final report for submission kebba.pdf

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THE UNIVERSITY OF ZAMBIA

SCHOOL OF ENGINEERING

DEPARTMENT OF CIVIL AND ENVIRONMENTAL

ENGINEERING

PROJECT TITLE:

GROUNDWATER RESOURCES ASSESSMENT OF LOWER

KAFUE BASIN USING GIS REMOTE SENSING AND

MODELLING- CASE STUDY OF ALBIDON NICKEL MINING

AREA IN MUNALI HILLS AREA

FINAL YEAR REPORT

by:

Lungu Kelvin Agabu


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UNIVERSITY OF ZAMBIA

THE SCHOOL OF ENGINEERING

DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING

Groundwater resources assessment of Lower Kafue Basin using GIS, remote sensing and

modelling- Case study of Albidon Nickel Mining area in Munali hills area

FINAL YEAR PROJECT REPORT

By

Lungu Kelvin Agabu

Computer number: 10035494

“Report submitted as partial fulfilment of the requirements for the Degree of Bachelor of

Engineering in Civil and Environmental University of Zambia”. June 2015


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DECLARATIONThis dissertation of Lungu Kelvin Agabu (10035494) meets the standard for reports

submitted in partial fulfilment of the requirements for the degree of Bachelor of

Engineering, University of Zambia. Having supervised the project and satisfied myself with

the content of this report, I approve that it can be submitted for examination.

Supervisor’s Name:

……………………………………………………………………………..

……………………………………….. …………………………………...

Supervisor’s Signature Date


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Abstract

Water is a precious natural resource needed for the sustenance of life. It may exist in various

forms in the hydrological cycle including existing as vapour within the atmosphere, as liquid

in surface storage, such as in lakes; and in subsurface storage, such as in rock formations.

Groundwater is a vital and critical source of water supply as it supplies fresh water and can

provide water in areas where extended droughts cause stream flow to stop. Elsewhere, base

flow (water from surface streams) is the main source of recharge for the groundwater.

The study focused on the Albidon mine area (Munali) ,in Mazabuka district of Southern

Province, which lies at the south-western foot of the Munali Hills, which form a

northwest-southeast trend line of ridges (Sichingabula and Nyambe 2008).

As extracted from Sichingabula and Nyambe 2008, evaporation exceeds precipitation for

most of the year in the selected area. These adverse climatic conditions together with the

existing mining activities in this area give rise to need of efficient water resources

management as both quality and quantity are threatened.

Within the study the hydrogeology was investigated and a conceptual groundwater model

produced. The findings in this study indicated that the general flow of the ground water was

in the North-East from South-West direction.

In 2014, a research was conducted by IWRM centre at UNZA through a postgraduate final

year project research. The study aimed at determining effects of mining activities on the

Quality, availability and sustainability of groundwater through analysing Acid mine drainage,

Heavy metal Contamination and dewatering process from Munali nickel mine. A

recommendation was provided by Kalibe Phiri, the postgraduate researcher, suggesting that a

detailed study be carried out on the flow of groundwater in Munali hills area. With the

completion of this project the flow contaminants or particles could be traced, thus,

consolidating earlier research on quality of water by IWRM centre.

The real life applications of the model produced are only limited with the lack of one’s

imagination. But the main applications focussed on are discussed later in detail.


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Acknowledgements

Many thanks to my supervisor Engineer Kabika Joel, I am highly indebted to you for the

support and guidance offered and continues to offer. Your support and assistance is fully

appreciated.

Take a bow, Dr. Paul Oberholster and Professor Keith Kennedy at CSIR in South Africa for

the Sub-Grantee funding to the University of Zambia through the African Union

ACT4SSAWS project which has made study field work immeasurably possible.


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ContentsCHAPTER 1: ............................................................................................................................. 1

INTRODUCTION ..................................................................................................................... 1

1.1 Introduction ...................................................................................................................... 2

1.2 Rationale........................................................................................................................... 3

1.3 Research Question ............................................................................................................ 4

1.4 Objectives of study ........................................................................................................... 4

1.5 Scope of the project .......................................................................................................... 4

CHAPTER 2: ............................................................................................................................. 5

LITERATURE REVIEW .......................................................................................................... 5

2.1 Groundwater ................................................................................................................ 6

2.1.1 Introduction ............................................................................................................... 6

2.1.2 Aquifers and water table ...................................................................................... 7

2.1.3 Steady flow in aquifers ........................................................................................ 9

2.1.4 Movement of Groundwater ................................................................................ 10

2.1.5 Groundwater quality .......................................................................................... 12

2.1.6 Groundwater depletion....................................................................................... 13

2.1.7 Groundwater resources and distribution ............................................................ 14

2.1.8 Groundwater Monitoring ................................................................................... 14

2.2 Groundwater modelling............................................................................................. 17

2.2.1 Introduction ........................................................................................................ 17

2.2.3 Computer Software used for Groundwater modelling ....................................... 18

2.2.4 Applications of PMWIN groundwater models .................................................. 20

2.2.5 Developing of Model ......................................................................................... 21

2.2.6 Calibration of Model .......................................................................................... 21

2.2.7 Model errors ....................................................................................................... 21

CHAPTER 3: ........................................................................................................................... 22

STUDY AREA ........................................................................................................................ 22

3.1 Location and physical setting .................................................................................... 23

3.2 Climate ...................................................................................................................... 25

3.3 Landforms and Topography ...................................................................................... 25

3.4 Local Geology and Hydrogeology of the Munali Hill Area ..................................... 26

3.5 Groundwater quality and monitoring boreholes........................................................ 28

3.6 Agriculture ................................................................................................................ 28

3.7 Environmental Study Problem in area ...................................................................... 28

3.8 Delineation of project area for model ....................................................................... 29

CHAPTER 4: ........................................................................................................................... 30


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METHODOLOGY .................................................................................................................. 30

4.1 Tools .......................................................................................................................... 31

4.2 Hydrogeological analysis .......................................................................................... 32

4.3 Meteorological analysis............................................................................................. 34

4.4 Borehole analysis ...................................................................................................... 35

4.5 Design of the groundwater model ............................................................................. 36

4.5.1 Selection of suitable modelling software ........................................................... 36

4.5.2 Dimensional units adopted in modelling ........................................................... 36

4.5.3 Selection of Control point for modelling ........................................................... 36

CHAPTER 5: ........................................................................................................................... 39

RESULTS AND ANALYSIS .................................................................................................. 39

5.1 Model visualisation from PMWIN8 based on hydraulic heads ................................ 40

5.1.1 ‘2-D visualisation’ for result type: Hydraulic heads .......................................... 40

5.1.2 Checking final calibration results using results of all observation boreholes ......... 41

5.2 Particle tracking in case of spillage in Mine area into groundwater .............................. 42

5.3 Capture zone as result of Dewatering at Albidon mine area .......................................... 42

CHAPTER 6: ........................................................................................................................... 45

DISCUSSION, CONCLUSIONS AND RECOMMENDATIONS ......................................... 45

6.1 DISCUSSION ................................................................................................................ 46

6.1.1 Interpretation of the Groundwater model .......................................................... 46

6.1.2 Divergence from Observed data ........................................................................ 46

6.1.3 Discussion of Results ......................................................................................... 46

6.2 CONCLUSSION ............................................................................................................ 47

6.3 RECOMMENDATIONS ............................................................................................... 47

APPENDIX .............................................................................................................................. 48

APPENDIX A: Hydraulic characteristics of aquifers .......................................................... 48

APPENDIX B: Symbols used in MODFLOW .................................................................... 48

APPENDIX C: Borehole site location from GeoDin database ............................................ 48

