Sediments and nutrients input to a small reservoir in the tropical semi-arid region

ABSTRACT The sediment and nutrients that are input to surface reservoirs compromise the quality and quantity of the stored water. The aim of this study was to investigate the dynamics of sediment and nutrient input along the drainage basin of a small reservoir in the semi-arid region. The reservoir under study was built in 1956 and has a storage capacity of 5.01 hm3. Seven trenches were dug along the drainage basin of the reservoir following the river. Sediment samples were collected at increasing depths of 20 cm until reaching the original riverbed. An analysis of particle size, total organic carbon (TOC), total nitrogen (TN), available phosphorus (P), exchangeable aluminium (Al), total iron (TFe) and pH was carried out. Approximately 60% of the sediment in the reservoir is composed of clay and silt, and 40% of sand. The greatest thickness of the sediment layer, as well as the greatest concentration of fine sediment, was registered in the section nearest to the dam. The values for TOC (2.47 < TOC < 34.47 g kg-1) and TN (0.69