ENGR3851/8951 Groundwater Flow and Pollution Assignment Solution

This assignment solution for ENGR3851/8951 Groundwater Flow and Pollution covers two main parts: a pump test and drawdown tutorial, and a contaminant transport tutorial. The first part involves calculating transmissivity and storativity using the Thiem and Jacob's equations based on given pumping rates and drawdown measurements in observation wells. It also determines the drawdown at a spring due to pumping from multiple wells and calculates the maximum pumping rate to avoid exceeding a drawdown limit. The second part focuses on contaminant transport, calculating groundwater velocity and dispersion coefficient, and estimating contaminant concentration at a specific distance downstream after a certain period. The assignment addresses practical problems related to groundwater management and pollution assessment.

ENGR3851/8951 Groundwater flow and pollution assignment 1
ENGR3851/8951 GROUNDWATER FLOW AND POLLUTION ASSIGNMENT
by [Name]
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ENGR3851/8951 Groundwater flow and pollution assignment 2
Part 1: Pump Test and Drawdown Tutorial
Question 1
Solution
Given; Pumping rate = 35 L/sec
Observation well distance = 17m
Transmissivity (T) is calculated using the Thiem Equation;
T = Kb = Q
2 π (s 1−s 2)ln ( r 2
r 1 )
Where; Q = well discharge rate in (m3/d) = 35 L/sec = 3024m3/d
r1, r2 = piezometer distances from pumping well = 17m, 5m
s1, s2 = steady-state drawdowns in piezometers (m) = 0.2m, 0.4m
T = Kb = 3024
2 π (0.4−0.2)ln ( 17
5 )
= 2943.74
Storativity (S) is derived from the Jacob’s Equations
S = 2. 25 Tto
r 2
From the graph,
T = 2.303 Q/ 4 πΔs
= 2.303 x 3024 / 4 π x 0.2
= 2769.88

ENGR3851/8951 Groundwater flow and pollution assignment 3
= 2. 25 x 2769 . 88 x 3024
17 x 17
= 65212
Question 2
Step 1
Distances of wells from spring = Spring coordinate x (m) + Well coordinate x (m)
Well 1 = 4100
Well 2 = 4100
Well 3 = 4100
Well 4 = 4200
Well 5 = 4200
Well 6 = 4200
Well 7 = 4300
Well 8 = 4300
Well 9 = 4300
Step 2
Total pump rate = 30 ML/day, divided by 9
= 3.33 ML/day
Step 3
Drawdown for each well;
Drawdown (Sw) = H-hw = Q
2 π T ln (R/r) where R is radius of influence, rw is well
radius
Well 1 = 0.4

ENGR3851/8951 Groundwater flow and pollution assignment 4
Well 2 = 0.4
Well 3 = 0.4
Well 4 = 0.8
Well 5 = 0.8
Well 6 = 0.8
Well 7 = 1.0
Well 8 = 1.0
Well 9 = 1.0
Step 4
Drawdown at the spring after 10 years of proposed pumping;
= (0.4 x 3) + (0.8 x 3) + (1.0 x 3)
= 6.6 m
Question 3
Maximum rate that the bores could be pumped at without exceeding the 5m drawdown
limit at the spring;
(Sw) = H-hw = Q
2 π T ln (R/r)
Drawdown = 5m
5 =
Q
2 x 22
7 x 2769.88 ln (4000/9)
= 14278.47L/day/pump
Part 2: Contaminant transport tutorial
Question 4.

ENGR3851/8951 Groundwater flow and pollution assignment 5
Velocity = Kl/n; where K = conductivity
L = hydraulic gradient
n = porosity
V = (1 x 0.01) / 0.2
= 0.05 m/day
Question 5.
dispersion coefficient = dispersivity/ molecular diffusion
= 1/0.0001
=0.11 m3/sec
Question 6
concentration of groundwater is 25m downstream of where the contaminant was released after:
= (Concentration x Distance)/ No of days
Days Concentr
ation
100 0.25
200 0.125
300 0.083333
400 0.0625
500 0.05
600 0.041667
700 0.035714

ENGR3851/8951 Groundwater flow and pollution assignment 6
800 0.03125
References
Bear, J. and Verruijt, A., 2012. Modeling groundwater flow and pollution (Vol. 2). Springer
Science & Business Media.