The source of water derived from wells— Essential factors controlling the response of an aquifer to development

The paper presented herewith, as a Ground Water Note, was first published by the American Society of Civil Engineers in its Civil Engineering magazine (p. 277-280) for May 1940. A number of years ago the Ground Water Branch reprinted the paper in limited quantity for distribution to the field offices and some field personnel. The original paper is faithfully reproduced herein, except for minor changes in notation to conform with current Branch usage.

Theis’ extremely lucid discussion of the source of water discharged by wells should be clearly understood by all who would attempt to analyze how a preexisting balanced hydraulic system will adjust to newly imposed well discharge.