how to tag a salt flat

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how to tag a salt flat

joost
Hi,

I haven't found much about the subject. A salt flat is a large deposit of salt. They are usually where a river ends in the middle of a desert. Or where a valley is completely surrounded by mountains, leaving no way out for any water. So salt starts accumulating as salty waters evaporate. Some of them rarely see any water, others are inundated every year or might be under water a lot of the time. Because they tend to be dry most of the time, and plants tend to dislike pure salt, they tend to look like a desert.

How should one tag such a thing? I've seen three very different ideas:

- they are a kind of desert, which happens to inundate from time to time. Hence natural=desert and desert=salt. This seems to be the most popular option (see http://www.openstreetmap.org/changeset/32082629 and 
- they are a kind of lake, which happens to be dry most of the time. Rarely this is combined with water=salt_lake (for example: http://www.openstreetmap.org/relation/1290108#map=10/-19.3280/-68.1139)
- they are a kind of wetland, which happens to be completely devoid of vegetation (see http://wiki.openstreetmap.org/wiki/Talk:Tag:natural%3Dwetland#Salt_plains_.2B_intermittent_salt_lakes )

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Re: how to tag a salt flat

Christoph Hormann
On Tuesday 29 September 2015, joost schouppe wrote:
> Because they tend to be dry most of the time, and plants tend to
> dislike pure salt, they tend to look like a desert.
>
> How should one tag such a thing? I've seen three very different
> ideas:
> [...]

There is no established tagging for this, none of your suggestions seems
particularly good:

- natural=desert is wrong for the salt flat itself in any case.  If it
is a desert by whatever definition of desert it won't end at the edge
of the salt flat usually.
- natural=wetland means water saturated soil which is correct only for a
very short time span between the water covered state and the dry state.
- natural=water is questionable for areas that are never or only very
sporadically covered by water.

For areas with regular (i.e. seasonal) saltwater cover natural=water +
intermittent=yes/seasonal=yes + salt=yes would be right, otherwise
there is no well matching established tagging.

You could of course think about tagging it geological=salt_pan but it
might not be such a good idea to make the dominance of salt the
defining criterion here - the more generic term would be 'dry lake'.

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Re: how to tag a salt flat

Warin
On 30/09/2015 5:47 AM, Christoph Hormann wrote:

> On Tuesday 29 September 2015, joost schouppe wrote:
>> Because they tend to be dry most of the time, and plants tend to
>> dislike pure salt, they tend to look like a desert.
>>
>> How should one tag such a thing? I've seen three very different
>> ideas:
>> [...]
> There is no established tagging for this, none of your suggestions seems
> particularly good:
>
> - natural=desert is wrong for the salt flat itself in any case.  If it
> is a desert by whatever definition of desert it won't end at the edge
> of the salt flat usually.
> - natural=wetland means water saturated soil which is correct only for a
> very short time span between the water covered state and the dry state.
> - natural=water is questionable for areas that are never or only very
> sporadically covered by water.
>
> For areas with regular (i.e. seasonal) saltwater cover natural=water +
> intermittent=yes/seasonal=yes + salt=yes would be right, otherwise
> there is no well matching established tagging.

Lake Eyre in Australia (a very large salt water lake in Australia .. that may have water in it once every 10 years) is tagged

natural=water

water=lake

salt=yes

intermittent=yes

That, to me, is suitable as it matches my impression of what it is.



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Re: how to tag a salt flat

André Pirard-2
In reply to this post by joost
On 2015-09-29 17:29, joost schouppe wrote :
Hi,

I haven't found much about the subject. A salt flat is a large deposit of salt. They are usually where a river ends in the middle of a desert. Or where a valley is completely surrounded by mountains, leaving no way out for any water. So salt starts accumulating as salty waters evaporate. Some of them rarely see any water, others are inundated every year or might be under water a lot of the time. Because they tend to be dry most of the time, and plants tend to dislike pure salt, they tend to look like a desert.

How should one tag such a thing? I've seen three very different ideas:
You might find some inspiration by searching for "marais salant", which is French for similar areas, but fitted for salt production.  The discussions will take you further to tags as salt_pond, natural=wetland and the like.
As salt is cheap, this is just 2 ¢. €¢.

