The effect of local wind field on water circulation and dispersion of imaginary tracers in two small connected lakes

This study considers the effects of wind field forcing data on a 3-D hydrodynamic model of two connected urban lakes in Central Finland, one of which is used as municipal water source. We consider the wind data from a nearby official weather station, local winds measured at several sites at the target lakes, and winds obtained by spatio-temporal modelling. Dispersion of tracers was simulated in the lakes in order to assess the propagation of a contaminant cloud and especially the possibility of contaminants reaching the municipal water source. We found that there can be important differences in tracer transport timing and path depending of the wind field used in the model. No clearly superior method for obtaining the wind field was found. Spatial wind fields can improve lake model predictions when lakes are fragmented and sheltered. Lake model performance can be further improved by ensemble modelling approach.