Page 54 - Green Builder Sept-Oct 2019 Issue

Tips, Technology and Common Sense
Solutions for a Thirsty World

Nature’s Freefall

As the world’s water need grows, rainwater harvesting is gaining popularity.

BY MICHAEL TOBIAS
P UT SIMPLY, WATER IS LIFE—we simply cannot exist THE RAIN GAME
Also known as rainwater recycling systems, rainwater harvesting
without it—which is why, after serious, sustained periods
can decrease demand on city water supplies and even reduce utility
bill charges for water. In places where water is exceptionally scarce,
of drought in many regions, the concept of harvesting
rainwater is gaining momentum worldwide.
systems can help reduce (not resolve) water shortage problems.
Rainwater harvesting systems may be as simple as a rain barrel
While it certainly isn’t a new idea (it’s been used
for millennia), rainwater harvesting hasn’t been widely used in with a downspout, to an arrangement of large cisterns or tanks
industrialized countries where centralized water distribution systems connected via a series of pipes. Sometimes rooftop systems, including
provide communities with all the water they need. blue roofs and green roofs, are incorporated into systems used for
The fact is that rainwater is free and it provides an inexpensive harvesting rainwater.
supply of water that can be used for irrigation and non-potable uses In general terms, there are passive and active rainwater harvesting
indoors. With filtration and relatively minor treatment, it can also systems:
be used to augment drinking water supplies. ■ ■ Passive harvesting systems can be mere rain barrels that catch
Additionally, harvested rainwater helps reduce storm water runoff from roofs, gutters and downspouts in relatively small
runoff, contamination and erosion that commonly occur in urban volumes. They are great for smaller residential applications, but
environments. It is particularly useful for fire protection, and some barrels and cisterns should always be made from opaque materials
insurance companies offer discounts if water is stored on site for and they need to be located where sunlight doesn’t encourage
emergency use. algae growth.
What’s not to like? ■ ■ Nevertheless, the water captured is considered non-potable and in
most states, it can only be used outdoors. There are also regulations
relating to drowning hazards as well as prevention methods to
stop vectors from breeding in or around the barrels.
■ Active rainwater harvesting systems, on the other hand, deal with
■
much larger volumes (up to about 100,000 gallons) and rainwater
is captured from all kinds of surfaces, including roofs. Because of
this, there is a need for water quality treatment, as well as pumps
that can supply water to a suitable distribution system.
Cisterns may be made from a variety of materials including
concrete, metal, plastic, and even wood, and, like barrels used for
passive systems, they should be constructed and placed to minimize
penetration of light that would result in the growth of algae.
Water from active systems is commonly used outdoors for
irrigation, and indoors for non-potable use including flushing of
toilets, evaporative cooling, and so on. Intended use impacts directly
on the way water is treated.

EVER-GREATER HARVESTS
CREDIT: MEG STEWART/FLICKR to ascertain specific requirements, including whether the water will
Anyone planning to install a rainwater harvesting system will need
be stored for later use or used immediately. If it is going to be used
for farming, to irrigate crops, the water treatment system will be a

While homeowners who are harvesting rainwater will usually
Backup plan. Rainwater systems can hold thousands of gallons of water vital element of the system. Thinking bigger. It’s free, it’s natural and it’s abundant—yet rainwater harvesting
for later use, making them essential for drought-impacted areas. be quite happy with a simple rain barrel that captures more than is only now starting to become a viable, logical option for thirsty nations.

52 GREEN BUILDER September/October 2019 www.greenbuildermedia.com

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