Question

Consider the following statements.
In case of flood routing in a river channel by Muskingum method, the coefficient x represents:
1. A dimensionless constant indicating the relative importance of inflow and outflow in determining storage.
2. A storage constant having the dimension of time.
3. In natural channels, x usually varies between 0.1 and 0.3.
4. When the values of x equals 0.5, there exists the influence of both inflow and outflow on storage.
Which of these statements are correct?

• A. 1, 2, 3 and 4
• B. 1, 3 and 4 only
• C. 1, 2 and 3 only
• D. 2, 3 and 4 only

Answer 1

The correct option is B 1, 3 and 4 only

Muskingum equation relates the storage in a reservoir to the outflow (Q) and inflow (I)
$S=K[x.I+(1-x).Q)$
In this the parameter x is known as weighting factor and takes a value between 0 and 0.5.
The coefficient K is known as storage-time constant and has the dimensions of time. Normally, for natural channels, the value of x lies between 0 to 0.3. For a given reach, the values of x and K are assumed to be constant.
When x = 0, S = KQ, valid for linear reservoir.
When x = 0.5. S = K(0.5/ + 0.5 Q]. There exists the influence of both inflow and outflow on storage.