The Mysterious Lakes in Badain Jaran Desert located in China and Mongolia
Yesterday I got the opportunity to participate in the Boussinesq Lecture in Amsterdam. I would like to highlight one of the subjects of a presentation from Yijian Zeng concerning mysterious lakes within the Badain Jaran Desert (the name stands for mysterious lake in the Mongolian language). It is a remarkable occurrence seen the low amounts of annual rainfall and the fact it is simply a desert. I elaborated some information from this presentation combined with information found on the internet. Hereby I would like to share with you a short overview.
Badain Jaran Desert
The Badain Jaran (BJ) Desert is the third largest desert of China with a size of 49.000 km2. Although presumingly not a lot of people are familiar with this desert, it is known for having the tallest stationary dunes on earth. It has an extreme continental climate with an annual precipitation of less than 90 mm where potential evaporation counts for 2500 mm.
Despite the extremely low rainfall quantities, one process is quite remarkably: the existence of the so-called mysterious lakes within the desert. The BJ desert contains more than 140 lakes, of which the most occur in the southeast. You can find impressive figures on the internet. Lakes contain salt water with a highly varying concentration. The salinization through time is caused by the high evaporation. Some lakes even became covered by sand dunes.
Lakes within the desert
There are two types of lakes with regard to their morphometry. Elongated shallow lakes appear in the compound star megadune area in the southeastern margin of the desert. Their depth is less than 2 m, and their size less than 0.2 km2. Oval-shaped, deep lakes prevail in the compound transverse megadune area. Their maximum depth reaches 15 m, and their maximum size attains 1.5 km2. The lake water is saline. The shallow lakes at the southeastern margin of the desert have a low salt concentration, less than 20 g/l, while the others show higher salt concentrations, up to 334 g/l. Most lakes are surrounded by meadow or shrubs about 1 m high.
Combination with the high dunes
Subsaline and fresh water allows the development of fixed dunes. These dunes are replaced by semi-fixed and migrating dunes as the distance to the lake increases. In several saline lakes, small travertine islands, with fresh spring water, are found. The areas of the interdune lakes or basins are controlled by the scale of the megadunes. The base area of the megadunes and those of the interdune basins are linearly related.
What caused the forming of these oases?
The deserts in the arid regions of China are usually surrounded by high mountains that provide the water, this is also here the case. Water collected from the mountains flows under the gravel deposits on the slope as concealed ground water and exits at lower elevations where the deposits become fine-grained and the water flow is blocked. The amount of emerging ground water in the Tarim Basin, Jungger Basin and Hexi Corridor is sufficient to form oases. There are many oases in the basins because the snow and ice cover on the surrounding mountains provides lots of water.
Most of the information above is taken from:
Dong, Z., Wang, T., & Wang, X. (2003). Geomorphology of the megadunes in the Badain Jaran Desert. Geomorphology , 191-203.