Don’t look now, but your lake is leaking!

Did you know that lakes leak? Usually, that’s nothing to worry about. It’s normal for water to seep past the rock and sediment that form a lake’s basin. It’s also normal for lakes to be affected by evaporation—water getting drawn up into the sky by the heat of the sun. Have you ever wondered how, with all this leaking and evaporating, lakes hold any water at all?

The answer is simple. Lakes keep getting refills! Rain keeps falling. Ice keeps melting. Streams and groundwater keep flowing into lakes. Thanks to all that, lakes stay full.But they are not always full of the same kind of water. There are two kinds of lakes: open lakes and closed lakes. In an open lake, water moves out of the lake in streams. Water stays in open lakes just a little while before moving on. It stays fresh because it keeps moving.But no streams move out of closed lakes. The water in a closed lake can only leak out or get sucked up by the sun. During evaporation, the sun takes the water, but leaves bits of salt behind. This is how closed lakes—including Lake Poopó—get so salty. Some closed lakes, like the Dead Sea in Israel, have grown so salty that no animals can live in their waters!