CVEN4503 Wellington assignment – 2024 - Final
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CVEN4503 Wellington Field Course
Assignment 3, 2024 – Final
This is a group assignment (3 students to a group). It is due Friday the 26th of April at 5 pm as one
(1) electronic pdf-document submitted to the hand-in assignment box in Moodle. Note that this
assignment contributes 50% towards the total course mark.
Background
The University of NSW is studying groundwater resources at the Wellington Research Station. Two
topics are considered here:
(a) The general hydrogeology at the Wellington Research Station,
(b) The hydrogeochemistry and interactions with the river
(c) Geophysical interpretation of the geology on the hill side site
IMPORTANT NOTES:
Notes on the marking: This assignment contributes 50% towards your total course mark. Each student
will be marked individually on their part of the work (e.g. the Hydrogeology, Hydrogeochemistry or
Geophysics). Once the individual marking is finalised for each component, we will scale the three
components so that there won’t be significant differences between the components. It is important to
note that each of you will get a contribution to your mark from your fellow group student’s marks. That
way if they do well on their part, then you will benefit!
 Your report should be no longer that 10 typed pages, excluding the title page. Attach as
many maps, graphs, and figures as you think is needed to demonstrate your findings. They
should be appended after the 10 typed pages and clearly referenced in the report. Submit one
pdf document per group.
 For repeated calculations, please show one detailed example (including equations) of how
you arrive at the end result. Do not attach endless pages of printed numbers from Excel
spreadsheets!
 The assignment is a group assignment with 3 students to a group. Groups should be organised
at the beginning of the field trip.
 Copying and plagiarising is not accepted. Reports will be checked for plagiarism in Turnit-in.
Report structure
 Introduction (~5-10 lines)
 Methodology (brief and concise)
 Results
 Interpretation, discussion and synthesis
Most of your report should focus on the last two points! You should use the data that you and your
colleagues collected during the course and other data provided to present, discuss and synthesise in
the context of the topics outlined below.
CVEN4503 Wellington assignment – 2024 - Final
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Data
Shared data, when made available, will be uploaded to a OneDrive folder (see link under Week 5 in
Moodle). Each daily field activity has its own subfolder with information and data such as: manual
borehole dips; comprehensive site survey; lithological logs; relevant logger files from slug testing;
relevant data files from pump testing; and water quality data. Note also the folder containing
supporting information such as satellite maps with borehole locations and borehole geological logs.
Importantly it contains a comprehensive site survey done by SAGE students in 2018, which you can
use to understand the relative location of bores. The file boreKLM.kmz can be opened in Google Earth
and inspected. You can click on individual bores for more details.
SPECIFIC POINTS TO ADDRESS FOR EACH COMPONENT
(Where necessary state your assumptions)
PART 1: HYDROGEOLOGY
All relevant data is contained in the subfolder “Activity 1 Hydrogeology”.
a) Construct a horizontal flow net at the Wellington Research Station using the 2018 SAGE site survey
in combination with your manual dip data. The GPS survey of Macquarie River levels did not work
this year. Instead, please use the 2018 GPS data in the file River Gradient Prelim.xls (from the Data
Repository in the Supplementary Information folder (Please consider: is it defensible to mix data from
different years?). Comment on your work: Where do we see the highest/lowest hydraulic gradients?
Does the general flow direction fit with your understanding of the site topography? Justify the answer.
b) Prepare a cross-sectional geological plot across the Macquarie River Valley at the Wellington
Research Station. Follow the line of bores from MS02 (near the river) to WRS20 (on top of the hill).
Include the hydraulic heads in your plot. As above, include a Macquarie River level from the GPS
survey picked from an appropriate location. Comment on the direction of surface water groundwater
interactions at the time of hydraulic head measurement. How does the geology affect groundwater
flow?
c) Calculate the hydraulic conductivity of the aquifer for the piezometers that were slug-tested. Bore
screen lengths are 1 m, and the inner diameter is 50 mm and outer diameter is 60 mm of the
piezometers. Illustrate in one detailed example how the calculation was done. Address the following
questions:
 If different locations were tested, why are the results different?
 Why would the hydraulic conductivity obtained from the slug test be dissimilar to that obtained
from the pumping test?
 Are any of the slug tests affected by turbulent flow conditions? Hint: Assume that the mean
grain size in the aquifer d50 is 1 mm.
 If so, how could the slug test be evaluated to avoid errors arising from turbulence?
d) Three pumping tests were conducted near the Macquarie River. For selected piezometers,
evaluate and compare the aquifer properties (S and T) using Jacob’s straight-line approximation
(constant r, variable t). This can be done separately for hydraulic head drawdown and recovery.
