Friend and member of the SF Permaculture Guild Daniel Catalaa sent this update on his swale project.
During the summer of last year I excavated numerous swales on my homestead and, with the higher-than-normal El Nino rains, they were put to the test this winter. I will start by saying that my homestead is located in a semi-arid zone (less than 10 inches of yearly precipitation) so I decided to implement two dry-climate strategies: to sink the water underground as fast as possible using a series of swales (versus creating a large pond where the water would evaporate), and to plant inside the swale instead of downslope from the berm.
Thanks to what I learned from my permaculture instructors, Kevin Bayuk and David Cody, the swales performed very well; they filled up to capacity and then released the excess water over level spillways. My neighbors felt nervous about my earthworks and I had to talk to them many times. But, now that they have seen the swales perform during downpours, they are reassured that their properties will not get flooded. After the rains, the water took 1-2 weeks to infiltrate because of the heavy clay soils and hardpan beneath. At its peak, the water was knee-high and algae started growing on the surface forming a green film.
Overall, the effect of the rain in combination with the swales was to turn the landscape very green, promote repeated spurts of grass growth, and to impart an Irish look to a very dry and thirsty countryside. The sheep belong to my neighbor and were invited to come over for some controlled grazing; through their urine and droppings they will help to increase the fertility of the land. In the pictures you will also see a smaller, hand dug swale where I planted succulent cuttings. I collect succulent clippings during my walks around San Francisco and then transplant them to the farm.