Question

Which of the following is true about the relation of the Energy Grade Line (EGL) to the Hydraulic Grade Line (HGL) at a reservoir?
A. EGL is above the HGL.
B. EGL is below the HGL.
C. EGL is the same height as the HGL.

Answer 1

Answer:

C. EGL is the same height as the HGL.

Explanation:

The energy grade line is the sum of the hydraulic grade line and the velocity head (V²/2g).

EGL = HGL + V²/2g

In a reservoir, the Energy Grade Line (EGL)  is equal to the  Hydraulic Grade Line (HGL) since the fluid is at rest (V = 0).  

EGL = HGL

EGL which is the height to which a liquid will rise. This cannot rise above the reservoir level, unless additional work is introduced into the reservoir by the means of a pump.

Therefore, the correct option is "C. EGL is the same height as the HGL."