Study of the limnology of wetlands through a one-dimensional model for assessing the eutrophication levels induced by various pollution sources

Eutrophication of lakes and wetlands, resulting from the discharge of excess nutrients, has become a matter of primary concern. The entire ecology of a eutrophic wetland gets severely affected due to the substantial degradation of its water quality. Formulation of ecological models assists in determining the nutrient dynamics of a particular ecosystem, thereby providing an idea of the significant causative parameters aiding eutrophication. The present study aims at providing a suitable foundation for the development of an eutrophic-ecological model for Deepor Beel, India. Water, sediment, and water hyacinth samples were collected from various parts of the wetland and subjected to analyses on a continuous basis from Oct’ 2017 to Feb’ 2019. The collected samples were analysed for various physico-chemical parameters, quintessential for the development of a eutrophication based ecological model. A conceptual diagram was first constructed, and the corresponding differential equations about different functions were formulated. Subsequently, a code was developed in MATLAB based on the logic formulated through the conceptual diagram. Sensitivity analysis was first performed on various state variables, identifying the parameters most sensitive and thus, exhibiting maximum variability in the model. The model was then subjected to calibration for defining the rate constants based on which; it was subjected to further validation. Finally, the model was simulated for two plausible alternatives to verify the reduction of the eutrophication levels in Deepor Beel; (i) Harvesting of water hyacinths and (ii) Setting up of a treatment unit for nitrogen and phosphorus removal. The results obtained for both cases indicated that, harvesting of water hyacinths would not provide a suitable long-term and effective solution. However, setting up of a treatment unit for phosphorus and nitrogen removal can aid in a significant reduction in the nutrient levels in the wetland, thereby assisting in curbing the eutrophication levels. The results obtained through this study would provide significant assistance to the various government as well as private agencies and policymakers for carrying out effective solutions for the increasing eutrophication levels in Deepor Beel, which would thereby help in reviving the wetland.