Catching the rain
Mankind's essential connection with the rain is a relationship that defies measurement. With ease we recall the ancient irrigation systems, examples of water being lifted from rivers, streams and irrigation channels by the Archimedes Screw (illustration on left) and by buckets on wheels. India and Turkey (illustration below) are examples of civilizations that developed huge underground cisterns that supported large populations. And of course we know of the Roman aqueducts, water parks and fountains.
Although some of these waterworks were astonishingly beautiful and all were artfully engineered, in all cases their construction was driven by the certainty that WATER IS LIFE.
UNDERSTANDING THE WATER CYCLE
That vital point has been dulled a bit over time since most of us are used to the familiar convenience of turning a tap to receive water. In many cases we have lost the basic understanding of the water cycle, wise water use, the function of water moving through soil and catching the rain in cisterns and rain barrels.
For gardeners in the Black Hills, the lessons of history can be utilized. More and more persons are creating extremely simple and inexpensive water catchment and storage systems by harvesting the rainwater from the roofs of their homes and outbuildings.
HARVESTING ROOF WATER
The following guide provided by the City of Portland, Oregon Bureau of Planning and Sustainability illustrates how to compute the potential amount of gallons that can be harvested from our rains.
Step one: Determine your collection area (see the examples of roof size and amount of rainfall in the chart below), multiply by the rainfall in inches per year or per rain event then divide by 12 (inches in one foot to determine cubic feet of water).
Step two: Multiply the cubic feet of water by 7.3 to determine gallons per cubic foot. That will give the amount of gallons of water collected.
Definition of terms:
- Roof or collection area – multiply length times width
- Rainwater – yearly, monthly average or total of a single rain event
- /12 – divide by 12. 12 inches = 1 foot. This function is used to convert roof rain amount to cubic feet.
- 7.3 – It is necessary to multiply the amount of cubic feet by this number to determine number of gallons in a cubic foot.
The figures in this chart allow you to easily determine the amount of harvestable water from a typical garage (12' x 24') roof or that of a shed (10' x 20').
Containers for holding rainwater
For the homeowner and hobby gardener, the easiest, most inexpensive and efficient rainwater storage unit is a 55 gallon plastic barrel (many persons get these from car wash businesses). Considerations when outfitting a rain barrel are:
1. Make certain that the top of the barrel is screened or otherwise closed to stop mosquito breeding areas and to discourage squirrels and other small animals from demonstrating that they cannot swim. (Mosquito "dunks" are floating doughnut-like tablets that kill mosquito larvae.)
2. Lengthen the downspout so that it will enter a small opening that has been cut in the top of the barrel and extend 4-6 inches into the barrel. Or, remove the downspout from the roof gutter and install a rainchain (a length of inexpensive, plastic chain) which will guide the rain into the barrel.
3. Drill a hole about 4" from the top of the barrel and thread it to accomodate a hose to channel overflow water.
4. Drill another hold about 4" from the bottom of the barrel and thread it to accomodate a hose. This can be used to channel water to the garden, trees or hooked to another barrel to create a series of rain barrels.
There is abundant and varied information and photos on the Internet. Google phrases like "making a rainbarrel" or "using a rainbarrel". Remember that people have been catching rainwater for centuries. Keep it simple, inexpensive and appropriate for your needs.