AVALIAÇÃO DO ASSOREAMENTO EM RESERVATÓRIOS: ANÁLISE CRÍTICA COM BASE EM RESERVATÓRIO DE ABASTECIMENTO PÚBLICO EM REGIÃO URBANIZADA

Código

PAP063

Autores

Matheus G. da Silva, Stephan Hilgert, Kladji Sotiri, Heloise Garcia Knapik, Cristovão Vicente Scapulatempo Fernandes, Mauricio Dziedzic, Maurício B. Scheer, Tobias Bernward Bleninger, William Bonino Rauen

Tema

PROCESSOS HIDROSSEDIMENTOLÓGICOS E MORFOLÓGICOS: FLUVIAIS, LACUSTRES E COSTEIROS

Resumo

Passauna is one of four reservoirs of the integrated public water supply system for Curitiba and metropolitan region, providing water to around half a million inhabitants. This study aimed to quantify and critically assess siltation in this reservoir between 1990 and 2016 ? the years of lake formation and realisation of a bathymetric campaign, respectively. Stage-area and stage-volume curves were updated for the reservoir, from which key areas and volumes were determined and contrasted between the two historical scenarios. With emphasis on the minimum normal volume (MNV, located below the barrage weir crest), an analysis was conducted of uncertainties and relative importance of parameters involved in the siltation process, such as the total fluvial sediment load, bulk reservoir bed density, internal plankton production and data uncertainty of the bathymetric (for 2016) and altimetric (for 1990) surveys. Discrepancies in the area results between 1990 and 2016 were lower than the corresponding uncertainty. In 2016 the areas associated with the dead volume and MNV were 4.60km2 and 8.26km2, respectively, each with an uncertainty of ±0.5km2. Concurrently, the MNV was estimated as 70.2hm3, while the dead volume was 20.4hm3 and the minimum working volume was 49.8hm3, with uncertainties of up to ±0.4hm3 each. A reduction of 1.4hm3 was noted for the MNV, which was supposedly caused by siltation at a rate of -0.1%volume/year. The uncertainty analysis showed that only 20% of such volume loss could be explained by watershed inputs, as estimated using historical data and a sediment rating curve; that bulk bed density estimates obtained using the Lara & Pemberton method were uncertain to a range of 10% to 50%; that internal production could only explain up to 10% of such siltation; that the volumetric uncertainty of the bathymetric survey corresponded to around a third of the estimated volume loss; and that the uncertainty of initial reservoir volume information was higher than the volume loss estimate and all other uncertainties assessed herein. Reflections were made on the determination of the working life of such reservoirs, the impact of siltation on future water availability and their role in promoting water security in urban regions.