152 / 2024-02-21 23:39:12

Hydro-Environmental Modelling and Eutrophication Monitoring in the Putrajaya Lake, Malaysia

Eutrophication, lake monitoring, hydro-environmental modelling

Many lakes/ reservoirs were constructed for various purposes such as water resources, flood detention, recreation, hydropower, etc. In Malaysia, more and more reservoirs being constructed for water storage purposes including off river storage (ORS) with shallower water depth. Many lakes/ reservoirs are facing huge challenges in water quality management due to uncontrolled discharges, continuous developments, and its associated anthropogenic activities. One of the major issues is eutrophication. In monitoring eutrophication, many lake/ reservoirs manager only conducted water quality measurement at selected points of the whole reservoir area due to budget constraint. This may not be able to provide a representative water quality of the whole reservoir, and sometime overlooked certain areas which can be critical. This study utilised the hydro-environmental modelling technique to produce the Eutrophication Index for study area at Putrajaya Lake in Malaysia. This lake is in the Malaysian Government Administrative Centre and formed by dam-up of the Chuau River. It has a catchment area of 52 km², reservoir area of about 400 ha and 25 million m³ (MCM) of water storage. A study of two-dimensional (2D) depth average hydrodynamic modelling was carried out using Delta3D to model the lake hydro-environmental processes for both wet and dry seasons. The model was calibrated against the measured flow velocities and directions over 17 points in the lake. Water quality modelling was conducted for phosphorous & chlorophyll-a and the results was used to produce the Lake Eutrophication Index for Putrajaya.  A modified Trophic State Index was also developed specifically for Putrajaya Lake and being used to produce the 2D Eutrophication Map. The findings have resulted in recommendations being made for the best management practices for lake, which, in turn, have a key impact on the lake hydro-environmental processes.