WATER SUPPLY OP PASTERN AND SOUTHERN PEORIDA. 131 
saturated. The evaporation at this time is slow, and the part 
returned to the atmosphere directly from the land is an almost 
negligible amount. This is especially true of a soil into which the 
water enters quickly. Some of the water clinging to the leaves 
of plants is re-evaporated, as well as a part of that which falls 
into lakes, ponds and temporary pools. While an estimate of the 
amount evaporated must be regarded as only in the roughest way 
approximate, yet it is probably safe to assume that not more than 
two or three per cent, of the total rainfall is returned to the 
atmosphere by direct evaporation without having entered the 
earth. 
(2) SURFACE RUN-OFF-. 
The relative proportion between the surface run-off and the 
surface in-take of water is dependent upon the character of the 
surface and the deeper formations and upon the topography. The 
former affects rapidity of in-take of water into the earth; the 
latter the rapidity of surface run-off. 
With regard to topography Peninsular Florida is either flat 
or rolling. Rarely can a locality within this section be described 
as hilly. The elevation increases gradually from sea level at the 
coast to a maximum of scarcely more than 200 feet inland, while 
large sections are so flat as to present no perceptible slope. Top¬ 
ographically the conditions are, therefore, very unfavorable to 
surface run-off. On the other hand, the conditions are exception¬ 
ally favorable to large surface in-take. The soils are sandy and 
receive and store the rainfall with great readiness. 
(3) RAINFALL ENTERING THE EARTH. 
Of the water which enters the earth, a part is ultimately 
returned to the atmosphere by evaporation. The water retained in 
soils is slowly given up through evaporation during dry weather. 
As the evaporation takes place near the surface, the capillary 
attraction draws a new supply from beneath, thus maintaining to 
some extent the moisture content of the soil. The amount of water 
thus brought to the surface and evaporated, while varying with 
climate and with soils, is, in the course of a year, considerable. 