Discuss the differences between results obtained from different locations as well as drawdown and
recovery. Please consider why piezometers at the same distance from the extraction well can show
vastly different water level responses.
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e) Calculate the groundwater hydraulic head time-series for bores WRS02 and WRS05 based on the
logger data (in the Gradient time series folder) and present graphically as hydrographs (heads vs
time) covering the last year (Mar 2023 – Mar 2024). You will need the barometric data from the
weather station to correct the logger data (in the same folder). Comment on the causes for any
significant changes visible in the hydrographs. Calculate and plot the horizontal hydraulic gradient
time-series between the two bores and infer interactions over time with the Macquarie River. On
average was the site gaining or losing during the last year according to this data?
PART 2: GEOPHYSICS
All relevant data to complete this task is contained in the subfolders “Activity 2 Geophysics” and
“Supplementary Information”. which contains information and instructions regarding useful software
and data processing steps. For spatial orientation, use the Google Earth file “BoresKML.kmz” as well
as the “SurveyLines_days1-3.kmz” in the supplementary folder on the OneDrive archive. Borehole
reports including lithology and geophysical logs for relevant locations are also available there and
should be used to aid the interpretation of the geophysics data. The document “CVEN4503 Notes on
processing geophysics data.pdf” shows how to do the following using similar programs but the videos
below are probably more useful.
There are two sets of data with two lines of acquisition each:
 Resistivity (Day 1-2 / Day 3)
 Seismic (Day 1-2 / Day 3)
Geoelectrical Survey:
Describe briefly how a 2D resistivity image line is created. Invert the raw field data. Save the output
as an image file, add to your report and discuss the results. Use all datasets to support your
interpretation (the inversion process is rapid and processing multiple datasets should not take very
long).
Note: See the notes on processing geophysics data for more details. Download ResIPy software to
create the 2D resistivity image. You will need to load the data, either from Day 1-2 or Day 3. Create
a mesh, complete an inversion and look for borehole control. Check the video here:
https://www.youtube.com/watch?v=jcEkcjeRlJk&list=PLAPsrKfdjuA00vBagLUyR64ukA3c-fjya
Seismic Refraction (SR) Survey:
Use the two seismic lines in the data archive and pick the arrival times for each of the 24 geophones
and each of the 5 shots along the line. I will recommend SeisImager-2D.
1. Start with PickWin (see https://www.youtube.com/watch?v=zt1R1BNxHeE for help).
Then with each shot file (Shot_??.sg2):
 Display the data according to your satisfaction
 Automatically pick first arrivals
 Correct first arrival picks manually (to zero for data that is very poor/missing)
When finished save the picks.
2. Go on to Plotrefa (see https://www.youtube.com/watch?v=lvGMI-VzsBY)
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 You will first need to clean the data by deleting strange points (associated with the bad data)
– look for points that don’t fit the smooth trend of the curve
 Then you will need to associate points with “Layer 2” (layer 1 is the top layer). Click on a point
where the line changes gradient. All points after that will be associated with layer 2.
 Create an elevation text file from the kmz file that includes 2 columns:
o Geophone distance (from origin)
o Elevation
For example (with a 2.5 m geophone spacing):
0.0 120.5
2.5 122.8
 Do the inversion (loading the elevation file)
Have a look at typical seismic velocities for P-waves and tie in with the borehole data (e.g. water
table/bedrock).
Integrated Interpretation of Results:
After processing each of the above techniques you should be able to interpret the lithological
properties of the shallow subsurface uphill from the field station. Use relevant borehole reports (see
Google Earth file for orientation) in the data repository to provide an interpretation of any obvious
features or trends. Please make sure you clearly explain and document your reasoning.
Finally, create a kmz file alongside your report with all your data including images of your cross-
sections from the inversion included for submission as supplementary data to your report.
PART 3: HYDROGEOCHEMICAL DATA
All relevant data is contained in the subfolder “Activity 3 Hydrogeochemistry”.
