Rainwater Harvesting is a key component of Water Neutral Gardens™. In the Monterey Bay region, we receive a range of 28 – 80 inches of rainfall from September to June each year. Rainwater is the best water for our plants, because it is the purest, lacks salts and other minerals, and is without chemicals that our chlorinated municipal water systems supply. Plants love it, so it is a great way to flush any build up of salts in our soils. Here are some ways you can start collecting water:
Rainbarrels: An easy way to start is with a simple rainbarrel or rainbarrels in series system. Some advantages of these are the water is free and you have an opportunity to connect with nature through the hydrological cycle. In addition to this, a 55 gallon rainbarrel has the potential of collecting over 250 gallons per season. Since there are periods of drought during the fall, winter and spring, the rainbarrel can be emptied repeatedly during that time and filled with the next rainfall. Cost: from $50 – $200 depending on whether your do the work yourself and find recycled rainbarrels. Setting up first flush diverters and pipe overflow to garden contributes to increased cost.
Infiltration Galleries and Basins: Another way to harvest rainfall reasonably is to make a direct deposit of it from the roof into the soil. Infiltration Galleries are deep trenches filled with wood chips or rock that allow water to slowly percolate into the soil instead of running into drains, out to the street, and into the Monterey Bay or creeks.
Infiltration Basins are shallower 6 – 18” deep areas where water can collect. Both systems allow for “banking” of water on-site in excess of what normal rainfall provides and conserve water during the dry season. Roots of shrubs and trees find these basins and develop deeper rooting to withstand drought. These systems can cost a few hundred or several thousand dollars depending on the scope of the project. A complete soil analysis is recommended in the early planning stages. Note: both of the pictured basins were filled with wood chips from local tree companies.