Sediment retention rate in reservoirs of the Brazilian semiarid environment

Abstract

Due to the current degree of importance of superficial reservoirs in meeting the demand for water in semiarid environments, it is necessary to investigate the processes that affect their quantitative and qualitative productivity. Among these processes, that of sedimentation stands out. The purpose of this study is to evaluate the relationship between the sediment retention rate (ξ_m) and the reservoir storage volume, drainage area and time of operation. An empirical equation that demands a few parameters has been used. Analysis of 25 reservoirs located across the State of Ceará, Brazil, was performed. The investigation showed that: a strong positive correlation was observed between ξ_m and the volume of the reservoirs up to the limit of 10 hm³; for volumes greater than this value, the correlation proved to be weak and negative; there are two clusters of reservoirs concerning the relationship between ξ_m and drainage area: one with those whose catchment areas are less than 160 km² and another with those whose areas are above this threshold value, both with strong positive correlations. A strong negative correlation of ξm with the time of operation of the reservoirs was observed as well.