ρ = density of water
g = specific gravity
y = depth of the body of liquid
The main principles of hydraulic engineering is fluid mechanics, fluid flow, behavior of real fluids, hydrology, pipelines, open channel hydraulics, mechanics of sediment transport, physical modeling, hydraulic machines, and drainage hydraulics. Other things that hydraulic engineers create are water distribution networks, water collection networks, sewage collection networks, storm water management, and sediment transport.
The hydraulic engineer can date all the way back to the roman aqueducts and the Nile Irrigation System of the ancient Egyptians. Hydraulic engineers have been an essential job since the beginning of time.