Another tenet of managing water in permaculture is building swales along contour lines. A swale is depression of land between two ridges. To make a swale, you need to identify the contour line of the slope, and dig a trench along that line, depositing the excavated soil on the underside of the slope. It is very important that the swale is along the contour line, and does not have any slope, else it can quickly become a drain!
To make swales, we used an A Frame. Its a simple structure made of 3 pieces of wood of the same length - like an equilateral triangle, with a plumbing line hanging down the middle and calibrated to the centre of the lower stick. You know you are on flat land when the plumbing line meets the middle point. Now with this A frame, start at one end of the land where you want to make the swale, and walk the A frame from one end to the other by rotating it from one leg to the other. At the point that the plumbing line touches the mid point, drop a marking. Then connect all these dots and you will get a swale.
We dug several swales across the farm - maybe 25 or more. In naturally sloping land, swales are very useful in slowing down the water off the slopes, and building a water lens on the underside ie creating more ground water for trees and plants to benefit from.
We noticed later, that trees planted along the swales did much better over the years, as they definitely got more water than others.
For more information on water management, you can watch the following videos: