Wetlands for improving water use efficiency of an urban green university campus
Marinus L. Otte1, Wei-Ta Fang2, and Eli Cohen3
1
Wet Ecosystem Research Group, Department of Biological Sciences, North Dakota State University, Fargo, USA, www.ndsu.edu/werg/,
[email protected] 2
Graduate Institute of Environmental Education, National Taiwan Normal University, Taipei, Taiwan, www.ntnu.edu.tw/ed/eng/,
[email protected] 3
Ayala Water & Ecology, Moshav Zippori, Israel, www.ayala-aqua.com,
[email protected]
Presented at National Taiwan Normal University, Taipei, Taiwan (RoC) on 23 March 2015.
Abstract Many urban landscape designs include wetlands, but few utilize the full potential of wetlands to provide ecosystem services such as cleaning water ad recycling in addition to those of providing places for recreation and relaxation. This paper discusses ways in which wetlands can be incorporated in integrated water management systems in urban settings, such as university campuses.
Introduction The incorporation of wetlands in urban landscape design, including university campuses, has been common practice for centuries. Often these were incorporated because they were already naturally present, or they were constructed. Either way, wetlands provide places for recreation and relaxation (Ferguson 2013). In recent decades, the ecosystem services provided by wetlands, particularly that of habitat for organisms and their ability to improve water quality have been drivers for their design and incorporation into urban landscapes (Shutes et al. 1997). Here we discuss how the services of wetlands can be integrated even more in urban landscape design, with a focus on university campuses, by taking the water management of the entire location into account.
The need for water management The ever increasing world population has led to urbanization and the development of large metropolises on every continent. Production of clean water and food, and their transportation to where people live, has been an ever growing problem. The intrinsic link between the production of water and energy (the so-called water-energy nexus, see for example Kenway et al. 2011) has led to the realization that water, energy and food production are now at such a scale, that the production of energy is in direct competition with that of food and supply of clean water (Ringler et al. 2013). This is very eloquently
explained in a recent TED-talk by Dr. Jonathan Foley, University of Minnesota, USA (Foley 2010). In places where there is more evapotranspiration than precipitation, for example in the southwest of the USA, the water-energy nexus is immediately visible. In times of drought the area being planted with crops is drastically reduced, because the people living in big cities such as Los Angeles need the water, and the energy to cool their homes (Nijhuis 2014, Strom 2014). In Fargo, North Dakota, the loss of water due to evapotranspiration is more or less equal to precipitation (see http://www.inkstain.net/fleck/wpcontent/uploads/et.jpg), and in Taiwan precipitation is much higher than evapotranspiration (see Chen et al. 2005 for evapotranspiration, and http://eng.wra.gov.tw/ct.asp?xItem=48142&CtNode=7674 for precipitation data). But neither Fargo nor Taipei should be complacent about their water use, because excessive discharge of polluted water still creates problems downstream. In addition, in countries such as Taiwan, that heavily depend on imports for their energy needs (Liao and Jhou 2013), the lack of water elsewhere may seriously impact on the availability and costs of energy. The need for clean water means that wise use of water is necessary regardless of which way the water balance tips.
Integrating water capture, quality improvement and re-use The thinking on how to better manage water use is particularly driven in places that have a general lack of water. An example of this is Israel where Eli Cohen’s company AYALA has been at the forefront of developing wetlands that are fully integrated in water management at scales ranging from simple homes to large industries. AYALA’s technology, the Natural Biological System (NBS) is used, for example, at hard industrial sewage sites to meet regulatory guidelines for heavy metals, boron, petroleum byproducts, organic compounds, suspended solids, pathogens and nutrients. NBS is also applied to protect sensitive ecological zones such as rivers and aquifers from landfill leachate, gas station runoff, sanitary and agricultural sewage. Almost all major rivers carry treated and sometimes untreated sewage and NBS is integrated in urban parks to passively upgrade the quality of the rivers to the regulatory demands. The advantages of NBS have been recognized and applied in more than ten countries at a variety of scales, ranging from wastewater treatment and reuse for urban/commercial buildings (Indian Green Building Council, Hyderabad), sewage treatment plants for entire neighborhoods (Calla Campeche, Mexico) and the holistic design and management of entire watersheds (Plan du Var, Nice, France). AYALA’s sustainable NBS technology for wastewater treatment is being adopted as one of the primary strategies in purifying the Ganga River, with partners of global importance such as United Nations Environmental Programme (UNEP), National Green Tribunal and major industrial and public officials throwing their support behind AYALA’s holistic, decentralized strategies for water management. AYALA is spearheading the “green” revolution in India with the adoption of Smart Cities and Smart Streets campaigns that include holistic management of watersheds, treatment of storm drains, sewage canals, rivers and domestic sewage. The approaches used in Cohen’s systems can also be applied to university campuses. Water from precipitation can first be captured by green roofs. Storm water that does not fall on roofs but falls on streets and pavement, and which often is quite polluted (e.g. Gnecco et al. 2005), can also be captured, cleaned and subsequently used in gardens. Gray water as well can be captured and pumped by solarpowered pumps where needed. And in a situation such as campuses in Taiwan, where more water falls as precipitation than is lost via evapotranspiration, most water needs other than drinking water can thus
be met via cycling and recycling of rainwater. Any excess water that must be discharged can again be led through a wetland first, so that relatively clean water is discharged. Concerns to be considered Though common knowledge holds that wetlands are the birthplace of mosquitoes, this is only true for situations where predators have no access to the larvae. For example in wetlands that dry out, small puddles without predators are the perfect breeding grounds for mosquitoes, as are other small amounts of water, such as bird baths. Wetlands that are permanently wet and deep enough to hold predators, such as salamanders and fish, will not create a nuisance (Dale and Knight 2008). Similarly, a concern about wetlands is often that they smell bad. This too is not a problem if wetlands are constructed to be heterogeneous, with diversity in vegetation and water depths (Kadlec and Wallace 2009). A more pressing concern is that the system must be constructed to deal with the flashiness of the water supply, which can show a wide range particularly for locations that have monsoonal climates, such as Taiwan (Scholes et al. 1998). Care must be taken to construct the system such that high rates of precipitation do not lead to washing out of the wetlands. This requires that the wetland system is large enough to deal with high input rates, and a bypass channel may be constructed to deal with extreme input rates, such as may occur during typhoons.
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