24
in surface streams and being evaporated and transpired cannot be regarded as having been rejected by the aquifer. One could not expect, then, to induce much additional recharge merely by pumping. Additional recharge can be effected only by causing more water to pass through the water-tight blanket. This might be done by drilling artificial-recharge wells, through which surplus water may be diverted from the land surface into the aquifer.
Aquifer Functions as a System of Pipelines
One attractive feature of the artesian water, and of ground water in general, is its proximity to places where water is in demand. Generally, the isolated rural dweller, the farmer, the city or industry needs only to drill a few hundred feet to obtain an adequate supply. The aquifer through which the artesian water moves is a natural conduit, a distribution system reaching almost everywhere in the region. From where it enters the aquifer the water may travel long distances, commonly 50 miles and more, to where it is withdrawn for use. Not only does it move to the very premises of the consumers-over a large part of the State it is delivered under artesian pressure, so that the consumers are saved the expense of pumping.
We have learned the general directions in which the water moves by mapping the height of water levels in many wells
FIGURE 15.-Recharge through sinkhole.
Limestone is slightly soluble in water and gradually dissolves as water moves through it. Over the ages this process of solution creates large caverns, and forever enlarges them until ultimately they collapse under the load of rock and earth above. Collapse of a cavern causes the overlying material to subside, and so breaches the watertight blanket that confines the aquifer. Water from the land surface and in the thin sandy mantle then has a portal through which it may drain into the aquifer.