onsdag 26. juni 2013

WoGE #385

And yet another WoGE.

After finding Wogelix' wonderfully geology-rich little area of Schwäbische Alb, it seems to be my turn again.

This picture comes with a lot fewer clues, and is really a classic WoGE since it is obviously in a desert somewhere.

There is something unusual with the water here. What is it, and what  is the (or "an") explanation for it?

It's time for a "limited Schott":
Schott's Rule requires waiting one hour before answering for each previous WoGE win. A limited Schott requires waiting two hours for each win in the last 20 rounds.

9 kommentarer:

  1. Maybe a hint could be useful, but there aren't any hints I can give except one: This is the first WoGE in this country.

  2. The general direction of the winds in the picture is also useful.

  3. Wind direction, and the fact that it actually TURNS in this picture. But that ought to be clear from the picture, so I didn't count that as a possible hint. ;)

  4. I found it!
    18º56´N 20º52'E (http://goo.gl/maps/Wh8Fz) in Chad!
    Give me a couple of minutes and I'll be back with the (hidro)geology!

  5. The Saharan lakes of Ounianga Serir – a unique hydrological system - an UNESCO World Heritage site (2012).
    "The Ounianga lakes are almost exclusively fed by permanent groundwater outflow from a regional aquifer that was recharged for the last time during the early Holocene humid phase and that continuously replaces the immense evaporation losses" and the "mere existence of these lakes is amazing in a practically rainless region with annual evaporation rates exceeding six meters".
    The sand dunes have subdivided the once continuous freshwater lake into some 10/15 separate lakes.
    The central lake, Lake Teli, suffers most of the evaporation since all the others have a thick mat of floating reeds which maintains the water levels in Teli because freshwater is drawn from the more elevated peripheral lakes (and ... from the regional aquifer) through the permeable dune barriers.
    It's importance isn't all geologic, these Ounianga lakes have a biological (a few endemic species), paleoclimatical (the savannah/desert transformation) and archaeological (the human migrations) importance (and limnological, hydrological, paleontological...).
    The hydrological system of the lakes of Ounianga Serir, in conjunction with the reed cover and the regional aquifer is responsible for the formation of the largest freshwater lake ecosystem in a hyper arid area.
    Refs: - (primarily) http://www.uni-koeln.de/sfb389/sonstiges/kroepelin/239%202007%20Atlas%20Kroepelin%20Ounianga%20Serir.pdf;
    - http://whc.unesco.org/archive/2012/whc12-36com-8B2inf-en.pdf and;
    - http://en.wikipedia.org/wiki/Lakes_of_Ounianga.

  6. Congratulations on winning this round, Luis!

    Not only is a freshwater lake in the middle of a desert a very unusual thing to find, but the sequential increase in salinity from the edges to the center lake makes it an even more interesting place.

    The Great Nubian Aquifer is slowly being depleted, not only by natural evaporation but also by extensive use of water for irrigation. The Ounianga lakes are in no immediate danger, but the water is a finite resource.

    Now I wonder what place you will find for us to find. ;)

  7. I'm planning to publish #386 in (about) 20H!

  8. Here it is: http://woge-luis.blogspot.pt/2013/07/woge-386.html

  9. Just after posting this, I thought that the picture looked somewhat familiar. So I put it into Google image search, and got an immediate hit! First on the list was this: http://fr.wikipedia.org/wiki/Lac_Teli - French Wikipedia listing on the central lake. Complete with map location...