The treatment and pumping processes required for municipal water and wastewater services can be the largest consumer of electric energy for the region that they service, so saving treated water can also significantly impact energy production needs. One of the interesting findings of a study published by the EPA in 2008 was that 50-78 percent of typical residential water use was in non-potable areas. The energy savings alone, to treat water to potable standards, including that required for pumped delivery to the customer, is substantial. Taking these non- potable uses off the table would result in huge savings in energy. This in turn would reduce our need to build more power plants, as well as eliminating any related pollution from those processes.
Additionally, pumping wastewater (blackwater) to sewage treatment facilities requires tremendous energy and water resources in and of itself. Treating wastewater onsite (septic systems) or reducing wastewater, through onsite composting, should be further considered in order to reduce municipal infrastructure and processing inefficiencies. Not only are we realizing that water is a valuable resource, we can also recognize that this type of “waste” has value as well.
Where Does the Water Go?
The remainder of this article will follow the course of what each of us can do to be part of the solution or at least stop contributing to the problems we have discussed up to this point. We will present possible solutions that each of you can incorporate into your construction project to secure a more sustainable water future for your family. We will address those strategies first that provide the biggest impact. To determine what those efforts will be, it is important for us to analyze where we are currently using the most water and to what extent each use requires water treatment. So this section will look at consumption from the biggest piece of the pie down to the crumbs. For those of you who might question the importance of the little things, just remember that, as we make significant achievements in the larger arenas, those little things represent a larger portion of what remains to be addressed.
Rethinking Our Landscapes
It’s probably no surprise to anyone that 50-70 percent of total household water usage continues to go to the landscape. This is the greatest portion of the non-potable water use described in the 2008 EPA study mentioned above. So reductions here will have the greatest impact. The first issue we must look at is our current landscaping practices. Many new developments have mandated landscape packages, defined by an architectural control committee, neighborhood deed restrictions, or government agencies like the Federal Housing Administration (FHA) or Veterans Administration (VA). Many are defined for aesthetic consistency, not water efficiency. Although some residents might agree that a common interest in maintaining property values might allow these authorities to dictate such details, they often lack information on alternatives that could achieve both attractive landscapes and water conservation.
There has been some press coverage lately regarding homeowner association deed restrictions that penalized members who followed mandated water restrictions during drought periods at the expense of their prescribed landscape maintenance requirements. In response, contractors have started to install artificial turf to provide that manicured lawn look. As green building consultants, we have been asked for our opinion on whether that could be considered a green feature, as it requires no watering. We think that there is a trade-off between the water savings and the greenhouse gas emissions resulting from the manufacture of that product, as well as the embodied energy to get it to the site. Artificial turf doesn’t do anything to support nature or wildlife. We have to think that there are better alternatives, including xeriscapes, wildscapes and mulch or rock gardens.
- Soil Amendments:
Adding high volumes of organic soil amendments and continuously improving the quality of the landscape soil will increase its ability to hold moisture, thereby reducing the frequency of supplemental watering. Expanded shale (hadite) is a porous rock that holds 38 percent of its weight in water, releasing it back into the soil as the soil dries out after being wet. When used as a soil amendment, especially in heavy clay soil, this material can extend periods between scheduled watering. Better yet, this amendment only has to be added once since it does not decompose like compost.
Soil amendments should be used in all areas of the landscape, including turf areas. The right soil conditions provide the best environment for any type of plant — grass, flowers, shrubs or trees — to flourish under even the most extreme conditions. Compost and shale not only improve the water-holding capacity of the soil, they also improve drainage and create the right living environment for microorganisms, which feed and support the plants’ ability to absorb nutrients from the soil.
- Plant Selection:
Next, select only native or adaptive plant species for your area’s climate, especially those that are able to live off average rainfall. In an arid region, succulents are a good choice, while in a marine climate, choose only water-loving species. The best selection of plants for your area will be the same ones that you see growing in natural environments locally.
- The Right Irrigation:
It is important to use supplemental irrigation for the first year, in order for the plants to establish healthy root systems. After that, wean them off supplemental irrigation to get them acclimated to natural rainfall patterns. Supplemental irrigation should only be used then in periods of extended drought.
When it comes to making difficult choices, the first should be to eliminate unnecessary outdoor water use. In consideration of this, mechanical irrigation systems should be avoided. Using supplemental irrigation indicates that you have selected plant species that cannot survive naturally in the landscape. Using it on a continual basis will only cause the landscape to become dependent.
If you must install an irrigation system, make sure that you hire a WaterSense-certified installer and that the system includes high- efficiency heads, a rain sensor and a soil moisture sensor to optimize its performance. These systems often pay for themselves in less than three years in water savings and yield a healthier lawn. They measure rainfall, soil type, humidity, solar exposure, wind and soil moisture levels using wireless probes then run all of that data through an algorithm to determine when and how much to water each zone. It is better to run the system to deliver one inch of water once a week than to water half an inch twice per week. Or better yet, skip the automatic settings and just run it manually when it is really needed.
The only exception to this is if you are able to capture water onsite specifically to provide natural irrigation for your landscape. This will be discussed later in this chapter when we look at available water sources. However you source your water, it is important to use it wisely, otherwise it may actually be a waste of both the resource and your efforts. Remember, every drop that you capture is one less drop of runoff that replenishes ground and surface water supplies that are dedicated to other water needs (like farming for our food supply).
New methods of landscape irrigation are also gaining ground. Trench beds utilize mulch as a base material to capture and absorb excess moisture and release it back into the bed, as needed. You can also use straw bales to border raised beds and achieve similar results.
Wicking beds involve encasing the landscape bed in a watertight enclosure, either using raised bed systems or by excavating your landscape bed and lining it with a heavy, impermeable pond liner. Add a 4-inch perforated pipe along the bottom of the enclosure (use flex pipe or a 90- degree connector), bringing the end of the pipe up to the level of the top of the enclosure. Provide an overflow drain hole in the side of the enclosure about the same level as the top of the perforated pipe. Then cover the bottom of the enclosure to a depth above the top of the pipe with clean, small gravel.
Use the drain pipe to fill the bottom of the reservoir with water, up to the top of the gravel. Fill the remainder of the enclosure with a blend of good-quality planting soil and compost. The soil layer should be at least six to eight inches deep. Plant your landscape as you would in a traditional planting bed or use this system for your vegetable garden. The plant roots will search for the water, developing deep roots down into the gravel bed. Add water, as needed, using only the perforated pipe, as this bed captures and retains the water with minimal evaporation or irrigation losses. The overflow pipe will indicate that the proper depth of water has been achieved. This is the most efficient irrigation system that we have ever come across, so it will have the greatest impact in reducing landscape or gardening water requirements.
- Minimize Evaporation:
Don’t forget the mulch. A good one-to-three-inch layer of mulch over any type of landscape bed, including your vegetable garden, will also significantly extend periods between watering. Use mulch from local materials, as it breaks down over time into compost that provides nutrients missing to the native ecosystem, further improving soil quality.
Dry-farming methods use mulch as walkways between planting rows, so the mulch captures runoff and, again, wicks moisture back to the soil as it dries out.
