The Putrajaya constructed wetland system comprises of six arms with 23 cells as described in Figure 1. All the arms (except of Upper Bisa) eventually discharge 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 Sungai Chuau, Sungai Bisa and three tributaries. A series of rockfilled weirs was constructed along the six arms of the wetland to divide the 24 cells. Although all the six arms are connected, they differ in size, depths, plant communities and pollutant loads that it is designed to handle.

The basic processes happening in the cell zones are illustrated in Figure 2. Typical longitudinal cross-section and typical layout of a wetland cell are shown in Figure 3 and Figure 4 respectively.

The design features a multi-cell multi-stage system with flood retention capability to maximize the space available for colonisation by water plants. The roles of the plants are to intercept pollutants and to provide a root zone where bacteria