Keylines are enhanced contours which collect and direct water on sloping land without the need for terracing. The water collected by the keylines is directed into dammed ponds and is then drip-fed by gravity irrigation for crops and animals.
The key lines are carefully chosen to ensure maximum water collection potential. As well as collecting water, key line design reduces soil erosion and flooding and gathers nutrients which build up soil fertility over time.
The key line principle was developed in Australia in the 1950s by P.A. Yeomans and had strong influence on permaculture pioneer David Holmgren.