Data from this year that you collected from the river, and the alluvium will be available from the Moodle
link once results are returned from the lab. The dissolved ion analysis data will be made available as
soon as results are back from the laboratory. For the data processing please do the following steps:
a) Calculate the alkalinities from the field titrations using the spreadsheet program Alkalinity
Analyser.xls. Make sure that for each analysis the data plot on a straight line in the plotting window
in the software. If that is not the case, then identify and exclude faulty data points if the regression is
too impacted. Convert the Fe absorbance data to mg/L or µg/L.
b) Organise your field water chemistry data (pH, EC, DO, Fe2+, and Alkalinity) that you and your group
collected during the fieldwork into one spreadsheet. Then merge each day’s results into a spreadsheet
with data from all 3 days to be shared among all groups. Please use the data example from the
previous year as a template of how to organise the data from the flow cell readings, the field alkalinity
titrations and the Fe analysis. For the flow cell readings for each bore use the last reading just before
the samples were taken (check for major changes in readings before and after the sample was taken
and comment on these).
c) Once you receive the lab reports, for major ions calculate the electrical balance (or charge balance)
errors. Remember to convert from [mg/L] (or [μg/L]) to [mmol/L] by dividing by the atomic weight (or
CVEN4503 Wellington assignment – 2024 - Final
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molecular mass [g/mol] or [mg/mmol]) obtained from the periodic table. Then convert to charge
[meq/L] by multiplying with the ionic charge. Finally sum up positive and negative charges and
calculate the charge balance error. Identify unacceptable charge balance errors (> 5%). NOTE: in the
pH range 6-9, Alkalinity = bicarbonate ([HCO3-] in meq/L).
d) Divide the field EC (electrical conductivity), [μS/cm] with a factor of 100 and compare with both the
sum of the cations and the anions (in meq/L). Using this and the charge balance errors calculated in
c) try to investigate the source of possible analytical errors (you did this in Assignment 2). Can you
determine whether any analytical problems are associated specifically with the anions or the cations?
e) As alkalinity data is missing from the third day can you come up with at least two ways of estimating
the alkalinity (HCO3-) from the data you do have? Please describe the assumptions and uncertainties
with both methods.
f) Make plots of key water chemistry parameters. Construct maps (area plots), vertical cross-sections
(reuse the cross-section from Part 1a)). Do not do this for every single parameter but be selective and
consider which parameters show something useful and representative about processes on the site.
Are there spatial trends? Perhaps in relation to distance from the river or pumping bore?
g) Make depth profiles of data from the multilevel bores MS01 and MS02. Comment on any spatial
patterns you observe. For bores that were sampled on several days, how much change you observe
over the three days for levels that were sampled more than once? Are the changes what you should
expect due to the pumping activity? Note that the two multilevel bores and bores that were sampled
more than once are located between the pumping bore and the river.
h) Plot data in a Piper diagram. The software package to plot Piper diagrams can be obtained from
the OneDrive Data repository. Comment on how the data group on the diagram.
i) Investigate possible processes leading to the observed water chemistry. I.e. what are the major
water-rock interaction processes and hydrologic processes on site that could explain the water
chemistry? First explain the major ion chemistry (Ca2+, Na+, Mg2+, HCO3- Cl- and SO42-). The major
ion chemistry may be affected by both physical and chemical processes. Then explain the redox
chemistry (by looking at O2, Mn2+, Fe2+, NH4+ and DOC). What electron donor is driving the redox-
reactions and where is it coming from? Write correctly balanced reaction equations for all chemical
reactions that you discuss. Make plots that support your arguments. Be creative and explore different
plots (i.e. bi-variate plots linked to the stoichiometry of reactions for example plotting Ca2+ vs HCO3-
to explore possible carbonate mineral dissolution).
OVERALL SYNTHESIS
Based on the appropriate data and your answers above from the geology, hydrogeology, surface
water - groundwater interaction and hydrogeochemistry write a 1-page synthesis of the water resource
(quantity and quality) at the Wellington Research Station. Please consider:
a) Which way was groundwater flowing across the research station during the field course
(before and during the pumping)? How much does the direction vary over the property? How
much certainty does the data provide?
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b) Based on the hydraulic gradients and hydraulic conductivities derived from slug- and pumping-
test results, how fast is the groundwater flowing? What assumptions are you making here and
are they reasonable?
c) How does the geophysical surveys aid your interpretation of the hydrogeology?
d) Locally on the river flat, is there any physical or chemical evidence that the pumping test is
moving river water further into the aquifer towards the pumping bore? Can you estimate how
far the water would be moving during the pumping test?
e) During the three days at Wellington, the team collected a range of physical and chemical data
on a range of scales. In addition, we also monitor groundwater levels continuously over the
year; and surface water levels and flow data from the Macquarie River is available in the public
domain. Based on the range of data discuss the surface water–groundwater interactions: was
the river gaining or losing during the field course? And how about throughout the year? Do all
the various types of data support your conceptual understanding or is there conflicting
evidence? If there is conflicting evidence, can you come up with explanations to reconcile the
data? If not, what data is more reliable? Provide evidence for your answers.
f) Is the water fit for human consumption? Compare the chemistry data to relevant guidelines for
drinking water.