How can I model the equation for hydroelectric power using Simulink?

I'm trying to implement a model for the equation of hydroelectric power in a dam which is as follows: Ph = rho x g x Q x H

Obviously it's a physical system and each parameter has different units. However, I'm totally new to Simulink and I have no idea how to implement this. I had the idea that since the flow rate inside a dam is never constant, I can model it using a sine wave and neglect the negative parts. So, how do I make my inputs physical quantities?