Graywater and the Hydrology Cycle

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For most people living in urban areas of California, water is supplied through large-scale intervention in the natural water cycle, in the forms of dams, river flow diversions, or pumping ground water from slow-to-recharge aquifers. The methods and quantities of water removed can have damaging effects on natural aquatic systems. Once water is treated to drinking quality standards, we usually use it once and send it to the sewer treatment plant. Nutrients are removed and the water is disinfected, then released back into a waterway, typically a bay, river or ocean.

Reusing graywater on-site is one way to reconnect our practices with the natural water cycle. Potable or rain water coming into buildings can be reused, reducing the draw on natural water systems. Applying graywater to landscapes utilizes the natural capacity of soil and mulch instead of the energy-intensive water treatment plant system to purify it.

Nutrients from soap and organic matter can either be a beneficial fertilizers or problematic sources of pollution. If released into natural waterways, nutrients cause algae to grow, using up oxygen needed by other living things. By using nontoxic products in clothes washers, sinks and showers, graywater irrigation for plants can add beneficial nutrients that act as fertilizer when absorbed by plant roots. The organic matter is broken down into plant nutrients by soil micro-organisms. The billions of microbes in healthy topsoil provide excellent treatment and nutrient removal in graywater.

Living with a graywater system reduces overall water consumption and stress on natural systems that provide the water. At the same time, graywater use prompts water users to better understand the impacts of the products they use. Sending this water outside to the landscape encourages awareness and education about what products are safe for the environment, leading to an overall improvement in water quality as people shift away from harmful products.