Emily Zehner, age 10, of Selman, Okla., for her question:

HOW DOES WATER GET UNDERGROUND?

Ground water is water held beneath the surface of the earth. It is usually pure and is one of the best sources of water for man's use. There are three kinds of ground water: meteoric water, juvenile water and connate water.

Meteoric water makes up most of the 2 million cubic miles of ground water in the earth. This water filters through the soil after a rain seeps into the ground from lakes and rivers.

Juvenile water is formed through a chemical process in rocks deep in the earth, while connate water is a salt water trapped in rocks yrhen the rocks were laid down in ancient seas.

When underground water meets the surface, ground water flows openly in springs and streams. It may also form lakes or water holes.