APPENDIX D: Borehole BH log data from GeoDin database ............................................ 48

APPENDIX E: GeoDin database terminologies .................................................................. 49

APPENDIX F: Kafue River levels using gauging station for Nakambala in Mazabuka ..... 49

APPENDIX G: Water Budget produced from run model for zero recharge ....................... 50


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List of Tables

Table 1: Confined aquifer Vs. Unconfined aquifer ................................................................... 8

Table 2: Approximate values of K m/d and n % for various soils and rock types* ................ 10

Table 3: Commonly typical values in Southern province (Bäumle 2007) ............................... 11

Table 4: Ground water monitoring activities at different scales .............................................. 15 Table 5: MODFLOW vs. FEFLOW ........................................................................................ 20

Table 6: UTM coordinates for delineated area in Figure 14 .................................................... 29

Table 7: Hydrogeological analysis........................................................................................... 33

Table 8: Temperature parameter .............................................................................................. 34

Table 9: Long-term rainfall and evaporation for stations in Southern Province ..................... 34

Table 10: Mine site Seasonal Rainfall ..................................................................................... 34

Table 11: BH log data .............................................................................................................. 35

Table 12: PUMPING WELL BH7 useful data for modelling ................................................. 36

Table 13: Dimensional analysis ............................................................................................... 36

Table 14: Kafue river levels for 2013/2014 (see APPENDIX F) ............................................ 36

Table 15: Model extent ............................................................................................................ 37 Table 16: Grid position coordinates ......................................................................................... 37

Table 17: Lithology of model .................................................................................................. 37

Table 18: Vertical and Horizontal Hydraulic conductivity parameters ................................... 37

Table 19: Model summary ....................................................................................................... 38

Table 21: Calibration Verification for run 5 ............................................................................ 41

Table 22: Correlation verification ............................................................................................ 41

Table 23: Abstraction point data .............................................................................................. 42

List of Figures

Figure 1: Rationale ..................................................................................................................... 3

Figure 2: Types of aquifers and location of wells (Source: Raghunath, 2006) ......................... 6

Figure 3: Diagrammatic representation of the types of Aquifers (Source: Rausch, 2009) ........ 9

Figure 4: Types of aquifers based on media (Source: Rausch, 2009) ....................................... 9

Figure 5: Flow of groundwater (Source: Raghunath, 2006) .................................................... 10

Figure 6: Features of an Aquifer System that can be simulated by MODFLOW (Source:

Rausch, 2009 ............................................................................................................................ 19

Figure 7: Discretization scheme for MODFLOW* (Source: Rausch, 2009)........................... 19

Figure 8: Schemes of vertical discretization (Source: Rausch, 2009) ..................................... 20

Figure 9: Location of Lower Kafue Basin area located south-eastern part of Kafue catchment

area (Source: BID, 2014) ......................................................................................................... 23 Figure 10: Locations of Munali Nickel Mine area, groundwater monitoring stations around

mine area (MAD/GW), in Resettlement and Local Community areas (RAP) and surface water

monitoring stations (SW) an area impacted by the mine. (Source: BID, 2014) ...................... 24

Figure 11: Digital Elevation Model (DEM) with elevation zones at 200 m- intervals (Source:

Bäumle R 2007) ....................................................................................................................... 25

Figure 12: Aerial photograph showing surface projection of Geology (Source: AMC, 2006) 26

Figure 13: Geology map of Munali hills area (Source: BID, 2014) ........................................ 27

Figure 14: Project area delineation .......................................................................................... 29

Figure 15: Input Parameters required for modelling................................................................ 31

Figure 16: Hydrogeological map of project area (Source: Bäumle, 2007) .............................. 32

Figure 17: Psuedosection of Munali mine area (Source: Albidon mine)................................. 33 Figure 18: Shaded relief and block diagram generated from the DEM ................................... 35


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Figure 19: Schematic diagram showing flow direction ........................................................... 40

Figure 20: Schematic with contours filled ............................................................................... 40

Figure 21: Scatter diagram using all observation BH .............................................................. 41

Figure 22: Particle tracking for one particle ........................................................................... 42

Figure 23: Abstraction effect if pumping out 700 .................................................... 43

Figure 24: Dewatering effect when Mine is in full operation .................................................. 43


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List of Abbreviations and Acronyms

AMC African Mining Consultants

Asl Above sea level

Bgl Below ground level

BH Borehole

BID Background Information Document

COORD Coordinate

DEM Digital Elevation Model

DWA Department of Water Affairs

EIA Environmental Impact Assessment

GIS Geographical Information Systems

GPS Geographical positioning satellite

GS Ground surface

GW Groundwater

GWT Groundwater table

IWRM Integrated Water Resources Management

MODFLOW Modular 3-dimensional finite difference Groundwater model

PCG Preconditioned Conjugate-Gradient

UNZA University Of Zambia

USDA United States Department of Agriculture

UTM Universal Transverse Mercator

WHO World Health Organisation


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CHAPTER 1:

INTRODUCTION


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1.1 Introduction

Groundwater hydrology is a subdivision of the science of hydrology which deals with

the occurrence, movement and quality of water beneath the earth’s surface. It is a science

whose successful application is of critical importance to the welfare of mankind.

Groundwater refers to the water that occupies the void space within the geologic

stratum beneath the earth. A further distinction from soil moisture is that groundwater

is the water within the saturated zone and the top is called the water table. A unit of

unconsolidated deposit is called an aquifer when it yields a usable quantity of water. An

aquifer may either be called confined or unconfined. A confined aquifer is bounded above

and below by aquicludes and an unconfined aquifer only has an aquiclude below and not

above.

Groundwater is often withdrawn for agricultural, municipal and industrial use by constructing

and operating extraction wells. This study focussed on assessment of groundwater resources

subject to the mining activities in Munali hills area of Southern province, Zambia.

Among the adverse effects of these mining activities include depletion of surface and

groundwater resources. In mining the need for dewatering of the mining area requires

pumping of groundwater which can result in significant depletion of groundwater storage.

Groundwater is normally hidden from view; as a consequence, many people have difficulty

visualizing its occurrence and movement. This difficulty adversely affects their ability to

understand and to deal effectively with groundwater-related problems.

To simulate the groundwater resources available, groundwater models can be used. Ground

water models are useful tools to investigate the hydrogeological conditions of aquifers. This

means they may be used to investigate the movement of water and even solutes or

contaminations. A model developed gives conceptual approximation of the physical system

being modelled. However, it is important to note that there are some assumptions made in

orders to assist in correcting the errors in the mathematical model which include direction of

flow, geometry of the aquifer, contamination transport, chemical reaction, etc. MODFLOW

software is but one means of groundwater modelling. The grid data used for modelling is

provided by Geographical Information Systems (GIS) grid data for study area.

The groundwater model’s applications include:

Used to describe and simulate the groundwater system to analyze various

assumptions.

Used in water management for urban areas


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Used to generate a hypothetical simulation in order to study principles of groundwater

flow

Observing the water balance, thus, providing a water budget

Observing chemical migration, thus, tracing particle movement in ground water and

therefore, in turn help setting up groundwater protection zones

In this study the groundwater resources of the Lower Kafue basin in the Munali hills area

were investigated using groundwater flow modelling.

1.2 Rationale

The environmental problems in this area include adequate supply of quantities of water for

domestic and mine operations and maintenance of acceptable levels of quality in terms of

physical, chemical and biological characteristics for especially human consumption.

The environmental problem of concern, apart from groundwater quality degradation, in this

area includes the potential depletion of groundwater storage. In mining, pumping of

groundwater may result in significantly reducing groundwater storage which in turn can

result in lowered water levels in wells, hydraulic interference between pumping wells,

reduced surface water discharge, land subsidence, and adverse changes in water quality. The

Munali hills area receives low rainfall as the area is in a drought prone area which results in

lower groundwater recharge as extracted from BID, 2014.Monitoring and observation of water resources is a vital part of conserving water resources.

