Water conservation and management is becoming a worldwide survival issue due to accelerating water shortages, uncontrolled development and population growth, aging infrastructures, growing agriculture demands, a general warming trend, and the ever-increasing cost of and demand for natural water resources. Rainwater harvesting is a viable solution to help meet this demand and help solve our water crisis and storm water runoff problems here in Atlanta.
According to US Census data over the last five years approximately 404,000 new homes were built in GA. Based on an average roof size of 1500 square feet, this would produce 12 billion gallons of storm water runoff from these roofs. This runoff carries with it pollutants such as oil, pesticides, fertilizers, and bacteria. These pollutants along with our precious top soil flow into rivers and streams and eventually make their way to the ocean. Collecting water from rooftops and storing it for our non-potable and potable uses can significantly decrease this storm water runoff and pollution.
Rainwater harvesting reduces the strain on our aging infrastructure. How often do we hear on the news or local traffic report that another water main has burst. Most of our infrastructure is reaching the end of its lifespan. We rely heavily on municipally supplied water sources to provide us with non-potable water for irrigation, flushing toilets, and washing clothes. This growing reliance places unnecessary pressure on our infrastructure. Utilizing rainwater can supply our homes and businesses with a decentralized water source for non-potable uses, and even potable water uses if necessary.
How much water can be harvested? For every 1000 square feet of roof space approximately 620 gallons of water can be collected. This means on a 2000 square foot roof 1240 gallons of water can be collected from a 1” rain event. During the extreme drought of 2007 this one home would have produced 37,200 gallons of free unrestricted water. This non-potable water could provide 620 showers, 1240 loads of laundry, or 6200 toilet flushes. If using water saving devices these numbers would increase significantly to 2976 showers, 2066 loads of laundry, or 24,800 toilet flushes. This would supply the average 3 person household with 70% of their water needs in this drought year. In a normal rainfall year it would supply them with 100% of their water needs. When rainwater is used for outdoor watering with traditional style irrigation the typical rainwater harvesting system would supply 1 month worth of watering if it didn’t rain in that month. If used with drip irrigation the typical system would rarely, if ever, run out of water. It’s not hard to see that the use of rainwater harvesting with water saving fixtures, appliances, and irrigation equipment can greatly reduce our demand on municipal water supplies.
The cost of a professionally installed rainwater harvesting system can start around $2000, but average cost is around $9000 for a system that will supply a significant amount of water. If looking at the payback it may take a while for the existing homeowner to recoup this money from reductions in water bills, however for the newly built home the economics work in favor of rainwater harvesting, especially for the homeowner who irrigates. The average cost of a system amortized over 30 years is around $60 per month. Most homeowners will spend at least this much without using irrigation. For those who don’t irrigate it is a break even proposition on the water bill, but the systems have proven to receive 100% credit upon appraisal, therefore the homeowner would still end up ahead. For the homeowner who does irrigate they are cash flow positive on day one, and they don’t have to deal with the cost of replacing dying plants in their new landscape.
There are also the offsets of ever increasing storm water impact fees. If the plans for a properly sized rainwater harvesting system are presented to a civil engineer, they cannot deny that the impervious surface of the new home has been eliminated by the rainwater harvesting system, since the predevelopment hydrology can be restored. Entire developments have been built in VA and TX using this methodology. These systems have also proven to help with the marketability of a home. With the “green movement” becoming more main stream potential homebuyers are looking for homes that are more environmentally friendly.
If looking for a system you should be careful to find a qualified installer using quality components. While the cistern (tank) is an integral part of the system and should be of quality construction, it is equally important that the filtration system and system for removing the water be from a proven manufacturer. In North America modern rainwater harvesting is still a relatively new concept, so manufacturers of subpar products have made their way into this niche marketplace. There are also homemade systems being sold and installed on a regular basis. A properly designed system consists of fine filtration before the water enters the tank. This will foster the formation of a natural enzyme in the bottom of the tank that will oxygenate the water and eliminate growth of bacteria. The tank should never be completely emptied or cleaned as this would kill the enzyme. If not properly filtered debris in the water will decompose, sucking precious oxygen from the water, which quickly causes stagnation and degradation of the water quality. When removing the water from the tank it should always be pulled through a floating suction filter positioned just below the surface of the water. This prevents disturbance of the natural enzyme on the bottom of the tank, and eliminates the opportunity of pulling any pollens that may be floating on the top. It is also important that any above ground cisterns be dark in color so that no light can get into the tank. This prevents the growth of algae. If a system is installed with quality components by a professional installer the water quality will be good and the maintenance required will be minimal.
Rainwater Harvesting has been utilized all over the world for thousands of years. With the increasing population and demand of water increasing at twice the rate of population growth, it is a viable solution for solving water issues around the world. In Germany 74% of homes have a rainwater harvesting system and all new structures over 400 square feet are required to include this during construction. In Australia they are now close to 100% of homes having a rainwater harvesting system. In the state of TX any government building newly constructed is required to have a rainwater harvesting system. In addition they are sold tax free in TX and several municipalities are now offering rebate programs. In the state of VA rainwater harvesting is commonly used in high growth areas that are having trouble keeping up with water demands. Like any new concept it may take some time for rainwater harvesting to become recognized as one of the solutions to our water problems in GA, but it is inevitable that it will ultimately be required in order for us to sustain growth and maintain our current standard of living. Every rain drop is important to us, therefore we should be stewards of each drop.