June is typically a dry month, but don’t wait until July to start thinking about rainwater catchment, by then it might be too late to take advantage of the heavy deluges brought on by the Monsoons (we hope).
In Santa Fe, the heaviest months for rain are typically July and August after the Monsoonal flow is upon us. In a typical year, we can anticipate that we will get an inch of rain or less each month from October through June, then in July and August we are often blessed with 2″ or more each month. September is a bit of a wild card, typically we have received an average of 1.5″ or so in September, but the last couple of years we have had a couple of surprise storms that brought over 2″ of rain in a very short period of time, making up for some deficit from the summer months. Over a 24 hour period, most individual storm events are typically 1.5″ or less, though every 10 years or so, we may expect a 24 hour storm to bring us 2″-3″ of water at one time. In Santa Fe, these figures seem to be highly dependent on what part of town you live in, as there is often a downpour on one part of town with sunny skies in another part of Santa Fe. Nevertheless, having the capacity to store rain water is critical to being able to fully utilize these downpours.
The two main types of rainwater catchment are Passive and Active Catchment. Passive catchment involves using the slopes and hard surfaces around your house to your advantage by channeling the water into strategic areas using berms, swales, dry stream beds, pumice wicks, check dams, and ponding areas to capture as much water on site as possible. The other category of rainwater catchment is Active rain water harvesting systems. This includes both above ground and below ground options. Below ground options typically involve burying a large polyethylene tank underground and tying it to your automated drip system.
Above ground tanks can be as simple as placing a plastic tank under your canale, these can range in size anywhere from a 110 gallon tank to 850 gallon tanks. Tanks should be sized in relation to the square footage that funnels into the canale or gutter which in turn leads to the tank. For example, a roof area of 300 square feet will fill a 200 gallon tank in a 1″ rainstorm. Typically the common 55 gallon barrel is too small and overflows quickly. Ferro cement tanks are another type of above ground tank that Ecoscapes Landscaping installs. These are constructed from steel supports and cement. Circles and ovals are the most common shapes, but they can really be built in almost any shape or size. Typically, Ferrocement tanks have 3′-4′ buried below ground and 3′-4″ rising above ground. The most cost effective size for ferrocement tanks tends to be 6500 gallons or more.
Whatever you choose, act now before the rains come!
Peggy Wright (Masters in Landscape Architecture)