Question

Inflow and outflow hydrograph of a channel reach are triangular in shape and plotted simultaneously as shown. The peak of inflow hydrograph is 10,000$m^3/hr$, base time 96 hr and peak occurs 1 hr after the start, Peak of outflow hydrograph is 8000 $m^3/hr$ and occurs on the recession limb of outflow hydrograph. The value of maximum storage and time at which it occurs is :

• A. 90,000 $m^3$ and 18 hr
• B. 96,000 $m^3$ and 16 hr
• C. 90,000 $m^3$ and 20 hr
• D. 96,000 $m^3$ and 20 hr

Answer 1

The correct option is D 96,000 $m^3$ and 20 hr

Time at which maximum storage occurs

$\frac{8000}{96-t_0}=\frac{10,000}{95}$

$(\because \Delta \text{CBE and}\Delta \text{CHF are similar})$

$\therefore t_0=20hr$

$\text{Volume of maximum storage}=\text{Area of}\Delta \text{AEF}$

$=\text{Area of}\Delta \text{AEC}-\text{Area of}\Delta \text{AFC}$

$=\frac{1}{2}\times 10000\times 96-\frac{1}{2}\times 8000\times 96$

$=96000m^3$