Question

The infiltration rate f in a basin under ponding condition is given by f = 30 + $10e^{-2t}$, where f is in mm/h and t is time in hour. Total depth of infiltration (in mm, up to one decimal place) during the last 20 minutes of a storm of 30 minutes duration is

• A. 11.7

Answer 1

The correct option is A 11.7
Infiltration rate ,
$f=30+10e^{-2t}$

Infiltration during last 20 minutes of a storm of 30 minutes duration (i.e., t = 10 min to 30 min)

$=\underset{1/6}{\overset{1/2}{\int }}fdt$

$=\underset{1/6}{\overset{1/2}{\int }}(30+10e^{-2t})dt=11.74mm$

$\simeq 11.7mm$