Design of canals to maximize hydrokinetic energy

My company Hydrovolts is developing hydrokinetic turbines for big canals. These canals can create a lot of energy if they are occasionally narrowed so the water flows fast. The turbines make power according to cube of velocity so if current flow doubles then power increases 8x. As long as the canal has enough freeboard, the turbines do not reduce the flow of water through the canal. The first turbine has to be downstream far enough from the headgate or first drop so it does not cause backpressure into the headgate. Comments welcome.