The Tale of the Pristine Putrajaya Lake.

The landscape of Putrajaya is dominated by the picturesque Putrajaya Lake. Putrajaya Lake is a 400 hectares water body encircling the Core Island of Putrajaya.

The landscape of Putrajaya is dominated by its picturesque lake.

  The presence of the lake helps to moderate the temperature and humidity, making it much more pleasant to the surrounding population. When the hot air mass moves across long expanses of cooler lake water, it cools the lower layer of air, thereby cooling the weather when it hits the leeward shores.

 The lake is also is the site of various outdoor activities such as boating and kayaking. The jogging and cycling paths around the lake provides another avenue for healthy activities. For the annual Putrajaya Ironman 70.3, usually held in April, the lake is where the swimming leg of the event is held.

Swimming leg of Putrajaya Ironman 70.3 held in Putrajaya Lake.

Yet the water of Putrajaya Lake were sourced from two polluted river systems,  Sungai Chua and Sungai Bisa.

Flooded section where Sungai Bisa enters the Wetlands.

These two river systems were polluted with domestic sewage discharge, livestock excreta, agricultural runoff and waste water from factories. So how does such one comes up with a lake filled with water with a quality index of Class IIb, suitable for recreational use from such a highly polluted source?

Che Mohd Adib cycling through the section where Sungai Bisa enters the Wetlands.

The flooded section where Sungai Bisa enters the Wetlands.

 The answer lies within the 200 hectares of Putrajaya Wetlands, a vegetated horizontal surface flow multi-cell wetland system, with different water levels in each of its 23 cells.

The 23 cells of Putrajaya Wetlands.

Each cells is separated from one another by a weir.

One of the many broad-crested weirs separating the cells at Putrajaya Wetlands.

One of the sharp-crested weirs in Putrajaya Wetlands.

 The water of Sungai Chua and Sungai Bisa are filtered by these cells at Putrajaya Wetlands.

What is so special about these cells that they are able to filter these polluted water?

Each cell consists of the following layout;

Layout of each cells.

Water will enter through the inlet area. The forebay allows sedimentation, thus reducing the sediment load of the water. The reed beds has waterplants which will enhance organic flocculation and filtration of pollutants via microbial biofilms. The open pond area after the reed bed allows UV (sunlight) penetration into the water for disinfection. The process will continue through the various cells.

The waterplants differ between the cells by its classification. The cells will be classified according to the following criteria and it is determined by its location within the wetlands, to provide the optimum filtration and water treatment. The classification is as follows;

• Shallow marsh
• Marsh
• Deep Marsh
• Pond
• Deep Pond
• Fringing Swamp
• Swamp Forest

Graphical explanation of the classification of the cells.

The Putrajaya Lake lies at the southern part of the wetland. About 60% of the lake water were filtered through the wetland and the remaining 40% came from bordering promenade and through runoffs from the drainage system in the catchment area. The water depth of the lake is in the range of 3 to 14 metres with an average depth of 6.6 metres.

The level of the Putrajaya Lake is regulated by the Labyrinth Weir at Taman Seri Empangan, near the Putrajaya International Convention Centre (PICC).

Labyrinth Weir, also known as the Forbidden Bridge (picture courtesy of Adib Noh).

The excess water from the Labyrinth Weir, enter a spillway which led to a stream. The stream joins into Sungai Langat, which led to Selat Melaka.

The spillway leading to a stream.

Thus a lot of effort and resources had been invested to ensure that Putrajaya is known as a waterfront city and its lake water is safe for recreational water activities. So the next time you swim or take part in any water activities at Putrajaya Lake, take heed of the effort that has gone into ensuring the water quality of Putrajaya Lake.

The water from the lake is so clear in contrast to the murky Sungai Langat.

Caveat (warning);
Tale = "a fictitious narrative or story, especially one that is imaginatively recounted."
Pristine = "in its original condition; unspoiled."
Bisa river system really refers to the valley located west to Bukit Bisa (IOI Resort). There is a series of interconnected lakes towards north east near to a lake at UNIPERTAMA Golf Club, UPM Serdang. The lake has a small stream which connects to a another lake within UPM. Sungai Bisa connects to the northeast section of Putrajaya Wetlands via a stream that runs underneath a bridge at SKVE as illustrated at the beginning of the article.
Chua river system apparently flows from Kajang to Putrajaya but I can't identify it's location within Putrajaya.