Brazil has great potential for cage aquaculture, especially in hydroelectric reservoirs. In western Paraná, the Itaipu Reservoir offers favorable conditions but remains underutilized. Defining the environmental carrying capacity is essential to ensure the sustainability of the activity and to avoid impacts such as eutrophication. The Brazilian National Water Agency (ANA) adopts the Dillon and Rigler model, which considers phosphorus and residence time as limiting factors. This study evaluated the influence of the hydrodynamics of the central body of the Itaipu Reservoir on the residence time of the Passo Cuê River embayment, aiming to improve the estimation of aquaculture carrying capacity.
Two 2D hydrodynamic models were simulated using Delft3D software: a simple model, considering only the downstream water level variation of the Passo Cuê embayment , and a coupled model, which integrates the hydrodynamics of the reservoir’s central body. The simulations used bathymetry and historical data on water levels, regionalized flows, wind, and precipitation. The average residence time was estimated using the Eulerian method with conservative tracers.
The average residence time differed between the models (p < 0, 05). For the coupled model, the average residence time was 129 days, while for the simple model, it was 161 days, as shown in Table 1.
The coupled model allowed for greater accuracy in estimating residence time, highlighting the importance of considering the interaction between compartments and the central body of the reservoir. The compartmentalized morphology of Itaipu directly influences water circulation and renewal, impacting nutrient dynamics and, consequently, the local carrying capacity.