Example : A weir is resting on a find sand soil of permeablity 2 x 10^-5 m/s. the water level on the upstream of weir is 6m and that on the downstream is 0.5m. Determine the amount of seepage per meter through the base of the weir per day.

Solution :

Given that:

Permeability of soil : 2 x 10^-5 m/s

Head difference of water flow : 6 - 0.5 = 5.5m

number of flow channels : 3

number of equipotential drops : 7

We know discharge through flow net can be given as :

by substituting values :

q = 4.7 x 10^-5 m_³/sec

to calculate per day seepage :

q = (4.7 x 10^-5 ) x (24 x 60 x 60)

q = 4.07 m³/day