Provided for Non-Commercial Research and Educational Use Only. Not for Reproduction Or Distribution Or Commercial Use
Total Page:16
File Type:pdf, Size:1020Kb
Provided for non-commercial research and educational use only. Not for reproduction or distribution or commercial use. This article was originally published by IWA Publishing. IWA Publishing recognizes the retention of the right by the author(s) to photocopy or make single electronic copies of the paper for their own personal use, including for their own classroom use, or the personal use of colleagues, provided the copies are not offered for sale and are not distributed in a systematic way outside of their employing institution. Please note that you are not permitted to post the IWA Publishing PDF version of your paper on your own website or your institution’s website or repository. Please direct any queries regarding use or permissions to [email protected] 635 © IWA Publishing 2012 Water Science & Technology | 66.3 | 2012 Assessing the urban water balance: the Urban Water Flow Model and its application in Cyprus Katerina Charalambous, Adriana Bruggeman and Manfred A. Lange ABSTRACT Modelling the urban water balance enables the understanding of the interactions of water within an Katerina Charalambous (corresponding author) Adriana Bruggeman urban area and allows for better management of water resources. However, few models today Manfred A. Lange Energy, Environment and Water Research Center, provide a comprehensive overview of all water sources and uses. The objective of the current paper The Cyprus Institute, fi fl P.O. Box 27456, was to develop a user-friendly tool that quanti es and visualizes all water ows, losses and Nicosia, inefficiencies in urban environments. The Urban Water Flow Model was implemented in a Cyprus E-mail: [email protected] spreadsheet and includes a water-savings application that computes the contributions of user- selected saving options to the overall water balance. The model was applied to the coastal town of Limassol, Cyprus, for the hydrologic years 2003/04–2008/09. Data were collected from the different authorities and hydrologic equations and estimations were added to complete the balance. Average precipitation was 363 mm/yr, amounting to 25.4 × 106 m3/yr, more than double the annual potable water supply to the town. Surface runoff constituted 29.6% of all outflows, while evapotranspiration from impervious areas was 21.6%. Possible potable water savings for 2008/09 were estimated at 5.3 × 103 m3, which is 50% of the total potable water provided to the area. This saving would also result in a 6% reduction of surface runoff. Key words | semi-arid areas, urban water balance model, water demand management, water savings INTRODUCTION Urban communities are facing a critical challenge to intensive, SUDS would not only facilitate the effective drai- manage and protect their water resources under the pressure nage of stormwater, but may also offer the potential of using of climate change and population growth. The current the captured water for fit-for-purpose productive use. approach to water management in urban areas involves sup- Chanan et al.() and McArdle et al.() present plying potable water and removing wastewater and examples of rainwater harvesting integration in urban stormwater (Mitchell et al. ). There are many who areas and emphasize that rainfall harvesting and its treat- agree that this conventional approach has to change in ment should be included in the planning of new order to adapt to urbanization trends and current and developments. future climatic changes (e.g. Ashley et al. ; Wong & Although the increase of impermeable areas decreases Brown ). With competition for freshwater resources groundwater recharge in cities, there are additional sources increasing, wastewater and stormwater should be viewed of recharge within urban areas, such as leaks from water net- as alternative sources of water and not just nuisances. work systems and septic tanks, storm drains, recharge and The increase of impermeable areas in cities has led to an retention basins and over-irrigation of gardens (Lerner increase in the quantity of stormwater runoff with conse- ). These new sources tend to reduce the quality of quences such as floods. Sustainable Urban Drainage groundwater in cities, resulting in decreased urban abstrac- Systems (SUDS) are proving to be of major importance tion, which in many cases contributes to flooding (Davison with regards to stormwater management (Marsalek & et al. ; Lerner ; Wakida & Lerner ). Borehole Chocat ; Bastien et al. ). In semi-arid areas, positioning is critical as water for different uses can be especially in regions where sporadic rainfall tends to be abstracted from different areas of a city (Davison et al. ). doi: 10.2166/wst.2012.188 636 K. Charalambous et al. | The Urban Water Flow Model Water Science & Technology | 66.3 | 2012 Wastewater production is another issue for urban Water saving awareness is promoted on the island by communities, as it increases with population growth the Water Development Department (WDD), including