UNIVERSITI PUTRA MALAYSIA

ABDUL SAMAD CHANDIO

FK 2012 22

THREE-DIMENSIONAL FINITE ELEMENT MODELING OF GROUNDWATER FLOW AND SOLUTE TRANSPORT

FOR THE LOWER INDUS BASIN, PAKISTAN

© COPYRIG

HT UPM

THREE-DIMENSIONAL FINITE ELEMENT MODELING OF

GROUNDWATER FLOW AND SOLUTE TRANSPORT

FOR THE LOWER INDUS BASIN, PAKISTAN

ABDUL SAMAD CHANDIO

DOCTOR OF PHILOSOPHY

UNIVERSITI PUTRA MALAYSIA

2012

© COPYRIG

HT UPM

THREE-DIMENSIONAL FINITE ELEMENT MODELING OF

GROUNDWATER FLOW AND SOLUTE TRANSPORT

FOR THE LOWER INDUS BASIN, PAKISTAN

By

ABDUL SAMAD CHANDIO

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,

in Fulfilment of the Requirement for the Degree of Doctor of Philosophy

January 2012

© COPYRIG

HT UPM

ii

DEDICATION

I wish to dedicate this work to my parents and teachers.

© COPYRIG

HT UPM

iii

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfillment

of the requirement for the degree of Doctor of Philosophy

THREE-DIMENSIONAL FINITE ELEMENT MODELING OF

GROUNDWATER FLOW AND SOLUTE TRANSPORT FOR

THE LOWER INDUS BASIN, PAKISTAN

By

ABDUL SAMAD CHANDIO

January 2012

Chairman: Professor Ir. Lee Teang Shui, PhD

Faculty: Engineering

A relatively thin layer of fresh groundwater exists over a dense saline layer in the

study area. A scientific approach is required to harness this fresh water from this

layer. Improper well design and indiscriminate pumping might lead to the saline

water intrusion from the native dense saline layer. The partially penetrated wells

known as skimming wells have been effectively used to restrain the upward

movement of the underlying saline water into the overlying fresh zone. The

skimming wells not only supplement the scarce irrigation supplies to meet the crop

water requirements at critical times but also control the waterlogging. This study was

aimed to develop a numerical model that simulates groundwater flow and solute

transport. The ultimate goal was to provide feasible solution for skimming the fresh

groundwater from the overlying thin layer without saline upconing from the dense

layer in the study area.

A three dimensional finite element model (FEMGWST) was developed that

simulates the groundwater flow and hydrodynamic dispersion of solute in confined

and unconfined aquifers under steady and transient flow conditions. The three

dimensional finite element method is relatively complex and requires large memory

© COPYRIG

HT UPM

iv

and more computational time but it is flexible to simulate the field system precisely

and effectively. The model is capable of handling free surface moving boundaries,

aquifer geometry, aquifer heterogeneity and anisotropy, well configurations and

constant head and concentration boundaries. The saline and fresh waters are miscible

fluids with different densities and a layer of marginal groundwater quality is formed

between them, hence the assumption of a sharp interface is avoided in the model.

The model is calibrated against field data collected at different agricultural farms

located in the Khairpur district in the lower Indus Basin lying between latitudes of

27o20’42” N and 27

o19’23” N and longitudes of 68

o32’17” E and 68

o35’57” E. The

main objective of model calibration is to minimize the spatial and temporal

difference between observed and model predicted results. The six statistical indices

Adjusted R2, mean absolute error (MAE), root mean squared error (RMSE), Nash-

Sutcliffe efficiency or model efficiency (ME), BIAS, and index of agreement (d)

were employed to evaluate the goodness of the model simulation for groundwater

flow and solute transport. The values of these statistical performance indices showed

that the overall model performance for groundwater flow and solute transport mirrors

closely that of the corresponding observed data.

The calibrated model was next used to assess the impacts of different well

configurations and boundary conditions such as variation in the pumping rate, tube

well operation time, number of well strainers, horizontal distance between well

strainers, thickness of fresh saline water interface, well strainer length, water levels

in the Rohri and KFE canals and their impact on local groundwater levels and

salinity of the surrounding area. It was observed that the well pumping rate is the

dominant factor in controlling the waterlogging rather than the fluctuation in canals

© COPYRIG

HT UPM

v

water level and well screen length. The simulated groundwater salinity was assessed

in terms of the temporal variation in the quality of the pumping water and

groundwater salinity at the bottom of the well.

