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Landscape for Life - Water Workbook

Landscape for Life - Water Workbook



Landscape for Life - Water Workbook

Landscape for Life - Water Workbook



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    Landscape for Life - Water Workbook Landscape for Life - Water Workbook Document Transcript

    • a c k n ow le d gementsLandscape For Life is a project of the United StatesBotanic Garden and the Lady Bird Johnson WildflowerCenter at The University of Texas at Austin.Landscape For Life is based on the principles of SITES,The Sustainable Sites Initiative , the nation’s first rating TMsystem for sustainable landscapes (www.sustainablesites.org), an interdisciplinary effort by the American Society ofLandscape Architects, the Lady Bird Johnson WildflowerCenter at The University of Texas at Austin, and theUnited States Botanic Garden in conjunction with adiverse group of stakeholder organizations. SITES offerstechnical tools for professionals who design, construct,operate, and maintain landscapes of all sizes. LandscapeFor Life presents this information in an easy-to-use formfor homeowners and gardeners.The information in this workbook is also available on the A sustainable garden in TexasLandscape For Life website (www.landscapeforlife.org). includes a buffalograss lawn and other native plants that nurtureWritten by Janet Marinelli wildlife.Designed by Elizabeth Ennis Illustrations page 8, Sustainable Sites Initiative; page 10, Elizabeth Ennis Cover photos, left to right: first two images, Bigstock.com, H. Zell, last two images, Bigstock.com. Photo page i, Andy and Sally Wasowski, Lady Bird Johnson Wildflower Center; page ii, Steve Greer/VIREO; page iii, public domain image via Wikipedia; page 1, Manual Broussard/FEMA; page 2, Ward Wilson; page 5 public domain image via Wikipedia; pages 7 and 8, Nancy Arazon; page 11 left and right, Walter Siegmund; page 15, Holly Shimizu i
    • I n t rod uc tIonw o r kI ng w I th nature to create ah e a lt hy, be autI ful home l andscapeLandscape For Life shows you how to work with naturefor a beautiful, sustainable garden, no matter where youlive, whether you garden on a city or suburban lot, a 20-acre farm, or the common area of your condominium.Conventional gardens unintentionally often work againstnature. They can damage the environment’s ability toclean air and water, reduce flooding, combat climatechange, and provide all the other natural benefits thatsupport life on earth—including us.The good news is that even one home garden can beginto repair the tattered web of life. It’s possible to create agreat-looking garden that’s healthier for you, your family,your pets, and the environment—and that saves you timeand money.The Landscape For Life workbooks help you transformyour home garden into a beautiful and healthy refugefor you and your family. You can download the completeworkbook, or individual workbooks on Getting Started, Soil, Water, Plants, Materials, and HumanHealth. Each workbook includes helpful advice on gardening practices that take advantage of naturalprocesses at work on your property. ii
    • c o n t entsWater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Create a water-thrifty landscape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Select plants adapted to local precipitation patterns . . . . . . . . . . . . . . . . . . . . . . . 3 Use alternatives to drinking water for irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 A guide to water-thrifty irrigation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Smart strategies for managing stormwater. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Create a rain garden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Limit impervious surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 A guide to green roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Protect and restore vegetative buffers along waterways and wetlands . . . . . . . . . . .14 Sustainable water features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 iii
    • wat e rSo much of the earth is covered with water, it’s sometimes calledthe “water planet.” About 97 percent of the water is oceansaltwater. Most freshwater is locked up in the polar icecaps.Only .003 percent of the earth’s water is available for humanconsumption.Water is chronically in short supply in arid areas, and can bescarce even in places that historically have had a lot of rain. Yetwe often lavish it on our landscapes—typically drinking water,which we pay a lot of money to treat and pump. Meanwhile,instead of capturing and using rainwater in our gardens, we’vecreated an entire infrastructure of gutters, downspouts, andsewers to get rid of it. The resulting stormwater runoff cancontaminate local waterways with fertilizers, pesticides, and other Public water supply andpollutants. treatment facilities consumeThe good news is that it’s possible to harvest enough non-potable enough electricity to power morewater to meet landscape needs and prevent polluting stormwater than 5 million homes