Yes, Rainwater Harvesting is legal, and encouraged in New Mexico! Rainwater harvesting is either active or passive. Active rainwater harvesting involves the use of gutters, cisterns, and related equipment. Passive rain harvesting uses your soil as the storage medium for the rain via features like swales and basins ("planting the rain").
There are many different variables - house design, roof design, personal aesthetics, existing obstacles, local ordinances, etc. - and different ways - dry vs. wet systems, gravity supply vs. pressurized supply, above or below ground tanks - to design an active rainwater harvesting system.
Many people in New Mexico live entirely off rainwater year-round.
Generally, you can collect 0.6 gallons per 1 square foot of roof per 1 inch of rain. That means a 2,000 square foot roof will capture 1,200 gallons of rainwater from just 1 inch of rain. Your roof type, slope, the temperature, and the size of the rain event can all affect the volume you can collect. Depending on your goals, you may want to capture as much as you can, or only as much as you need.
The cleanest part of the water is just below the surface of the tank. There might be debris floating on top, and there is sediment in the bottom of the tank.
How much you filter water depends on the application. At a minimum you want to keep "gunk" out of your tank and prevent critters or kids from getting in, but for irrigation only, you don't need to worry about treating water to potable standards. You also want to avoid creating a mosquito breeding tank.
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CONS OF RAINWATER SYSTEMS |
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Rainwater Tanks
The tank or cistern is the centerpiece of an active rainwater harvesting system. It requires the most attention since it drives not only the efficiency of the system, but also the aesthetics. We think rainwater tanks can be a beautiful part of your landscape!
It’s a good idea to get the biggest tank within your budget and appropriate for your space.
If you're in need of a tank, give our products tab a quick visit.
https://www.cactusrainnm.com/services-products
Site Prep for Above Ground Tanks
The tank needs to be installed on a solid base supporting the entire bottom. We recommend crushed rock or a similar base. Limestone block, brick, pavers, or a concrete pad can also be used.
When installing on bare soil, you can simply add a layer (about 3" thick) of a base crushed rock material and compact it until it is firm and level, using a tamper. Avoid round substrates like pea gravel or river rock.
You can frame your foundation pad, though this is not necessary. A frame adds a nice visual touch and can make it easier to level the site if you build it above grade and back-fill with gravel. The tank can sit directly on the crushed granite.
Some people like to build a raised platform, which helps if using gravity irrigation. A platform needs to be incredibly robust to support the weight. Water weighs 8.3 pounds per gallon, so a 200-300 gallon tank weighs around a ton when full!
Pumps and Controllers
There are a variety of pumps and accessories to complement your tank. Please see our products page for recommended pumps and controllers.
Gravity is the first choice for moving water. You can manually withdraw water from an above ground tank with no pump. However, when water needs to be pressurized or lifted in elevation, the most typical way to power water transport is a pump.
Pumps make it possible to deliver rainwater from the tank to your end uses at pressures high enough to convey water through drip irrigation systems. Once you have a pump and drip irrigation, smart controllers are great – they can be used to “set it and forget it”. Your veggies and landscape will get water when they need it, even if you are busy or out of town.
Here's a quick list of some common psi for possible rainwater applications.
Passive Rainwater Harvesting
A passive rainwater landscape can be designed and installed by a local landscaper familiar with these passive and sustainable strategies.
Start passive rainwater harvesting at the highest elevation of the site and manage the water in small increments.
Zigzag the flow of water for maximum absorption. Harvest water in multiple small basins to infiltrate it throughout the landscape.
Over 95% of surface water in New Mexico evaporates or is transpired by plants. Reduce evaporation loss of rainwater from soil in passive structures by applying mulch.
Safely overflow water through predetermined overflow paths, and direct overflow to beneficial uses on site.
Design the passive systems to serve multiple functions: grow beneficial plants, reduce erosion and flooding, recharge shallow aquifers, provide shade, etc.