It is observed that the saline water intrusion into the fresh groundwater layer is

directly related to the well discharge and the intermittent pumping. The depth of

useable groundwater below the bottom of the well is a key parameter to suppress the

salinity mound developed at the bottom of the well. The model results suggest that

the multi strainer wells could effectively suppress the development of salinity mound

compare to single strainer wells. However, when the thickness of fresh saline water

reduces to 4 m then the quadruple strainer wells can induce the salinity and a salinity

mound can develop. From the evaluation of different scenarios it is concluded that

strainer spaced at the distance of 12 m offer better performances than those spaced at

8, 4 and 2 m distances to reduce pumping water salinity in all configurations, except

for the quadruple strainer well with fresh saline water interface of 4 m. The results of

this study provide guidelines to the farmers, managers, scientists, and engineers to

adopt appropriate sustainable groundwater development policy and skimming well

design to harness the fresh water overlying saline water for irrigation without

deteriorating the quality of land.

© COPYRIG

HT UPM

vi

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai

memenuhi keperluan untuk ijazah Doktor Falsafah

PEMODELAN BERUNSUR TERHINGGA TIGA-DIMENSI AIR

BAWAHTANAH DAN PANGANGKUTAN BAHAN-LARUT

UNTUK LEMBANGAN HILIR INDUS, PAKISTAN

Oleh

ABDUL SAMAD CHANDIO

Januari 2012

Pengerusi: Profesor Ir. Lee Teang Shui, PhD

Fakulti: Kejuruteraan

Di dalam kawasan kajian terdapat sehelai lapisan nipis air bawahtanah segar terujud

di atas satu lapisan masin tumpat. Satu pendekatan saintifik diperlukan demi

mengambil air segar daripada lapisan ini. Reka bentuk telanga yang tidak baik serta

pegepaman tanpa memilih boleh menyebabkan pencerobohan air masin daripada

lapisan masin tumpat yang asli. Perigi tertusuk separa dikenali sebagai perigi

menyiring berkesan diguna untuk menghalang pergerakan air masin bawah masuk ke

zon segar di atas. Perigi menyiring bukan sahaja menambah kepada sumber air

pengairan yang berkurangan demi untuk memenuhi keperluan air tanaman pada masa

kritik tetapi juga dapat mengawal bertakungan. Kajian ini bertujuan memajukan

sebuah model berangka untuk menyelakukan aliran air bawahtanah dan

pengangkutan bahan larut. Tujuan muktamad ialah menghasil jawapan boleh

mungkin untuk memungut-siring air bawahtanah segar daripada lapisan nipis di atas

tanpa ujud kon masin daripada lapisan tumpat di kawasan kajian.

Sebuah model berunsur terhingga tiga dimensi (FEMGWST) telah dibentukkan

untuk menyelakukan aliran bawahtanah dan serakan hidrodinamik bahan larut di

dalam akuifer terkurung dan tak terkurung dalam keadaan aliran mantap dan

© COPYRIG

HT UPM

vii

berubah. Kaedah ansur terhingga tiga dimensi agar complex dan memerlukan ingatan

besar serta lebih masa menggira tetapi ianya lebih boleh suai demi menyelakukan

keadaan sebenarnya dengan lebih persis dan berkesan. Model itu sesuai untuk

menghadapi sempadan permukaan bebas bergerak, geometri akuifer, keheterogenan

akuifer dan tak isotropi, konfigurasi perigi dan tulus tetap dan sempadan tumpuan.

Air masin dan segar adalah bendalir boleh-larut campur bertumpatan berbeza dan

satu lapisan air bawahtanah berkualiti jidar ujud diantara, oleh itu anggapan antara

muka tajam diabaikan di dalam model.

Model tersebut ditentukur dengan data yang dikumpulkan di berberapa ladang

pertanian di daerah Khairpur di Lembangan Hilir Indus terletak diantara latitud 27o

20’ 42”U dan 27o 19’ 23”U dan longitud 68

o 32’ 17”T dan 68

o 35’ 57”T. Objektif

utama penentukuran model ialah untuk mengurangkan perbezaan ruang dan masa

keputusan ramalan model dan data. Enam indeks statistik: R2 terlaras, ralat mutlak

purata (MAE), ralat punca min kuasa dua (RMSE), kecekapan Nash-Sutcliffe atau

kecekapan model (ME), BIAS dan indeks persetujuan (d) dipakaiguna demi

menilaikan kejituan penyelakuan model bagi aliran bawahtanah bertepuan dan

pengangkutan bahan larut. Nilai indeks prestasi berstatistik menunjukkan bahawa

prestasi model keseluruhan aliran bawahtanah dan pengangkutan bahan larut

mencerminkan data cerapan.

