150 
FLORIDA STATE GEOLOGICAL SURVEY. 
numbered chronologically in the order of the date when com¬ 
pleted. 
This table shows conclusively that, although the rate of flow 
is variable for different wells and for the same wells at different 
periods, yet in this group of wells there is a continuous and 
progressive loss of flow. That the same is true of other wells 
throughout this area, there can be no reasonable doubt. Those 
who give no special attention to their wells suppose, as a rule, 
that the.flow remains unaffected indefinitely. Many other well 
owners, however, have observed this loss in flow with succeed¬ 
ing years. The reduced flow is best observed near the margin 
of the flowing area in wells located on somewhat elevated ground. 
Many of the wells from which the water will flow only a few 
feet above the surface when first drilled may, in time, cease to 
flow. In these cases the pressure which originally caused the 
flow having been partly relieved, the water no longer rises above 
the surface of the ground. 
Exhaustion and ultimate failure of an artesian reservoir is 
not unknown. It is, probably, true that, in nearly all artesian 
sections, the original pressure gradient in the water-bearing rock 
is appreciably lowered by the drafts made upon the subterranean 
supply, with a consequent actual decrease in the capacity of the 
wells. In this connection, Professor C. S. Slichter states :* “It 
must be kept well in mind that there is a limit to the amount of 
water that can be withdrawn from an artesian basin. There is 
no such thing as an inexhaustible supply in this connection. The 
amount of water available is limited on the one hand by the 
amount of rainfall upon the catchment area, and the facility with 
which the rainfall can obtain entrance to the porous stratum and, 
oh the other hand, by the capacity of the water-bearing rock to 
transmit the water over long distances and diminution through 
leakage and seepage. These two limiting conditions are usually 
of sufficient magnitude to render the overdrawing of the supply 
a practical and present danger, which should be constantly kept 
in mind.” 
With regard to the artesian basin at Denver, Colorado, the 
*U. S. Geol. Surv., Water Supply Paper, No. 67, p. 94, 95, 1902. 
