In 1952, a U.S. patent for a "Self-Propelled Sprinkling Irrigating Apparatus" was issued to Frank L. Zybach of Strasburg, Colorado (No. 2,604,359). A centre-pivoted pipe supported on a series of water-piston-powered wheels rotates and sprinkles water on the crops.A control system ensures that each wheel advances at the correct rate. This is the now-familiar centre-pivot machine that waters large circles of crops in those areas of a country which have limited rainfall but have a supply of surface or well water. It provides irrigation for large areas of even closely-spaced crops for which irrigation ditches are not practical and wasteful of water, or that would be expensive to supply with full coverage with stationary sprinklers.«[Image: a modern example showing the sprinkler pipe carried above a series of large wheels.]