Harvesting rainwater at home for conservation and profit

The rain falls freely, yet is everywhere in demand. In a state and an era of increasing water scarcity, how can we let this precious resource escape us? The ancient practice of rainwater-harvesting is becoming again a virtue if not a necessity.

Individual households can collect rainwater during the wet season and store it for use during the dry season. In the Bay Area, where 30 - 50% of the water used during the summer months goes for landscaping and gardening, rainwater-harvesting is mostly used by gardeners. With proper filtration systems, it can also be used for drinking water.

In a natural ecosystem, rainwater runs off gradually, much of it seeping into the ground. In our urban and suburban society, a large proportion of rainwater runs off almost immediately from impervious surfaces such as roads, roofs, sidewalks, driveways, and parking lots into storm drains that dump it rapidly into waterways. Such fast runoff causes creek volumes to fluctuate much more rapidly and widely than is natural, causing increased erosion and flooding, while depleting the supply of water that can sink into the soil and water table. Such runoff also carries sediment, oil, pesticides, pet waste, and litter directly into our streams and bays. In San Francisco, which has a combined storm- and waste-water system (the only such in the Bay Area), storm runoff regularly pushes wastewater volumes beyond the treatment capacity, forcing discharges of minimally treated sewage directly into the Bay and ocean.

Individuals, by catching roof runoff during storms and directing it through spouts into rainbarrels, cisterns, or tanks, can harvest and store the water for use during dry months. These systems can be cost-effective and easy to use. At the simple end, barrels can be attached to downpour spouts from roofs, and the water held until needed for summer landscaping. Sturdy, good-quality barrels are recommended to preserve water quality, prevent the growth of algae and mosquitoes, and protect children and wild animals from drowning. They should be opaque to sunlight and include a debris screen and lid. Barrels or tanks come in a variety of sizes and designs. They can be hidden on the side of a house, under decks, or even underground. For larger devices, professional designers and installers are recommended.

Depending on the technique used, the landscape area to be covered, and the size and complexity of the systems, water-catchment devices can cost anywhere from free (do-it-yourself barrel attached to a downspout and a hose), to around $100 for a 60-gallon rain barrel, to a few thousand dollars for complex tank systems with sophisticated pumping and filtering systems. Water-catchment devices can be found on the internet or by checking with local water districts or nurseries.

Raingardens

Raingardens are a natural accompaniment to catchment systems. During the rainy season, unless you have a huge storage system, your storage will quickly fill up.

Raingardens involve landscape changes made to direct overflow from the catchment system, as well as natural runoff from the landscape, into small depressions (about a foot deep) dug into the landscape and filled with mulch or other absorbent substances which hold water but allow it to seep slowly into the soil. These can be dug easily with a shovel. Over and around these, one plants native plants that are attuned to the natural rain cycles of the area. Retention ledges or berms can also be built around lawns and gardens to detain runoff and encourage it to percolate into the soil. People are also replacing impervious surfaces such as driveways and walkways with porous cement and pavers. In all these cases the aim is to allow rainwater to seep into the soil without creating standing water where mosquitoes can breed. This encourages the recharging (replenishing) of groundwater. It also allows microorganisms in the soil to break down pollutants such as petroleum products and pesticides before they reach waterways.

In short, by harvesting rainwater, you can:

• lower demand for municipal water;
• help reduce flooding, erosion, and sedimentation into creeks;
• reduce strain on local sewer districts;
• protect local streams and habitat for salmon and other wildlife;
• prevent pollutants from reaching streams and bays;
• reduce your carbon footprint by saving energy used to treat and pump municipal water;
• save money.

WhatYouCanDo

There are a number of easily accessible resources for learning more about water catchment and raingardens. The Bay Area is home to a number of water-harvesting projects such as the 10,000 Raingardens Project, which developed from a partnership between the Salmon Protection and Watershed Network (SPAWN) and the Marin Municipal Water District (MMWD). Water districts such as North Marin Water District are providing financial incentives for water conservation programs including rainwater harvesting.

Click for further information and a list of valuable resources and workshops.

Other informative web sites are: Occidental Arts and Ecology Center; Sustainable Fairfax; and North Marin Water District

The Bay Area has always been a pioneer in the development of environmentally friendly technologies. Rainwater harvesting is a natural fit for those of us who live here. The better we can learn to adapt to our water footprint, the less we will have to rely on water from distant watersheds or from costly, energy-intensive sources such as desalination.

Michele Barni, Sierra Club Marin Group Executive Committee