A Swale is a method used to harvest rain water. They are long shallow trenches that run along the contour of the land, & are perfectly level. Swales do not direct water flow, but collect water. The soil removed from the swale is piled on the downhill side to make a slightly raised berm. When rain falls, water collects in the swale. Water will slowly seep into soil & collect in underground pockets that will supply the roots of plants through weeks & even months without rain.