for a year.from running off our properties. In most cities, pumping and treating water and wastewaterInformation on selecting plants adapted to the precipitation accounts for 25 to 50 percent ofpatterns in your area, alternatives to drinking water for irrigation, the entire municipal energy bill.and how to irrigate efficiently follow. For details on using organicmulches to conserve water, see the Soil workbook.Conventional And Sustainable Landscapes: How They Compare Conventional Landscape Sustainable Landscape • Treats rainwater as a waste to be removed from • Manages rainwater as a resource to be used on the site the site • Can generate stormwater runoff that pollutes local • Designed to keeps stormwater on site and waterways protect local waterways • Usually irrigated with municipal drinking water • Irrigated with alternatives to potable water • May result in high water bills • Can be cheaper to maintain 1
    • cr e at e a water -t h r Ift y la ndsc a peAmericans consume more than 7 billion gallonsof water a day outdoors. One to two thirds of thedrinking water we use is for irrigation.It is a popular misconception that this is the onlyway to have a healthy lawn and garden. A beautifullandscape can be in tune with the amount ofprecipitation that falls naturally in the area.Sometimes irrigating makes sense. New transplantsneed to be watched carefully throughout the firstyear and watered when the soil dries out or theplants look stressed. In arid climates, gardens maygo dormant and look brown in summer without somesupplemental water. Vegetables often require moremoisture than nature provides via rainfall.Information on selecting plants adapted to theprecipitation patterns in your area, alternatives todrinking water for irrigation, and how to irrigateefficiently follow. For details on organic mulches andhow to use them as a water conservation measure,see the Soil workbook. Rainfall flowing off a home’s roof into a rain barrel is used to irrigate the garden. How Low Should You Go? You can measure your progress against benchmarks used in the Sustainable Sites Initiative (SITES) (www.sustainablesites.org), the new rating system for sustainable landscapes on which Landscape for Life is based. SITES awards two points for gardens that reduce the use of potable water by 75 percent from a local baseline case. Three points are awarded for gardens that use no potable water for irrigation once plants are established, and a garden that consumes no potable water both during and after establishment is awarded five points. 2
    • SELECT PLANTS ADAPTED TO LOCALPRECIPITATION PATTERNSGrowing plants adapted to the conditions found on your property is one of the basic principles of sustainablegardening. You’ll find a detailed discussion on how to choose the right plant for your site in the Plants workbook.Following are some tips to help you create a garden that’s suited to local precipitation patterns:• Preserve as many well established trees and shrubs as possible, because they generally require less water than newly planted specimens.• When selecting plants, avoid those labeled “hard to establish,” as they often require large amounts of water.• Favor plants native to your region, which are adapted to the local climate. Be sure to choose native plants that match the specific conditions at the planting site.• If you’re considering a non-native plant, make sure it is not a known invasive species in your region. Some invasive plants are water guzzlers and can transform the natural hydrology of natural areas, making it even more difficult for the native species to survive.• To speed establishment and minimize water use, plant at the recommended time for a particular species. They key to successful transplanting is getting the roots to grow into the surrounding soil as soon as possible. For many plants in areas with regular rainfall in the warmer months, this is in spring, when roots are growing most actively and there is enough moisture in the soil to support new growth. In warmer areas, fall is a much better planting period, and the best time to plant many woody species is when they are dormant in the winter. Consult plant labels or your local nursery or public garden (http://www.publicgardens.org/gardens) about the best time to plant.• The size of your lawn and what type of turf grass you grow can have a huge impact on the amount of irrigation your landscape requires. Read more about creating a regionally appropriate lawn in the Plants workbook.USE ALTERNATIvES TO MUNICIPAL DRINKINg WATERFOR IRRIgATIONWith a little ingenuity, you can use non-potable water from a variety of sources both indoors and outdoors toirrigate your garden. Non-potable water is not fit for humans to drink, but is generally safe for plants. Accordingto the American Water Works Association Research Foundation, households that irrigate with alternative watersources can slash their water bills by as much as 25 percent.Rainwater CollectionRainwater collected in barrels or other storage tanks has been used for irrigation for centuries. Rain barrels areconnected