GROUND-WATER INVESTIGATIONS—SAYRE 223 
Various other Federal and State agencies are obtaining some data on 
ground water in connection with special phases of their work. 
The ground-water investigations of the United States Geological 
Survey began more than 50 years ago. At that time ground-water 
supplies were little developed. Consequently, most of the early field 
investigations were of the exploratory type. Laboratory and field 
studies by King, Slichter, and later by Meinzer outlined the broad 
principles of ground-water occurrence and movement. However, 
before the deep-well turbine pump was developed in the early part of 
this century, use of ground water in large quantities was limited to 
areas of springs or artesian flow, or to areas where the water level was 
within reach of suction pumps. After the turbine pump was intro- 
duced, it became possible to pump economically even where water 
levels are deep; power costs also decreased, and well drilling and finish- 
ing methods were improved to increase the efficiency of wells. Because 
of these advances, ground water came to be used in ever-increasing 
quantities, first in areas where surface water was not readily available, 
and later in areas where ground-water supplies were more economical 
because they obviated the long pipe lines, collection works, and costly 
treating plants needed for surface-water supplies. ‘The first great 
expansion of ground-water supplies was made largely without technical 
guidance. Because of their immense storage capacity, the ground- 
water reservoirs were regarded as inexhaustible, and in many places 
development was well advanced before progressively declining water 
levels brought about the realization that ground-water reservoirs may 
be depleted. As a result, demands for detailed ground-water studies 
steadily increased. These studies are thorough, systematic investiga- 
tions which include areal geologic mapping; subsurface studies occa- 
sionally augmented by geophysical surveys and test drilling to deter- 
mine the structure, thickness, and the sequence of water-bearing and 
non-water-bearing beds; collecting data on fluctuations of water levels 
in relation to precipitation and to pumpage; determining the recharge 
and perennial yield; inventories of ground-water withdrawal; test 
pumping to determine coefficients of permeability, transmissibility, 
and storage; determining the quality and temperature relationships, 
and the relations between surface and ground water. The work does 
not include supervision, construction, or control of water supplies. 
The United States Geological Survey is now making cooperative 
ground-water investigations in 42 States and in Alaska, Hawaii, the 
Virgin Islands, and Puerto Rico. In general, the State or local 
authorities are most familiar with the needs in their States, and they 
are largely responsible for designating the areas in which investigations 
are to be made. Most of the ground-water staff of the United States 
Geological Survey now have headquarters in field offices, of which 
there are about 40. 
