Análise espaço-temporal dos processos hidrossedimentológicos e sedimentação no reservatório da UHE Caçu

• Autor(a) principal: Braga, Celso de Carvalho
• Data de Publicação: 2017
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/8119
• topic: Hidrossedimentologia; Assoreamento; Depósitos em reservatórios; Hydrosedimentology; Silting; Deposits in reservoirs; CIENCIAS HUMANAS::GEOGRAFIA

The useful life of dam depends upon exclusively on the soil use model of a watershed and the amount of leavings and nutrients that are laid up in its riverbed, diminishing the useful volume of the dam. Due to the water crisis of the last decade, the studying of the amount and distributions of the leavings became imperative for the decision making process of preventive measures about the silting process as well as the electricity generation in Brazil. This research has the goal of evaluating the level of silting and the quality of the leavings on the Caçu power plant (UHE Caçu), located in the Goia's south east region, with the purpose of taking preventive measures against the silting process. To locate the main areas susceptible to the silting process, It was detected areas of greater and lesser levels of environmental fragility in the watershed of the dam, by using different kinds of parameters (soil, geology, geomorphology, rain density and vegetal cover). It was created a map with a varying levels of fragility as proposed by Ross (1994), describing and discussing the potential for contribution for the environmental degradation of the watershed. The results founded shows that the watershed has 75% of the area classified as low fragility, but, 25% of it classified as medium or high fragility, showing the necessity of planning and using conservational practices in the soil using model. The evaluation of the water data relied in six gathering of samples in the field, between the years of 2014 and 2017, divided in three gathering during the rainy season (January and February), and three gathering during the wet season (July and august), it was analyzed the concentration of suspended solid (CSS) founded in the epilimniun, the turbidity, and the transparency of the water through the Secchi disc (SEC). According to the analyzed data, there is a greater uniformity of data both CSS and TURB during the wet season and greater uniformity of SEC during the rainy season, highlighting the correlation between the variables CSS, SEC and TURB. To evaluate the depositional models that happens in the dam, it was analyzed the facies and deposition models to understand the process of sedimentation in the dam. IT was detected different kind of facies that differentiate from silt-clay to sandy material, providing depositional models from stream deposit, riverbed deposit facies and delta deposit facies. From the beginning of the dam until the the Cachoeirão stream and in the river mouth of the córrego Caçu, it was founded leavings from the deep with greater granulometry, representatives of stream deposit, in the river mouth of some tributary rivers, it was spotted representative delta deposit facies, and in the greatest part of the dam, the central part, representatives deposits of riverbed deposits. Qualitative analysis of leavings were made from heavy metals that were found as: lead, cadmium, mercury, copper, nickel, zinc. There was a high concentration of cadmium in all samples analyzed, according to the stipulated parameters from the CONAMA 454/2012 act, showing a great possibility of adverse effects on the biota. It was made a bathymetric data collection during the wet season between the years 2014 and 2016, with the goal of evaluating the silting process in the whole dam, the result showed a high level of silting of 0,3% during the period, the approximate dam volume is 245 hm3. If there were no changing in the soil use model and rainy levels in the watershed, it would take the dam more than 667 years to be silted completely. Nevertheless, the silting process in the backwater area is to worry about, due to the accentuated of depth, causing for instance, problems in the local navigation.