to the downspouts of a home’s roof gutters and typically hold around 50 gallons. They come with ascreened cover and an overflow spout and hose to divert excess water away from the home’s foundation. Thetypical house has at least four downspouts, at each corner of the house, and rain barrels can be connected to oneor more of them. Of late, designers have been creating versatile variations on the rain barrel, including modelswith sleek profiles that can fit along narrow passages, under decks, or in other underused spaces. Modular designsenable you to add on capacity or even put the tanks in multiple locations.Cisterns, storage tanks made of stone, mortar, plaster, or cement, were once very common in the U.S., especially inrural areas where homes relied on private wells for water. Today, prefabricated cisterns are available in various materialsand sizes. A cistern is a more complicated undertaking but can store a lot more water than a rain barrel. Check with thenearest Cooperative Extension office (www.csrees.usda.gov/Extension/) for information on the best systems for yourregion and how to construct them. 3
    • For More InformationOther useful resources on harvesting rainwater are U.S. EPA’s rainwater collection handbook (http://www.epa.gov/npdes/pubs/gi_munichandbook_harvesting.pdf) and the American Rainwater Catchment SystemsAssociation (www.arcsa.org/content.asp?pl=6&contentid=6).Many states also have resources on rainwater collection. See, for example:Texas Water Development Board (http://www.twdb.state.tx.us/iwt/rainwater.asp)Rainwater harvesting case study for Florida (http://www.harvesth2o.com/floridahouse.shtml)Rainwater harvesting at North Carolina State University (http://www.bae.ncsu.edu/topic/waterharvesting/)Collecting Air Conditioning CondensateCondensate is produced when warm, moisture-laden air passes over the coils of an air-conditioning system. Theaverage single-family home produces 5 to 10 gallons of condensate per day.Condensate is an attractive irrigation option for several reasons. It’s produced through the normal daily operationof air-conditioning equipment. Unlike rain, which is sporadic and unpredictable, condensate is producedregularly during the hottest months when the need for irrigation is greatest. Inquire about the components of acondensate collection system at local home improvement centers and farm and ranch supply stores. For moreon collecting and reusing air conditioning condensate, see the Alliance for Water Efficiency website (www.allianceforwaterefficiency.org/Condensate_Water_Introduction.aspx).Water From DehumidifiersWater pulled from the air by dehumidifiers is a high-quality source of water for irrigation. Because the watertypically ends up in a basin that is easily removed for emptying, no additional equipment is necessary.Graywater CollectionA variety of appliances and fixtures produce used water called graywater. An estimated 50 to 80 percent ofresidential “wastewater” is dish, shower, sink, and laundry water. Because graywater often contains soaps,detergents, shampoos, or other substances as well as bacterial and other pathogens, its use is regulated by stateand local governments (see below).Graywater is most often recommended for subsurface irrigation of non-food plants. Graywater systems vary fromsimple and low-cost to complex and costly. The simplest way to collect graywater is to plug the drain and employa bucket to transport bath or shower water for use outdoors. Another common practice (but illegal in somelocations) is to drain the washing machine directly onto outside vegetation. Sophisticated systems involve separateplumbing for graywater as well as settling tanks and sand filters to remove solids and pathogens.State And Local RegulationsStates and local governments have different regulations on what kinds of graywater are permissible for use. Someprohibit the collection of graywater entirely, so be sure to investigate what qualifies as graywater and whether anyrestrictions apply in your area. A list of some states and municipalities with graywater policies can be found here.(www.oasisdesign.net/graywater/law/index.htm)Different Systems For Different ClimatesKeep in mind that different alternatives make more sense in some regions than others. For example, harvestingrain flowing off the roof in rain barrels or other storage systems may be cost effective in rainy climates, but inparts of the country with dry summers, rainfall may be too infrequent to make them worthwhile. In these areas,capturing condensate from an air conditioning system is a better option. 4
