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THE 28TH CONFERENCE OF THE FEDERATION OF ENGINEERING ORGANIZATIONS
THE 28 TH CONFERENCE OF THE FEDERATION OF ENGINEERING ORGANIZATIONS CAFEO 28, HANOI VIETNAM, 30 TH NOV. - 2 ND DEC., 2010 TITLE: AUTHOR(S)’ NAME(S): Ir. Ellias Saidin 2 , Assoc. Prof. Dr. Ismail Atan 1 , Rosadibah Mohd Towell 1 and Assoc. Prof. Ir. Dr. Aminuddin Baki 1* ORGANIZATION & DESIGNATION: 1. Faculty of Civil Engineering, Universiti Teknologi MARA, Malaysia 2. Perunding Ikatan, Malaysia ADDRESS: Faculty of Civil Engineering, Universiti Teknologi MARA, Shah Alam 40450, MALAYSIA TEL: +603 55436179 FAX: +603 55435275 EMAIL: aminbaki2@gmail.com Requirements: 1. The report is obliged to have above information 2. The report should not be longer than 10 pages (A4 size); if longer then an executive summary of the paper is required. 3. Font: Times New Roman, Single line, 4. Font size: 12 Rainwater Harvesting as an Alternative Water Resources with Potential Flood Reduction CAFEO28 2 RAINWATER HARVESTING AS AN ALTERNATIVE WATER RESOURCES WITH POTENTIAL FLOOD REDUCTION Ellias, S. 1 , Atan, I. 2 , Mohd Towell, R. 2 and Baki, A. 2* 1. Perunding Ikatan, Malaysia 2. Faculty of Civil Engineering, Universiti Teknologi MARA, Shah Alam * Corresponding author: aminbaki2@gmail.com ABSTRACT In any building, there are demands for water, for various usages: domestic use, commercial use, industrial use and fire protection use. Ability to be close to being self-sufficient on water resources would render the building to be sustainable in terms of water resources. In order to be self-sufficient, alternative water resources should be utilised instead of relying on public water supply. One of the alternative is rainwater harvesting. Rainwater has the quality to be used for various purposes including cleaning, toilet flushing and gardening, which can be up to 38% of total water consumption. If rainwater harvesting can be implemented in significant number of buildings the demand for treated public water supply will only be limited to drinking water and direct contact usage, such as showers and cooking. This will reduce the demand for public water supply and the development can become sustainable in terms of water resources. Another added benefit of rainwater harvesting is the potential reduction in flood peaks. If rain that fell on the roof can be captured for rainwater harvesting purposes, then significant quantities of rain water will not reach the waterways. This will reduce the runoff generated from the rainfall. KEYWORDS: Flood reduction, Rainwater harvesting, Water resources 1.0. INTRODUCTION Urban population worldwide has exceeded the rural population (UNEP, 2009). Cities are considered as artificial ecosystems, in terms of water and energy flows. Around the world rainwater harvesting has been promoted for alternative water supply as well as for flood peaks attenuation. In Australia, rainwater harvesting has been utilised to overcome the problems of water scarcity (UNEP, 2009). In Jakarta, Indonesia, rainwater harvesting has been used to reduce health impacts of flooding by providing cleaner alternative water resources (Wilandari and Sirait, 2008). Rockström (2002) promoted the implementation of rainwater harvesting in agriculture sector, which itself has very high demand for water. Implementation of rainwater harvesting will reduce the demand for fresh water in agriculture sector. This was also supported in studies by Mohamed et al. (2010). GDRC (2010) reported several success stories on rainwater harvesting including: about 28-30% of water demand can be met by rainwater harvesting in Singapore; about 750 buildings in Tokyo implemented rainwater harvesting; rainwater harvesting systems had been implemented in Berlin since 1998; and there are many other examples around the world. In short, rainwater harvesting has been proven to be successful in many parts of the world. In any buildings in the urban areas, there are demands for water, for various usages: domestic use, commercial use, industrial use and fire protection use. Ability to be close to being self-sufficient on water resources would render the building to be sustainable in Rainwater Harvesting as an Alternative Water Resources with Potential Flood Reduction CAFEO28 3 terms of water resources. In order to be self-sufficient, alternative water resources should be utilised instead of relying on public water supply. It is not economical to use potable quality water just to flush the toilets. At the source, grey-waters from households can be filtered and reuse for toilet flushing (Baki et al., 2009). The other alternative would be rainwater harvesting (Ellias and Baki, 2010). This paper however, will only focus on rainwater harvesting, as an alternative water resources for toilet flushing and general cleaning. Another potential benefit of rainwater harvesting, namely, flood peaks attenuation will also be discussed. 