There is a very timely comment in the Introduction to Volume I, I want to share. The last two pages of the Introduction, pages 20 and 21, is a FAQ. What follows is one of the questions and the first paragraph of Brad's response.
Are there rainwater-harvesting building codes.Over the last 30 years, the laws in Australia have gone from reasonably fair to draconian. Up until about 1980 water was tied to land title, it management and use was integrated into the landholders management practices for each individual farm. Due to changes in technology (bigger pumped and earth moving gear), some law reform was needed in the 80s. The states governments used these reforms to not tweak, but to grabbed water and make it a tradeable profit centre for their budgets.
Surface water laws vary around the country (Brad is based in Arizona), so it's wise to check in with local authorities. In my area folks can harvest all the water that falls directly on their site, but there are restriction on harvesting runoff within established waterways that pass through their site. Some arid countries have draconian laws prohibiting the harvesting of rainwater runoff generated on site. In such instances, harvest the rain before it becomes runoff.