    • A gUIDE TO WATER-ThRIFTy IRRIgATIONConventional irrigation practices waste a lot of water. Irrigating with traditional sprinklers or when it is hot or windyleads to water loss through evaporation. Watering too quickly or too much leads to runoff. The goal of water-wiseirrigation is to reduce these losses but still supply as much water as is necessary.What To Do• Irrigate only when your plants need water. How often to water depends on a number of factors, including what type of soil you have, the type of plants you’re growing, whether your plants are established, the season, and weather conditions. Don’t irrigate on a fixed schedule, which wastes water by providing it when your plants don’t need an extra drink.Frequent, shallow watering leads to weak, shallow-rooted plants. Less frequent, deep watering encourages roots togrow deep, where the soil stays moist longer.• Use a rain gauge and/or soil moisture probe. A variety of relatively simple tools can help you determine when you need to water. The simplest and most inexpensive of all is a rain gauge to measure weekly rainfall. Soil moisture probes employing different technologies are commercially available at varying prices. They measure the moisture level of your soil, giving you a more precise indication of how much, if any, water your plants require.Rain gauges and soil moisture probes should be used in conjunction with basic knowledge about how much watervarious parts of your landscape require. For example, vegetables generally need more than established woody plants.And even edible plants require less water when it is overcast and relatively cool than when it is sunny and hot.• Hand water. According to an American Water Works Association (AWWA) Research Foundation study, manual watering with a hand-held hose tends to conserve more water than other irrigation methods.If you are going to have an in-ground system, makesure it is a drip system as it used the least amountof any automatic system—but still 16 percent morethan watering by hand. In-ground spray systems used35 percent more water than hand watering, and anautomatic spray system used 47 percent more.• Use drip irrigation systems or soaker hoses. Drip irrigation systems deliver water through tubing and emitters placed alongside your plants. The emitters slowly drip water into the soil in a plant’s root zone where it is needed, not in gaps between plants where it is wasted. They also reduce water loss due to evaporation, and the low flow rate minimizes the potential for water leaching below Watering by hand conserves more water than any other the roots or running off the surface. Drip irrigation irrigation method, according to a study by the American can be used in vegetable and flower beds and Water Works Association. The same study also found that drip irrigation consumes much less water than the in-ground around trees and shrubs. spray irrigation systems used in most home gardens. 5
    • As the AWWA study discussed above shows, however, drip systems must be operated properly to be truly water-thrifty. To maximize their efficiency, install climate-based controllers such as sensors that prevent the system fromturning on during and immediately after rainfall. Even better are sensors that activate irrigation only when soilmoisture drops below a pre-determined level. So-called “smart” or weather-based irrigation controllers take intoaccount a range of factors to determine when supplemental water is necessary, including temperature, rainfall,humidity, solar radiation, and soil moisture levels.Soaker hoses, which have perforations that slowly leak water into the ground, can also be efficient and effective.If you’re in the market for a water-conserving irrigation system, it’s worth checking out WaterSense. (www.epa.gov/WaterSense/) Sponsored by the U.S. Environmental Protection Agency, the program seeks to do for irrigationproducts and services and plumbing fixtures what the Energy Star label has done for electric appliances. Irrigationtechnologies and services that have been awarded the WaterSense label are listed on the program’s website.• Use alternatives to potable water for irrigation. Take advantage of the various sources of non-potable water around your home. See page 3 for details.• Water your plants early in the morning. Mornings are cooler, so water doesn’t evaporate as readily as it does in the heat of the afternoon. Evenings are cool, too, but water sitting on leaves overnight can cause fungal diseases.For More InformationThe Irrigation Association website (www.irrigation.org/) has a section for consumers with tips on how to hire anirrigation contractor, when an irrigation designer is necessary, and “smart” technology that saves water, time,and money. 6
    • s m a rt s t r at e gIes forman a g I ng s to r mwat e rIn a natural landscape, the soil and vegetation absorbprecipitation like a sponge. In developed areas,however, much of the land has been paved over, andthe soil itself is often compacted and impervious. Theamount of rainfall exceeds the land’s ability to absorbit, resulting in stormwater runoff.Rainfall flows from our roofs to gutters anddownspouts, over compacted lawns and drivewaysinto roads, and down storm drains. In most oldercities this stormwater can overwhelm sanitarysewers, sending raw sewage as well as runoffcarrying fertilizers, pesticides, motor oil, and otherpollutants into nearby waterways. Runoff also resultsin less water infiltrating through the soil to replenishgroundwater supplies. For a comparison of runoffamounts from different types of landscapes, fromwoods