Water bodies restoration as an optimal control problem with integrated internal and external strategies. The inclusion of artificial floating islands

Abstract

In this work, we propose an integrated water quality model of an artificial reservoir that is the drinking water source for two cities and undergoes recurrent algal blooms. The integrated model is formulated within a dynamic optimization framework as an optimal control problem to address its restoration through the combination of different restoration techniques. The model includes a global mass balance that takes into account inflows from tributaries and rain, and outflows for drinking water and evaporation. Composition gradients are considered along the water column, rendering a Partial Differential Algebraic Equations (PDAE) system. Dynamic mass balances are formulated for the main biogeochemical variables in both reservoir and wetland, as well as artificial floating islands (AFIs) platform. The PDAE is then transformed into a DAE. Numerical results allow analyzing the performance of the different restoration strategies and their joint application on a eutrophic reservoir, showing the efficiency of AFIs as complement of artificial wetlands.