André.





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Re: how to tag a salt flat

joost
I don't think a landuse tag is sensible, as the salt flats I have in mind (look up some images of Salar de Uyuni to get an impression) are definitely not something human centered. However, it might be a good tag for some of the smaller  areas where salt is actually harvested.

The combination of natural=water , intermittant=yes and salt=yes sounds reasonable. I do think it is a bit confusing as the saltiness is more a property of the lake bed when it dries out than of the water when it is filled. Maybe adding that geological=salt_pan could clarify this enough.

I don't see how the natural=desert would be wrong because of the outline not coinciding with the deserts' end. In fact, you could argue that the desert does end at the salt's edge; there is a very sudden shift in vegetation and barren-ness there. The "islands" within it are really like oasis in the desert. But even if the argument does hold, why couldn't there be a natural=desert / desert=salt surrounded by natural=desert /desert=sand ?

In South Americe, these things are just called Salar, or "salted". That's for a reason: the salt is as much the defining feature here as water is in a lake or tree cover in a wood. So natural=salt_flat might be worthy of existing. 

2015-09-30 0:39 GMT+02:00 André Pirard <[hidden email]>:
On 2015-09-29 17:29, joost schouppe wrote :
Hi,

I haven't found much about the subject. A salt flat is a large deposit of salt. They are usually where a river ends in the middle of a desert. Or where a valley is completely surrounded by mountains, leaving no way out for any water. So salt starts accumulating as salty waters evaporate. Some of them rarely see any water, others are inundated every year or might be under water a lot of the time. Because they tend to be dry most of the time, and plants tend to dislike pure salt, they tend to look like a desert.

How should one tag such a thing? I've seen three very different ideas:
You might find some inspiration by searching for "marais salant", which is French for similar areas, but fitted for salt production.  The discussions will take you further to tags as salt_pond, natural=wetland and the like.
As salt is cheap, this is just 2 ¢. €¢.

André.







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Re: how to tag a salt flat

dieterdreist
In reply to this post by Warin

2015-09-30 0:28 GMT+02:00 Warin <[hidden email]>:
Lake Eyre in Australia (a very large salt water lake in Australia .. that may have water in it once every 10 years) is tagged

natural=water

water=lake

salt=yes

intermittent=yes

That, to me, is suitable as it matches my impression of what it is.


a place which has once every 10 years some water in it wouldn't be tagged as natural=water by me.
According to the wiki, intermettent is "used to indicate that a waterway (river, stream, etc.) does not have a permanent flow. Or that a water body (lake) disappears seasonaly."

10 years aren't a "season" typically.

Cheers,
Martin





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Re: how to tag a salt flat

Christoph Hormann
In reply to this post by joost
On Wednesday 30 September 2015, joost schouppe wrote:
> I don't think a landuse tag is sensible, as the salt flats I have in
> mind (look up some images of Salar de Uyuni to get an impression) are
> definitely not something human centered. However, it might be a good
> tag for some of the smaller  areas where salt is actually harvested.

The Salar de Uyuni is somewhat special since there is permanent water
(brine) below the salt crust across large parts of it and partial water
cover above the salt during wet season.  natural=water for the whole
area seems wrong here.

> I don't see how the natural=desert would be wrong because of the
> outline not coinciding with the deserts' end. In fact, you could
> argue that the desert does end at the salt's edge; there is a very
> sudden shift in vegetation and barren-ness there. The "islands"
> within it are really like oasis in the desert. But even if the
> argument does hold, why couldn't there be a natural=desert /
> desert=salt surrounded by natural=desert /desert=sand ?

Depending on definition a desert is either defined by aridity (lack of
water) or lack of vegetation.  Neither of these generally applies to a
dry lake area and not to the immediate area around as well.  But it
does not really matter since deserts can be considered non-verifiable
and not mappable within the scope of OSM anyway.

