Policy and Implementation of Rainwater Harvesting in Putrajaya, Malaysia

Transcription

1 Policy and Implementation of Rainwater Harvesting in Putrajaya, Malaysia Akashah Hj. Majizat, Roslan Bin Sahat, Maisarah Binti Ibrahim Putrajaya Corporation Environmental, Lake and Wetlands Division City Planning Department 24, Perbadanan Putrajaya Complex, Precinct 3, Putrajaya, Malaysia. Abstract Being the local authority for Malaysia s new Federal Government Administrative Centre of Putrajaya, Putrajaya Corporation has made a proactive effort in encouraging the application of rainwater harvesting concept to be considered in all its planning, development and post-development phases. The 600 hectares of the Putrajaya Lake and Wetlands, serving as a big detention pond storing an estimated volume of 24.5 million cubic metres, is one of the rainwater harvesting concepts which has been constructed in stages as early as in Having the big lake in place, which also acts as a natural climate moderator and cooling system for Putrajaya, will require a water quality and quantity management enhancement and thus making this concept even more important. Furthermore, the reduction of the lake water volume could be managed or controlled in prolonged drought events with the implementation of this concept. The slowing down of surface runoff flowing into the lake from the city (surface) and the gradual seepage of the rainwater into the ground as groundwater recharge enables the water quality enhancement process to occur. For that purpose, Putrajaya Corporation implements the rainwater harvesting concept as recommended in the guidelines on Installing a Rainwater Collection and Utilizing System introduced by the Housing and Local Government Ministry in 1999 for residential houses as well as commercial and government offices in Putrajaya. The application of rainwater harvesting in Putrajaya serves its purpose in terms of the water quality improvement aspects such as the prevention of rubbish, debris, chemical agents and other pollutants entering the Putrajaya Lake. The Putrajaya Lake will thus receive most of the inflow water that is naturally purified which in turn improves the lake water quality to its best condition. 1

2 1.0 Introduction The use of rainwater for various activities such as general cleaning, toilet flushing, washing vehicles, watering of plants and other non-drinking purposes helps in reducing the demand for the use of treated potable water. In capturing the rain, the rainwater collection and utilization system comes in many means, such as the above ground rainwater storage tanks, the underground rainwater storage tanks with the integration of a series of drainage system and the construction of large ground surface retention or detention ponds. In the transformation of Putrajaya from an idyllic oil palm estate plantation into a new federal government administrative centre of Malaysia bustling with various activities, the rainwater harvesting (RWH) concept was already creatively designed as early as in 1996 with the construction of a large Putrajaya man-made lake and wetlands ecosystems. Apart from the functioning as an urban flood control and sustainable drainage system, the quantitative demand management with the water quality in its best condition throughout the lake and wetlands system within the Putajaya lake catchment area was also incorporated in the initial design stage. Furthermore, a constant groundwater recharge demand throughout the Putrajaya lake and wetlands area was considered and incorporated in the design stage and maintained at the required level. The introduction of the guidelines for the Installing of the Rainwater Collection and Utilisation System in 1999 (Rainwater Guidelines, 1999) was an added value and advantage for Putrajaya to further encouraged its consultants, designers, the developers as well as the residents of Putrajaya to implement this concept. 2.0 Background The presence of the 600 hectares of Putrajaya lake and wetlands that has been constructed in stages as early as in 1997 provides a large surface area for the rainwater harvesting concept. Planned and built with the objective of achieving aesthetic and multi-functional use, the large water body also provides the opportunity of an urban diversification of flora and fauna species with the water quality and quantity management as one of its environmentally-friendly approach in the planning and development of Putrajaya. A brief description of the lake and wetlands of Putrajaya which have already incorporated the RWH concept is as explained below. 2.1 The Putrajaya Wetland The Putrajaya constructed wetlands system, with the water surface area of about 200 hectares, comprises of six arms with 23 cells as described in Figure 1. All the arms (except of Upper Bisa) eventually discharges the lake water to the Central Wetland, which make the 24 cells in all, before the water flows down into the Putrajaya Lake. They straddle the water courses of originally Sungai Chuau, Sungai Bisa and three small tributaries. 2

