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Harvesting Water

This is a very old idea with some new possibilities.  The essential concept at play is to store rainwater for use when it is not raining.  Categorically, there are two major branches of rainwater collection.

Rainwater Collection

 

1 inch of rain over 1000 sq ft yields 600 gallons of water.  The implications of this simple metric are staggering. For all but desert environments, this makes the possibility of storing *all* your rain quite difficult.

Landscape harvesting

Landscape rainwater harvesting makes use of topography to direct surface water and rainwater falling directly onto a landscape in advantageous ways. It is usually designed to be passive: a series of channels and basins where water flows based on gravity.  The use of ditches, berms, swales, key lines and trenches are all part of passive rainwater collection.  This is one of the oldest systems of water management by humans.  The key to designing low-input water harvesting systems is creating channels for water that move it, without losing more elevation than necessary. These systems can be disruptive to install, so they are best designed and implemented on a property before extensive building or landscaping has been done.  Because they involved digging, trenching, etc they can be very disruptive to existing gardens and infrastructure. In an ideal situation - water can be directed to ponds, lakes, or to flat low-lying areas to allower for undergroud water aquifer recharge. 

 

Diagram of roof footprint with example rainwater harvest yield

Roof harvest

Roof harvest rainwater systems typically begin at the gutter or downspout of a roof.  These can be installed effectively on existing roofs, usually without the advance planning required for landscape water harvesting.  Most systems direct downspout water through coarse filtration to remove roof and gutter debris and into storage tanks for future use.

 

 


Storage

From the example shown here, you can see how quickly this rainfall adds up. Storing 27,000 gallons of water is probably not feasible in tanks on small urban lots and much of that water will be directed through overlow channels. The largest system I have seen in an urban environemnt is 7,500 gallons in three separate tanks.

In more spacious environments, the possibilities open quite a bit.

Cisterns & Tanks

Ponds

 

 


Water Recycling

Greywater Reclamation

Greywater recovery or greywater reclamation systems are based on creating a second use for water, often diverting it from municipal sanitation systems all together. Water that has been “used” for an initial purpose in the home is often directed to ornamental landscaping or food producing crops. This secondary use often provides more value than the first. The most common of these systems make use of laundry, shower and/or handwashing water and divert it to fruit trees, landscaping plants, and otherwise non-potable uses that would otherwise be pulling from the tap. Any use where non-potable water is acceptable to you is a good candidate for these simple, effective systems.  "Laundry to landscape" systems are the least intrusive to install, and using your washing machine's pump are able to deliver water within 100 feet of the laundry room on a flat property.

Constructed Wetlands