Question

Water flows through a sand aquifer with a piezometric head gradient of 0.05. (a) If the hydraulic conductivity and effective porosity of the aquifer are 1 m/d and 0.2, respectively, estimate the specific discharge and seepage velocity in the aquifer; (b) estimate the volumetric flow rate of the groundwater if the aquifer is 20 m deep and 850 m wide; (c) How long does it take the groundwater to move 75 m?

Answer 1

given,

head gradient = 0.05

hydraulic conductivity = 1 m/d

effective porosity = 0.2

from Darcy's law

V = k i

v = 1 × 0.05

= 0.05 m/day

seepage velocity

`v_s = (v)/(n)`

`v_s = (0.05)/(0.2)`

`v_s = 0.25 m/day`

specific discharge

`q = (Q)/(A)= k(dh)/(dl)`

q = 1 × 0.05

q = 0.05 m/day

b) Q = A V

=20 × 850 × 0.05

Q = 850 m³/day

c) time require to move 75 m

`t = (75)/(v_s)`

`t = (75)/(0.25)`

t = 300 days