and meadows to urban business districts, seepage 8.A sustainable home landscape is designed to keepstormwater on the property, minimizing damage towaterways and aquatic life. The typical house has at least four downspouts, at each corner of the house. Connecting rain barrels to one or moreOn the pages that follow, you’ll find information of them not only captures water for irrigating the garden buton stormwater management strategies such as also helps minimize stormwater runoff.creating a rain garden, limiting impervious surfacesin your landscape, and restoring vegetative buffersalong any wetlands and waterways adjacent to your property. You’ll also find a guide to green roofs. Collectingrainwater that flows from your gutters not only provides an alternative to drinking water for irrigation but alsoreduces stormwater runoff; see page 3 for details. It is important to use landscape materials that do not pollutestormwater. For information on polluting materials and alternatives, see the Materials workbook. 7
    • RUNoFF AMoUNTS FRoM DIFFERENT LANDSCApES .6 inches of .6 inches of runoff runoff 2.4 inches 2.4 inches 1 inch of of infiltration of infiltration runoff 2 inches of 1.6 inches of infiltration 2.5 inches of runoff runoff 1.4 inches of .5 inch of infiltration infiltration Impervious Impervious Impervious Impervious Impervious surface 0% surface 0% surface 0% surface 38% surface 85% WooDS MEADoW RoW CRop RESIDENTIAL URBAN AGRICULTURE (0.25-ACRE LoTS) BUSINESS DISTRICTAs development increases, so do soil compaction and impervious surfaces. Compacted soils, along withdriveways, roads, parking lots, rooftops, and other impervious surfaces, make it difficult for rain to infiltrateinto the soil, as in a natural setting. As a result, the more impervious surface in a landscape, the less infiltrationand the more stormwater runoff it generates. The illustration above shows the percentage of impervioussurface and the amount of infiltration and runoff following a 3-inch rainstorm for each kind of landscape. 8
    • CREATE A RAIN gARDENOne of the most effective ways to prevent stormwater runoff in a home landscape is to create a rain garden.Basically, a rain garden is just a strategically located low area where water can soak naturally into the soil. Like therest of your ornamental garden, it can be full of colorful plants.Rain gardens have other benefits, too. They help protect your community from flooding. They protect localstreams and lakes from the many pollutants carried by stormwater as well as the physical damage it causes. Byincreasing the amount of precipitation that filters naturally into the ground, they replenish underground watersupplies. And rain gardens also provide valuable habitat for birds, pollinators like butterflies and bees, and manyof the beneficial insects that help keep your garden healthy by keeping pest populations in check.Following are some things to consider when planning a rain garden.• Where to put it Locate your rain garden either near the house to catch only roof runoff, or farther away to collect stormwater from the lawn as well as the roof. A rain garden can also capture precipitation flowing off of paved areas. Keep it at least 10 feet from your house to prevent moisture problems.• How big? A typical residential rain garden ranges from 100 to 300 square feet, but the time needed to dig the depression, the cost of plants, and the size of your property will help determine how large yours should be. The size of a rain garden that can manage most or all of your runoff also depends on what type of soil you have and how much roof and/or surface area will drain into it.• How deep? A rain garden should be 4 to 8 inches below the level of the surrounding land.Rain gardens such as this one in Seattle can be attractive elements of your home landscape. They can also provide valuablewildlife habitat, especially when native species are planted in drifts of three to seven of each for maximum impact. 9
    • • When the soil should be amended If your soil drains poorly, you may need to add a layer of sand or gravel at the bottom of your rain garden to prevent it from becoming an ephemeral pond. If you have clay soil with enough rock or other aggregate, or you have clay loam, the sand and gravel bottom is probably unnecessary, unless you want the water to drain very quickly. If your soil is heavy clay, you may also need to amend it with sand and compost.• How to connect it to a downspout To direct stormwater from a downspout, bury a length of plastic pipe in a shallow trench that slopes down to the rain garden, or create a grassy swale.• What to plant It’s helpful to think of a rain garden as comprised of three wetness zones: In the lowest zone, plant species that can tolerate short periods of standing water as well as fluctuating water levels, because a rain garden will dry grassy swale porous soilA rain garden should be 4 to 8 inches below the surrounding land. You can direct stormwater from a roofdownspout to the rain garden with a grassy swale, as above, or with buried plastic pipe. The soil in a raingarden should be porous, so if you have heavy clay soil you may need to amend it with sand and compost. Raingarden plants should be appropriate for your region and tolerate both wet and dry periods. 10
