Which of the following statement is correct regarding critical depth (h)?

I. Critical depth is defined as that depth of flow of water at which the specific energy is maximum

II. The mathematical expression of critical depth is obtained by differentiating the specific energy equation with respect to depth of flow 

Explanation:

Let's analyze each statement based on the definitions and principles of open channel flow.

Statement I:
"Critical depth is defined as that depth of flow of water at which the specific energy is maximum"

• This statement is incorrect. Critical depth is actually defined as the depth of flow at which the specific energy is minimum, not maximum. The specific energy is a function of the depth of flow and velocity, and at critical depth, the specific energy has a minimum value.

Statement II:
"The mathematical expression of critical depth is obtained by differentiating the specific energy equation with respect to depth of flow"

• This statement is correct. The critical depth is determined by differentiating the specific energy equation with respect to the depth of flow and setting the derivative equal to zero. This process finds the minimum specific energy, corresponding to the critical depth.