Lake Banyoles, of karstic origin, is continually heated by the incoming groundwater. This water enters the lake at certain places which are basin-shaped, keeping sediment in suspension. The temperature of suspended sediment is 2¿--3¿C higher than that of hypolimnetic water in summer, and 8¿--10¿C higher in winter. Because of this the cooling of the lake is measurably lessened. In this work a model to calculate the heat flux from underground is presented where both diffusive and advective heat fluxes are considered. The degree of turbulence of the water at the interface of suspended sediment is also evaluated. Finally, this model is applied over a 1-year cycle. ¿ American Geophysical Union 1988