    • out during droughts or at times of year when precipitation is sparse. Species that can tolerate extremes of wet soils and dry periods are also appropriate for the middle zone, which is slightly higher. Put plants that prefer drier conditions at the highest zone or outer edge of your rain garden. To enhance the garden’s value as wildlife habitat, plant native species in drifts of three to seven of each for maximum impact. After planting, apply a layer of organic mulch 2 to 3 inches deep to keep down weeds and protect and enrich the soil.• Maintenance Although rain gardens require some initial effort, they are easy to maintain. Until your plants become established, you’ll have to weed out undesirable volunteers. Leave the dormant plants standing over the winter in cold climates to provide seeds and shelter for overwintering birds and butterflies. In spring you can cut back or mow the stalks of herbaceous plants if you prefer a neat-and-trim look.For More InformationRain Gardens: A how-to manual for homeowners (http://learningstore.uwex.edu/assets/pdfs/GWQ037.pdf),published by the Wisconsin Department of Natural Resources and the University of Wisconsin-Extension, containscomprehensive, step-by-step instructions on all aspects of creating a rain garden “based on a goal of controlling100 percent of the runoff for the average rainfall year while keeping the size of the rain garden reasonable.”It includes a number of rain garden planting designs and plant lists for varying sun and soil conditions that areespecially appropriate for the Midwest.An extensive list of plants (www.bbg.org/gardening/article/rain_gardens/rain_gardens_2) appropriate for raingardens and native to the eastern two-thirds of the U.S. and Canada, which was compiled by Temple University, isavailable on the Brooklyn Botanic Garden website.Your state or county Cooperative Extension office (www.csrees.usda.gov/Extension/) is also a good place toseek information on rain gardens appropriate for your area. See the next page for some recommended Extensionpublications.Among the lovely native plants recommended for Pacific Northwest rain gardens are Nootka rose, left, and westerncolumbine, right. 11
    • “Adding a Rain Garden to Your Landscape” (www.umext.maine.edu/onlinepubs/PDFpubs/2702.pdf ),University of Maine Cooperative Extension“Rain Gardens” (www.csgc.ucsd.edu/BOOKSTORE/Resources/GS3%20Rain%20Gardens_8-10-09.pdf ),Sea Grant California and University of California Cooperative Extension“Backyard Rain Gardens” (www.bae.ncsu.edu/topic/raingarden/), North Carolina Cooperative Extension“Rain Gardens” (www.water.rutgers.edu/Fact_Sheets/fs513.pdf), Rutgers University Cooperative Extension“Rain Gardens” (www.sustainability.uconn.edu/pdf/raingardenbroch.pdf), University of ConnecticutCooperative ExtensionRain Garden Handbook for Western Washington Homeowners (www.pierce.wsu.edu/Lid/raingarden/Raingarden_handbook.pdf), Washington State University Extension Pierce CountyFor ideas on what to plant, you’ll find links to native plant societies of the U.S. and Canada here (http://www.michbotclub.org/links/native_plant_society.htm). The Wildflower Center Native plant Database (www.wildflower.org/plants) is another helpful resource.LIMIT IMPERvIOUS SURFACESImpervious surfaces are mainly constructed surfaces—rooftops, sidewalks, driveways, roads—covered byimpenetrable materials such as concrete, blacktop, and mortared brick or stone. But urban and suburban soils,which are often compacted by intense foot traffic or construction equipment, are also highly impermeable. Asurbanization increases, so does the amount of impervious surface. Studies have shown that the pervasiveness ofimpervious cover is directly related to the poor quality of many urban watersheds.Because they prevent precipitation from seeping down into the soil, impervious surfaces are a primary cause ofstormwater runoff. Torrents of destructive runoff are generated as rainfall strikes rooftops and pours into guttersand downspouts, picking up volume, speed, and pollutants as it rushes over paved surfaces and into storm drains.What To Do:Following are some of the ways you can reduce impervious surfaces to enable water to seep into the ground.• Two ribbons of pavement with a low groundcover in between is a more porous alternative to a solid driveway of concrete or blacktop.• Use stepping stones surrounded by creeping groundcovers instead of continuous impermeable pathways.• Opt for “dry laid” instead of “wet laid” or mortared patios and walkways. Set in stone dust or sand, these allow some stormwater to infiltrate into the soil, unlike the impervious cement products typically used as mortar.• Green spaces between patios, pathways, and other impermeable spaces can help prevent stormwater from accumulating and running off your property. Plant a rain garden to capture stormwater runoff from your roof.• Restore the structure of any compacted soil on your property, and take steps to prevent soil compaction elsewhere in your landscape. See the Soil workbook for details.• Various types of permeable paving, such as concrete products with a porous structure that allows water to pass directly through, can be expensive but are worth considering.• Some green roof systems can help manage stormwater and are worth considering if you’re in the market for a new roof. 12
