B, are flowing parallel to each other. A new factory starts to operates on River
ID: 114999 • Letter: B
Question
B, are flowing parallel to each other. A new factory starts to operates on River ns releasing a chemical into the river as part of its waste stream. orivers A and begi Use the steady state equation for a confined aquifer with no recharge. Assume the following aquifer characteristics: Thickness b: 5 m River A hA: 333m River B he 330m Distance L: 3km Porosity 0.35 River A River B hB Calculate the time it would take for water to travel via the confined aquifer to RiverB aSn a) The aquifer is made up of sand with a hydraulic conductivity of 1x10 md b) The aquifer is made up of clay with a hydraulic conductivity of 1x10 md Derive the effective hydraulic conductivities of the soil configurations below c) Beds in Parallel Ki b/2 b/2 d) Beds in Series Now using the expressions you derived in part (c) and (d) recalculate the time it would take for water to travel via the confined aquifer to River B assuming: e) The top half of the aquifer (b/2) is sand and the bottom half is clay; and ft) The first half of the aquifer is a sand (1.5km) and the second half is clay (1.5km).Explanation / Answer
Equation of Steady state equation of confined aquifer; h = -vL/K
where, h= head loss
v= Darcy's velocity
L= Length of flow direction
K= hydraulic conductivity
a) Given; K= 1x 10 m/day
t=?
h= hA - hB
(333-330)m = 3m
h=-vL/K or h=bL/tK ( where b=5m as given in question)
3m= 5m x 3000m/ t x 1x10 m/day ( 3 km=3000m)
t = 500 days ans.
b) Given: K= 1x10-4 m/day
t = ?
by formula, h = bL/tK
3m = 5m x 3000m/ t x 1x10-4 m/day
t = 5x107 days
c) K for parallel beds,
K = K1 x thickness of bed(a) + K2 x thickness of bed(b) / a+b
=1 x 10 m/day x 2.5 m + 1x 10-4 m/day x 2.5m / (2.5 + 2.5) m
= 10-3 m/day
d) K for beds in series,
K = a+b/ a/K1 + b/K2
= 5m+ 5m/ 5m/1 x 10 m/day + 5m/ 1x10-4 m/day
= 1.8 x 10-4 m/day
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