[Talk-us] Shorelines of highly variable lakes

Alexander Roalter alex at roalter.it
Fri Jun 29 21:16:27 BST 2012

On 06/29/2012 09:22 PM, James Umbanhowar wrote:
> I have just had a correspondence with another mapper who was remapping
> Lake Mead shorelines to match new imagery.  Due to a multi-year drought,
> Lake Mead and other reservoirs in the west have had significantly
> declining water levels.  However, the lake levels could increase
> dramatically if there were a couple of years of normal/high water.
> Alternately, Devil's Lake in North Dakota has had many years of
> increasing water levels as the closed basin it drains has had relatively
> high precipitation.
> The question I have for y'all is do we have any recommendations for how
> to map these?  For the reservoirs, I think that one could make an
> argument for mapping the full level and tagging it with landuse
> reservoir (which is rendered as water), but is there any value in
> drawing lower lake levels if they persist for many years?  Would it be
> useful to date the imagery/ survey date used for the shoreline?

Although this answer probably won't help you much, I'd much like to see 
it like it is done on some maps with lake Aral, where the 1970's 
shoreline is shown in a lightblue outline (and a small text by it). But 
that's a renderer thing, and I'm at a loss to find a tag for it.

It could then look something like these two images:

As far as I know, with OSM the shoreline should be drawn at the highest 
point/high tide (see 
http://wiki.openstreetmap.org/wiki/Tag:waterway%3Driverbank, under 
Varying water level)


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