A concept that is mentioned frequently in permaculture is “keyline”. I started reading about it when I reviewed “ catch and store energy ”, but I got stuck, and now that I’m up to “ design from patterns to detail ”, I thought that I'd better figure it out. What is keyline? P. A. Yeoman (1904 – 1984) was an Australian engineer and agronomist who lived and worked in New South Wales. He observed how water flowed over the land and developed a system for harnessing water to build soil fertility without chemicals, which he called the keyline system. A keyline plan is developed for a property using the concepts of the keyline system. His ideas are published in four books, three of which are available free online: Yeomans, P. A., The Keyline Plan (1954) Online version Yeomans, P. A., The Challenge of Landscape : the development and practice of keyline , Keyline Pub. Pty., Sydney, (1958). Online version Yeomans, P. A., The City Forest : The Keyline Plan for the Human Envir...