With the keeping track of water resources, planners are given a chance to access the quantity

of water available, predict movement of pollutants and make plans for future populations in

turn creating a sustainable water budget. Before any assessments of the water is made there is

need to create an effective model of the water resources of the surrounding area.

Figure 1: Rationale

Water resourcesmanagement andwater planning

requires...

Monitoring andobservation of water

resources which in turnrequires...

Assessing of waterresources requires...

Ground watermodelling can be

applied to...


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1.3 Research Question

How is the Ground water movement in Albidon mine area?

1.4 Objectives of study

In this project, groundwater will be modelled using MODFLOW software. Thus, the overall

objective of this project will be to model the groundwater in the Albidon mine area thus,

assessing groundwater flow in this area.

The specific objectives to attain the aforesaid mentioned objective include:

Determine the hydrogeological properties of the area and the meteorological

conditions of the area

Analysis of groundwater levels

Use the parameters to create a model; simulate the groundwater resources by

developing a groundwater model using MODFLOW

1.5 Scope of the project

The scope of the project included assessing the groundwater availability in the Lower Kafue

Basin in selected area-Albidon mine area.

The assessment was achieved by developing a model for a suggested delineated area in the

Albidon mine area.

The research covered:

1) Analysis of Geological layers

2) Analysis of meteorology

3)

Groundwater flow

4) Groundwater flow predictions


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CHAPTER 2:

LITERATURE REVIEW


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2.1 Groundwater

2.1.1 Introduction

Figure 2: Types of aquifers and location of wells (Source: Raghunath, 2006)

Groundwater is water in the zone of saturation. Groundwater is one of the renewable water

resources that can be exploited in a sustainable way to help rural communities in terms of

clean domestic water and irrigation. Groundwater is widely distributed under the ground and

is replenish able unlike other resources of the earth.

The main source of groundwater is precipitation, which may reach the groundwater directly

by penetrating the soil or enter surface waters and reach groundwater by base flow from the

channels. It should be stressed that groundwater has the lowest precedence on the water from

precipitation. Before any large amount of water can recharge groundwater interception,

depression storage and evaporation must be satisfied. Groundwater recharge is an irregular

process.

Other sources of groundwater include fossil water carried upwards in intrusive rocks and

water trapped in sedimentary rocks during their formation.

Management of groundwater resources is important as the quality and quantity are

significant to the sustenance of life. Irrigation benefits from groundwater and other domestic

uses as well. Mining and industrialisation cause adverse effects to this water. The mining

activities for instance, by the Munali Nickel mine pose a threat to the groundwater by

degrading and depleting the groundwater resources.

The problems in Groundwater Investigation are the zones of occurrence and recharge. The

modern trends are to create more opportunity for recharge of groundwater from natural

sources like rain, percolation dams, etc.


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static level of water in wells. A high water table is characteristic under the hills than under the

valleys.

This aquifer under water table conditions is called an ‘unconfined aquifer ’ and a well drilled

into this aquifer is called a water table well. An unconfined aquifer is a permeable rock

formation which recharges by water from the soil zone and is also called a water table

aquifer . A ‘confined aquifer’, also called an artesian aquifer, however, is a formation

confined between two impermeable layers or rock layers of low permeability. Its source of

recharge is separate from the unconfined aquifer above it.

On the other hand, a geologic formation which can absorb water but cannot transmit

significant amounts is called an ‘aquiclude’. These include clays and shales for instance.

Also, a geologic formation with no interconnected pores and hence can neither absorb nor

transmit water is called an ‘aquifuge’. These include basalts and granites for instance.

Table 1: Confined aquifer Vs. Unconfined aquifer

CHARACTERISTIC AQUIFER

CONFINED UNCONFINED

Water table None Free

Aquitard location Aquitard is found on both the

top and bottom layer of theaquifer

Aquitard on bottom layer of the

aquifer

Ground water recharge From source separate to the

Unconfined aquifer above it

By water from the soil zone

Recharge area Away from the borehole Around borehole


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Figure 3: Diagrammatic representation of the types of Aquifers (Source: Rausch, 2009)

As extracted extensively from Rausch, 2009, Hydraulic properties of an aquifer arecharacterized by permeability and storativty. These depend on the porosity of the rock

formations.

Figure 4: Types of aquifers based on media (Source: Rausch, 2009)

2.1.3 Steady flow in aquifers

Groundwater flow can either be transient or steady with respect to time. Steady flow in

aquifers, as described by a scholar T. Ettrick, refers to the situation where water does not

change with time.


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Steady state conditions are the basis of assumptions in solving groundwater problems.

However, it is important to note that this is not practical but considered as the ideal starting

point for groundwater analysis.

2.1.4

Movement of Groundwater

Figure 5: Flow of groundwater (Source: Raghunath, 2006)

Where:

V = velocity of flow through the aquifer

K = coefficient of permeability of aquifer soil

i = hydraulic gradient= ratio of ∆h: L, ∆h = head lost in a length of flow path L

A = cross-sectional area of the aquifer (=); w = width of aquifer and b = thickness of

aquifer

T = coefficient of transmissibility of the aquifer

Q = volume rate of flow of ground water or yield

Table 2: Approximate values of K m/d and n % for various soils and rock types*

Soil and rock types Porosity n % Permeability K m/d

Clay 45 0.0002-0.0004

Quartzite, Granite 1 0.0004

Limestone, Shale 5 0.041-0.94

Sand 35 2.5-45

Gravel and sand 20 150-450


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Table 3: Commonly typical values in Southern province (Bäumle 2007)

Soil and rock types Transmisivty Expected yield

Schist 21.6 1.19

Quartzite, Granite 10.2 1.08Calc-Silicate/

Carbonates

22.8 1.19

Unconsolidated

clastic sediments

13.5 1.49

*The above table developed shows the various values of permeability and porosity of materials as extracted

from different read texts and not directly extracted from any particular text.

The parameters of importance to groundwater hydraulics include:

1)

porosity (n):

This is the ratio of the total volume of voids in the aquifer to the total volume. It is a measure

of the water bearing capacity of the formation, all this water cannot be drained by gravity or

by pumping from wells as a portion of water is held in the void spaces by molecular and

surface tension forces. See table 2 for the porosity characteristic to the different materials.

2) effective porosity ():

This is the ratio of the volume of void space available ) to water flow divided by the

total volume of the aquifer (V).

3) specific yield ():

The volume of water expressed as a percentage of the total volume of the saturated aquifer

that will drain by gravity when the groundwater table drops due to pumping or drainage.

Specific yield depends upon grain size, shape and distribution of pores and compaction of the

formation. The values of specific yields for alluvial aquifers are in the range of 10 – 20% and

for uniform sands about 30%.

4)

specific retention (:

This is the percentage volume of water, which will not drain by gravity. It corresponds to

‘field capacity’ which is the water holding capacity of soil.

Thus,

Porosity = specific yield + specific retention

Equation 1


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5) hydraulic conductivity ( K ):

This is the measure of soil permeability.

6)

transmissibility (T ):

The transmissibility is the flow capacity of an aquifer per unit width under unit hydraulic

gradient and is equal to the product of permeability times the saturated thickness of the

aquifer.

In a confined aquifer, it is independent of the piezometric surface and found by equation 2

Equation 2

Where:

b is the thickness of the aquifer.

In a water table aquifer,

T = KH Equation 3

Where:

H is the saturated thickness. As the water table drops, H decreases and the transmissibility is

reduced. Thus, the transmissibility of an unconfined aquifer depends upon the depth of

Ground water table.