3 Figure 1 : The Putrajaya Wetland Cells The Putrajaya Wetland cells and its structural components and vegetation act as kidneys and are the keys to the functioning of the wetlands for the cleansing of the river water. One of the important functions is in maintaining the hydrological protection by providing flood detention area, reducing peak discharges and flow velocities and recharging groundwater storage. The design features a multi-cell multi-stage system with flood retention capability to maximize the space available for colonisation by water plants. 2.2 The Putrajaya Lake The lake is at the southern part of the wetlands. About 60% of the lake water flow from the wetlands and the remaining 40% is the direct discharge from lateral flows which is bordering the lake promenade. The 20 meter width promenade is the buffer feature along the 38.0 km total length of the lake shorelines. The water surface area of the whole lake is about 400 hectares. The total volume of the whole lake water is about 24.5 million cubic metres and the water depth ranges from 2.0 to 14.0 meters. The principle features of the lake and wetland are shown in Table 1 below. Table 1 : Principal features of the Putrajaya Wetlands and Lake Principal Features of Putrajaya Wetlands (Area in hectares) Planted Open Weirs & Zone of Intermittent Maintenance Total Area Area Water Islands Inundation Tracks

4 Catchment Area Water Level km 2 RL m Principal Features of Putrajaya Lake Surface Area 400 ha (4 km 2 ) Storage Volume 24.5 mil. m 3 Average Depth 6.60 m Average Catchments Inflow 200 million liters/day Average Retention Time 132 days 2.3 The Putrajaya Masterplan In the planning and development of Putrajaya, the Putrajaya Masterplan outlines the various landuses that have to be incorporated for the successful construction of Putrajaya. One of the most important landuse features of Putrajaya is the creation of the man-made lake and wetlands of Putrajaya, also known as the Jewel of Putrajaya. With the presence of the 400 hectares of lake and 200 hectares of wetlands, it forms part of the 37.0% of the total open spaces (greens, parks, wetlands and lake). The Putrajaya Masterplan which incorporate the Putrajaya lake and wetland feature is as shown in Fig. 2. Government - 5.8% Residential % Commercial - 2.8% Public Amenities / - 9.4% Civic & Cultural Infrastructure & Utilities % Open Space % (green, parks, lake & wetlands) Figure 2 : The Putrajaya Landuse 4

5 3.0 Planning and Implementation challenges 3.1 Planning challenges The Malaysian Cabinet has approved the guidelines for the installing the Rainwater Collection and Utilisation system in June 1999 (Rainwater Guidelines, 1999) and monitoring was done by the Housing and Local Government Ministry in the nonmandatory implementation of the RWH concept to all the local authorities in Malaysia. The guidelines outline the recommendation for the general principles, alternative creative designs, layout and installation of the rainwater collection and utilization system to be adopted in Malaysia. However, there were issues enquired by the Putrajaya developer as well as the public on the implementation of the RWH system. Among the issues addressed were: i) the high capital cost of installing the rainwater tanks by the developer that will have to be eventually borne by the house owners and this will further increase the price of the houses in Putrajaya; ii) maintenance problems in the long term period such as cleaning of the choked conveyance pipes, leaves in gutters and periodic pump maintenance; iii) water-related issues such as polluted rainwater from bird feces, breeding of mosquitoes which might pose a danger of spreading of diseases to the public. During a steering committee meeting of Putrajaya Corporation in July 2002, a decision was made stating that the installation of the rainwater collection and utilization system as stipulated in the Rainwater Guidelines was not a mandatory requirement for the development of Putrajaya area. The decision was made based on the following criteria: i) Putrajaya already have the lake and wetlands with a combined water surface area of 600 hectares that acts as a large storage detention pond in retaining rain water with the flood control capability through a network of drainage systems; ii) iii) Putrajaya utilizes the water from the lake and also a part of the treated sewage water discharge from the water treatment plant in Precinct 5 and 14 for the irrigation of the landscape areas and other related areas in Putrajaya with the intention to conserve water usage as well as to minimize the dependency of the potable water supply from the Water Supply Department (WSD); and to avoid the risk of the breeding of mosquitoes which could lead to contagious diseases in the long-term event. 5

