Landscape and Irrigation is read by decision makers throughout the landscape and irrigation markets — including contractors, landscape architects, professional grounds managers, and irrigation and water mgmt companies and reaches the entire spetrum.
Issue link: https://read.dmtmag.com/i/129601
be a destructive force. It can erode hillsides, dig gullies, undermine paving and foundations, push over trees, and deposit mud, rocks, and debris in alarming places. Every designed landscape walks a balance between having too little water and too much. Figure 1.4 Xeriscape by Panayoti and Gwen Kelaidis, teeming with plants that need no supIf we have plemental irrigation, in Denver. — Photo by Travis Beck. matched our namic, holistic systems," that is, ecosystems. plants to our climate, then what we grow Franklin's approach was to line the censhould be able to survive on natural preter of the depression in order to maintain a cipitation alone. But within each biome minimum water level but leave the edges live many different communities of plants, unlined. Water from the spring is collected some in drier sites, others in wetter. Main a sump beneath the pond and pumped nipulating the flow of water with contourvia a slender waterfall off the rock outcrop ing and rainwater harvesting techniques and into the pond. In spring the pond can move water away from where it is a overflows, recharging groundwater in the problem to where it is a resource, dissipate area. The margins are planted with trees its destructive power, and create a range of and other plants that are adapted to this conditions suitable to growing a variety of seasonal flooding. Between the open plants. water, the planted wetland at the pond's Where we do not want water, such as edge, and the seasonal wetland beyond, the around the foundations of buildings, we design provides diverse habitat. When can use grading and drainage channels to water levels drop to the level of the liner, direct the water away. These areas then bethe wetted margins dry, mimicking the come places to plant more droughtcycle of vernal pools. If water levels drop tolerant plants, and the water directed further, the sump pump and waterfall can away becomes a resource for other areas make up the difference from the recharged of the landscape. Just as Wenk Associates groundwater. Because the pond is in the did at Menomonee Valley Community forest, however, evaporation and the need Park, slowing the water, spreading it out, for makeup water are minimal. and getting it to infiltrate recharges This forested pond is now a hub of life groundwater and keeps it available for and the center of the entire landscape. local ecosystems. When this practice is Rather than create a sterile water feature of carried out fully, dry springs can resume dissociated elements, Andropogon created their flow, and once-ephemeral streams an ecosystem, with natural physical cycles can become perennial. Although the best and plants and animals adapted to them. place to store water is in the ground, rain barrels and cisterns can also be used to Meet plant water needs through capture seasonal surplus water that would contouring and drainage otherwise leave a site and make it available Water is not merely something to be during later dry spells. slowed, cleansed, and sent on its way. It is a Water drained from other areas of a resource that keeps alive every living thing landscape can help certain plants grow in on the planet. That is why we love founregions where the annual precipitation tains and pools in our landscapes. And it is figures make it seem as if they should not. why nearly every garden includes a source Say, like Brad Lancaster of Tucson, Ariof water, if not an entire computerzona, you wanted to grow a tree in the controlled irrigation system. Water can also Sonoran Desert, the home of saguaro www.landscapeirrigation.com (Carnegiea gigantean) and cholla cacti.You would start by selecting a tree that is adapted to the climate, such as velvet mesquite (Prosopis velutina). Mesquite grows naturally on seasonally flooded terraces next to rivers and streams and along washes that concentrate rainwater from the surrounding area. Lancaster (2008, 2012) took advantage of similarly concentrated flows of water on the impervious street beside his house. With all the appropriate permissions, Lancaster cut a series of openings in the curb that separated that street from the barren public right-of-way that ran along his and his brother's property. Behind each curb cut they dug a sunken infiltration basin and used the dirt from their excavations to build a meandering raised path through the right-of-way. Now when it rains, each basin fills with water, then overflows back into the street, sending water along to the next curb cut and basin. Lancaster also placed layers of organic mulch in each basin to keep the water that has infiltrated from evaporating away. Thanks to these simple techniques, the previously sun-baked right-of-way is now shaded by maturing trees, without the need for extensive watering. Starting in 2010, the City of Tucson now requires all new commercial landscapes to provide 50 percent of their landscape water needs through rainwater harvesting, primarily passive techniques such as those demonstrated by Lancaster (City of Tucson 2009). Curb cuts and infiltration basins planted with trees have also been used in cities such as Portland, Oregon; these features are not for arid regions only. A properly graded landscape will preserve built structures, create dry routes for access and circulation, and infiltrate rainwater in areas where it can recharge groundwater and nourish plants with higher relative water needs. The microtopography thus created opens opportunities to grow communities of plants with different water needs across a site. LI Travis Beck is Landscape and Gardens Project Manager with the New York Botanical Garden. He is a registered landscape architect and LEED Accredited Professional with a Master's degree in horticulture from The Ohio State University.The excerpts presented here are reprinted with the author's permission. Landscape and Irrigation 17