    • A gUIDE TO gREEN ROOFSMost green roofs currently being installed in North America are so-called extensive roofs that consist of four majorcomponents: a waterproof and root-repellent membrane to keep water from leaking into the building, a drainagesystem, 3 to 6 inches or less of lightweight growing medium, and vegetation that is adapted to the extremeconditions on rooftops and requires little or no maintenance. Living roofs cost a lot more than conventional roofs,but last about twice as long.Green roofs help reduce the urban heat island effect—the difference in temperature between urban areasand the surrounding countryside caused by the lack of vegetation and large number of paved and builtsurfaces that absorb heat. Research (www.wildflower.org/greenroof/) at the Lady Bird Johnson WildflowerCenter shows that green roofs can be up to 80 degrees cooler than adjacent buildings with traditional roofs.By insulating your home, they also can significantly reduce energy consumption and heating and coolingbills. They filter pollutants, improving air quality in towns and cities. In urban areas especially, they canprovide valuable wildlife habitat (www.nwf.org/News-and-Magazines/National-Wildlife/Gardening/Archives/2007/Green-Roofs-Take-Root.aspx). And they add aesthetically pleasing green space, reducing the monotony ofbarren city skylines.A green roof’s ability to manage stormwater runoff, however, has been debatable. The growing media usedon green roofs typically contain slow-release fertilizer, which can be carried away in excess stormwater runoff,polluting local waterways and harming aquatic life. A 2009 study by the U.S. Environmental ProtectionAgency comparing the quantity and quality of runoff from green and flat asphalt roofs concluded that greenroofs are capable of removing 50 percent of annual rainfall volume, although this varied seasonally fromabout 95 percent in summer to less than 20 percent in winter. The study, which was conducted by the PennState Center for Green Roof Research, also concluded that green roof runoff did contain some nutrients, butbecause the volume of runoff was reduced significantly, green roofs actually led to less nutrient pollution thanasphalt roofing. And the runoff can be directed from the roof to a rain garden, where the nutrients can helpnourish the plants.The Wildflower Center found that some green roofs are better at reducing runoff than others. Researcherscompared the performance of six extensive green roof systems from six different manufacturers to each otheras well as to traditional non-reflective blacktop and somewhat cooler reflective white roofs at the Center’sheadquarters in Austin, Texas. Each roof was planted with the same 18 native species chosen for their widetolerance of both drought periods and saturation after rainstorms. The plants were provided with the sameamount of water for irrigation each week when rainfall wasn’t sufficient.Compared to both conventional and reflective roofs, the green roofs were much better at preventing thetemperature of the inside air from spiking on warm days. Some of the roofs were able to capture a significantamount of stormwater (80 percent of a half-inch rain event and 40 percent of 1-inch and 2-inch events),but others were not significantly better in this respect than the white or blacktop roofs. What’s more, whilesome of the roofs had nearly no adverse effect on water quality, others were worse than the typical suburbanlawn—the more fertilizer in the planting medium, the worse the water quality (and the faster the plantgrowth), although water quality dramatically improved after the first growing season. In short, no one systemexcelled at providing all the benefits often attributed to green roofs.What To Do:• Green roofs are substantial investments. Although they’re not space-age contraptions, building one isn’t simply a matter of hauling potting soil and plants to your rooftop. It’s important to consult a landscape architect, engineer, or roofing contractor with experience in green roof installation. A directory of accredited green roof professionals is 13
