A Detailed Safety and Risk Assessment of Pequenos Libombos Dam

Abstract

At the request of the Mozambican National Directorate of Water Program (DNGRH) and as part of the National Climate Resilience Program, a study aimed to evaluate the current safety of the Pequenos Libombos dam and downstream valley was developed by the Consortium COBA/LNEC/SOLOMON. The objectives encompassed a range of activities designed to ensure a thorough assessment and enhancement of dam safety, a critical issue to guaranty the integrity and reliability of this key water infrastructure of Mozambique. In this paper, structural and hydraulic-operational safety results are presented, as well as its adaptation to the new Mozambican dam regulations. The Pequenos Libombos Dam, located on the Umbelúzi River, serves as the primary water supply for Maputo city. It features a 1,540-meter-long and a 46-meter-high earthfill structure, with a 100-meter-long central gravity concrete dam where all the appurtenant structures are located. The study involved a comprehensive evaluation of dam performance, including a review of operational procedures and detailed site inspections. It analyzed existing monitoring data and assessed current safety conditions. A thorough safety assessment identified both structural and non-structural mitigation measures. The comprehensive assessment approach taken for the Pequenos Libombos dam revealed strenghts and weaknesses in current dam safety practices. By implementing the recommended measures, the safety and functionality of these dams will be signficantly enhanced. Key lessons underscored the critical need for regular monitoring and robust risk assessment procedures. This will contribute to overall resilience and security of the region’s water infrastructure and ensure the safety of populations living downstream.