In general it is probably best to think of it in terms of what
characterizes what you would like to map.  There are:

- the hydrological aspect - the presence of standing water or water
saturated ground
- the topographic aspect - the presence of a very flat area
- the physical aspect - the presence of soluble salts and non-soluble
young fine grained sediments at the surface
- the geomorphological aspect - the mechanism that formed the area in
question, i.e. deposits left by local evaporation of water

Depending on what aspect is key for you different tags make sense and it
might be a good idea to choose tags that refer to indivisual aspects
rather than a combination of all of them (which is what
natural=salt_flat would imply).

--
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http://www.imagico.de/

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Re: how to tag a salt flat

Warin
In reply to this post by dieterdreist
On 30/09/2015 6:06 PM, Martin Koppenhoefer wrote:

2015-09-30 0:28 GMT+02:00 Warin <[hidden email]>:
Lake Eyre in Australia (a very large salt water lake in Australia .. that may have water in it once every 10 years) is tagged

natural=water

water=lake

salt=yes

intermittent=yes

That, to me, is suitable as it matches my impression of what it is.


a place which has once every 10 years some water in it wouldn't be tagged as natural=water by me.
According to the wiki, intermettent is "used to indicate that a waterway (river, stream, etc.) does not have a permanent flow. Or that a water body (lake) disappears seasonaly."

10 years aren't a "season" typically.



Local conditions...

A 5 day week is also not 'typical', yet there are places that have 5 day weeks, places with 2 seasons per year and other places with 5 seasons in a year.
And those would be regarded as 'typical' values for a week or seasons in a year.

What is 'typical' in one part of the globe does not mean all other parts of the globe have the same condition, and may have a different nuance to the word 'typical'.

Synonyms for the word typical ...
common place
natural
normal
regular

And 10 years is a typical season for Lake Eyre....
https://en.wikipedia.org/wiki/Lake_Eyre
Direct quote from wikipedia .. note the use of the word typical!!
"Typically a 1.5 m (5 ft) flood occurs every three years, a 4 m (13 ft) flood every decade, and a fill or near fill a few times a century. "

The 1.5 meter is not enough for yachts and does not fill the lake, the 4 meter is enough to fill the lake and run yachts.... and they do have a yacht club ...

So anyone who knows what is typical, natural for Lake Eyre would call it intermittent.

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Re: how to tag a salt flat

dieterdreist


sent from a phone

> Am 30.09.2015 um 12:03 schrieb Warin <[hidden email]>:
>
> Local conditions...
>
> A 5 day week is also not 'typical', yet there are places that have 5 day weeks, places with 2 seasons per year and other places with 5 seasons in a year.
> And those would be regarded as 'typical' values for a week or seasons in a year.
>
> What is 'typical' in one part of the globe does not mean all other parts of the globe have the same condition


there's a huge difference between a week or a month and a year or a day, the latter have an astronomical definition (and are indeed the same on all other parts of the globe). A season is a part of a year, regardless how many of them there are.

cheers
Martin
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Re: how to tag a salt flat

dieterdreist
In reply to this post by Christoph Hormann


sent from a phone

> Am 30.09.2015 um 11:58 schrieb Christoph Hormann <[hidden email]>:
>
> But it
> does not really matter since deserts can be considered non-verifiable


deserts are verifiable, the definitions may vary, but ground truth, ask the locals and they will tell you ;-)
There may be edge cases, but that's true for almost everything that we map


> and not mappable within the scope of OSM anyway.


likely yes, at least for now and with the established data types (no sharp borders, mostly)

cheers
Martin
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Re: how to tag a salt flat

Warin
In reply to this post by dieterdreist
On 30/09/2015 8:28 PM, Martin Koppenhoefer wrote:

>
> sent from a phone
>
>> Am 30.09.2015 um 12:03 schrieb Warin <[hidden email]>:
>>
>> Local conditions...
>>
>> A 5 day week is also not 'typical', yet there are places that have 5 day weeks, places with 2 seasons per year and other places with 5 seasons in a year.
>> And those would be regarded as 'typical' values for a week or seasons in a year.
>>
>> What is 'typical' in one part of the globe does not mean all other parts of the globe have the same condition
>
> there's a huge difference between a week or a month and a year or a day, the latter have an astronomical definition (and are indeed the same on all other parts of the globe

I assume you are taking of a calendar that is used to define the year?
The calendar in common use (Gregorian) is not as good as one used in at least one area of the globe ..
the Persian calendar is a much better match to the astronomical 'year'.

