Eutrophication has emerged as one of the main threats to surface water bodies. The parameters for assessing eutrophication are not generally measured regularly from the lakes of India as part of monitoring programmes and it is necessary to express the trophic status in terms of secondary indicator variables that are included in the routine analysis by the State/Central government. In this paper, the trophic status of Ashtamudi Lake has been studied, considering its international importance and socio-economic relevance. The cause and response variables such as total phosphorus, Secchi disc depth, chlorophyll-a and the secondary indicator variables such as pH, turbidity, DO, EC, Salinity, TDS and BOD were analysed during the pre-monsoon season. The lake was predominantly classified as eutrophic, with some areas coming under a hypereutrophic state. A comparison was made among the five methods of water quality index by the use of secondary indicator variables to identify the appropriate method for simulating trophic status and the WQI based on the logarithmic method considering pH, turbidity, DO and BOD was identified to predict the trophic state very well. Further, the application of numerical strategy such as fuzzy logic was used to determine water quality indexes and trophic status, which can define the quality of a water body as a consequence of the variation of environmental parameters. The developed approach was further validated by using historical data for the years 2013–2015, which were regularly monitored by the Kerala State Pollution Control Board. The trophic state predicted by the approach was found to be in agreement with that estimated using Carlson's method. Thus the developed model, based on secondary indicator parameters that are readily available from government agencies, can be used to assess the trophic state of lakes, thereby assisting policy makers to frame regulations to minimize eutrophication.

富营养化已成为地表水体的主要威胁之一。评估富营养化的参数通常不会作为监测计划的一部分从印度的湖泊中定期测量，因此有必要根据州/中央政府的常规分析中包含的二级指标变量来表达营养状态。在本文中，考虑到阿什塔穆迪湖的国际重要性和社会经济相关性，研究了它的营养状况。在季风前季节分析了总磷、Secchi 圆盘深度、叶绿素 a 等原因和响应变量以及 pH、浊度、DO、EC、盐度、TDS 和 BOD 等次要指标变量。该湖主要被归类为富营养化，一些地区处于超富营养化状态。对5种水质指数方法进行比较，通过二级指标变量确定适合的模拟营养状态的方法，并基于对数法确定考虑pH、浊度、DO和BOD的WQI预测营养状态。状态很好。此外，应用模糊逻辑等数值策略来确定水质指标和营养状态，可以将水体的质量定义为环境参数变化的结果。通过使用 2013-2015 年的历史数据进一步验证了所开发的方法，这些数据由喀拉拉邦污染控制委员会定期监测。发现该方法预测的营养状态与使用卡尔森方法估计的营养状态一致。