Flow of suspended particulate matter in the lower Guadiana estuary, and exchange with the adjacent inner shelf, during a tidal cycle

Abstract

Hydro-sedimentological investigations were carried out during a spring tidal cycle in the Guadiana estuary and just off its mouth, in September 1999 when river runoff was negligible. No significant turbidity values were observed along the lowest part of the estuary, where the salinities were similar to the coastal ocean values. Off the river mouth, turbidity was restricted to the bottom layer, and only to the stations closest to the river channels. An estimated residual downstream flow of 4.6 m3/s, certainly smaller to the computation error, agrees reasonably with the Guadiana run-off into the estuary at that time. Regression between turbidity and concentration of suspended particulate matter (SPM) in the lower estuary, allowed the computation of a net downstream transport of SPM was estimated as 0.011 kg/s. The results preclude that tidal flushing may act alone as a generator of a turbid plume over the shelf, at least in low run-off, low-SPM conditions