Load Duration Curves as a New Approach to Water Resources Management
Keywords:
load duration curves, water quality, water resources management, TMDLAbstract
This study contributes to qualitative-quantitative water resources management in the Alto Iguaçu River Basin, located in the Metropolitan Region of Curitiba (RMC), by integrating quantitative (streamflow) and qualitative (BOD and phosphorus) parameters through the application of load duration curves. The objective is to assess compliance with water quality classifications established by Coaliar Resolution No. 04/2013. The method involves the analysis of historical streamflow and water quality data (1980–2022) from nine monitoring stations, developing load duration curves for BOD and phosphorus, and identifying required load reductions under different hydrological conditions. Results indicate partial compliance with classification standards for the evaluated parameters. The central reach of the Iguaçu River, particularly near the Guajuvira station, was identified as a critical area due to intense urbanization, industrial development, and multiple pollution sources, requiring prioritized BOD and phosphorus load reductions. The analysis suggests that BOD primarily originates from point sources, whereas phosphorus has a greater contribution from diffuse sources, although the influence of reservoirs is also significant. The application of load duration curves proved useful for diagnosing water quality, identifying priority areas for intervention, and setting load reduction targets across various hydrological scenarios.
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