[Tagging] The saga of landuse=reservoir vs water=reservoir

[Graeme Fitzpatrick]

I should have added ...

So really, they're not "natural" in any way (except for the water in them!,
& even that is frequently pumped in).

Thanks

Graeme


On Thu, 17 Dec 2020 at 12:20, Graeme Fitzpatrick <graemefitz1 at gmail.com>
wrote:

> In an Australian context, the most common are known as Turkey's Nest dams,
> because they're mounded up above the ground eg
>
> https://c8.alamy.com/comp/A6T7R0/turkey-nest-dam-on-outback-cattle-station-queensland-australia-A6T7R0.jpg
>
> For a full explanation:
> https://www.agric.wa.gov.au/water-management/excavated-tanks-farm-dams
>
> Thanks
>
> Graeme
>
>
> On Thu, 17 Dec 2020 at 11:53, Joseph Guillaume <josephguillaume at gmail.com>
> wrote:
>
>> That Wikipedia page is right.
>> The artificial grading mostly involves creating an (earthen) dam wall
>> (which is often also mapped), and the purpose is generally retention of
>> water rather than infiltration or detention, which is why the distinction
>> between reservoir and basin isn't clear cut to me.
>>
>> I'm having trouble thinking of it as a basin, but it does seem like this
>> is the intended tag. Thanks!
>>
>>
>>
>> On Thu, 17 Dec 2020, 12:29 pm Joseph Eisenberg, <
>> joseph.eisenberg at gmail.com> wrote:
>>
>>> What is a farm dam in this context? We don't have that term in American
>>> English.
>>>
>>> Is this perhaps an example of landuse=basin (or if you prefer
>>> water=basin) with basin=detention or basin=infiltration?
>>>
>>> https://wiki.openstreetmap.org/wiki/Tag:landuse%3Dbasin
>>>
>>> https://en.wikipedia.org/wiki/Dam_(agricultural_reservoir)
>>>
>>> -- Joseph Eisenberg
>>>
>>> On Wed, Dec 16, 2020 at 1:29 PM Joseph Guillaume <
>>> josephguillaume at gmail.com> wrote:
>>>
>>>> This discussion has convinced me not to use landuse=reservoir.
>>>>
>>>> It sounds like the only benefit is its historical use, whereas I've
>>>> personally seen benefits of the natural=water approach.
>>>>
>>>> I've mapped quite a number of farm dams as natural=water without being
>>>> sure what subtag to use.
>>>> I now think that's because there isn't an appropriate subtag. I
>>>> definitely don't want to tag it as a pond. While a farm dam is structurally
>>>> and functionally a reservoir, there are clear differences with large
>>>> reservoirs.
>>>>
>>>> Already now, farm dams tend to be mapped more prominently than I'd
>>>> expect. The dominant feature of these grazing landscapes is fencing, and
>>>> I'd therefore expect farm dams to appear on a similar scale to fences.
>>>> water=reservoir and landuse=reservoir wouldn't do that.
>>>>
>>>> One of the things I love about OSM is the ability to map incrementally,
>>>> which by definition results in incomplete, lower quality maps that are
>>>> constantly improving. If the priority was a high quality map, we'd map
>>>> systematically (like Missing maps, but for everything that will appear on a
>>>> render) and not release an area until it was done. I wouldn't be mapping.
>>>>
>>>>
>>>> On Thu, 17 Dec 2020, 1:26 am Tomas Straupis, <tomasstraupis at gmail.com>
>>>> wrote:
>>>>
>>>>> 2020-12-16, tr, 16:01 Mateusz Konieczny rašė:
>>>>> >
>>>>> https://wiki.openstreetmap.org/wiki/Tag:landuse%3Dreservoir#water.3Dreservoir
>>>>> > (just added)
>>>>>
>>>>>   Thank you. Maybe it is better to discuss here before adding to wiki?
>>>>>   My arguments on the points you've added:
>>>>>
>>>>>   1. Regarding benefit of having a combining level/tag natural=water.
>>>>> If today you would query all data with natural=water - you will get
>>>>> not only lakes and reservoirs grouped, but also riverbank polygons
>>>>> (totally different beast) and micro elements like water=pond. This
>>>>> could only be partly useful in the largest scale maps and only if you
>>>>> make very simple maps and for some reason use the same symbolisation
>>>>> for such different water classes. For example ponds usually have less
>>>>> complex and less prominent symbolisation because of their size and
>>>>> importance. Riverbanks would not need polygon labelling, but rather
>>>>> use river (central) line for label placement. Most of GIS/Cartography
>>>>> work goes in middle/small scales and it will be impossible to use only
>>>>> natural=water there, you would have to add "and water not in
>>>>> ('riverbank', 'pond', ...)". This erodes the benefit of "one tag" and
>>>>> makes it of the same complexity from coding perspective as original
>>>>> water scheme.
>>>>>
>>>>>   2. Very important disadvantage of water=reservoir from
>>>>> cartographic/gis perspective: it allows mappers to NOT differentiate
>>>>> between natural lakes and man made reservoirs. If first point
>>>>> describes how different classes are USED, this second point is about
>>>>> how these classes are CAPTURED.
>>>>>
>>>>>   Did I miss anything?
>>>>>
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