or canal. For me, that leaves "intent" or "use" as a part of the reservoir/basin distinction. Retaining water year-round (or most of the year) for irrigation, drinking water, etc. is much more "reservoir" like, while a structure that is typically empty, and exists to provide stormwater detention or infiltration is more "basin" like. If that isn't how we want to handle things then perhaps the basin definition needs some clarification (and we might end up needing something like reservoir=detention in addition to basin=detention).

A quick example is this "East Lake Number 2" (https://www.openstreetmap.org/way/667816898#map=18/39.91859/-104.95654). At the time it was built, it was an agricultural reservoir, with an earthen dam in the waterway. Later the neighborhoods on the north and south side were built, and the road on the west side, which built up the four sides, making it more like a basin. It stopped being used to store water, but the remaining depression is used as a detention basin for stormwater from the new neighborhoods. It was imported originally as a GNIS reservoir point (probably entered in the 70's, when it was a more traditional reservoir), and then later updated in OSM to basin to describe the current use of the water structure. I'm sure other examples could be found, this is just one that caught my memory (I expanded the GNIS point to a reservoir a few years ago, and other mappers changed it to a basin (correctly, in my view).

One reason I thought to add the "change to basin" example was to cover cases like this where maybe it was "basin-like" all along, but due to the GNIS import, it came in as a reservoir, and there have been mapper questions in CO about how to handle cases where it actually seems like a basin (either because it always was a basin OR because the shape and use of the structure changed over time). --Phidauex (talk) 20:06, 30 December 2020 (UTC)

That's a good example (https://www.openstreetmap.org/way/667816898) where landuse=basin (or water=basin) now makes sense, especially since the roads have been built up around it. Certainly the tagging now makes sense. But I suspect this is a rare situation. --Jeisenbe (talk) 04:43, 31 December 2020 (UTC)

I added two brief notes in "see also" about evaluating GNIS imported basins, since this is where I've seen this come up several times, rather than in the options for disused reservoirs. Hopefully that captures the lessons learned from my work on US reservoirs without implying that it is a regular occurrence. Thoughts? --Phidauex (talk) 17:59, 8 January 2021 (UTC)

Reservoir drawdown

I think that we should have a tag, e.g. reservoir:minele=number, where we could specify the lowest normal water level. If I take https://fr.wikipedia.org/wiki/Réservoir_Manicouagan as example, the highest normal (which can be ele value) is 359 meters, the lowest is 342 meters. I think this information could be useful, what do you think? --Yann Tombmyst Tremblay (talk) 15:25, 26 May 2021 (UTC)

I agree that this information could be useful. (Note, though, that for reasons of copyright and licences, this information should be collected on site and not be copied from Wikipedia). However, i would omit reservoir: because this seems unnecessary. There are 111 uses of ele:min=* on reservoirs in Norway (example). --Dafadllyn (talk) 19:43, 26 May 2021 (UTC)

I will opt for ele:min=*, and I think ele:max could be ok also for the maximum water height. And yes, I take good note of not collecting data from Wikipedia. --Yann Tombmyst Tremblay (talk) 19:54, 26 May 2021 (UTC)

Are you sure ele:min=* would mean the lowest water height, not the reservoir bottom level? There's also depth=*. ---- Kovposch (talk) 09:45, 27 May 2021 (UTC)

I think yes, because one could determine the reservoir bottom level using depth and ele:max=* --Yann Tombmyst Tremblay (talk) 12:32, 27 May 2021 (UTC)

Forebays

Is this value suitable for forebays? See on this chart
Forebays are a kind of reservoirs used to collect water from a free flow canal before it enters pressurised penstocks. They ensure no air can't get in the downstream pipes by maintaining an appropriate amount of water on the pipe's inlet. Don't we miss a reservoir=* to hold reservoir=forebay for instance? Fanfouer (talk) 00:15, 22 December 2022 (UTC)

Not a bad idea to add. I've found maybe a handful of them in Norway, mostly older power plants. A reservoir=* would be useful for defining its purpose as well. Like drinking, irrigation or hydro power.Gazer75 (talk) 11:23, 26 March 2023 (UTC)