THE 28TH CONFERENCE OF THE FEDERATION OF ENGINEERING ORGANIZATIONS

THE 28TH 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 Saidin2, Assoc Prof Dr Ismail Atan1, Rosadibah Mohd Towell1 and Assoc Prof Ir Dr

Aminuddin Baki1*

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

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

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

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

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 m3 can be achieved for this school

Table 1: Rainfall for Shah Alam

(Source: Ahmad, 2007)

Figure 1: Location of Shah Alam (Source: Dromoz, 2010)

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)

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 33m3 to 84m3 with an average of 53m3 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)

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

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

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, BOD5, 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)

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

(NTU)

TDS (mg/l)

Colour (TCU)

Conductivity (mmhos/cm)

Sulfate (mg/l)

Nitrate (mg/l)

Nitrite (mg/l)

IIB

6-9 50 No

limit

15.3.2010 A 6.17 2.35 25.0 50 59.6 4.0 0.11 -0.05

20.3.2010 A 7.23 1.62 11.3 18 24.9 1.0 0.09 0.07

25.3.2010 A 6.10 1.80 23.5 45 38.3 1.0 0.07 0.022

27.3.2010 A 6.40 0.79 12.7 18 23.0 0.0 0.09 0.025

28.3.2010 A 6.21 2.23 19.5 61 39.3 1.0 0.09 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

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 690m2 Thus, the average volume of water fell on the roof is about 125m3 Figure 3 shows that the average potential monthly

storage of about 53m3 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

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unpublished

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