I'm wondering if rather than deprecating water=pond, it would be better to keep it as a value with overlapping usage to lake (like river/stream) and instead focus tagging on the actual differences between different bodies of water.
I'd suggest two new tags that get at the heart of what I've been hearing people suggesting as distinctions between all these water-bodies other than size, their origin (natural or human-made) and whether they are naturally flowing at their outlets, have human-created outlet controls, or no outlet (in the case of endorheic basins <https://en.wikipedia.org/wiki/Endorheic_basin> or some quarries): - origination=natural/artificial - outlet_control=natural/artificial/no-outlet *(I wanted to use "origin", but that is currently used for goods from shops.)* These could of course be sub-tagged if desired to add more specificity. Examples: - origination:natural=glaciation - origination:natural=landslide (if a natural dam was formed by a landslide) - origination:natural=beavers - origination:artificial=quarry - outlet_control:natural=bedrock - outlet_control:natural=soil - outlet_control:natural=beavers Here are a few examples of lakes, ponds, and reservoirs that I'm familiar with that seem useful for this discussion: *Abbey Pond, Middlebury, Vermont*: OSM <https://www.openstreetmap.org/relation/6791744#map=17/44.03351/-73.05766>, photo <https://photos.app.goo.gl/hrXTB7qCHi8hW5QLA> This pond appears to have been scoured out during the last glaciation period and drains over a hard-rock ledge. It appears to not be very deep, but the presence of the ledge ensures that this pond will exist until silted in or the land is re-formed by glaciers. At the same time, beaver activity just upstream of the rock-ledge has raised the water level by 1-2 meters. This I would tag as: - water=pond - origination=natural - origination:natural=glaciation - outlet_control=natural - outlet_control:natural=beavers *Crystal Lake, Beulah, Michigan:* OSM <https://www.openstreetmap.org/way/41311866>, photo <https://www.flickr.com/photos/24574316@N07/8448455983>, outlet dam photo <https://www.flickr.com/photos/upnorthmemories/4275417296/in/photolist-2j7LeLi-7vNCBj-wkcYcg-7vJNza-2j7Lewf-2j7NM8R-2j7NLMf-2j7LezG-2j7NM1B-G8tmG9-aDeAYv-G8tmK5-8rsWwZ-pfqfdH-puTgMo-pfrimc-pfqzb3-pwDceM-xPF3Zy-yJopEQ-yKHREh-xPF3x1-ow479W-wiKKFy-287rZDA-bbdYVz-bbdWnx-287rZi5-bbdXTa-yu7aaq-287rZ7U-287rZs3> This large 3-mile x 9-mile lake was scoured out alongside Lake Michigan during the last glaciation period. It's origin is very natural. It's water level sat about 43 feet higher than Lake Michigan until 1873 when an attempt at digging a transportation canal spectacularly failed dropped the lake level by about 20'. (source 1 <http://betsiecurrent.com/index.php/who-pulled-the-plug-at-crystal-lake/>, source 2 <http://www.clarkehistoricallibrary.org/2018/11/the-tragedy-and-crystal-lake.html>). Today the lake-level is controlled by an artificial outlet dam <https://www.openstreetmap.org/node/354007942#map=15/44.6360/-86.1455> (really a weir) with its level changed seasonally. While this is by every definition a naturally formed lake, it is today controlled by humans. - water=lake - origination=natural - origination:natural=glaciation - outlet_control=artificial - outlet_control:artificial=weir A decorative human-made pond that empties over a rocky berm with no operable level-control structures might be tagged with - water=pond - origination=artificial - outlet_control=natural A totally natural lake with no human intervention might be: - water=lake - origination=natural - outlet_control=natural - outlet_control:natural=bedrock Very long story short, I think we might be able to worry a little less about what the body of still water *is* and more about its other properties that might be of interest. In programming languages this is referred to as "duck typing <https://en.wikipedia.org/wiki/Duck_typing>". On Thu, Nov 12, 2020 at 2:52 PM Paul Allen <pla16...@gmail.com> wrote: > On Thu, 12 Nov 2020 at 19:30, Joseph Eisenberg <joseph.eisenb...@gmail.com> > wrote: > >> Re: is water=* tag needed? >> > > >> But since water=pond is not clearly defined as natura/semi-natural vs >> man-made, we have a large number of features where the water=* tag is not >> providing this information. Since the previous tagging system clearly >> distinguished natural from man-made water bodies, this would be a loss for >> database quality. >> > > We often do not know if it is natural or artificial. Maybe it's a natural > depression in the ground that fills with water. Maybe it was created > by man as a water feature. Maybe it's an old quarry that has flooded. > Even if it was originally a result of something like quarrying it may have > happened so long ago that there are no records. > > What we can determine (at least in principle) is if it meets criteria > for a lake (large size or large waves or has aphotic zones) or a > pond. In principle, a suitably-qualified mapper could investigate > those things on site. We can accept using guesswork based on > size pending fuller investigation. A lake/pond distinction is > useful irrespective of whether it is entirely natural or entirely > artificial. > > Determining if it's entirely natural, or deliberately man-made, or > an unintended consequence of past human activity is harder. > Possible for retention basins that are still in use. Mostly > possible for reservoirs, although some reservoirs are > based around natural lakes. But historical records are > incomplete (and some mappers insist we should never > ever make use of historical data to inform our mapping). > > Maybe we need an artificial=yes/no. > > -- > Paul > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging >
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