What effects tributaries have on these processes is being investigated by Eawag researchers with mathematical models. These show that the outflow is shifting from summer to winter. In both of these periods, the lakes warm up to a lesser degree, because the rivers contribute significant volumes of water in mid-summer and in winter. In Lake Geneva this cooling effect is less pronounced, because the water remains in the lake for much longer than in Lake Biel. A surprising result is shown by the model for Lake Geneva: due to shrinking glaciers and greater outflow in the winter, the Rhone carries with it more suspended particles. The resulting heavier water sinks in the lake and thus transports oxygen into the deeper layers.