There are many types of rainwater catchment systems that are used to capture and store rainwater. Very simple systems capture rainwater for later use in the garden as a means to save the intermittent aqueous resource from a quick journey back to the sea. In urban areas, nearly 55 percent of rainwater becomes runoff that ends up in the ocean. More complex systems capture and store potable water for use in the home: drinking and showering. While gravity and the underlying Archimedes Principle remain constant for any system, one is only limited by imagination as to the design and scope: how much water to collect and where to put it. Jeremai Cann, environmental engineer at The Green House Sustainable Learning Center, demonstrates how to build a simple system to capture rainwater runoff from the rooftop and deliver it to thirsty plants in the garden.

What youíll need for a basic rainwater catchment system:
Barrel or other heavy-duty storage container, drill, 5/8" drill bit, threading tool, 1/2" tap, Teflon tape, 1/2" hose bib, 3/4" male hose adapter, hose, 3" flexible pipe (length depending on distance from rain gutter).

Step One
Acquire a suitable receptacle for holding a large amount of water. There are many options, but for this application, a 55-gallon high-density polyethylene (HDPE) barrel is preferred.

Step Two
If the barrel doesn't have two holes already precut in the top, then cut two holes in the top of the barrel, one for the downspout and one for aeration. Cover the aeration hole with shade cloth attached with rustproof tin coated copper staples to keep the mosquitoes away.

Step Three
Using a 5/8" bit, drill a hole near the bottom, about four inches up from the base.

Step Four
Lay the barrel on its side and thread the hole using a threading tool and 1/2" tap. Make sure to apply ample pressure downward as you turn the tap and be sure you are not threading at an angle.

Step Five
Wind Teflon tape around the threads of a 1/2" hose bib and insert the hose bib into the threaded hole.

Step Six
Drill an overflow hole near the top of the barrel using the 5/8" bit. Thread the hole and insert a 3/4" male hose adapter. This will allow you to connect a length of garden hose so the overflow water drains away from the barrelís foundation.

Step Seven
Place the barrel high enough off the ground to allow room to attach a hose to the hose bib at the bottom. Cinder blocks work well. Make sure the barrel is at a higher elevation than your garden or what you want to water, to allow gravity to create water pressure.

Step Eight
Using a piece of flexible 3" piping, direct the flow from the rain gutter downspout into the opening on the top of the barrel.

Add beauty and nutrients to your catchment barrel by putting water plants, like water hyacinth or a water lily, in one of the air vents on top of the barrel instead of covering it with screen. Also, put a couple small fish that can survive in low oxygen environments in the water. The fish add nutrients to the water and eat mosquito larvae while the water plants offer a hiding spot for the fish as well as foliage and flower for your garden.