Excluding large caverns and fissures, groundwater flow is almost entirely laminar. Thus, the

groundwater flow can be defined using Darcy’s equation.

Darcy (1856) developed a law, Darcy’s law, which showed the relationship between the

velocity of flow through a porous medium and the hydraulic gradient. However, it only holds

for laminar flow conditions and since groundwater flow has a characteristic Reynolds number

of less than 1 it holds here.

V = Ki Equation 4

Where:

K is the saturated hydraulic conductivity

i is the hydraulic gradient (see Figure 5)

2.1.5 Groundwater quality

In 2014, as part of the lower Kafue Basin Environmental Project, post graduate diploma

student in Integrated Water Resources Management (IWRM) at University of Zambia, Kalibe

Phiri, carried out a research with the objective of ensuring that the groundwater resources

being the only reliable source of water in the project area was managed in a manner that

maximizes the economic and social welfare in an equitable manner between Albidon Mine

and the surrounding villages without compromising the sustainability of the vital ecosystems.


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Albidon Zambia Limited has groundwater pollution monitoring points and publications such

as the EIA document prepared by African Mining Consultants, for the mine; show that

quality of groundwater was monitored. The water supply to Munali Nickel Mine is from

boreholes located within the mine area. There are a total of 23 boreholes in this area. Of the

23 boreholes only 13 are for monitoring purposes while 10 were for water supply to the plant

area and the mine Camp (BID, 2014).

As extracted exclusively from BID (2014), the research shown was that collected water

samples from three boreholes revealed that in terms of physical, chemical, and metals

characteristics of the water were generally good. The parameters where the observations

exceeded WHO and Zambian standards were Lead and Iron, Calcium, Arsenic, Selenium and

Mercury. However, one borehole exceeded the requirements for Total Coliforms (TC) and

Faecal Coliforms (FC) in the bacteriological analysis. These results indicated that the quality

of groundwater in the local community area (boreholes located at Chinkomba Village, SDA

Church, Kazungula Village) was not suitable for human consumption.

Dissolved contaminants (primarily metals, sulphate, and nitrate) can migrate from mining

operations to underlying ground water and surface water. Process water, mine water, and

runoff and seepage from mine waste piles or impoundments can transport dissolved

contaminants to ground water (Bozeman and Montana 2008). The quality of the groundwater

can be affected by the contaminants dissolving and traveling from mine waste materials to

ground water. However, this depends on:

the nature and management of the waste materials

the local hydrogeological setting

the geochemical conditions in the underlying aquifer

2.1.6 Groundwater depletion

Dewatering may be required to lower the water table so that mining can proceed in the case

of underground mines such as Munali Nickel mine, regardless of whether the mine is in

operation or not. When the mine is not in operation it is put under care and maintenance,

dewatering should be continuously implemented to avoid flooding of the mine.

Depending on the stratigraphic occurrence of the mineral beds and the aerial extent of the

economic mineral seams, dewatering can result in a cone of depression that can extend for

miles in the up gradient direction. Water levels can be lowered in groundwater wells that are

in the same hydro stratigraphic unit as the mineral. Mineral ore beds are often characterized

by high hydraulic conductivity, and the associated high transmisivty often makes them


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attractive for accessing groundwater for domestic use, livestock, and irrigation (United States

Department of Agriculture and Forest Service, USDA, 2007).

The adverse effects of these groundwater depletions include lowered water levels in wells,

hydraulic interference between pumping wells, reduced surface water discharge, land

subsidence, and adverse changes in water quality.

Underground mining directly leads the overlying strata to break and fracture as subsidence

occurs. This fracturing of the overlying strata changes the intrinsic permeability of the strata,

and can alter groundwater flow paths, create areas of increased permeability, and cause

fluctuations in the water table. Where the overlying rock strata are thin between the mined

seam and the land surface, rock fracturing associated with underground mine subsidence can

also directly affect surface water. With respect to groundwater, shallow aquifers could drain

into subsidence fractures, or surface waters and recharge could be diverted into fractures.

2.1.7 Groundwater resources and distribution

A study of the hydrology, hydrogeology and water resources conservation in 2008 was done

by Sichingabula, H. M. and Nyambe, I. A. Most of the research does not stress on the

assessment of groundwater resources but on the surface water resources and hydrogeology of

this area. One of the major negative impacts of mining activities includes the

reduction/deterioration in groundwater supply. To facilitate underground mining;groundwater entering the mine area will be pumped out. During dewatering the surrounding

water table may be lowered. Since the main water supply in the area is derived from

groundwater boreholes, any reduction in the groundwater level in the area could result in a

reduction of available potable water in the area. Albidon monitors groundwater levels around

the mine using groundwater monitoring bores.

This project provided a complete environmental assessment when integrated with the quality

of water research done already in this area.

2.1.8 Groundwater Monitoring

Groundwater has a significant role in the environment: it replenishes watercourses such as

rivers, tributaries, and also replenishes wetlands. Groundwater helps in the sustenance of

wildlife and human habitat; this is as it is used as a primary source of drinking water and also

contributes significantly to agricultural and industrial activities.

With the escalation of human activities there has been return in increasing stress on

groundwater resources. Climatic changes also impose a threat on the groundwater resources.

This aggregated pressure on groundwater resources yields inevitable reductions in


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groundwater storage. The following are identified implications as a result of groundwater

reductions:

implicating the water cycle as groundwater supplies the base flow in many rivers and

it supports evapotranspiration in high water table regions

implicating water quality as the salinity of the extracted water frequently increases

as the volume of the reservoir decreases

Referring to the second implication of groundwater reduction, once groundwater resources

are contaminated, groundwater can be very costly to restore. It is for this reason that

groundwater resources need to be carefully protected. This can be achieved by groundwater

monitoring and tracing movement of contaminants using conceptual models.

A groundwater monitoring programme includes:

groundwater quantity monitoring.

How? By monitoring groundwater level and recharge rates

quality monitoring

How? By analysis of selected physical and chemical parameters

The resolves of groundwater monitoring as investigated are:

i. collecting, processing and analysing the data as a baseline for assessment of the

current groundwater quantity and quality

ii.

providing information for enhancements in the management of groundwater resources

iii. providing information for improved policies to be put in place

iv.

providing accumulated data that gives a practical depiction of the state of groundwater

resources, thus, providing foundation for all groundwater resource planning

Table 4: Ground water monitoring activities at different scales

Local scale Regional scale Global scale

monitoring activities include

a great bulk of:

monitoring wells

multilevel groundwater

sampling

high sampling frequency

analysis of chosen

parameters

numerical models are

used to fill in spatial and

temporal gaps in on site

monitoring

Satellite observations are

now playing an

important role in global

groundwater resources

assessment and groundwater

storage change


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As already discussed, measuring of the groundwater level is an activity required in

groundwater monitoring. Different methods can be used to measure the groundwater level

within the piezometer or well.

