Background Putrajaya is a city planned and built to meet the challenges of the new millennium. It is A City in a Garden that turns to nature for inspiration, resulting in a landscape dominated by the picturesque Putrajaya Lake. A high standard of lake water quality is one of the most important factors for the success of this scenic centerpiece, and the solution was found in simulating yet another gift of nature - with the construction of Putrajaya Wetland.
Malaysia's new Federal Government Administrative Centre of Putrajaya is not just a new city. It also represents the coming-of-age of Malaysia as a dynamic and progressive member of the global community committed to the concept of sustainable development.
Wetland - definition Wetland are defined by the Convention of wetland of International Importance (the Ramsar Convention 1971) as; "Land inundated with temporary or permanent water that is usually slow moving or stationary, shallow, fresh, brackish or saline, where the inundation determines the type and productivity of soils and the plant and animal communities".
Constructed wetland The role of wetland in water resource management is fast gaining ground resulting in the construction wetland in most developed countries. Constructed wetland are man-made system that involves altering the existing terrain to simulate wetland conditions. They primarily attempt to replicate the treatment that has been observed to occur when polluted water enters the natural wetland. These wetland have been seen to purify water by removing organic compounds and oxidizing ammonia, reducing nitrates and removing phosphorus. The mechanisms are complex and involve bacterial oxidation, filtration, sedimentation and chemical precipitation.
Most constructed wetland attempt to imitate the ecosystem's biochemical function as filtration and cleansing agents, followed closely by the hydrological function that is centred on flood mitigation.
Functions of wetland The use of constructed wetland to treat urban surface runoff and remove nutrients from diverse sources in rural catchments has received much attention lately. Thus, wetland are essentially the filtering area, the 'kidneys' of the catchment, intercepting water flow, trapping sediment and pollutants, removing toxic substances (pesticides, herbicides, metals) and assimilating nutrients and energy derived from the upstream catchment area.
Wetland has the ability to filter nutrients from inflowing waters which represent the base of many food chains that not only start and finish within the wetland but extend beyond the wetland complex itself. Where there is food there is life, and hence wetland act as breeding grounds, nurseries and homes to numerous plants, invertebrates, frogs, reptiles, fish and waterbirds. In fact, wetland are best known as habitats for fish and waterbirds.
Wetland are becoming increasingly popular as ecotourist destinations. Their biodiversity, open space, aesthetics and the development of public amenities make them attractive propositions for passive recreational activities and social pursuit.
It is generally accepted that wetland have the potential to attenuate flooding. Wetland provide retention storage for storm water by spreading the water over a wide flat area. Wetland vegetation retards surface water flow to varying extents depending on the type, density and water depth.
Wetland are a fertile ground for scientific study and research. In fact, there is also a growing interest in wetland among school children who are beginning to embark on a voyage of discovery of their environment by being introduced to this dynamic ecosystem. This may well be the first step in public education of wetland, which are the collective responsibilities of all users.
Putrajaya Lake The 400 hectares Putrajaya Lake was created by inundating the valleys of Sungai Chuau and Sungai Bisa. Construction was undertaken in two phases. The first phase of approximately 110 hectares involved the construction of a temporary dam across Sungai Chuau.
The dam was completed in May 1998 and the impoundment of the Phase 1A Lake commenced in September 1998 and was fully inundated in January 1999. The lake has been primarily designed to enhance the aesthetic appeal of Putrajaya. It is also planned to be used for sport and recreation as well as a tourist attraction.
Studies of the Putrajaya catchment, however, showed that the water carried elevated level of pollutants derived from upstream sources and outside of the Putrajaya development boundary. Future development of the Sungai Chuau catchment is expected to increase run-off and pollutant concentration will either be maintained or increased.
This is expected to result in increased pollutant loadings in Sungai Chuau and Sungai Bisa which drain into Putrajaya Lake. As a result, the use of constructed wetland as a natural treatment system was recommended to treat primary upstream inflow to the lake. The wetland is to be complemented by riparian parks and gross pollutant traps.
Putrajaya wetland is the first man-made wetland in Malaysia and one of the largest fully constructed freshwater wetland in the tropics. The 197 hectare project resulted in transforming an oil palm site into wetland ecosystem with the helps of modern technology and stringent environmental management methods in design and construction.
The wetland straddle the water courses of Sungai Chuau, Sungai Bisa and three tributaries. Their primary function is to ensure that the water entering the lake meets the standard set by Perbadanan Putrajaya.
To achieve this, the wetland have been planted with a variety of aquatic plants that act as a natural filtration system, removing nutrients and pollutants from the catchment water. They treat natural run-off from the 50.9 sq km Sungai Chuau catchment.
In addition to being a water cleansing and filtration system, the wetland also help in flood mitigation, nature conservation, ecotourism, recreation, research and education and protection against soil erosion. Construction of Putrajaya wetland began in March 1997 and was completed in August 1998.