Then there is the Julian Day calendar .. no weeks, months nor years here ... just a single (now large) number...

As for a day being the same on all parts of the globe?
The old definition of a day was from sunrise to sunset. Monasteries typically ran this way, and most farmers still do.
Those are different durations if your latitude is different... and yes they varied seasonally too..

> ). A season is a part of a year, regardless how many of them there are.

Well if you want to have lake Eyre 'qualify' for the tag 'intermittent'
then I could say it 'typically' gets water once per year ... when the 'Queensland rains' fall (assuming they do)
of course the water might only be 5 mm deep and only in the northern part of the lake (the lowest part).
And then it might only be there for a week.
And then there are the years when the water does not get even that far. Bit dry for those years.

But if you want to see Lake Eyre full .. 'typically' that is once every 10 years or so...
So to me a full cycle of Lake Eyre in all its 'seasons' would be 'typically' 10 years.


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Re: how to tag a salt flat

David Bannon-2


On 30/09/15 21:28, Warin wrote:
> ......
> Well if you want to have lake Eyre 'qualify' for the tag 'intermittent'
> .....
> But if you want to see Lake Eyre full .. 'typically' that is once
> every 10 years or so...

> So to me a full cycle of Lake Eyre in all its 'seasons' would be
> 'typically' 10 years.
Warin, I think you will find that Lake Eyre has only 'Filled' three
times since (white man's) records have been kept, 150 years ? Its a very
big place, when water flows in on those ten year cycles, it just gets a
bit damp in one small corner, you could not say thats the defining cycle
for the whole lake.

Does 'intermittent' still apply to a 50 or 100 year cycle ? Honestly,
the natural state of Lake Eyre is dry. And thats how we like it !

David

>
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>
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Re: how to tag a salt flat

Warin
On 1/10/2015 8:49 AM, David Bannon wrote:


On 30/09/15 21:28, Warin wrote:
......
Well if you want to have lake Eyre 'qualify' for the tag 'intermittent'
.....
But if you want to see Lake Eyre full .. 'typically' that is once every 10 years or so...

So to me a full cycle of Lake Eyre in all its 'seasons' would be 'typically' 10 years.
Warin, I think you will find that Lake Eyre has only 'Filled' three times since (white man's) records have been kept, 150 years ? Its a very big place, when water flows in on those ten year cycles, it just gets a bit damp in one small corner, you could not say thats the defining cycle for the whole lake.

'Full' ... http://www.lakeeyrebasin.gov.au/about-basin/water  States the 'typical' inflows ...

And the yacht club has a graph of the water depth from 1975 ...  http://www.lakeeyreyc.com/fldhist.html


Does 'intermittent' still apply to a 50 or 100 year cycle ?

I would say YES!

I think the OSM wiki is wrong in putting the word "seasonal" as a qualifier to the tag intermittent!
Seasonal things should be tagged with the tag seasonal!
In fact I'll be brave and remove the  word! It was looks to be added by Chrabros  in April 2014..
So I have removed the word seasonal from the meaning of intermittent and added a 'common mistakes' section for seasonal things...
And added my comments to its discussion page.

Honestly, the natural state of Lake Eyre is dry. And thats how we like it !

Naturally! With the occasional damp bit, and then the rarer wet bit.

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Re: how to tag a salt flat

David Bannon-2

Anyway, we agree that Lake Eyre does not fill seasonally, we agree it does fill intermittently (but maybe disagree on "full", not important). 

"seasonal" may be a good qualifier for a lake that depends on the seasons and responds to the season cycle most times around. But thats not intermittent IMHO. I don't think "intermittent" and "seasonal" go well together.