    • on the Green Roofs for Healthy Cities website (http://greenroofs.org/index.php?option=com_comprofiler&task=us ersList&Itemid=&limitstart=0&search=&listid=4&name=&company=&city=Chicago&state=IL).• Determine why you want a green roof—whether it’s aesthetic value, habitat value, or its ability to save energy or retain stormwater. Make sure that a green roof is the most efficient way to achieve your goals.• If you decide to pursue a green roof, make the consultant or manufacturer you are working with aware of your goals and ask which green roof system is most likely to achieve them.PROTECT AND RESTORE vEgETATED BUFFERS ALONgWATERWAyS AND WETLANDSIn undisturbed natural areas, waterways and wetlands are typically protected by adjacent vegetation. Grassland,woodland, or wetland plant communities reduce runoff by increasing the land’s capacity to absorb stormwater.Less runoff means less pollution of all kinds entering the water, including nutrients from fertilizers, pet wastes, andother sources—excess nutrients are the primary cause of the algal blooms that rob oxygen from the water and killfish. Plant roots stabilize the soil and protect against erosion. The vegetation also improves wildlife and fish habitatby providing food, shelter, and shade.In many areas, however, the native vegetation has been removed and these important ecological functions havebeen reduced or destroyed. In residential areas, turf grass often extends all the way down to the water, polluting itwith stormwater runoff carrying fertilizers and pesticides routinely used in lawn care.In developed areas, vegetated buffers can fulfill the same important ecological functions as undisturbed watersidevegetation. As the name suggests, these are thickly vegetated strips of land that protect waterways and wetlandsfrom polluted runoff and erosion. They also provide habitat for a variety of wildlife year round, including “stopoverhabitat” for migrating birds in spring and fall.Research shows that as the width of a vegetated buffer increases, its ecological benefits also grow. Buffers lessthan 50 feet wide offer minimal protection, while those 200 to 300 feet in width improve water quality and protectaquatic habitats. Vegetated buffers more than 300 feet wide can function as wildlife corridors and even harborimperiled and sensitive species.What To Do:• If your property borders a waterway or wetland, create a thickly vegetated and undisturbed buffer at least 50 feet wide. These riparian and coastal zones are often regulated, so contact local and regional government agencies for information on appropriate vegetation buffers in your area.• Do not use any pesticides or fertilizers—even organic fertilizers including compost—in a vegetated buffer area.• Undisturbed buffers provide the best protection. If you need access to the water, create an elevated walkway made from untreated wood to protect the vegetation as much as possible. 14
    • susta I na b l e wat e r fe at u r e sFrom decorative fountains and tubs to pre-formedpools and ponds, water features have becomepopular garden amenities, and for good reason.The sight and sound of water is relaxing, and maypromote stress reduction and healing. Wetlandplants can be spectacular, whether the delicatewater-lilies that float on the still surfaces of ponds,the brilliant cardinal flowers that populate marshedges, or the carnivorous pitcher plants that grow inspongy bogs. The sound of a cascading waterfall,a trickling stream, or even a bubbling urn addsanother dimension to a landscape and can drown outunwanted clatter. What’s more, water features willattract birds and other delightful wildlife to your yard.Countless tomes on how to create a water featurehave been published in recent years, but they almostnever tell how to construct a feature that conservesenergy and potable water.What To Do:• Use alternatives to potable water, such as collected rainwater or air-conditioning condensate, in your water feature; see page 3 for details. Systems are now available that combine a rainwater harvesting This sustainable water feature uses rainwater channeled from the gutter. When rainfall is sparse it becomes a dry creek bed. and storage system with a decorative water feature.• Use solar recirculating pumps, which conserve water and are powered by a renewable source of energy.• Consider using an ecological design approach, creating a water garden that includes plants appropriate for local conditions and functions as a natural ecosystem. A streambed that goes dry for part of the year may be appropriate in an arid area. An in-ground pond that mimics the natural zones of vegetation found in natural ponds may be appropriate for a good-sized property in a high-rainfall area—complete with floating plants like water-lilies in deep areas; pickerel weed, arrowheads, grasses and sedges that grow partially in water in the emergent zone; and colorful wildflowers, shrubs, or trees found where the wetland grades into upland.For More InformationThe Natural Water Garden: Pools, Ponds, Marshes & Bogs for Backyards Everywhere(http://shop.bbg.org/mm5/merchant.mvc?Screen=PROD&Store_Code=BGGS&Product_Code=BBG-NAT-151&Category_Code=BBG-NAT),edited by C. Colston Burrell and published by Brooklyn Botanic Garden, takes an ecological design approach towater gardening, with step-by-step instructions and recommended plants for the Northeast and Mid-Atlantic, theSoutheast and Deep South, South Florida, the Midwest and Great Plains, the Western Mountains and PacificNorthwest, and California. 15
    • ww w. l a nds ca p e f o r l If e . o r g