PERGAMON LONGITUDINAL SOLUTE TRANSPORT IN THE UPPER CLYDE ESTUARY, SCOTLAND

The paper discusses vertical profiles of salinity and longitudinal vel ocity observed in an 11-km study reach of the Upper Clyde Estuary in S cotland. Corresponding tide level measurements and calculated area mea n velocities are also presented. The data indicate that the upper estu ary was highly stratified during two survey periods and was almost wel l mixed during a third. This is broadly consistent with an earlier cla ssification of the estuary as a type 2b within the scheme proposed by Hansen and Rattray (1966). When the upper estuary is stratified, the s alinity data demonstrate the existence of a classical multi-layer flow structure consisting of an approximately well-mixed upper layer, an a pproximately well-mixed lower layer, and an interfacial layer containi ng a large vertical density gradient. The velocity data, obtained from one of the stratified flow periods, reveal a commensurate velocity fi eld with water moving seawards in the upper layer and landwards in the lower layer. As a consequence of strong vertical shear, longitudinal dispersion coefficients of the order of 1000 m(2)/s are estimated. Sin ce the data only describe conditions on a limited number of occasions, they are more illustrative of possible conditions than representative of typical ones. Nevertheless, they clearly indicate that water quali ty models of the upper estuary need to be capable of resolving the dep th variation of environmental parameters.