The most conventional ones being:

i. electrical sounder : here the insulated wires for a pair of electrodes are fused into a

calibrated flat tape. A circuit is completed when the electrodes come into contact with

the groundwater surface, indicated by the activating of a buzzer or a light, and this is

the depth of static water level

ii. automatic water level recorders: these are similar to that used in surface water bodies

such as pressure transducers

The groundwater hydraulic head at a point can be described using the elevation of water

above mean sea level at that point. This can be found using a simple relationship between

topography and water static level (see Equation 5)

Equation 5 Where:

E W = Elevation of water above mean sea level (m)

E = Elevation above sea level at point of measurement (m)

D = Static water level; Depth to water (m)

Tools in groundwater management include models and thematic maps produced from ground

water monitoring:

a. Groundwater models

Modelling, whether numerical or mathematical, plays a significant role in groundwater

management. The tenacity that comes with numerical models includes:

allows the analysis of the present conditions as well as provides basis for future

predictions

can simulate and predict the migrating ,or in other words the spreading, of solutes ingroundwater

provides a basis for an estimation of the impact of factors such as temperature and

change in recharge

are a vital tool for the protection of groundwater and the development of measures to

be taken in case of pollution

b. Groundwater resources maps

As earlier discussed, groundwater is monitored mainly by measuring groundwater levels,

groundwater recharge and water quality. The results of these measurements can be combined


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with other information pieces to produce various groundwater thematic maps covering

regions of interest.

2.2 Groundwater modelling

2.2.1 Introduction

What is a Groundwater model? This is the first question that comes to mind when first

encounter the concept of ground water modelling. A groundwater model is like any other

model which is a simulation of actual field conditions and states. The use of groundwater

models is extended to the simulation of:

groundwater flow

travel of pollutants as transported by the groundwater

Therefore, a groundwater model can either be a flow model or a transport model.

Applications of a flow model would consist of the following:

preparation of transport simulation for instance using the extension of MODPATH in

PMWIN modelling software

delineation of well head protection zones

estimation of water budget

interpretation of observed heads

assessing the impact of changes of a groundwater regime on the environment

Applications of a transport model would consist of the following:

observing chemical transport

interpretation of concentration data

planning of monitoring strategy

Groundwater modelling is considered nowadays as a very useful tool in support of

groundwater management. However, lack of long-term meteorological, hydrological, and

hydraulic data in the basin makes accurate assessment of groundwater resources a difficultchallenge. The behaviour of the groundwater system can be simulated using the modelling

software Modular 3-dimensional finite difference Groundwater model (MODFLOW), of the

United States Geological Survey. The reliability of groundwater modelling is largely

constrained by the quality of input data. However, the techniques of input data acquisition are

still much less developed compared to the numerical modelling tools.

Therefore, effective management of groundwater calls for the prediction of subsurface flow

and the response of fluid to changes in natural or human-induced stresses (Konikow and

Reilly, 1999). The prediction can be helped by groundwater modelling.


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2.2.3 Computer Software used for Groundwater modelling

The initial and boundary conditions for the model developed can be classified in the

following categories:

i. Time: steady flow or transient flow conditions

ii. Dimensionality:

0-D: regional balances

2-D horizontal: regional flow and transport problems

3-D: small scale problems, density effects and vertical flow

iii. Physical options:

Confined/ unconfined

Flow/transport

iv. Parameters: these include for instance permeability and transmisivty for each layer

2.2.3.1 FEFLOW

This is a finite-element subsurface flow system. Hence, the name FEFLOW as it stands for

Finite-Element subsurface FLOW system. It uses finite element analysis to solve the

groundwater flow equation of both saturated and unsaturated conditions.

2.2.3.2 MODFLOW

MODFLOW is the United States Geological Survey (USGS) modular finite-difference flow

model. It is a computer code that solves the groundwater flow equation. It is an extension of

software such as Process modflow software for Windows operating systems (PMWIN8 for

instance). The latest version is MODFLOW-2005 and is used as the modelling extension in

PMWIN5 and PMWIN8.

PMWIN8 was the modelling software used to model the selected project area in this study. It

requires the use of consistent units throughout the modelling process.

Important software extensions of PMWIN8 include:

MODFLOW-2005: used to construct the numerical model while

MODPATH: used to compute the capture zone of a pumping well

MT3D and MOC3: simulate constant transport

PEST and UCOD: calibrate the flow model


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Figure 6: Features of an Aquifer System that can be simulated by MODFLOW (Source:

Rausch, 2009)

Figure 7: Discretization scheme for MODFLOW* (Source: Rausch, 2009)

*Columns (J): correspond to x-coordinate

Rows (I): correspond to y-coordinate

Layers (K): correspond to z-coordinate


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a) Aquifer cross section with rectilinear grid superimposed

b) Aquifer cross section with deformed grid superimposed

Figure 8: Schemes of vertical discretization (Source: Rausch, 2009)

With reference to Figure 8, the convention in MODFLOW is to number layers from the top

down. The stratigraphic units as determined in the field from borehole log data can be used as

a premise for the layers.

Table 5: MODFLOW vs. FEFLOW

MODFLOW FEFLOW

Finite-difference flow model Finite-element flow model

Heads are only defined at cell nodes Heads are defined at any point within an

element by an approximate interpolation

function

Continuity is fulfilled at every node Continuity is fulfilled for every patch of

elements

Used by engineers and scientists Commercial computer program

2.2.4 Applications of PMWIN groundwater models

Some of the applications are as extracted from the already mentioned general applications of

any groundwater model:

observing the water balance using MODFLOW extension

observing chemical migration using MODPATH extension


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assessing the impact of changes of groundwater regime on the environment using

MODFLOW extension

setting up groundwater protection zones using MODPATH extension

estimation of a water balance using MODFLOW extension

Mass balance of contaminants using MODPATH extension

2.2.5 Developing of Model

i. Define the problem and establish purpose of the model. This is the basis of the

formulation of a conceptual model, which again is required prior to development

of mathematical model (Konikow and Reilly, 1999).

ii. In formulating a conceptual model, evaluation of which processes are important

in the system being studied for the specific problem at hand.

iii. Decide on the appropriate dimensionality for the numerical model.

iv. Select code appropriate for the problem at hand. The code must be adapted to the

specific site or region being simulated.

2.2.6 Calibration of Model

The objective of calibration is to minimize differences between the observed data and

calculated values. Thus, when the produced values by the model are within some acceptable

level of accuracy, the model is considered calibrated. According to Konikow and Reilly

(1999), although a poor match provides evidence of errors in the model, a good match in

itself does not prove the validity or adequacy of the model.

2.2.7 Model errors

Some of these errors include:

numerical errors arising in the equation solving algorithm. These errors include

round-off errors, truncation and numerical dispersion.

conceptual errors, which are misunderstandings about the basic processes that are

incorporated in the model.

errors arising from uncertainties and shortfalls in the input data that mirror the

inabilities to describe comprehensively and exceptionally the aquifer properties,

stresses and boundaries.


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CHAPTER 3:

STUDY AREA


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3.1 Location and physical setting

Figure 9: Location of Lower Kafue Basin area located south-eastern part of Kafue catchmentarea (Source: BID, 2014)


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Figure 10: Locations of Munali Nickel Mine area, groundwater monitoring stations around

mine area (MAD/GW), in Resettlement and Local Community areas (RAP) and surface water

monitoring stations (SW) an area impacted by the mine. (Source: BID, 2014)

The Munali Nickel Mining project area lies within the Kafue River catchment and lies at the

south-western foot of the Munali Hills, which form a northwest-southeast trend line of ridges.

The project area is defined in the Lower Kafue Sub-Basin which is part of the Kafue Basin. It

is located in the central part of Zambia between Latitude 1425-1639’ South and Longitude

273’-2931’East and covers an area of about 23,783 (Figure 2). The topographic

elevation ranges from 980m around Nega Nega area to 1215m above sea level in the

mountain areas of Kafue town.

The selected study area for this project is the Albidon Mine area. With reference to figure 3,

the area under study, is located in the Southern Province of Zambia, approximately 60km

south west of Lusaka, the capital of Zambia and 16km south of the town of Kafue. The

project is located 2.5km from the main sealed bitumen road between Lusaka and Livingstone.

It is approximately 20km from the Nega Nega railway siding on the Lusaka – Bulawayo

railway line with the Kafue River running approximately 20km to the north of the project

(Africa Mining Consultants, AMC, 2006).


