Water wise rainwater collection and drip irrigation systems.
Here in Atlanta, Georgia, our company discovered rainwater catchment systems, in the summer of 2007, in response to a continued severe drought that still threatens our whole areas water supply. Our own garden, as well as our livelihood as a residential landscape architectural design/build company, was in jeopardy after, some individual counties then, the entire state declared a total ban on outdoor watering. (That restriction has since been eased, somewhat, but it's still very hard on homeowners and landscapers alike to maintain our gardens.)
We quickly scrambled to gather information on alternatives to using city water for that purpose and discovered that our choices came down to either drilling a well or catching rainwater. The latter would also involve storage in tanks or cisterns.
So we checked into drilling a well, at our own home, and found that we did have enough water available to be tapped. It would cost about $10,000 just to drill the well and install the pump. From there we would need to clean up the really big mess made from the huge drilling machine access and the pile of debris resulting from drilling the hole. . It was a really big surprise to us to learn that this would also involve not only renovating the surrounding landscaping, but also replacing the main water line and meter, which most likely would be destroyed in the process. After that we would have to pipe and then process the water in order to be able to use it, as it would contain way too many minerals, which would foul any irrigation system. As we started calculating the costs it became clear that we'd be well over $25,000 by the time we had a system for usable irrigation. (Not including the cost of the updated irrigation system itself.)
Simultaneously, we continued our investigation of rain catchment systems. There were no local resources at that time. As we researched using Goggle it was discovered that there were many places we could purchase most of the needed parts and have them shipped in. The best systems were coming out of Germany and Australia and others out of Texas. We started putting together some rough numbers, on these systems, and found that it could cost us between $25,000 and $55,000, for our home, depending upon the type of irrigation system we installed. Since that time many companies have attempted to fill the void locally still, the prices haven't changed much and, the expertise and reliability of these new companies aren't yet proven.
So from our experience a drilled well seems to definitely be the way to go if you've got enough water below, room for the drill rigs to get in, and the money in your pocket to make it all happen. If not, rainwater collection might be your best, albeit more costly, option to solving this kind of problem.
We opted for a rainwater catchment system because it was something we could do ourselves, in a step-by-step fashion, and keep the costs down to a manageable level while learning more about it from first hand experience. Here's some of what you need to know about rainwater irrigation systems that we learned the hard way:
A system for catching, containing and distributing rainwater needs to be a professionally designed, engineered and installed.
1- Determine the amount of rain that can be collected, in your area, on a yearly and month-by-month, basis.
This can be done using the Internet to find the information. We've discovered that most local municipalities and even some neighborhood community websites have all the information needed.
After you know how much rain falls, and when, you'll need to calculate how much roof area that you have with which to collect it. All you need is the total square footage of the house foot print including the overhangs and multiply that number by .62 per inch of rain. The roof pitch is irrelevant.
2- Determine the amount of water that your irrigation system will need on a, per season and monthly cycle.
If you presently have an irrigation system, and you have a separate water meter for it, you can go back through your past bills to get that information. If not you may need a professional irrigation person to access your system needs.
More than likely your present system will need to be overhauled in order to reduce the amount of water needed. Refer to the "Irrigation system" information below if you currently do, or do not, have an irrigation system.
3- Determine the minimum amount of water needed to be stored on a seasonal, weekly and monthly basis.
More capacity for storage is always better then less except for when it comes to the final cost of the system. The typical "rule of thumb" for storage is $1.00 per gallon not including the following:
Delivery and installation of the tank:
This varies tremendously. There are many types of tanks and, in our area, all installation sites very greatly. Sometimes above ground tanks are required because of underground granite. Above ground tanks cost more then underground tanks but the installation is much more expensive.
Gutters:
If you currently have a good leaf prevention system installed you will be a little ahead of the game as it prescreens most of the litter from the system. If not that roof litter can still be easily handled with an inline pre-filter.
Downspout collection system:
Which includes the primary filtration screen and first rain diverter. All downspouts need to be both prescreened and pre-filtered.
We've found that use of a first rain diverter is mandatory for most of the southeast due to the tremendous amounts of spring pollen. Pollen not only clogs the system but also ferments in the tanks and stinks to high heaven. This device diverts a predetermined amount of rainwater away before sending the cleaner water into the collection tank.
Piping to the storage tanks:
These should be a minimum of 4" per downspout regardless of in-ground or aboveground tank installation.
Storage tank water level gauge:
Above ground tanks need to be as impervious to light, as underground ones naturally are, in order to prevent algae growth. Thusly so some form of gauge is necessary as you wont be able to look at the tank and see how much water is in it.
Storage tank overflow system:
When the tank is full the extra water needs to be handled in a proper manner to prevent erosion. It's best if excess water is first allowed to dissipate into an underground system that charges the local water table.
Distribution
Gravity system:
This can be used for tanks that are elevated but they are unsightly and ineffective in most urban settings as the elevation requirements, at least 35 feet, aren't practical or permitted. Lower lever gravity fed systems work best with soaker hoses and so are not as efficient, or effective, as a pump fed system.
Pump system:
There are many kinds of pumps on the market. Your pump needs to be properly sized according to the particular needs of your own irrigation system. Additional plumbing and wiring will also be needed dependant upon those variable necessities. When using a pump system the tank can be located almost anywhere in your yard that works for your particular circumstance.
Irrigation system:
Maximize the irrigation systems distribution efficiency.
Install automatic drip irrigation. Conventional spray irrigation systems are only 45 to 60 percent efficient. . From our experience, soaker hoses though far more efficient that regular irrigation, still waste way too much water. Drip Irrigation is 90%, or more, efficient
Install a remote rain sensor away from trees and buildings.
Determine how many zones will be needed according to all the variables such as type and size of plants, soil conditions, and location in regards to sun/shade.
Install soil moisture sensors in every zone.
Obliviously over watering means that you'll need a much larger tank to keep your water wasting system running. (Remember the $1.00 per gallon rule?) Also it's been proven that more plant disease problems are created by over watering than any other.
Determine the proper type, placement, and quantity of emitters
There are now emitters available for, just about, every conceivable requirement.
Best practices for a water wise garden irrigation system.
A retrofitted irrigation system can still be made water wise, but a landscape that's planned from the very start to be water wise is actually the very best thing that can be done. A properly designed and installed landscape will require far less water and the cost of the rainwater catchment system will be much less.
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