2.0. RAINWATER HARVESTING 2.1. As alternative Water Resources The practice of Rainwater Harvesting (RWH) is making a comeback in developed society after it had almost completely surpassed by the modernisation of piped water supply (Ellias, 2009). The age old technique of capturing or trapping rainwater on roofs or some other surface before it touches the ground and storing it for reuse had been practiced since ancient civilizations. Roman villas and Indian forts have been discovered to have installed large rainwater storage tanks below and above ground (Pacey and Cullis, 1986). The rainwater was used for agricultural and domestic consumption. In rural areas in Malaysia, the practice of storing rainwater was discouraged with the implementation of government development policy to supply reticulated treated water to rural areas. It was also reported that rainwater were used in schools, mosque and community centres until by policy, new public buildings then were connected to existing reticulated supplies ( Uzir and Hamidon, 1991). The capture and utilisation of rainwater is the most sustainable practice of alternative water supply (Ellias and Baki, 2009). Abundant amount of energy and materials used to physically and chemically treat the raw water and then transport it for long distances from where it falls, only to be used for toilets flushing, general cleaning and gardening in the home; whereas rainwater can be harvested and used at source where it falls. With basic screens and first flush diverters, quality water is available with less damage to the environment from chemicals, greenhouse gases and destruction of forest and biodiversity (Ellias and Baki, 2010). From a typical consumption in a household in Malaysia (Baharuddin, 2007), 55% of the total daily consumption may be substituted with rainwater i.e.; toilet flushing (30%), laundry (13%), outdoor use (7%) and general cleaning (5%). To encourage domestic RWH practices, the government has to introduce incentives in the form of grants, subsidies or tax returns for new installations or retrofitting and acknowledge the quantum as costs to environmental damage. The sustainable practice of RWH is further enhanced when it was estimated (Pidwirny, 2006.) that the hydrologic cycle time for rainwater is about nine days as contrasted to the cycle time of groundwater which can be 100 years for shallow wells and up to 10,000 years for deep wells. This means that the water molecule in rainfall is being used many times over than say the groundwater molecule. In cities with groundwater supply, water is not being replenished fast enough resulting in receding groundwater levels and shortages. Rainwater Harvesting as an Alternative Water Resources with Potential Flood Reduction CAFEO28 4 Ellias (2009) studied three houses in Selangor and found that rainwater has contributed about 38.5% of total water consumption in a residence. This can be translated into water supply conservation efforts to reduce the demand on the existing public water supply system. These three houses can be considered sustainable in terms of water resources. 2.2. Potential Volumes The potential for rainwater harvesting in terms of water volume can be illustrated by assessing the rainfall for that area. Table 1 shows the rainfall amount and potential storage volume for a school in Shah Alam City in Selangor, Malaysia. Figure 1 shows the location of Shah Alam. The average annual rainfall is about 2200mm, indicating good potential volume of rainwater can be captured in this city. Table 1 indicates that the potential monthly storage of 53 m 3 can be achieved for this school. Table 1: Rainfall for Shah Alam (Source: Ahmad, 2007) Catchment Area (km 2 ) 290.3 Total Rainfall (mm) 119372.0 Total Storage (L) 34653692.0 Average Annual Rainfall (mm) 2220.7 Average Annual Storage (L) 644665.1 Average Monthly Rainfall (mm) 185.1 Average Monthly Storage (L) 53734.5 Figure 1: Location of Shah Alam (Source: Dromoz, 2010) Rainwater Harvesting as an Alternative Water Resources with Potential Flood Reduction CAFEO28 5 AVERAGE RAINFALL FROM 1943 - 2007 0 500 1000 1500 2000 2500 3000 3500 1943 1948 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998 2003 TIME (YEAR) RAINFALL (mm) ANNUAL AVERAGE = 2220.69 mm Figure 2 shows the annual rainfall patterns, which fluctuated over the years. The annual rainfall is ranging from zero to 3200mm with an average of about 2200mm. Figure 3 shows the potential average