6 3.2 The Implementation of the Irrigation Master Plan of Putrajaya Since the non-mandatory requirement of the Rainwater Guidelines, 1999, Putrajaya Corporation made an effort in encouraging the developer to build the rainwater system if it is found to be commercially viable in the planning submission for buildings and residential houses in Putrajaya in relation to the installation of the RWH system. In line with this, Putrajaya Corporation has also prepared a guidelines entitled Irrigation Master Plan for Putrajaya (2002) which provide a section outlining the installation of the rainwater collection systems as well as the sizes of the rainwater storage tanks (above and underground) to be installed in Putrajaya by the developer, government and commercial offices and individual house owners. The guidelines also outlined the recommendation for the extraction of rainwater from the lake via construction of irrigation pump houses at strategic locations and the consumption of part of the treated sewage water from the sewerage treatment plant for the irrigation of landscape areas in Putrajaya. 3.3 Implementation of the RWH system in Putrajaya A directive from government was declared in March 2006 to install the rainwater collection and utilization system which only applies to large buildings such as factories, schools and large bungalows. With the directive in March 2006, Putrajaya Corporation has stepped up its efforts in the implementation strategy of RWH. An example of the implementation of the installation of the RWH system in Putrajaya is in the Precinct 16 development. The development of 19 units of type C private bungalows in Precinct 16 is being planned to be installed with the RWH system as a common feature and will be constructed in two phases. In the first phase of construction, 4 units of bungalows have already been fitted with the RWH system while in the second phase, only 1 unit has been fitted with the RWH system and the remaining 14 units of bungalows are still under construction. Basically, every unit of the bungalow is fitted with a 3000 litres capacity of underground RW storage tank equipped with a suction pump, located near the back portion of the house, connected to a poly storage round water tank of m x 1.524m (H) situated at the roof level with a storage capacity of 500 gallons (2,250 litres) via the 25 mm Acrylonitrile Butadiene Styrene (ABS) system of incoming flow and 32 mm diameter ABS of outgoing flow of pipeline. The storage tank at the roof floor is separated from the domestic cold water plumbing provision tanks. The RW is pumped to the roof by the electrical pump which is then utilised on demand by gravity flow to 7 nos. W.C. s (toilet flushing) and 2 nos. Garden Taps (GT s for general cleaning and watering of plants/turf areas). The RW tank is also supplemented with the SYABAS water to ensure constant supply for flushing during the dry season. The plumbing design is also separated from the cold water plumbing system. 6

7 Fig. 3 & 4. Concealed RW storage tank near the drying yard area. Fig. 5 & 6. Pump control valves situated near the RW storage tank. Fig. 7. The top cover of the RW storage tank during construction. Fig. 8. The 3000 litres underground RW storage before installation into the ground. 7

8 Fig. 9. The RW tank at roof floor. Fig.10. Schematic Diagram of the RW system. Putrajaya Corporation however, at the same time, made a proactive policy approach in outlining the importance of the RWH system installation for Putrajaya development. In the Structural Plan for Putrajaya Area and Local Plans for Precinct 5, 6 and 20 and 1, 17 and 19 of the Putrajaya area, the implementation of the RWH system will have to be considered for all type of developments. 4.0 Benefits Derived The benefits that have been acquired from the RWH concept in Putrajaya are: i) ensuring flood free environment with flood control and sustainable drainage, reduction of peak discharge, time to peak discharge and volume runoff; ii) maintaining a constant groundwater discharge in the Putrajaya lake and wetlands eco-systems; iii) reduce the dependency and demand on potable treated water from the water supply department with the general cleaning, toilet flushing and watering of plants around the houses as well as the irrigation of the landscaped areas using the lake water (37% green areas) in Putrajaya; and iv) meeting the demand for urban biodiversity, aesthetics, hydrology of the lake and wetlands, flora and fauna, human population and all the environment v) slowing down the surface water runoff at the same time encourage infiltration through the ground which in turn purify the water. 5.0 Conclusion The RWH concept has been incorporated in the Putrajaya development, in a unique way, even before the implementation of the Rainwater Guidelines (1999). Instead of the construction of many mini dams or rainwater containers, the only dam constructed in Putrajaya is the Putrajaya Dam. 8

9 However, the requirement of the mandatory rainwater guidelines is now being rigorously incorporated in the structural plan and local plans for Putrajaya especially for big buildings, schools and bungalows for all planning submissions. 6.0 References Rainwater Guidelines, Guideline for Installing a Rainwater Collection and Utilising System, Ministry of Housing and Local Government, Malaysia. Putrajaya Wetlands, Perbadanan Putrajaya and Putrajaya Holdings Sdn. Bhd. Proceedings of the Colloquium on Rainwater Utilisation, 19 & 20 April 2007, Putrajaya, Malaysia. Ministry of Natural Resources and Environment (NRE) and National Hydraulic Research Institute of Malaysia (NAHRIM). Irrigation Master Plan for Putrajaya, Perbadanan Putrajaya. 9