TIME LIFE THE “VELHA” DAM BASINS OF THE STREAM BARRINHA, PIRASSUNUNGA, SÃO PAULO STATE, BRAZIL

ABSTRACT

Conservation of continental waters is becoming increasingly necessary due to the growing negative environmental impacts and the acceleration of its scarcity. In the Center of Research and Management of Continental Fishing Resources (CEPTA/IBAMA), city of Pirassununga, SP, Brazil, located in the “Velha” dam. The lifespan of this dam was determined by sedimentation rate, comparing two different methodologies. One was the bathymetry with a hydrometric and other hydrometric using sedimentation chambers. The samples collections in these last ones had occurred in the water column the 50 cm above the sediment, in the dry and rainy periods, during twelve months. With this methodology can be calculated the sediment rate of 7.0 mg.cm^-2day^-1 and 0.66 mg.cm^-3 annual density. The calculation of lifetime for the “Velha” dam was 7.5 years. Through the bathymetry was determined the loss of depth along the entire length of this dam, with an average, of 0.07 m.year^-1. It was concluded it will take 72 years for this dam to be completely silted up, this time can be reduced if no mitigating actions for the current impacts and planning to avoid others who may possibly occur.

KEY WORDS
Dam; sedimentation rate; bathymetry; environmental impact