32 REPORT OF INVESTIGATIONS No. 50
mineralization, butbecause of adequate flushing during-the rainy season it is used successfully.
INDUSTRIAL USE
Water quality requirements for industry are so varied that it is impossible to set standards to meet the demands of all users. For some purposes, such as cooling, water of poor quality is often used when better quality water is not available. Water for some processes and for use in high-pressure steam boilers must approach the quality of distilled water. In general, most industrial water should be low in dissolved solids, soft, uniform in quality and temperature, and noncorrosive. Table 6 gives the quality requirements for several selected industries. The greatest industrial use of water in Orange County is for citrus processing and canning. (See section on use of water.) With a minimum of treatment most of the water in the county is suitable for most industrial uses.
SURFACE WATER
OCCURRENCE AND MOVEMENT
Most of the surface water in Orange County is from rain within the county, but some flows into the county from adjacent areas of higher elevation. Some of the streams that provide water, such as the St. Johns River, also drain parts of Orange County.
The amount of water on the land surface is determined by climate, geology, and topography. Only part of the rainfall remains on the surface long enough to be useful. Losses by evaporation and infiltration begin immediately and continue indefinitely unless the supply becomes exhausted. Some of the water that infiltrates into the soil and to the aquifers returns to the surface as seepage or as spring flow into lakes and streams. The part of the rain that doesn't evaporate or infiltrate collects in topographic depressions to form lakes, swamps, and marshes, or enters a stream channel and flows out of the county.
It is estimated that about 70 percent of the rain that falls on Orange County returns to the atmosphere by evaporation and transpiration, about 20 percent flows out of the county in streams and about 10 percent flows out underground.