H2O Harvest

Making the Most of Rainwater

By Virginia Hayes

Mother Nature is flirting with us as usual. A drizzle here, false alarm on a thunderstorm over there — no real rain yet for the new season, but it will come. Will you be ready? I’m not talking about patching that leaky roof, cleaning the leaves out of the gutters, or putting the lawn furniture in the garage. Are you ready to reap the harvest of rainwater offered up for free? With more and more of our urban world being paved or built over and increasing numbers of people straining the limited resources available from conventional sources of domestic water, it is high time we as individuals got into the act of water conservation.

We all bask in the great weather that is the norm here on the South Coast. Lots of sunny days also mean, however, that we live in one of the drier regions of the country. Our local rainfall average is less than 20 inches (depending on where you live). To cap it all off, the rainy season is short, typically starting late in October and finishing up in March. That also equates to a climate in which the warmest months are the driest ones. This puts a strain on gardens and gardeners alike. Just how do you go about saving the most precious resource, water? There is a wealth of information available to help you learn how to keep rain, first in your garden, and then in our local aquifers. One of the most comprehensive sources of practical instruction is the recently published book Rainwater Harvesting for Drylands by Brad Lancaster.

This is actually the first volume in a three-volume set, but for the beginning water harvester it will go a long way toward helping you understand how some simple techniques can make a significant change in the amount of water leaving your property. These methods do not require expensive tools or materials. The first of eight principles of rainwater harvesting, according to Lancaster, is to “Begin with long and thoughtful observation.” The idea is to watch how water moves over the land. What direction does it flow, what obstacles does it encounter, and how does it react to those obstacles? Only by beginning to understand the nature of water can one hope to find ways to redirect it to benefit our environment and us.

The other seven principles are equally logical. Since everyone knows that water flows downward, principle number two is to “Start at the highpoint of your watershed and work your way down.” You may not have thought of your own garden as comprising a “watershed,” but if you look at the roof of your domicile and the tallest trees as the start of a raindrop’s journey toward the sea, you will see another way to look at your surroundings. My favorite is the next principle: “Start small and simple.” Keep reading and researching and you will find your own comfort zone of change, but even the smallest changes will be of benefit to you and the overall environment.

The next four principles refer to more specific ways to look at the flow of water to achieve your goals. Number four, “Spread and infiltrate the water,” is a way to slow water down and give it a chance to soak into the soil. In the short run, this nurtures your landscape; in the long run, it replenishes the aquifers below. Numbers five and six mitigate the destructive properties of water: “Always plan for an overflow route, and manage that overflow as a resource” and “maximize living and organic groundcover.” Both of these rules will enable you to divert and use water to irrigate your landscape before letting the excess water follow its inevitable path. Principle number seven is “Maximize beneficial relationships and efficiency by ‘stacking functions.’” This one requires a little more thought and planning, and the book has lots of great illustrations and plans that you can adapt to your own situation. The eighth and last rule is as important as the first. In order to make sure that you learn from your own situation, you must “Continually reassess your system: the ‘feedback loop.’” Again, observation is the key to success.

Throughout the book, Lancaster has supported his thesis by summarizing his research in small sidebars with compelling information. One such “box” reveals some interesting facts about the efficiency of size in relation to the amount of water that can be stored and used by damming up waterways. It turns out that smaller is better. Large reservoirs are more disruptive to the local ecosystem and its inhabitants (plants, animals, and people). Also, in larger reservoirs, an increasing proportion of water is lost to evaporation and to the soil than in smaller bodies of water. According to the Centre for Science and Environment in India, “In a drought-prone area where water is scarce, 10 tiny dams with a catchment of 1 hectares (2.47 acres) each will collect much more water than one larger dam with a catchment of 10 hectares.” This should be an inspiration to small-scale water harvesters. In even the smallest landscapes, significant gains can be made through a human-scale endeavor.

The practicality of applying these concepts is not as daunting as it might seem. One of the basics of diverting water is to move a little earth this or that way to channel it where it can do the most good. Small changes in grade can accomplish large results in terms of redirecting storm water to your benefit. Some of the basic techniques involve mounding up soil into berms perpendicular to the slope (and water flow) to contain rainfall in a basin so that it has a chance to percolate into the soil instead of rolling right off. If you landscape these basins with plants, they can thrive on the free irrigation to provide food, shade (to reduce heating costs in your home), and habitat for other inhabitants of the ecosystem such as beneficial insects and birds (these are the “stacking functions” mentioned above). Many more easy-to-master techniques will allow you to modify your landscape to maximize water retention and utilization. Once you are hooked, you may want to progress to the more detailed information in the other volumes.

One other source of good information and networking is through Harvest H2O, the Online Rainwater Harvesting Community (

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