Lake Poopó is the second largest lake in west-central Bolivia, south of the largest lake: Lake Titicaca. It is 12,090 feet above sea level in a shallow depression on a high plateau, the Altiplano, which is filled with sediment.. Although it is about 56 miles long and covers 977 square miles, it is only about 8-10 feet deep and is never deeper than 15 feet.

The lake is fed by the Desaguadero and Márquez rivers and when it floods, the lake overflows into the Coipasa Salt Flat. The only known outlet is the Lacajahuira River and due to large amounts of evaporation, the lake has a very high salt content. Since the water filters into the land around the shore, the land around the lake is marshy and few people live there.

Sources:
http://www.eb.com
http://www.to-scorpio.com/earth0162b.htm