I am currently playing around with water harvesting ideas for a block of land. What is a reasonable rule of thumb for swale separation on a gently sloping block? I was thinking about one for every 2 metres of fall, which would give me roughly 20-30 metres separation between swales and catchment between 1- 2 acres (4000-8000 sqm) for each. I am looking at running the overflow into into hillside dams that each then drain into the lower swale. On a 10 acre block this would give me about 1500 metres of swales with about two acres of trees planted on the ridge above the first swale. Thoughts welcome.