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High-intensity land-use activities occur near lakes including in their watershed and increase of population density in areas neighbouring the lakes have caused overexploitation of lake water resources and discharge of large volumes of pollutants into lakes water. As a consequence led to escalating deterioration of lake water quality. Water quality conditions of lakes are significantly influence by their watershed behaviours. The lentic nature of lakes allows problems to build up and symptoms to go unnoticed for a lengthy period and commonly only appearing at a delayed and dangerous stage given that similarly a slow and often equally long period is needed to treat before positive results begin to show again. Hence, it is quite complex to comprehend types and strengths of pressures that impact water quality status, when do the changes will occur and what the status of water quality would be, not only on the presence situation but over the long term. Lake water quality and catchment relationship is an intricate issue and required the lake managers and planners to be attentive and prepared to engage in sustained actions over a long-term time frame relating to the development of lakes because progression of degradation inside a lake mostly takes place on a wider and deeper scale than is readily apparent. The comprehensive understanding on anthropogenic upheaval and hydrological linkages within lake watershed influences the dynamics of the lake water quality and is vital to the resulting livelihood including the cultural, biodiversity, and economic activities that are supported by lakes. This paper highlights the issues and challenges in managing lake water quality, variables that significantly influence lake catchment-water quality relationship, discussing the water quality parameters that must be regularly monitored, and proposing a management support tool as the expected research output to ensure lake water quality is not compromise while meeting the country's socioeconomic demand.

Putrajaya Lake and Wetlands being the centrepiece of Malaysia's administrative city is an important destination for recreation, sports and tourism in the country. The urban water body system with a total surface area of 400 hectares was designed and built so as to encircle the core island creating a complex morphometry. To ensure the water quality remains in its highest-level condition since its beginning, to perform its multi-functional uses, managing the lake catchment is of paramount importance. This paper describes the application of numerical simulation of Putrajaya Lake using coupled three-dimensional hydrodynamic-ecosystem model to assess the spatial dynamics of the lake water quality. The hydrodynamic model simulates the flow pattern under different meteorological forcing variables. The ecosystem model simulates the resulting spatial and diurnal water quality pattern. Wind is the dominant forcing variable driving the flow field. The lake exhibits spatial variation of physico-chemical variables with an overall high-quality of surface water. The model simulation illustrates the impact of potential discharges on the lake water quality, such as spread of pollutants, subsequently provides a useful tool to enhance the management of the lake sustainably under changing environment.

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