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3.2 Climate

The southern province is susceptible to drought and therefore an area of particular concern

(Bäumle R 2007). The Munali Nickel Mining project area lies within the Kafue River

catchment. The climate is sub-tropical and the climate averages for the region indicate

temperature variations of 10°C and 30°C and rainfalls of between 500 and 1,200 mm/annum.

The average rainfall data for Lusaka Airport, which represents the most continuous dataset

in the region shows that the area is affected by distinct wet and dry seasons with the

wet season extending from November to April. Based on Mount Makulu station south of

Lusaka data, the average annual evaporation exceeds the average annual precipitation with an

average evaporation of approximately 1960 mm. Evaporation exceeds precipitation for most

of the year (BID, 2014).

In Southern Province are four meteorological stations depended upon to give meteorological

data and the mean temperatures reported at the stations are subtropical and ranges from 19 °C

to 22.1°C (Bäumle R 2007).

A more precise presentation of meteorological data was presented by the records provided by

the Mine and is later presented in the researched results. The average annual rainfall from

these records was found to be 772mm with average annual evaporation as 667mm and

temperature of 21.6 °C.

3.3 Landforms and Topography

Figure 11: Digital Elevation Model (DEM) with elevation zones at 200 m- intervals (Source:

Bäumle R 2007)


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The topography is visualised in Figure 11 using a Digital Elevation Model (DEM). The

elevation of the ground above sea level is displayed at 200 m intervals. Within the Province

the altitude rises from approximately 400 m in the Zambezi valley to almost 1,400 m on the

central plateau. The highest area with an altitude exceeding 1,500 m above sea level is

formed by the Mabwetuba Hills in the south-eastern corner of the Mazabuka District,

approximately 60 km in east-north-east direction of Gwembe.

The project area lies in an undulating area with landscape varying between heights of 1000

and 1296 meters above mean sea level (BID, 2014). As extracted from Figure 4, the elevation

at the project area is about 800 m mean sea level rising to 1200 m in the hills. The ground

falls gently to the southwest down from the hills.

The project area is absent of large water courses. The minor ephemeral streams flow in the

southwest direction from Munali Hills. The Kafue River located 20 km to the north is the

only large permanent watercourse in the area (Nyambe and Sichingabula 2008).

3.4 Local Geology and Hydrogeology of the Munali Hill Area

Figure 12: Aerial photograph showing surface projection of Geology (Source: AMC, 2006)


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Figure 13: Geology map of Munali hills area (Source: BID, 2014)

The geology of Munali Nickel mining project consists of crystalline massive marbles, calc-

silicates, graphite and alusite schists, micaceous quartzites with lesser mica, schists,

massively bedded boitite- staurolite-garnet schists, and gabbroic intrusion (Nyambe and

Sichingabula 2008). These are rocks of low porosity and permeability. The hydrogeology of

Munali project area is therefore dominated by low permeability rocks, within which lie a

series of modest permeability features. These features mostly occur:

where the hanging wall sequence of meta-sediments is predominantly quartzite.

in an area alongside the northern extent of the enterprise reserve which seems to

course across the strike affecting the hanging wall and ore zones.

As extracted from the EIA report prepared by African Mining Consultants, for Albidon

(Zambia) Limited, the main geological feature in the Munali district is an intrusion of gabbro

which has an oval shaped surface projection. This gabbroic body which forms an elongate

rectangular body of about 2.7km length and 0.5km width at surface, concordantly intrusive

into Neoproterozoic sediments.

The topography of the area is defined by surface drainage to the Kafue River to the west. The

main topographic feature in this area is the Munali pass which rises to 1288m above sea

level. The Kafue river system flows to the north of the project area and annually floods the

Kafue Flats forming a large wetlands area. There are no perennial rivers within the project

area apart from seasonal streams of runoff water that flow during the rainy season (Nyambe

and Sichingabula 2008). The two streams located within the mine area include

Nsambabatumbu and Chinkomba. These seasonal rivers and lakes form part of the

catchments areas of the Kafue river system.


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The groundwater levels in this project area are generally between 20 and 40m Bgl. The

hydraulic gradient and hence groundwater flow is generally from Northeast to the southwest

away for the Munali hills which probably represent a groundwater divide (Nyambe and

Sichingabula 2008 ).

3.5 Groundwater quality and monitoring boreholes

Referring to figure 10, the locations of groundwater monitoring stations are shown. The water

supply to Munali Nickel Mine is from boreholes located within the mine area. There are a

total 23 boreholes. Of the 23 boreholes only 13 are for monitoring purposes while 10 are for

supplying water to the plant area and the mine camp (BID, 2014). Groundwater is used

widely in the project area for domestic and potable water. For the Chikomba settlement and

surrounding villages, groundwater is the main source of water. As of 2006, before the

settlement of the mine, the groundwater quality was found to meet WHO and Zambian

standards both chemically and bacteriologically (AMC, 2006).

3.6 Agriculture

Agriculture is done both commercially and subsistent. The Local land use in the area include

subsistence agriculture, livestock grazing and sand mining especially in the settlement

Kasengo Village area north of Munali Hills area (Nyambe and Sichingabula, 1995).

Commercial crops grown are maize and coffee, were also livestock rearing of cattle, goats

and pigs is also existent.

3.7 Environmental Study Problem in area

With reference to the extensive background study conducted by the IWRM centre at UNZA,

the identified study problems include:

inadequate supply of quantities of water for domestic and mine operations

inadequate maintenance of acceptable levels of water quality

socio-economic problems related to resettlement of local people from mine project

area


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3.8 Delineation of project area for model

a) (Source: Google Earth)

LEGEND:

Borehole

Main road T1 or T2

River

b) Extracted from Google Earth map above

Figure 14: Project area delineation

Table 6: UTM coordinates for delineated area in Figure 14

Point E m N m

1 601 999.716 825 8453.673

2 606 563.840 8263 504.637

3 632 488.066 8249021.149

4 618917.403 8233868.256

4

3

2

1


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CHAPTER 4:

METHODOLOGY


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4.1 Tools

• The hydrogeological properties of the area where obtained from pumping tests and

borehole completion reports from technical reports compiled for Southern Province

by DWA. Other sources included updated GeoDin Database data base for Southern

Province. The borehole completion form provided details on the soil stratification

units of the aquifer while the pumping tests were used to compute the hydrological

properties of the soil such as the hydraulic conductivity. The computed hydraulic

conductivity was provided for each borehole.

• Meteorological conditions characteristic to the project area were investigated by

collecting records from Albidon mine and reports compiled by DWA.

• Identification of borehole location and selection of boreholes to be used as observed

hydraulic heads in simulation of model and calibration. The groundwater levels were

obtained from the water affairs GeoDin database.

• The parameters of the earth obtained above were placed into a groundwater simulator.

In this project MODFLOW was used to create the groundwater model. Thus, last step

is the developing of model.

Figure 15: Input Parameters required for modelling

PARAMETERS TO ENTERINTO MODEL

Meteorological parameters

Hydrogeologicalparameters

Observedhydraulic headsfor Boreholes

selected


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4.2 Hydrogeological analysis

Figure 16: Hydrogeological map of project area (Source: Bäumle, 2007)

LEGEND:

Aquifer category

Stratum with intermediate characteristics

Aquifer classification system

Based on the aquifer classification system and the Hydrogeological map the aquifer in the

project area is intermediate to class B and E. Refer to Appendix A for the Hydraulic aquifer

characteristics.


