No offense, but that was a dumb and misleading post. You know way too much about the EC V and IHDR to be going through the exercise of scaling it to the size of the Hoover Dam.
The whole principle behind being able to scale the EC V upwards is to utilize low flows to create high energy. The idea behind the scaling (which you know, but conveniently choose to ignore) is NOT to make the EC V bigger, but rather to utilize the fact that one slice of the EC V can produce 7.5 kW of electricity from a low-flow source (note: the Hoover Dam does not fit the bill), and 4 slices can produce 30 kW from the SAME low-flow source. So theoritically, lining up ~134 EC V slices can produce 1 megawatt of constant energy from that SAME low-flow source. Granted, in practice that would probably not feasible, but that is the theory behind scalability. No hydroturbine can produce that much energy from a low-flow source, no matter how much/little that hydroturbine costs.