INTRODUCTION

In 1939 the Geological Survey, U. S. Department of the Interior undertook a thorough investigation of the water resources of southeastern Florida, with special reference to the water supplies of Dade County, Miami, Miami Beach and Coral Gables. The investigation was made with the financial support of these cities and of Dade County, and was requested because of the appearance of salty water in the Miami well field, adjacent to the Miami Canal, about six and one-half miles inland from Biscayne Bay. The objectives of the study were sufficiently broad to include an evaluation of all the water resources of southeastern Florida with emphasis on those supplies practicable of development for municipal use in the Miami area.
In order to carry out the investigation effectively, it waa necessary to obtain basic geologic, hydrologic, and chemical data. Specifically, it was necessary to determine the depth, thickness, and areal extent of the water-bearing rock formations; the capacity of these formations to transmit and yield water; the areas and rates of recharge and discharge, the quality and quantity of water in the different parts of the water-bearing rocks; the source and approximate rate of movement of salt water at all depths in the water-bearing rocks, factors controlling salt-water encroachment; the height of the water table and the direction of flow of the ground water at different times of the year; the stage and discharge of the canals throughout the year; the periods when the canals drained the nearby land areas and when they fed water to these areas; and the approximate quantities of water involved.
More than 60 exploratory test wells were drilled in order to obtain data on the geology and hydrology of the formations penetrated. One well was 812 feet deep, one 6oI4 feet deep and the rest ranged between 20 and 350