Rainmaking, also known as artificial precipitation or artificial rainfall, is the act of attempting to artificially induce or increase precipitation, usually to stave off drought. According to the clouds' different physical properties, this can be done using airplanes or rockets to sow to the clouds with catalysts such as dry ice, silver iodide and salt powder, to make clouds rain or increase precipitation, to remove or mitigate farmland drought, to increase reservoir irrigation water or water supply capacity, or to increase water levels for power generation.