Sprinklers have been used increasingly to irrigate agricultural land. Little or no preparation is needed, application rates can be controlled, and the system may be used for frost protection and the application of chemicals, such as pesticides, herbicides, and fertilizers. Sprinklers range from those that apply water in the form of a mist to those that apply an inch or more per hour. Various techniques have been tried to reduce losses of irrigation water. Two major sources of loss, particularly from surface supplies and surface systems, are evaporation and seepage from reservoirs and canals. Many studies have been made of techniques to suppress evaporation. One of the more promising appears to be application of a special alcohol film on the surface, which retards evaporation by about 30 percent and does not reduce the quality of the water. The primary problem in its use is that it is fragile; a strong wind can blow it apart and expose the water to evaporation. Seepage has largely been controlled by lining main and distribution channels with impervious material, typically concrete. Other materials used are asphalt and plastic film, though plastic tends to deteriorate if it is exposed to sunlight.