Proposal:Dry lake

Dry lakes
Proposal status:	Draft (under way)
Proposed by:	Pwhite119
Tagging:	natural=dry_lake
Applies to:
Definition:	An area of flat, dried-up land that is almost always dry, but rarely fills with water creating a very shallow lake. Found in desert climates.
Statistics:
Rendered as:	Pale beige, slightly lighter than how sand is rendered, with dot pattern?
Draft started:	2020-07-31

Proposal

Dry lakes, also known as playas, salt flats, salt pans, alkali flats, and endorheic basins/lakes, are natural basins or depressions that seldom contain water.

Rationale

They are large and distinct features that are important to the desert ecosystem, distinct from natural=water+intermittent=yes because they are almost never wet, filling with water for only a few days a year or less.

Examples

• 

  Chott el Djerid in Tunisia

• 

  Groom Lake with Papoose Lake dry lake also visible at lower right, Nevada, USA

• 

  Lunar Lake, Nevada, USA

Tagging

Draw an area around the dry lake and tag with natural=dry_lake. Subtags:

• dry_lake=salt for salt flats
• dry_lake=alkali for alkali flats

Comparison to similar landforms

Dry lakes in arid climates may take any of several forms and may exist on a continuum from wet to dry. The perennial or seasonal presence of standing water or saturated soil (mud) distinguishes the various types of features.

• If a lake bed is entirely covered with standing water (other than rare periods of drought), it is a lake or pond and should be tagged using natural=water + water=lake or water=pond.
• If a lake bed is mostly covered with standing water during wet seasons and partially covered with standing water, muddy, or dry during dry seasons in typical years (i.e. other than extremely wet or dry years), it is an intermittent lake or pond and should be tagged with natural=water + water=lake or water=pond + intermittent=yes.
• If a lake bed is perennially saturated with water but rarely has areas of standing water (i.e., only in extremely wet years), or if standing water quickly disappears due to evaporation or drainage, it may be tagged with natural=mud.
• If a lake bed is seasonally saturated with water and is otherwise dry, and rarely has areas of standing water (i.e., only in extremely wet years), or if standing water quickly disappears due to evaporation or drainage, it may be tagged with natural=mud + intermittent=yes.
• If a lake bed is normally dry and is never or rarely (i.e., only in extremely wet years) covered in standing water or saturated enough to be mud, and if any standing water or mud quickly disappears due to evaporation or drainage, it is a dry lake and should be tagged with natural=dry_lake + dry_lake=salt or dry_lake=alkali.

Caution! The differences between muddy lake beds and dry lake beds may be difficult to distinguish from aerial imagery alone. Mappers should use local knowledge or information from reliable sources to make the distinction between natural=mud and natural=dry_lake.

If any area accumulates a surface crust of minerals, it may be tagged with surface=salt or surface=soda (for alkali flats).

Lake beds of any type do not have substantial amounts of vegetation and are either covered in bare soil or standing water. For areas that are covered with vegetation, consider using natural=wetland + wetland=* instead.

For normally dry areas adjacent to perennial bodies of water that accumulate a mineral crust from occasional flooding, consider using natural=water + intermittent=yes + surface=salt instead.

Impacts of climate change

As our climate changes, normal weather patterns may change and areas may become wetter or drier than they have previously been. Extreme weather events such as flooding and droughts may become more frequent. These changes may affect the amount of water in natural lake beds. Rather than using a single season or year to determine the nature of a lake bed, consider the history of the area over the past several years.

Climate change may affect our perceptions of what "normal" seasons and years are like. For the distinctions described above, a "rare" or "extreme" event could be something that has not happened more than once in the last ten years.

Applies to

Areas

Rendering

Pale beige, slightly lighter than how sand is rendered, with dot pattern?

External discussions

Playa versus playa lake versus sabkha Science Direct

Comments

Please comment on the discussion page.