Efeitos da descarga de fundo de reservatórios em cascata: qualidade da água e fitoplâncton do reservatório de Xingó/AL

Abstract

Lake Xingó is the last of a sequence of reservoirs in the São Francisco River Basin, located in a semi-arid region of the Brazilian Northeast. In 2013, due to the drought, a process of reduction of the reservoir flow was initiated and in 2015, the reservoir, upstream, Delmiro Gouveia, carried out a bottom discharge in the previous portion of the lake of Xingó. The understanding of the effects of the high sediment load on the dynamics of the physical, chemical and hydrobiological variables of the waters is still a gap in the academic and technical-professional literature. Thus, this work evaluates the consequences of the discharge of solids from Lake Delmiro Gouveia on the water quality and dynamics of the phytoplankton of the lake of Xingó. Thus, in a temporal and spatial perspective, the interference, in the water quality, of the reduction of the average flow of the São Francisco River is analyzed. For this purpose, six monitoring points were defined in Lake Xingó, representing the anterior part (P 01 and P 02), intermediate (P 03 and P 04) and posterior (P 05 and P 06). The results showed that both the flow reduction and bottom discharge events caused variations in the physicochemical patterns of water quality, with a consequent change in trophic state and interference in the ecological dynamics of phytoplankton.