David

On 01/10/15 10:16, Warin wrote:
On 1/10/2015 8:49 AM, David Bannon wrote:


On 30/09/15 21:28, Warin wrote:
......
Well if you want to have lake Eyre 'qualify' for the tag 'intermittent'
.....
But if you want to see Lake Eyre full .. 'typically' that is once every 10 years or so...

So to me a full cycle of Lake Eyre in all its 'seasons' would be 'typically' 10 years.
Warin, I think you will find that Lake Eyre has only 'Filled' three times since (white man's) records have been kept, 150 years ? Its a very big place, when water flows in on those ten year cycles, it just gets a bit damp in one small corner, you could not say thats the defining cycle for the whole lake.

'Full' ... http://www.lakeeyrebasin.gov.au/about-basin/water  States the 'typical' inflows ...

And the yacht club has a graph of the water depth from 1975 ...  http://www.lakeeyreyc.com/fldhist.html


Does 'intermittent' still apply to a 50 or 100 year cycle ?

I would say YES!

I think the OSM wiki is wrong in putting the word "seasonal" as a qualifier to the tag intermittent!
Seasonal things should be tagged with the tag seasonal!
In fact I'll be brave and remove the  word! It was looks to be added by Chrabros  in April 2014..
So I have removed the word seasonal from the meaning of intermittent and added a 'common mistakes' section for seasonal things...
And added my comments to its discussion page.

Honestly, the natural state of Lake Eyre is dry. And thats how we like it !

Naturally! With the occasional damp bit, and then the rarer wet bit.


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Re: intermittent vs seasonal

Mateusz Konieczny-2
In reply to this post by Warin
On Thu, 1 Oct 2015 10:16:12 +1000
Warin <[hidden email]> wrote:

> > Does 'intermittent' still apply to a 50 or 100 year cycle ?
>
> I would say YES!
>
> I think the OSM wiki is wrong in putting the word "seasonal" as a
> qualifier to the tag intermittent!
> Seasonal things should be tagged with the tag seasonal!
> In fact I'll be brave and remove the  word! It was looks to be added
> by Chrabros <http://wiki.openstreetmap.org/wiki/User:Chrabros>  in
> April 2014.. So I have removed the word seasonal from the meaning of
> intermittent and added a 'common mistakes' section for seasonal
> things... And added my comments to its discussion page.

According to what I found "intermittent" is not excluding regular
changes - see for example "Intermittent streams flow seasonally in
response to snowmelt and/or elevated groundwater tables resulting from
increased periods of precipitation and/or decreased
evapotranspiration." from "Temporary streams" by Margaret Palmer, or
https://en.wikipedia.org/wiki/Perennial_stream " "Perennial" streams
are contrasted with "intermittent" streams which normally cease flowing
for weeks or months each year, and with "ephemeral" channels that flow
only for hours or days following rainfall." or
https://en.wikipedia.org/wiki/Stream#Intermittent_and_ephemeral_streams .

There is nothing wrong with adding both intermittent=yes and
seasonal=yes. Also, there is no good reason to break data consumers by
removing popular and correct intermittent=yes and adding a new tag
(seasonal=yes).

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Re: intermittent vs seasonal

Warin
On 1/10/2015 5:51 PM, Mateusz Konieczny wrote:
>
> According to what I found "intermittent" is not excluding regular
> changes - see for example "Intermittent streams flow seasonally in
> response to snowmelt and/or elevated groundwater tables resulting from
> increased periods of precipitation and/or decreased
> evapotranspiration." from "Temporary streams" by Margaret Palmer,

Meaning the streams ONLY flow sometimes and ONLY when there is snow melt /rain fall ..

So the two things combine to say ..

if there is snow melt or rainfall

then there MIGHT be water in the stream.

To me that is not seasonal.. unless you can say that the rain and snow only falls in given parts of the year and at no other time?

Given the weather does not conform that well to the 'season's .. I'd be more inclined to leave off the seasonal tag.



>  
>
> There is nothing wrong with adding both intermittent=yes and
> seasonal=yes.

intermittent= irregular = not regular.

seasonal= regular.

To say that something is both 'not regular' and 'regular' is a conflict. And should be resolved,

For me I would simply tag something that is irregular intermittent=yes, and leave out the seasonal.
 