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Figure 17: Psuedosection of Munali mine area (Source: Albidon mine)

The Lithology of the selected boreholes and their respective yields is presented in Borehole

log data (see section 4.4). For simplification of the groundwater model developed, the

predominantly general lithology that was adopted is shown below based on borehole log data

and other data analysed: (Refer to Appendix A for aquifer category)

Table 7: Hydrogeological analysis

Layer Thickness m Aquifer n % K m/s T

Aquifer

category

sand

(top)

2 Unconfined 35 0.000474537 0.00016 E-B

schist 15 Unconfined 2 0.000002314 0.00025 E

Quartzite

(bottom)

83 Unconfined 0.5 0.000000004 0.00012 E


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4.3 Meteorological analysis

Table 8: Temperature parameter

Station Latitude S Longitude E Altitude m

above sea level Temperature

Kafue polder 15.767 27.917 978 21.6Magoye 16.133 27.633 1018 21.3

With reference to Table 8, the temperature adopted was 21.6

Table 9: Long-term rainfall and evaporation for stations in Southern Province

Station Rainfall

Mm

Rainfall

days

Day

Actual

Evaporation

Mm

PET

mm

Net

Evaporation

Mm

Runoff coefficient

%

Kafue polder 767 68 667 1522 -726 17

Magoye 720 67 674 1634 -914 6

With reference to Table 9, the Evaporation parameters adopted were for Kafue polder station.

Table 10: Mine site Seasonal Rainfall

With reference to Table 10, the mean annual average rainfall is 772 mm which is

0.002115068 m/s recharge water from precipitation without considering losses to say,

evaporation.

0

200

400

600

800

1000

1200

2009/10 2010/11 2011/12 2012/13 2013/14

Rainfall data

Rainfall data


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4.4 Borehole analysis

i) DEM FOR DETERMINING TOPOGRAPHY OF PROJECT AREA:

Figure 18: Shaded relief and block diagram generated from the DEM With reference to Figure 18 the DEM gave a predominant topography of 800-1200m above

mean sea level in delineated project area. Adopting an altitude of 1090m above mean seal

level as average altitude, from borehole 8070439 (see borehole log data) centred in this area,

was agreeable as it fell within DEM range of values.

ii) BOREHOLE LOG DATA :

The boreholes in the project area were identified as shown in table below

Table 11: BH log data

Water

point

m E m N Altitude

(m asl )

Total depth

Of BH (m)

Static water

Level

(m bgl)

Observed

Hydraulic

Head

(m asl)

8070401 609633.71 8249535.34 1010 27.0 5.0 1005

8070439 623218.98 8241844.10 1036.6 89.5 11.6 1025

8070166 627189.94 8240872.96 1052 63.0 20.5 1032

Note: The Observed Hydraulic Head was calculated using equation 5 ( see section 2.1.8)


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iii) PUMPING WELL:

The selected pumping well is BH7 (35L0621163 m E, 8238512 m N) has the following

properties:

Table 12: PUMPING WELL BH7 useful data for modelling

E m N m Injection rate Transmisivty

621 163 8 238 512 -0.00174 0.00025

4.5 Design of the groundwater model

4.5.1 Selection of suitable modelling software

The selected software was based on the available data or input parameters readily obtainable

and this dictated use of MODFLOW. Therefore, PMWIN8 was the ultimate choice and

starting from section 4.5.2, the steps that follow are based on the already described software

(see section 2.2.3.2)

4.5.2 Dimensional units adopted in modelling

Table 13: Dimensional analysis

Dimension Units Description

[L] M Metres

[T] D Days

[]

[] Per day

[] Metres/day

4.5.3 Selection of Control point for modelling

The selected control point for modelling was based on water point 8070439 with highest

water depth of 89.5 m and most reliable borehole logged data as suggested by the GeoDin

database.

4.5.4 Initial prescribed Head

The initial guess for the initial prescribed head was assessed based on altitude and hydraulic

heads for selected boreholes. The adopted value was 1090 m asl. For the constant head see

section 4.5.5.

4.5.5 Constant head for Kafue river boundary

Table 14: Kafue river levels for 2013/2014 (see APPENDIX F)

OCT NOV DEC JAN FEB MAR APR MAY JUN JUL

TOTAL m 29318.40 26309.60 30282.05 30289.60 27365.10 30298.85 29317.85 30293.35 29319.50 30303.60

AVERAGE m 977.29 977.00 976.80 977.10 977.40 977.40 977.30 977.20 977.30 978.00


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With reference to Table showing Kafue River levels, the average constant head was analysed

as:

Constant head= ∑

=

= 977.3m

4.5.6 Model extent

With reference to Table 6, the model extent was determined and using a cell size of

100 x 100 the number of rows and columns resolved:

Table 15: Model extent

ROWS COLUMNS

MODEL EXTENT 31 100 43 500

NUMBER 311 435

4.5.7 Defining of Grid Position

The viewing window size must be larger than the worksheet for the model. It is for this

reason that the following data sets were adopted as input coordinates for the Grid position.

Table 16: Grid position coordinates

COORD E m COORD N m

598 000 8 265 000

598 000 8 233 000

642 000 8 265 000

NOTE: Value of A=0 was used for rotation of Grid

4.5.8 Model thickness and Layers

Table 17: Lithology of model

Layer

Number

Description Thickness m Top

elevation m

Bottom

elevation m

1 Sand 2 100 98

2 Schist 15 98 83

3 Quartzite 83 83 0

4.5.9 Hydraulic parameters

The following were used as initial guesses:

Table 18: Vertical and Horizontal Hydraulic conductivity parameters

Layer

Number

Description HK VK (

1 Sand 41 0.41

2 Schist 0.20 0.02

3 Quartzite 0.0004 0.00004


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4.5.10 Recharge

The effective recharge that was used was 105mm/yr. When introducing the recharge to

MODFLOW the units were converted from millimetres per year to metres per day yielding

0.000288m/d.

4.5.11 Calibration

Calibration was done by varying hydraulic conductivity. This was attained by manually

varying the horizontal hydraulic conductivity HK.

4.5.12 Model Summary

Table 19: Model summary

VARIABLE DETAILS

Rows 311

Columns 435

Grid Cell Size 100

Number of stress periods 1

Layers 3

Maximum Model Elevation 100

Simulation flow type Steady State

Solver Package PCG

Boundary Packages Well and Recharge

Observations Head Observation


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CHAPTER 5:

RESULTS AND ANALYSIS


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5.1.2 Checking final calibration results using results of all observation boreholes

i. This was done firstly manually using an excel sheet to do calibration verification (see

Table 20).

Table 20: Calibration Verification for run 5

ii.

Using correlation of Observed to Calculated borehole hydraulic heads, a scatterdiagram was produced.

Table 21: Correlation verification

Obsnam Observed hydraulic

head

Calculated

hydraulic head

Correlation

8070401 1005.00 1003.81 1.001

8070439 1025.00 1022.76 1.002

8070514 1032.00 1033.5 0.999

Figure 21: Scatter diagram using all observation BH

Remarks: The plot in Figure 21 and correlation table verify how well calibrated the

values are to simulate realistic values of hydraulic heads for the observation boreholes.


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5.2 Particle tracking in case of spillage in Mine area into groundwater

Figure 22: Particle tracking for one particle

Remarks: People settled downstream will be affected by spill for forward particle movement.

The shortest possible time for a particle to reach and contaminate the Kafue river

in case of spill is 6 days with the trajectory shown.

5.3 Capture zone as result of Dewatering at Albidon mine area

Table 22: Abstraction point data

Location of abstraction point 622 000 m E, 8 241 000 m N

Injection rate -2750

Purpose Dewatering of Mine

The injection rate is negative since the underground pumping of water implies a pumping

well. The effect to the ground water is shown below in the schematic diagram saved from

the developed model in PMWIN8.


