TRANSIENTS IN CANAL NETWORK

A study is made ot transients in canal networks using a mathematical model based on St. Venant equations. The transient effects of different combinations of types, location, and operation of control structures are studied. The results of 14 problems on two canal networks are presented. It is found that the wave reflection effects from control structures, especially fixed gates, are significant and, in some situations, may cause embankment erosion and possible overtopping. The time taken for the first wave to reach tail-end locations, and for the flow to reach steady state, is considerable. It is observed that steady state is reached faster in situations of canal start-up than in canal shutdown, even though shutdown transient effects manifest earlier. A comparison is made between the complete network model and a simpler model of the main canal system, with the branches treated as bulk lateral outflows. It is found that the depths and discharges in the main canal are significantly underestimated by the bulk lateral outflow model.