If it 'typically' flows seasonally then don't use intermittent, use seasonal=yes(winter,summer etc)!

Using your above snow melt example .. does snow not fall out of season occasionally? And then the stream would flow out of season too.


>   Also, there is no good reason to break data consumers by
> removing popular and correct intermittent=yes and adding a new tag
> (seasonal=yes).

seasonal is an existing tag. And should be used to mark things that are regular on a yearly scale.

The intermittent tag should NOT be used for things that are seasonal.

We should tag the truth. That is what the consumers expect.

==========================
Note that this came about because someone took intermittent to mean it happened on a regular yearly basis.. and that is wrong.



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Re: intermittent vs seasonal

Warin
 Mateusz Konieczny has reverted the changes I made to the wiki page ...

It again now says that irregular=regular.

Thanks ... black=white too.

--------------------------------------------------
Tell us .. what tag would you use for a stream that flows randomly .. say on average once every 3 years ?
Of course it may not flow for 20 years, then flow 5 times that year. Randomly.

Cannot use intermittent due to your definition... not a yearly (seasonal) flow.

Well?

From the web meaning of
intermittent;
occurring at irregular intervals; not continuous or steady.

synonyms:sporadic, irregular, fitful, spasmodic, broken, fragmentary, discontinuous, isolated, random, patchy, scattered;

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Re: intermittent vs seasonal

Mateusz Konieczny-2
On Thu, 1 Oct 2015 21:52:11 +1000
Warin <[hidden email]> wrote:

> It again now says that irregular=regular.
>
> Thanks ... black=white too.

Where?

> Tell us .. what tag would you use for a stream that flows randomly ..
> say on average once every 3 years ?
> Of course it may not flow for 20 years, then flow 5 times that year.
> Randomly.
>
> Cannot use intermittent due to your definition... not a yearly
> (seasonal) flow.

I thought that "The tag intermittent=yes is used to indicate that a
waterway (river, stream, etc.) does not have a permanent flow" is quite
clear but apparently it needs to be simplified. Can somebody help in
finding more understandable definition?

Maybe current definition should be changed but clearly at least some
consider seasonal waterways and water bodies to be intermittent
(including scientists publishing what seems to be reputable sources).

Changing definition of established tag requires really strong
justification that it is a good idea.

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Re: intermittent vs seasonal

Mateusz Konieczny-2
In reply to this post by Warin
On Thu, 1 Oct 2015 21:03:15 +1000
Warin <[hidden email]> wrote:

> On 1/10/2015 5:51 PM, Mateusz Konieczny wrote:
> >
> > According to what I found "intermittent" is not excluding regular
> > changes - see for example "Intermittent streams flow seasonally in
> > response to snowmelt and/or elevated groundwater tables resulting
> > from increased periods of precipitation and/or decreased
> > evapotranspiration." from "Temporary streams" by Margaret Palmer,
>
> Meaning the streams ONLY flow sometimes and ONLY when there is snow
> melt /rain fall ..
>
> So the two things combine to say ..
>
> if there is snow melt or rainfall
>
> then there MIGHT be water in the stream.
>
> To me that is not seasonal..

I am not sure how it is a problem, because it is definition of
intermittent waterway.

> unless you can say that the rain and
> snow only falls in given parts of the year and at no other time?

That is one of cases where waterway is intermittent and seasonal.

> Given the weather does not conform that well to the 'season's .. I'd
> be more inclined to leave off the seasonal tag.

It depends on location.

> > There is nothing wrong with adding both intermittent=yes and
> > seasonal=yes.
>
> intermittent= irregular = not regular.
>
> seasonal= regular.

According to your second mail one of synonyms of intermittent is also
"periodic". It is not 1:1 mapping, especially as "intermittent"
appears to have a defined meaning in hydrology.

> For me I would simply tag something that is irregular
> intermittent=yes, and leave out the seasonal.
> If it 'typically' flows seasonally then don't use intermittent, use
> seasonal=yes(winter,summer etc)!

