Ytan eller Botten? – en studie av avloppsvattnets inblandning & förhållanden i Inre Valdemarsviken / Surface or deepwater outlet – a study of effluent water entrainment & conditions inside Inre Valdemarsviken
The deepwater of the water area known as Inre Valdemarsviken, situated on the Swedish east coast, is a recipient of effluent water. Suspicions has arisen concerning bad conditions in the mouth area due to abnormal presence of bacteria in the surface water, overgrown perennial algae and turbid water. This may be effects of effluent water being disposed and in this article calculations are made to clarify the dynamics of Inre Valdemarsviken. According to theory and equations of selective withdrawal, (Stigebrandt, 1978a & 1978b), maximum withdrawal depth of different current velocities in the mouth was calculated. Current velocity in the mouth are known to a times reach 2 m/s. With a current velocity of 1.5 m/s, the maximum withdrawal depth would be 8 meters. Entrainment of effluent water has been calculated by a model based on conservation of volume and momentum in the created plume (Turner, 1973). The stagnation depth of effluent water varies throughout the year between 16 and 20 meters. In order to calculate occurrence/ frequency of high bacterial concentrations, measurements of these on different locations and depths are required combined with water level data from both sides of the mouth so that current velocities can be calculated with higher accuracy.