monthly storage of rainwater. The monthly storage volume is ranging from 33m 3 to 84m 3 with an average of 53m 3 . These amount of water stored definitely will not be able to meet the total water demand in the school. However, rainwater harvesting should be aimed at meeting the demand for toilet flushing and general cleaning, so that treated water need not be used for those purposes. Figure 2: Annual and average rainfall for Shah Alam (Source: Ahmad, 2007) Rainwater Harvesting as an Alternative Water Resources with Potential Flood Reduction CAFEO28 6 MONTHLY AVERAGE STORAGE 50163.84 47115.69 57537.46 65520.71 40554.91 33123.23 36839.07 42354.77 48915.55 72197.61 84070.88 66304.52 0 20000 40000 60000 80000 100000 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TIME (MONTH) STORAGE (L) Figure 3: Potential Average monthly storage. (Source: Ahmad, 2007) 2.3. Water Quality Mohamed et al. (2010) found that despite the numerous sources of atmospheric pollution, in most parts of the world, especially in rural and island locations, levels of contamination of rainfall are generally low. Contaminations are usually due to contact with the catchment surface (roof or ground) and due to subsequent delivery and storage. Mohamed et al. (2010) found that for rainwater harvesting system in Universiti Putra Malaysia, most of the parameters (pH, Turbidity, BOD 5 , Total Suspended Solids, Total Dissolved Solids, E.coli and Lead) are within the acceptable range, as shown in Table 2. Some slight concern with E.coli and Lead were detected, making rainwater not suitable for drinking purposes. However, rainwater can be used for toilet flushing and general cleaning. Table 2: Rainwater Quality at UPM (Source: Mohamed et al., 2010) Parameter Unit Untreated Malaysian Standard pH 5.71 6.5 – 9 Turbidity N.T.U 3.9 7 5 BOD 5 mg/L 1.20 3.0 Total Suspended Solids mg/L 10 50 Total Dissolved Solids mg/L 12 50 E.coli CFU/100mL 1 0 Lead mg/L 0.006 <0.003 Rainwater Harvesting as an Alternative Water Resources with Potential Flood Reduction CAFEO28 7 Measurements were also conducted in this study at Universiti Teknologi MARA (UiTM) Shah Alam, as shown in Table 3 below. The results in Table 3 shows that the levels of contaminations in rainwater are below the water quality standards for recreational use with body contact (Class IIB). It is therefore suitable for toilet flushing and general cleaning. Table 3: Result for Water Quality at UiTM Shah Alam. Date Sample pH Turbidity (NTU) TDS (mg/l) Colour (TCU) Conductivity (mmhos/cm) Sulfate (mg/l) Nitrate (mg/l) Nitrite (mg/l) INWQS Class IIB 6-9 50 No limit 150 No limit 250 7 0.4 7.3.2010 A - - - - - - - - B 6.30 2.52 21.5 90 44.8 1.0 0.22 0.033 C 6.35 2.96 18.1 117 40.1 1.0 0.17 0.043 15.3.2010 A 6.17 2.35 25.0 50 59.6 4.0 0.11 -0.05 B 6.27 1.25 20.1 27 49.6 4.0 0.28 0.026 C 6.31 1.57 21.8 36 53.8 10.0 0.26 0.051 20.3.2010 A 7.23 1.62 11.3 18 24.9 1.0 0.09 0.07 B 6.92 1.23 9.3 20 18.9 1.0 0.10 0.019 C 6.85 0.88 11.8 22 28.2 0.0 0.13 1.014 25.3.2010 A 6.10 1.80 23.5 45 38.3 1.0 0.07 0.022 B 6.35 1.20 31.2 23 50.3 2.0 0.18 0.031 C 6.37 1.32 20.1 48 62.0 4.0 0.24 0.030 27.3.2010 A 6.40 0.79 12.7 18 23.0 0.0 0.09 0.025 B 6.10 1.00 26.3 62 45.2 1.0 0.12 0.043 C 5.90 1.71 19.0 37 40.6 1.0 0.10 0.052 28.3.2010 A 6.21 2.23 19.5 61 39.3 1.0 0.09 0.021 B 5.90 2.50 23.4 50 52.7 3.0 0.15 0.033 C 6.00 1.35 20.0 51 51.3 1.0 0.13 0.021 Note: A = SAAS Tower UiTM B = Stadium UiTM C = Engineering Complex UiTM Class IIB – recreational use with body contacts (INWQS) Considerations of water quality in Malaysia based on two separate studies, Mohamed et al. (2010) at Universiti Putra Malaysia and in this study at Universiti Teknologi MARA Malaysia indicated that rainwater quality is suitable for non-potable use. Thus, both studies indicated that rainwater is suitable for toilet flushing and general cleaning. In general, rainwater can provide alternative water resources for the purpose of toilet flushing and general cleaning, and reduce the need to use treated water for these purposes. Rainwater Harvesting as an Alternative Water Resources with Potential Flood Reduction CAFEO28 8 3.0. FLOOD PEAKS ATTENUATION Apart from being an alternative source of water, rainwater harvesting also has the potential to attenuate flood peaks. If rainwater harvesting systems are widely implemented in urban areas, the rainwater harvesting interventions can reduce storm flow, decreasing incidence of flooding and short peak flows. Studies in South Africa indicated decrease in streamflow due to application of rainwater harvesting (UNEP, 2009). In the UK, the government supports the use of rainwater harvesting as a means of reducing flood (Bicknell, 2008). The concept