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Abstract. Rapid urbanization has known to have several adverse impacts towards hydrological cycle due to increasing impervious surface and degradation of water quality in stormwater runoff. In the past, urban waterways have been confined to narrow river corridors with the channels canalised and concrete and other synthetic materials forming the bed and banks of the river. Apart from that, stormwater pollutants such as litter, debris and sediments in drainage system are common problems that can lead to flooding and the degradation of water quality. To solve this problem, implementing stormwater Best Management Practices (BMPs) proves very promising due to its near natural characteristics and multiple effects on the drainage of stormwater runoff in urban areas. This judgment of using BMPs depends on not only relevant theoretical considerations, but also a large amount of practical experience and the availability of relevant data, as well. To fulfil this task, the so-called Decision Support System (DSS) in MSMA Design Aid and Database system are able to assist engineers and developers in management and improvement of water quantity and quality entering urban rivers from urban regions. This system is also helpful when an expert level judgment procure some repetitive and large amount of cases, like in the planning of stormwater BMPs systems for an entire city catchment. One of the advantages of an expert system is that it provides automation of expertlevel judgement using availability of checking tools system.

This paper presents a preliminary assessment of greenhouse gas (GHG) emissions from all major hydropower reservoirs in Malaysia from the period of 1930–2017. The GHG emissions are calculated based on the Tier 1 method as recommended in International Government Panel on Climate Change (IPCC) guidelines. The results showed that approximately 151.64 Gg of annual methane emission released from hydropower dams in Peninsular Malaysia. While in East Malaysia, hydropower dams release 235.7 Gg of methane emission annually. Bakun dam contributes the most 41.26% of total annual methane emission from hydropower dams in Malaysia. Ulu Jelai hydroelectric dam with design power capacity of 372 MW contributes the least CH4 emission of 0.02 Gg CH4 yr−1. It is seen that high head hydroelectric dam with small reservoir surface area is the most sustainable hydropower dam in reducing the GHG emission. However, long-term measurements must be made in order to clarify the net GHG emissions from reservoir surface, turbines, spillway and downstream river of hydropower dams in Malaysia.

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