lec- and, the more cities expand, the further wastewater tures to more than 40,000 school children in 2010. Spending will have to be carried to a treatment plant. Treated on water-saving campaigns reached €2.1 million in 2009. wastewater may be used for agricultural purposes, for Subsidies for four household water saving measures over reuse applications at household or neighbourhood the past 14 years have been estimated to result in savings level or for aquifer recharge. The selection of centralized of 1.7 × 106 m3/yr, which is 2.3% of the island’s domestic or smaller decentralized water supply and wastewater demand (I.A.CO Ltd ). Around 80% of these savings treatment schemes in urban areas requires optimization are from a borehole subsidy, which aims to replace the use and both options should be considered (Barton & of potable water with that of groundwater, but as such Argue ; Chanan et al. ; Makropoulos & Butler does not reduce the overall consumption of water. During ). 1997–2010 a total of 7,666 borehole subsidies have been The efficiency and effectiveness of water use in urban granted, costing €3.2 million to the Cyprus government. environments could be improved through water conserva- Cyprus’ programme of measures for the implementation of tion techniques, advanced technologies, planning the European Union’s Water Framework Directive rec- requirements and government incentives (Chung et al. ommends, among other things, the expansion of recycled ; Butler et al. ). In Zaragoza, Spain, in 1997 a water use as well as the introduction of rainfall harvesting new water efficiency culture was promoted through the for reuse and groundwater recharge, the reduction of leak- installation of individual water meters, water saving equip- age from supply networks, the continuation of water ment in homes and water saving awareness campaigns. saving subsidies and water saving campaigns, the establish- This resulted in water consumption of 96 L/d per person, ment of a swimming pool levy, regulations for the the lowest value in Spain (Dworak et al. ). installation of efficient water use systems in new buildings The requirement to view stormwater, wastewater and and increased water prices. potable water holistically rather than individually has led The objective of this research was to develop a simple, to the development of various models over the last few dec- user-friendly tool that provides a basic overview of the ades. These models simulate the urban water and water flows and losses in an urban area and computes poss- contaminant balances, investigating the impacts of alterna- ible water savings. The model can be used by water tive water management options from the household scale professionals such as local authorities and researchers to up (Mitchell et al. ; Hardy et al. ; Mitchell & identify and prioritize opportunities for optimizing water Diaper ; Chung et al. ; Makropoulos et al. ; management in urban environments, prior to conducting Barton & Argue ). These models undertake detailed more detailed modelling studies. At the same time, non- simulation of the complete urban water cycle, and inevitably experts can easily compute water savings without needing require significant data and information for setup as well as in-depth knowledge. The model was applied to the town of specialist knowledge to operate. Limassol, Cyprus for the hydrologic years 2003/04–2008/09. The island of Cyprus, located in the far eastern corner of the Mediterranean basin, often suffers from droughts, leav- ing inhabitants with limited supplies of water. Decades of METHODOLOGY groundwater pumping for irrigation have resulted in the depletion of groundwater reserves and salt-water intrusion. Limassol town is the second largest city of the Republic of A large number of dams has been constructed since the Cyprus, located on the south coast of the island, and is con- 1960s to catch as much surface water as possible, but a sidered an important tourist, trade and service centre. The step change in the precipitation time series at the beginning town has a semi-arid climate, with an extended summer of the 1970s, with a 15–25% decrease in mean annual pre- and average annual rainfall of 360 mm for 2003/04–2008/ cipitation (Rossel ), has led to less water runoff into 09. The case-study area coincides with the area served by the dams than expected. Desalination was introduced in the Water Board of Limassol (WBL), a potable water utility, Cyprus in 1997 to make up for the deficit in the island’s which includes the municipalities and communities of water balance. The latest drought was in 2008, which Limassol, Pano Polemidia, Kato Polemidia, Mesa Geitonia proved to be one of the most severe on the island as water and Agios Athanasios. The area covers approximately had to be imported from Greece. 70 km2, housing a population of 156,254 at the end of 637 K. Charalambous et al. | The Urban Water Flow Model Water Science & Technology | 66.3 | 2012 2009. No dams or ponds exist within the area and the two (including government, non-government, shops, schools, streams that cross the town are dammed upstream.