Physical Modeling of Flow Velocities at the Outlet of a Stilling Basin for Diversion Dams with Different Depths

Abstract

This study seeks to address the challenges posed by hydraulic head management in diversion dams, focusing especially on reducing scour and improving riverbed stability. To achieve this, mechanisms such as stilling basins, designed to reduce the kinetic energy of water flow and thus minimize downstream erosion risks, were evaluated. Using the "Tres Molinos" dam in Cajamarca, Peru, as a reference, a 1:25 scale physical model was built at the Water Resources Laboratory of the National University of Cajamarca, taking into account hydraulic similarity principles. Through experimental tests carried out on this model, the flow characteristics at different depths of the stilling basin could be analyzed. The results demonstrated a considerable reduction in flow velocity and scour downstream of the mitigation structure, with velocities ranging from 0.276 m/s to 0.667 m/s and scour depths varying from 1.5 cm to 6.9 cm, confirming the effectiveness of an appropriate design of energy dissipation structures not only to control flow velocity but also to reduce scour and improve the stability of hydraulic infrastructures. Furthermore, the results showed a remarkable efficiency in energy dissipation, reaching up to 56% in flow velocity reduction and up to 60% decrease in scour compared to a diversion dam without a stilling basin.