The Tinto River Estuary, located at the central sector of the Huelva Coast is a mesotidal estuary, where the mean tidal range is two meters. Tinto river has small mean discharges (100.48 Hm3) but it is strongly seasonal. Tidal wave propagates Into the estuary according a hyposynchronic model, that increases during neap tides. The study of the tidal behavior at 6 stations along the estuary, allows the construction of curves of the instantaneous water position. These curves show different hydraulic gradients interpretable as sense of tidal currents. Points without hydraulic gradient mean slacks with nule velocity of currents. These slacks can be convergent or divergent. Both types experiment a displacement to the inner part of the estuary, the former during the flood, the second during the ebb. The convergent slack remain in the tidal limit until the arrival of the divergent slack. Then both become link and dissappear generating a general ebb situation. Southwest winds can accelerate this proccess