We report on three-dimensional flow simulations carried out in order to describe the dominant water current patterns in the reconstituted lake Karla. The flow is considered to be generated mainly by wind shear while the influence of water inflow is evaluated as well. The effect of wind speed and direction and the resulting water recirculation currents are discussed based on meteorological data. The present results show that the contour of the lake boundary has a significant influence on the water velocity. The water in the lake is the less convective for SW and NE winds. Moreover, two dominant patterns in the lake are found to be formed due to different wind blow directions. The existence of surface water recirculation is found to be dependent only by the wind speed, however, possible horizontal water recirculation maybe submerged beneath the surface. The presented hydrodynamic model constitutes the basis for the development of models for heat and mass transport in the Karla reservoir. Results of the spatio-temporal distribution of a passive scalar in the lake have presented for an idealized mass transfer problem. Slow contamination zone formation and advection from the inflows to the outlet is found due to the weak water currents.