Ecoagrohydrological Modeling and Dynamic Optimization for Water Management in Integrated Aquatic and Agricultural Livestock Systems

DIAZ, MARIA SOLEDAD

BUenos Aires

Workshop; PASI-PSE 2023 (Pan-American Advanced Studies Institute on Optimization and Data Science for Net-Zero Carbon and Sustainability); 2023

Carnegie Mellon University, Universidad Nacional del Sur

Water is an extremely scarse resource and much work has been devoted to modelling of water bodies with different objectives and approaches. The identification of meteorological, hydrological and ecological components and driving forces behind problems such as eutrophication, floods and salinisation in water bodies, as well as the integration with agricultural and livestock activities constitutes a challenging problem towards achieving sustainability goals. In this work, we formulate optimal control problems to plan management strategies in eutrophic lakes and reservoirs, based on ecohydrological and biogeochemical models represented by differential algebraic equation systems that include mass balances, evaporation, kinetic equations, etc. Dynamic optimization problems are formulated within a control vector parameterization framework in gPROMS (PSEnterprise, 2022).On the one hand, we address the control of algal blooms in a reservoir that provides drinking water to two cities, by considering simultaneous application of different restoration strategies, including reduction of external nutrient charge to the water body through artificial wetlands (control variable: fraction of nutrient rich water stream that is diverted through wetlands), fish removal (control variable: fish removal rate) and artificial floating islands within the water bodies. On the other hand, we propose integrated models that include ecohydrological, agricultural, livestock and carbon capture submodels, to address the hydrological instability of a salt lake endorheic basin within a semiarid region, focusing on preserving valuable fish species, native and valuable crops and cattle. The objective is to propose water management policies to address mitigation of extreme events like droughts and floods through the formulation of an optimal control problem that allows a) Optimizing management of water resources in salt lakes and in constructed freshwater reservoirs; b) Keeping salinity in the lake within a desired value for valuable fish species growth, as well as salt lake volume, during dry and wet periods; c) Ensuring provision of drinking water, food and shade to cattle; d) Proposing restoration strategies for native tree species; e) Proposing combination of new plantations with drought resistant crops and pasture; f) During wet periods, preventing flooding of nearby towns by diverting part of lake tributary flows into constructed reservoirs; g) Addressing the economic valuation of ecosystem services in the basin. Numerical results provide useful insights on optimal management strategies and the effects of their implementation, as well as their impact on the valuated services in the watershed under study; which shows that the formulation of integrated models for ecosystems constitute valuable tools to help the sustainable socieconomic development focusing on water management in water bodies and their basins