Why not use both in cases of waterways that are not permanently
filled with water? To make it harder to use data?

> Using your above snow melt example .. does snow not fall out of
> season occasionally?

Depends on location.

> >   Also, there is no good reason to break data consumers by
> > removing popular and correct intermittent=yes and adding a new tag
> > (seasonal=yes).
>
> seasonal is an existing tag. And should be used to mark things that
> are regular on a yearly scale.

I am not protesting adding seasonal=yes, I am protesting removing
correct intermittent=yes tags.

> The intermittent tag should NOT be used for things that are seasonal.

And it should be used for things that are both seasonal and
intermittent.

> We should tag the truth. That is what the consumers expect.

Yes. I am also not aware about anybody disputing this.

> Note that this came about because someone took intermittent to mean
> it happened on a regular yearly basis.. and that is wrong.

Yes. This is clearly wrong.

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Re: intermittent vs seasonal

John Willis
In reply to this post by Mateusz Konieczny-2

Intermittant= is present irregularly. Larger objects tend to exist for longer than smaller objects. Smaller objects usually appear and reappear more frequently, but this frequency, overall is random.

Seasonal = present only during a certain time or times on the yearly cycle of the earth's journey around the sun.  Possibly driven by human choice, but those choices are driven by the seasonal cycle.


Intermittent means randomly. It may be more often in one season or another - but at some point the feature randomly exists or doest exist. This is good for lakes and other "sometimes there, sometimes not" features, as long as one state persists long enough to be noticed  /used - An intermittent like or river may be present for days or weeks, perhaps months. The water in a wadi or wash may only be present for a few hours and then dry the rest of the year, so it is not an intermittent river - it uses a tag for the more permanent state (wadi). Natural salt flats (that are nor marshes or covering a mushy liquid underneath) might also be similar.

A seasonal item appears and disappears according to some yearly based cycle (the seasons) - usually due to cyclical and repeating climate changes brought about by the earth's journey around the sun, not geologic (ice ages) or long term climate processes (el nino, global warming etc). A lake with water once every 3 years is intermittent at best. But if it is a lake for 3 months and used as a lake, then it is an intermittent lake.

The salt flats in Death Valley every 10 years or so get a few inches of water to smooth out the salt, and is gone very quickly. It isn't a lake, its a salt flat. Only an extraordinary storm causes it to be wet for very long.

A lake that forms during the rainy season in the summer in Japan, a lake that appears from rain in the desert in winter, a stream from snowmelt runoff in summer, etc are all seasonal. The rest of the year they are usually dry or gone, but during a useful/noticeable amount of time during a repeating time(s) every year (there are two rainy seasons in some places), they exist and are there - every season. (Hence seasonal)

Cyclical =/= seasonal. Seasonal is somehow linked to the 1 year earth-sun cycle, like our caleander and our concept of "the 4 seasons" - where we get the word.

El ninos and other things are linked to other cycles (sunspots, etc) or follow longer climate cycles - but those cycles are not part of nor implied in the word "seasonal".

Javbw

> On Oct 1, 2015, at 9:58 PM, Mateusz Konieczny <[hidden email]> wrote:
>
> On Thu, 1 Oct 2015 21:52:11 +1000
> Warin <[hidden email]> wrote:
>
>> It again now says that irregular=regular.
>>
>> Thanks ... black=white too.
>
> Where?
>
>> Tell us .. what tag would you use for a stream that flows randomly ..
>> say on average once every 3 years ?
>> Of course it may not flow for 20 years, then flow 5 times that year.
>> Randomly.
>>
>> Cannot use intermittent due to your definition... not a yearly
>> (seasonal) flow.
>
> I thought that "The tag intermittent=yes is used to indicate that a
> waterway (river, stream, etc.) does not have a permanent flow" is quite
> clear but apparently it needs to be simplified. Can somebody help in
> finding more understandable definition?
>
> Maybe current definition should be changed but clearly at least some
> consider seasonal waterways and water bodies to be intermittent
> (including scientists publishing what seems to be reputable sources).
>
> Changing definition of established tag requires really strong
> justification that it is a good idea.
>
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