ABSTRACT
An alternative method of precipitation modification is to supply the rain artificially at ground level by means of the sprinkler equipment. This method is used most commonly for crop irrigation in areas of supplemental irrigation or in arid and semi-arid areas with a highly capitalized agriculture. Since precipitation is the principal input into the hydrological cycle, man’s attempts to modify it will have consequences throughout the working of the cycle. Besides rain-making, other human interventions in precipitation involve the successful local dissipation of freezing fogs over airports by spraying with propane gas, brine, or dry ice, causing snow to fall and clear the air. An increase of the November-April precipitation by 15% over 14,200 square miles of target areas is expected to yield an average additional runoff of 1,870,000 acre-feet annually. Most precipitation comes in a few big storms, and since these storms are the main precipitation generators, it is important to take advantage of the limited opportunities they offer.