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CHAPTER 6:

DISCUSSION, CONCLUSIONS AND

RECOMMENDATIONS


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6.1 DISCUSSION

6.1.1 Interpretation of the Groundwater model

This model developed aims at conceptualizing the real field conditions and state of the

groundwater. Thus, it must not be confused with an accurate simulation as it is used for the

purpose of a conceptual model. The model shows that the water flows towards the Kafue

River away from the hills generally following the topography.

From the model it was easy to see that the hydraulic conductivity of the top layer affected the

rate of recharge. This is because as soon as the water reaches the second layer, the rate is

increased.

6.1.2 Divergence from Observed data

Apart from model simplification, divergence from observed data could be due to error in

hydraulic readings.

Like any other model, it’s simulation of data is limited to limiting factors such as:

Boundary conditions

Parameter estimates

Assumptions to flow such as assuming steady state flow

For some regions the assumptions made where realistic. However, the reliability and validity

of each estimate would still need scrutiny as they remained unknown.

6.1.3 Discussion of Results

The general direction of ground water flow is in North East direction. The reliability of the

results was dependent on the quality of the calibrated hydraulic heads in the modelled area.

This was shown by the scatter diagram having a correlation or gradient of about 1.00.

In case of a spill in the mine People settled downstream will be affected by spill for forward

particle movement. The shortest possible time for a particle to reach and contaminate the

Kafue river in case of spill is 6 days with the trajectory shown.

The reduction of hydraulic head was found to be significantly high in the capture zone of the

abstraction point. This caused drying in capture zone of pumping well hence satisfying

purpose of pumping which is dewatering of mine. The effect on the neighbouring hydraulic

heads was also shown using the model.


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APPENDIX

APPENDIX A: Hydraulic characteristics of aquifers

Aquifer

Category

Specific

capacity

(L/s/m)

Transmisivty

(

Permeability

(m/d)

Very

approximated

Expected yield(L/s)

Groundwater

Potential

A,C >1 >75 >3 >10 HIGH

B,D 0.1-1 5-75 0.2-3 1-10 MODERATE

E 0.001-0.1 0.05-5 0.002-0.2 0.01-1 LIMITED

F


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APPENDIX E: GeoDin database terminologies

TERMINOLOGY DESCRIPTION

Short name Water point number assigned for catalogue purposes

Hgps Hand held gpsWASTATIC Static level of water, depth to water in BH (m bgl)

ZCOORDE Depth of borehole (m)

XCOORD Latitude

YCOORD Longitude

ZCOORDB Altitude (m)

Bhp Borehole with hand pump

800 Southern Province database code807 Mazabuka district database code

APPENDIX F: Kafue River levels using gauging station for Nakambala in Mazabuka

KAFUE RIVER LEVELS 2013/2014 SEASON AT NAKAMBALA

DATE OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP

1 977.50 977.10 976.90 977.00 977.10 977.40 977.30 977.25 977.20 977.45

2 977.50 977.10 976.80 977.00 977.20 977.40 977.30 977.25 977.20 977.45

3 977.45 977.10 976.80 977.00 977.25 977.40 977.30 977.25 977.20 977.45

4 977.45 977.10 976.80 977.00 977.25 977.40 977.30 977.20 977.25 977.45

5 977.45 977.10 976.80 977.05 977.25 977.40 977.30 977.20 977.25 977.45

6 977.40 977.10 976.80 977.05 977.25 977.40 977.30 977.20 977.25 977.50

7 977.40 977.05 976.80 977.10 977.25 977.40 977.30 977.20 977.25 977.50

8 977.40 977.05 976.80 977.10 977.25 977.40 977.30 977.20 977.25 977.50

9 977.40 977.05 976.75 977.10 977.25 977.40 977.30 977.20 977.25 977.50

10 977.35 977.05 976.75 977.10 977.30 977.40 977.30 977.20 977.30 977.50

11 977.35 977.05 976.75 977.10 977.35 977.40 977.25 977.20 977.30 977.50

12 977.35 977.05 976.75 977.10 977.35 977.40 977.25 977.20 977.30 977.50

13 977.30 977.05 976.75 977.10 977.35 977.40 977.25 977.20 977.30 977.50

14 977.30 977.00 976.80 977.10 977.35 977.40 977.25 977.20 977.30 977.55

15 977.30 977.00 976.85 977.10 977.35 977.40 977.25 977.20 977.30 977.55

16 977.30 976.95 976.85 977.10 977.35 977.40 977.25 977.20 977.30 977.55

17 977.30 976.95 976.85 977.10 977.35 977.40 977.25 977.20 977.30 977.55

18 977.25 976.95 976.85 977.10 977.35 977.40 977.25 977.20 977.30 977.55

19 977.25 976.90 976.85 977.10 977.35 977.40 977.25 977.20 977.30 977.55

20 977.25 976.90 976.85 977.10 977.40 977.40 977.25 977.20 977.35 977.55

21 977.20 976.90 976.85 977.10 977.40 977.40 977.25 977.20 977.35 977.55

22 977.20 976.90 976.85 977.10 977.40 977.35 977.25 977.20 977.35 977.55

23 977.15 976.90 976.90 977.10 977.40 977.35 977.25 977.20 977.40 977.60

24 977.15 976.90 976.90 977.10 977.40 977.35 977.20 977.20 977.40 977.60

25 977.15 976.90 976.90 977.10 977.40 977.35 977.20 977.20 977.40 977.60

26 977.15 976.90 976.90 977.10 977.40 977.35 977.20 977.20 977.40 977.60

27 977.15 976.90 976.90 977.10 977.40 977.35 977.25 977.20 977.40 977.60

28 977.15 976.90 976.90 977.10 977.40 977.35 977.25 977.20 977.45 977.60

29 977.15 976.90 976.95 977.10 977.35 977.25 977.20 977.45 977.60

30 977.10 976.90 976.95 977.10 977.35 977.25 977.20 977.45 977.60

31 977.10 976.90 977.10 977.30 977.20 977.60


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APPENDIX G: Water Budget produced from run model for zero recharge

PMWBLF (SUBREGIONAL WATER BUDGET) RUN RECORD

FLOWS ARE CONSIDERED "IN" IF THEY ARE ENTERING A SUBREGION

THE UNIT OF THE FLOWS IS [L^3/T]

TIME STEP 1 OF STRESS PERIOD 1

=============================================================

WATER BUDGET OF THE WHOLE MODEL DOMAIN:

=============================================================

FLOW TERM IN OUT IN-OUT

STORAGE 0.0000000E+00 0.0000000E+00 0.0000000E+00

CONSTANT HEAD 0.0000000E+00 2.4500793E+02 -2.4500793E+02

WELLS 2.4500000E+02 0.0000000E+00 2.4500000E+02

DRAINS 0.0000000E+00 0.0000000E+00 0.0000000E+00

RECHARGE 0.0000000E+00 0.0000000E+00 0.0000000E+00

ET 0.0000000E+00 0.0000000E+00 0.0000000E+00

RIVER LEAKAGE 0.0000000E+00 0.0000000E+00 0.0000000E+00

HEAD DEP BOUNDS 0.0000000E+00 0.0000000E+00 0.0000000E+00

STREAM LEAKAGE 0.0000000E+00 0.0000000E+00 0.0000000E+00

INTERBED STORAGE 0.0000000E+00 0.0000000E+00 0.0000000E+00

RESERV. LEAKAGE 0.0000000E+00 0.0000000E+00 0.0000000E+00

--------------------------------------------------------------

SUM 2.4500000E+02 2.4500793E+02 -7.9345703E-03

DISCREPANCY [%] 0.00

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