Rainwater catchment systems can increase your backyard harvest, reduce storm runoff, recharge the aquifer, lower your water bill, and provide an emergency water source. On a 1000 Square foot rooftop you can capture 600 gallons for every 1 inch of rain, so in San Diego as an example that gets an average of 10 inches of rain per year you could capture up to 6,000 gallons! Here are some different ways to consider rain harvesting
1. RAIN GARDEN
The simplest way to harvest rainwater is to store it in the soil, or slow, spread in sink the rain water, rather than let it just run off your property. In a few hours, you can turn your backyard into a water harvesting landscape! Divert downspouts to shallow basins planted with water-loving plants. When it rains, the basin fills, then water seeps into the soil. In heavy clay soils, add compost and sand for drainage.
2. LIVING ROOF
A living roof catches rain before it hits the ground., and provides beautiful aerial wildlife habitat. Simple living roofs use succulents or native wildflowers, which can grow in 4” (10 cm) of soil and require no irrigation. These roofs consist of a waterproof membrane, gravel or crushed brick for drainage, and a lightweight, water-holding soil mix, and cost $5 to $20 per square foot.
3. CISTERN OR RAIN BARREL
Your roof can provide thousands of gallons of irrigation water if you harvest your rain! Tank storage costs vary widely and you typically get more cost effectiveness from large round tanks, than smaller slim line tanks. Even the largest tanks will quickly fill up, so make sure to direct the overflow to a rain garden. More complex systems can send rainwater indoors to replace city water all winter long.
4. CURB STRIP PLANTER
Curb strips can filter pollutants out of storm water flowing down the street. A small berm diverts stormawater through a curb cut into a rain garden. Pollutants sink into the soil rather than running into waterways.
Rainwater Harvesting Guidelines
Think of your house and yard as a rain catchment area. Try to prevent any rainwater from leaving your site, by reshaping the landscape to prevent runoff and catching it in cisterns. Capture runoff from all hard surfaces— roofs, sidewalks, patios, driveways, and the street!
You can harvest about 600 gallons from a 1000 square foot roof for every inch of rainfall! In San Diego we average 10 inches of rain per year, so a 1000 square foot roof can harvest 6,000 gallons of water.
It’s most ecological and economical to begin harvesting rainwater by shaping your landscape to catch and infiltrate rain. Ceate an infiltration zone (“swale” or “rain garden”) that is 20-30% of your runoff area (your roof, driveway, street, etc.). Dig basins 12” to 18” deep, add a few inches of well-drained soil, and plant water- loving plants.
Storage options include rainbarrels and cistern of many shapes, sizes, and materials. A simple rain barrel can provide a source of emergency drinking water, and a little extra irrigation water. Direct cistern overflow drains to basins in the garden.
Rainwater irrigation can be as simple as a shutoff valve and garden hose, or a more comples system of pumps and filters connected to a drip irrigation system
Keep your rainwater clean! Clean your gutters, install a “first flush” system to wash your roof, and store water in opaque containers to block sunlight and therefore inhibit algae growth. Screen tanks to keep mosquitoes out. Install a metal, slate or tile roof if you plan to drink your rainwater as this will provide the purest source.
Capture and infiltrate all rainwater that falls on your site using basins, swales, and cisterns.
Source: Greywater Action
Rainwater Resources
greywateraction.org/rainwater