of flood peaks attenuation is simply by releasing less rainwater to the drains (Bicknell, 2008). The amount captured by the rainwater harvesting tank would be the amount of water not release to the drainage systems. Thus, less amount of water becomes runoff. This will reduce the amount of stormwater runoff, which will result in reduced flood water. Table 1 shows that the average monthly rainfall in Shah Alam is 185.1mm. The estimated roof catchment area of the school is about 690m 2 . Thus, the average volume of water fell on the roof is about 125m 3 . Figure 3 shows that the average potential monthly storage of about 53m 3 . This indicates about 42% as the average rate of capture. Therefore, on average there is only 57% of rainwater discharged to the drainage systems. This reduction in rainwater will cause reduction in flood water in the drainage or river systems. 4.0. CONCLUDING REMARKS If rainwater harvesting can be implemented in significant number of buildings the demand for treated public water supply will only be limited to drinking water and direct contact usage, such as showers and cooking. This will reduce the demand for public water supply and the development can become sustainable in terms of water resources. Another added benefit of rainwater harvesting is the potential reduction in flood peaks. If rain that fell on the roof can be captured for rainwater harvesting purposes, then significant quantities of rain water will not reach the waterways. This will reduce the runoff generated from the rainfall. This paper has highlighted the dual benefits of rainwater harvesting, namely as an alternative water resources, and as a means of reducing the flood peaks. REFERENCES Ahmad, N. (2007), “Rainwater Harvesting: A Solution for Water Problem in Shah Alam Area”, Thesis – BSc Civil Engineering, Universiti Teknologi MARA, May 2007, unpublished. Rainwater Harvesting as an Alternative Water Resources with Potential Flood Reduction CAFEO28 9 Baharuddin, A. (2007). “Quality of Rainwater at NAHRIM’s Rainwater Harvesting System Pilot Projects”. Proceedings of the Colloquium on Rainwater Utilisation (2007).pg 62. Baki A., Jaafar J., Mohd Tajuddin R., Atan I., Ashaari Y. and Endut I.R. (2009), “Waste- To-Resource In Water & Wastewater Industry Revisited”, WATER MALAYSIA2009: Proceedings of the International Conference on Industry Best Practice, 19-21 May 2009, Kuala Lumpur, MALAYSIA. Bicknell S.A. (2008), “Flood Attenuation and SUDS: Use of a rainwater harvesting tank as a means of attenuating flood water flow”, http://www.rainwaterharvesting.co.uk/downloads/rainwater-harvesting-flood-attenuation- information.pdf (accessed on 18 July 2010) Dromoz website, Maps of Malaysia, www.dromoz.com (accessed on 29 July 2010) Ellias S. (2009), “A Study of Rainwater Harvesting Systems Installations at three Residential Houses in Malaysia”. Proceedings of the 14th International Rainwater Catchment Systems Conference 2009, 3rd-6th Aug 2009, PWTC Kuala Lumpur Ellias, S. and Baki, A. (2009), “Rainwater Harvesting – Potential Alternative Water Resources In Malaysia”, WATER MALAYSIA2009: Proceedings of the International Conference on Industry Best Practice, 19-21 May 2009, Kuala Lumpur, MALAYSIA. Ellias, S. and Baki, A. 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(1986), “Rainwater Harvesting: The collection of rainfall and run-off in rural Areas”. Intermediate Technology Publications, London, UK. Pidwirny, M. (2006), "The Hydrologic Cycle". Fundamentals of Physical Geography, 2nd Edition. Rainwater Harvesting as an Alternative Water Resources with Potential Flood Reduction CAFEO28 10 UNEP (2009), “Rainwater harvesting: a lifeline for human well-being”, United Nations Environment Programme and Stockholm Environment Institute, 2009. http://www.unep.org/Themes/Freshwater/PDF/Rainwater_Harvesting_090310b.pdf (accessed on 18 July 2010). Rockström J. (2002), “Potential of Rainwater Harvesting to Reduce Pressure on Freshwater Resources”, International Water Conference, Hanoi, Vietnam, October 14-16, 2002. Uzir, A. M. and Hamidon, O. (1991), “Rainwater Cistern System in Malaysia Reconsidered”. Proceedings of the 5th International Conference on Rainwater Catchment Systems, Taiwan. Wulandari A. and Sirait M.J., (2008), “Household Approach in Reducing Flood Disaster Effect in Jakarta, Indonesia”, YE Water Program, Jakarta, Indonesia, http://www.riversymposium.com/index.php?element=WULANDARI (18 July 2010) . THE 28 TH CONFERENCE OF THE FEDERATION OF ENGINEERING ORGANIZATIONS CAFEO 28, HANOI VIETNAM, 30 TH. be the amount of water not release to the drainage systems. Thus, less amount of water becomes runoff. This will reduce the amount of stormwater runoff,