**4. Conclusion**

to enable protection of the uses nor become an established regulatory criterion with legal ramification. However, the criteria can also be used by the respective agencies and stakeholders to assist in monitoring and to classify various lakes under their regulatory or management

In the proposed document, the sampling strategy was not described in detail. Water quality in lakes is known to differ temporally and spatially, both horizontally and vertically depending on lake depth. Seasonal and daily variations associated with irradiance, along with dissimi‐ larity in surface waters' mixing related to weather patterns can induce variations in tempera‐ ture, DO and the transportation of nutrients or pollutants. Thermal and chemical stratification are common features of deeper lakes which affect the water quality being monitored. Variations in water quality are also dependent on the composition of discharges over both short and extended periods. Discharges from housing, commercial buildings and industry can vary within a day, a week or a season. Domestic discharges depend on the homes' occupancy, which is usually higher during the early morning, at midday and in the early evening, while industrial discharges depend on operation hours. Higher home discharges and lower industrial dis‐ charges could happen during weekends and festive seasons. Exceedances of bacterial indicator to health risk were also temporally sporadic and geographically limited with the reduction of pollutant loading not necessarily reducing the health risk [43]. Narrative criteria were pro‐ posed in NLWQCS namely to consider the size and shape of the lake when choosing a sampling location, so that the site selection is representative of the whole lake. The choice of site for routine water monitoring sampling can make a significant difference to the classification of microbial water quality [44], owing to the hydrodynamics and proximity of pollutant sources.

With respect to the criteria for protecting aquatic life in the NLWQCS, many limitations exist due to unavailability of extensive data. The criteria in this are mostly based on chronic and acute effect values in temperate countries which have different species. Most of the water quality criteria were also based on a single pollutant model which mostly targeted single species instead of community response [3]. Some of the criteria for aquatic life protection adopted the same value for the human health protection criterion assuming that the effects to all types of aquatic life, all stages of their life cycle and the whole aquatic community are similar. Further research is much needed on deriving the chronic and acute effects of many pollutants on freshwater local species in order to establish more accurate criteria for protecting the

In these criteria, the sampling methodology aims at testing the ambient condition of the lakes via a minimum of three sets of samples, to be monitored at least twice a year, once in the dry and once in the wet season. The proposed depth is surface measurement, in accordance with standard methods [45]. However, adult chest depth at ∼1.2–1.5 m is the most common sampling depth recommended in the United States and Canadian recreational guidelines, due to strong evidence in the form of the mathematical relationship between indicator organism density and swimmer illness. Intensifying the number of samples and frequency of monitoring may provide a better representation of the lake's overall water quality and trends. A minimum frequency of once per week during the swimming season was recommended by Canadian guidelines [17] and monthly by the UK and a few US states [9, 46, 47], in order to make more

controls for their fitness for different uses.

308 Water Quality

Malaysian aquatic environment.

The importance of this work is to develop criteria that can be used for sustainable management of lakes and reservoirs in Malaysia. The lake criteria and standards are proposed to be non‐ regulatory to promote monitoring efforts by various stakeholders. The development of such a criteria and standard, however, may be limited by time constraints, fund allocations and expert knowledge as well as the variability of environmental data. Future work will look into governing the standard with an appropriate methodology and regulatory framework to ensure an effective national standard for application.
