One Dimensional St. Venant Equation

One Dimensional St. Venant Equation

I am often asked what this equation means. It is a simple equation that says that:

(1) water is neither created or destroyed or the water in the stream is conserved,
(2) water flows downhill,
(3) water slows down as the stream widens,
(4) water has to overcome friction loss from the sides and bottom of the stream,
(5) water slows down if there are obstructions in the stream or there are form losses such as bend, contraction and expansion losses.