Water and the Southwest

In a pluvial period associated with Wisconsin glaciation the closed basin of the Estancia valley in New Mexico held a lake which, at its maximum extent, was 150 feet deep and had a surface area of 450 square miles. This basin, with an elevation of about 6,000 feet, has at present an annual precipitation of about 16 inches.

Estimates have been made of the Pleistocene precipitation necessary to maintain this pluvial lake. Instead of the present annual average of 14 inches, it has been variously estimated that the precipitation must have been 20 to 24 inches. Lakes existed during Pleistocene time in many places in Western United States which are now true deserts. There is evidence in many places in this area that early man lived on the shores of these lakes. He must have adapted himself to the increasing aridity. Some of the forms of this adaptation can be seen even at present in the form of flood-water farming practices highly developed by the Hopi Indians.