68
Luis Felipe Niencheski . Maria da Gra~a Baumgarten· Gilberto Fillmann . Herbert L. Windom
Fig. 4.1. Map of Patos-Mirim lagoon system showing station locations in the estuarine area
the estuarine area there is a navigation channel with average deep about 12 m. Almost
80% of this area is less than 2 m deep (Hartmann 1988). Because of this, wind action,
waves and currents cause frequent resuspension of sediments. Additionally, the tidal
range within the estuary is small (0.47 m) due to the low diurnal tidal amplitude in
the adjacent South Atlantic (Moller et al. 1991).
Freshwater input to the estuarine region from Patos Lagoon originates from its main
tributaries located in the upper region (Fig. 4.1). The Guafba River, including the Jacuf,
Sinos, Caf and Gravataf tributaries, supplies 86% of the average total freshwater input
with most of the remainder coming from the Cam aqua River. These rivers (along with
inputs from the Southern Atlantic Ocean via the Patos Lagoon inlet canal) represent
the major transport pathway of materials, such as nutrients and suspended matter, to
the estuary. Nutrients originating from river inputs transits 250 km before reaching