Effect of Temperature on Channel Resistance

The effect of the increase of water temperature on the resistance in alluvial channels was studied in a tilting flume 2.3 ft (0.7-m) in width. One kind of sand of median diameter D₅₀ = 0.00154 ft (0.47-mm) was used as bed material. Twelve runs divided into three main groups were carried out. For each group the discharge and the depth were kept constant while the temperature was increased in successive values. The equilibrium conditions for each temperature value was maintained by adjusting the slope of the flume. The minimum and maximum water temperature recorded were 58.1°F (14.5°C) and 122.9°F, (50.5°C) respectively. Successive water temperature increases caused remarkable reductions in the total energy line slope, bed friction coefficient f'_b and the friction coefficient associated with the bed forms f_b. The reduction in f'_b and in f_b depends on the Reynold's number of the bed and on the ratio between the water depth and the median diameter of the bed particles. The bed configuration at the highest water temperature tended to be nearly a flat bed covered with a layer of coarse grains.