This entry was written by one of our members and submitted to our blog section. The author's views below are entirely his or her own and may not reflect the views of Green Home Guide.

In California, Water Efficiency Landscape Ordinances (WELOs) require or encourage new landscapes greater than 2500 square feet to keep or filter rainwater onsite. Whether its required or not, infiltration, like rainwater harvesting and graywater, produces great benefits for property owners and their communities.

Also called percolation, infiltration is where rainwater is guided by a combination of landscape strategies to permeate into the ground. Like rainwater harvesting, infiltration filters rainwater; however, it does not necessarily store this water on-site. Infiltration is also distinguishable graywater in that it is not utilizing water twice but simply a method for capturing on site run-off water from roofs and paving.

  • Infiltration protects homes and communities from floods caused by overtaxed public waterways;
  • saves aquifers from pollution; and
  • protects surfers and other ocean wildlife from the fertilizers, pesticides and animal waste that run off hardscapes into the ocean.

Infiltration also protects homes by slowing fast moving water to reduce erosion and sedimentation, increases local water availability by recharging the water table, and cleans water naturally, using vegetation and soil as natural filters.

While rainwater collection and greywater systems often require strategies for concealment to ensure the visual integrity of the landscape, infiltration can be used to enhance a design.

For example, the seemingly dry riverbed pictured above re-routes water away from the home and acts as a stabilizer. Like the dry stack walls on the slope, the riverbed is integral to the beauty and balance of the landscape design. This desert look is appropriate to the home's design and La Crescenta, California hillside neighborhood, but it is far from the only look infiltration systems can support. The dry riverbed below adds a rugged charm to an otherwise soft, lush, green space.

Likewise, this waterfall and biological pond,, while perpetually riparian, allow a certain amount of water to be captured and filtered prior to leaving the site.

Infiltration can be achieved using French drains, percolation pits, creeks and waterfalls or even thoughtful grading.

As you may have guessed, permeable patios, like more active infiltration strategies, encourage water to filter through their respective properties prior to leaving the site.

A critical caveat for infiltration: While rainwater harvesting can be a DIY activity, the cost of failure with infiltration is high.

A poorly designed or constructed dry riverbed, for example, could actually destabilize a slope or flood a home. A lovely, thoughtful design is not enough. Choosing a knowledgeable, skilled, licensed and trained construction team is a must to ensure both beauty and optimal benefits are achieved.