One of the key requirements of successful water quality management in lakes and reservoirs is a good understanding of the underlying processes within the system. Lake managers, however, need a very simple practical tool to support quality regulation and policy implementation in terms of protecting and restoring these ecosystems. Here, we communicate a starting point from which lake managers, particularly in Indonesia, can gain a better understanding of aquatic ecosystem processes through the integrated application of different models. Until now, numerical aquatic ecosystem models have been used rarely in designing lake and reservoir restoration programs in Indonesia. We highlight the importance of model applications, while noting the difficulties of advancing management plans for Indonesian lakes and reservoirs.

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Carbaryl, one of the carbamate insecticides are used extensively for pest control in agriculture. The chemical is highly valued for its rapid action and relatively short environmental persistence. Because of its widespread and intensive use, residues of carbaryl have the potential to contaminate the environment. This study aims to formulate a system dynamics model to simulate a degradation process of carbaryl. Since carbaryl was not readily volatilizing, this study only estimates the concentration and degradation of carbaryl in soil and water. The result revealed that carbaryl degraded rapidly, with a half-life of 7 days in soil and two days in water. The model was validated with a laboratory experiment using solid phase extraction reversed-phase high-performance liquid chromatography to determine carbaryl concentration. 12.82 % percentage error compared to the experimental value indicated that the developed model’s prediction was acceptable. The model can be used to estimate the presence of carbaryl pesticide in soil and water. Findings from this study can be used to assess the fate and the impact of carbaryl pesticide in the environment.

WHO declared a novel coronavirus in humans as Coronavirus Disease 2019 (COVID-19) on February 2020, and Indonesia as well as Bandung City have been suffering from COVID-19 since the first case in March, 2020. Currently, the outbreak of COVID-19 has occurred for more than a year. The COVID-19 pandemic had a severe impact on the environment, like the enhancement of household solid waste as a result of work and school from home policies to decrease the rates of COVID-19 cases. This study aimed to predict the amount of household solid waste generation and analyze the waste management during COVID-19 in Bandung City using a system dynamics model. Data for model input was obtained from questionnaire to 200 respondents from Bandung spread across the sub-districts. The results revealed that the household solid waste generation was increased by 1.3 to 3.8% compared to the year before the COVID-19 pandemic. The composition of household solid waste was dominated by food and plastic waste, which have increased to 76.43% and 25.81%, respectively. The system dynamics model has predicted the household waste generation from three management scenarios for 30 years of model simulation. Scenario I: the household solid waste was totally managed by a local sanitary agency (existing condition); Scenario II: each household manage their waste by recycling; and Scenario III: the utilization of a local waste bank to manage the waste. The scenario III showed the most effective waste management to reduce the amount of household solid waste generation up to 24% by using waste bank. This scenario can be applied for more prolonged landfill operations up to 17 years.

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