Watering harvesting means capturing water, where it falls, either through direct rainwater collection from roofs or through the careful placement of dams and swales. It also includes the recycling and re-purposing of gray-water. This collected water can be stored for later use or used to replenish groundwater.
One of the ways we catch rainwater where it falls is by digging swales to slow down the water, capture it and to passively seep it into the ground. Our soil is our biggest storage tank.
How can You Harvest Water
Capture runoff from rooftops, including shed roofs
About 200 000 litres of water runs off your roof and into the street, and then into the ocean. This water is getting cleaned, filtered and provided to you on payment.
When harvesting rainwater, keep the following in mind
Predicted rainfall for your area. You can obtain this information from the Meteorological Bureau for your area. If you have 600mm of rain every year and the surface area of your roof is 200 square meters, the total capacity of your storage tanks needs to be 10,000 liters. This quantity of water will give 10,000/30 about 33 liters water per day.
Underground storage tanks are favoured, as not only does this eliminate evaporation concerns, but they also help maintain the quality of the water.
Consider your water requirements: potable water is required for human and animals consumption and cooking, whereas, water with some impurities may be used for laundry, and gray water for growing vegetables and fruits.
How to Harvest Rainwater
Rainwater can easily be collected in above ground water tanks, which are easily obtained and installed. Careful considerations are needed when placing water tanks on a landscape. The placement of your water tanks will affect water pressure, aesthetics and available space. They are comparatively cheaper than underground tanks.
Plastic water storage tanks should be of a high grade plastic that will not leach chemicals into your water and should be shaded by some sort of trellising, with a creeper like a granadilla vine to shade the tank. This not only helps regulate the temperature of the water inside which deters the growth of algae, but also prolongs the lifespan of your tank.
Design for disaster
Plan and maximise your water stacking
Slow the water down, keep it in the soil or in an underground tank if possible and store
Place swales strategically to slow down the water and to prevent erosion
Never build in the path of a natural water source
Regular maintenance will be required to keep gutters clear of leaves and debris
Your tank must be mosquito free. A few drops of a high grade pure peppermint essential oil can be used
Drinking water should not be harvested from a zinc-alum roof, as aluminum can be toxic
Use a first flush to eliminate the risk of bird and animal contaminants
Air pollution will affect the quality of your rainwater
Benefits of Water Harvesting
Your taking care of your own needs
You have access to chemical-free drinking water
You have water for active or passive irrigation
You can help replenishes underground aquifers
You reduce the amount of chemically treated water being pumped back into the ocean