Aerial Application of Evaporation-Reducing Chemicals, Development and Evaluation of Equipment and Techniques

Aerial applications of both liquid and powder evaporation retardants have been made in parallel strips on large lakes for purposes of comparison. Films formed from powder spread more rapidly than did those from liquid, but usually both films ultimately spread to approximately equal widths and had the same degree of compression as determined with indicator oils. Evaporation retarding materials with large numbers of particles having diameters smaller than 75 microns are greatly affected by the wind. As the chemical is dispensed from the airplane. the fine particles drift with the wind and in some instances are carried onto the land areas surrounding the lakes. Materials with extra large particles are less affected by wind but are not as effective for film formation. Powders and sprays having mean particle diameters between 75 and 200 microns appear to be desirable for aerial applications.