Comparing dynamic and steady-state modelling to study the impact of pollution on the Cauca River
140The three Steps Strategic Approach (3-SSA) consisting of: 1) minimization and prevention, 2) treatment for reuse and 3) stimulated natural self-purification has been proposed as an integrated approach to efficiently address the problems associated with wastewater discharges and its impact on receiving water bodies. This study focuses on Step 3, comparing dynamic and steady state conditions of quantity and quality (DO and BOD5) in the Cauca River, Colombia, and the impact of pollution and wastewater discharges. Over the past 60 years, the Cauca River has lost much of its natural self-purification capacity, represented in the wetlands of its floodplain. A multipurpose reservoir (Salvajina dam) was built in 1985 for pollution control (dilution capacity), power generation and flood control. The results of this study show that selfpurification capacity in the Cauca River is strongly affected by abrupt changes in hydraulic flows, especially due to the operation of Salvajina reservoir and the type and size of the received pollution from point-source and non-point source pollutants. The results also show the importance of considering the dynamic behaviour of the system under Step 3 of the 3-SSA and the importance of improving policies and regulations for monitoring and pollution control.