This paper deals with wind-induced flows in a semi-enclosed water body in a microtidal environment that is subject to various wind-wave and river discharge conditions. The resulting currents are analyzed using numerical models supplemented by (and calibrated with) field observations. The emphasis is on the driving efficiency of wind fields in generating steady currents as a function of wind velocity and direction. The circulation generated is analyzed for the actual case of Cullera Bay and for a theoretical case in which the cape (limiting barrier) has been “removed” from the computational domain. The results obtained as a part of the EU research project ECOSUD, allow the barrier effect exerted by the cape to be partially quantified. The river plume dimensions and direction of spread are clearly influenced by the cape barrier. On a more local scale, the effluent discharge from the outfall was also found to be influenced by the two Júcar River jetties. Based on these results, a “retention” index that partly characterizes water quality in the bay is defined. This type of index is also a scientifically based indicator that supports more sustainable management of water quality in coastal bays of this type.