The Kara-Bogaz-Gol (KBG) is a large, shallow lagoon of the Caspian Sea. It normally covers about 18,000 square kilometers and is just a few meters deep. The Caspian Sea is the largest inland body of water in the world, often categorized as a large salt lake. It is salty because rivers (especially the Volga) flow into it, but none flow out. Water leaves only through evaporation, and the dissolved salts remain.
The Caspian is below sea level, and the KBG is 2–3 meters lower, so water flows from the Caspian through a narrow strait into the KBG, where it evaporates. The KBG is far saltier than the Caspian, and is one of the saltiest bodies of water in the world. Its salinity is 300–350 parts per thousand, while the Caspian’s is about 13 parts per thousand. (The ocean’s salinity averages about 35 parts per thousand.) Since the KBG’s water flows in from the Caspian, the Caspian’s fluctuations affect the KBG.
In 1980, the Soviets dammed the Caspian-KBG strait. The Soviets intended that some water would remain in the KBG, enough to keep the salt industry operating. It was believed that even without inflow from the Caspian, the existing water might last up to 25 years.
But by November 1983, the KBG had entirely dried up. In the spring of 1992 after the Soviet Union broke up, President Sapamurat Niyazov of Turkmenistan took a spade to the dam to symbolically begin its demolition. After the demolition of the dam, the KBG soon filled, and its level has remained stable.
In these images, you can see the difference in color between the Caspian to the west and the KBG to the east. Pure water absorbs light from the sun, but the KBG water has suspended solids (including precipitated salt) that reflect more light. The KBG is also shallow, so the bottom is reflecting some light back through the water. Dry or shallowly covered salt beds appear white because they are highly reflective. Also notice the general absence in these images of bright red, which would represent vegetation.