Model tertentukur kemudian diguna untuk menaksir impek konfigurasi perigi

berlainan dan keadaan sempadan seperti perubahan kadar pengepaman, masa

beroperasi perigi tuib, nombor saring perigi, jarak datar antara saring perigi, tebal

antara muka air segar masin, panjang saring perigi, paras air di dalam saluran terbuka

Rohri dan KFE dan impek terhadap paras tanahair tempatan serta kemasinan

© COPYRIG

HT UPM

viii

kawasan merangkumi. Diperhatikan bahawa kadar pengepaman perigi adalah faktur

berkuasa mengawal bertakungan dibandingkan dengan perubahan paras air dalam

saluran dan panjang tabir perigi. Penyelakuan kemasinan air bawahtanah ditaksirkan

berasas kepada perubahan semasa kualiti air dipam dan kualiti kemasinan air

bawahtanah pada dasar perigi.

Ia diperhatikan bahawa pencerobohan air masin ke dalam lapisan air bawahtanah

segar dikait terus kepada kadar aliran perigi dan mengepam terputus-putus.Ukuran

dalam air bawahtanah boleh diguna di bawah dasar perigi ialah satu parameter utama

demi menindas timbunan kemasinan yang muncul pada dasar perigi. Keputusan

perigi menggambarkan bahawa perigi bermulti-saring boleh menindas dengan

berkesan pembesaran timbunan kemasinan dibandingkan dengan perigi bersaring

tunggal. Akan tetapi, bila tebal lapisan air segar kurang sehingga 4m maka perigi

bersaring empat boleh aruh kemasinan dan satu timbunan kemasinan boleh terjadi.

Daripada penilaian scenario berbeza ianya didapati bahawa saring berjarak 12m bagi

prestasi yang lebih baik jika dibandingkan dengan yang berjarak 8, 4 dan 2m untuk

mengurangkan kemasinan air bagi semua konfigurasi kecuali perigi yang bersaring

empat dengan keadaan antara muka air segar masin sebanyak 4m. Hasil kajian ini

sebagai garispanduan kepada petani, pengurus, saintis dan jurutera supaya

mengamalkan polisi membangunkan sumber air bawahtanah yang sesuai dan

tertanggung serta mengguna rekabentuk perigi bersiring demi untuk memgumpul air

segar di atas air masin untuk pengairan tanpa kemerosotan kualiti tanah.

© COPYRIG

HT UPM

ix

ACKNOWLEDGEMENTS

I bow before Almighty Allah and express my humblest and sincerest words of

gratitude to him, who bestowed upon the feeble author the potential and ability to

make material contribution to the already existing ocean of knowledge.

I wish to express my first and foremost heart-felt thanks and respects to my

honorable research supervisor, Professor, Ir. Dr. Lee Teang Shui, for his guidance

throughout duration of this research. I would also be grateful Professor Ir. Dr. Desa

Ahmad for his valuable guidance and support.

I would like to express my distinguished acknowledgement to the Professor Dr.

Muhammad Saffar Mirjat for his continuous and immeasurable support in my field

work. I gratefully express appreciation to staff of Drainage and Reclamation Institute

of Pakistan and farmers of study area, without their cooperation I could not managed

to collect the field data.

A special word of thanks to my parents and friends, especially to my father, for all

their support, encouragement and understanding throughout the project.

© COPYRIG

HT UPM

x

I certify that an examination committee has met on January 10, 2012 to conduct the

final examination of Abdul Samad Chandio on his Doctor of Philosophy thesis

entitled “Three-dimensional finite element modeling of groundwater flow and

solute transport for the lower Indus Basin, Pakistan” in accordance with the

Universities and University Colleges Act 1971 and the Constitution of the Universiti

Putra [P.U.(A) 106] 15 March 1998. The committee recommended that the student

be awarded the Degree of the Doctor of Philosophy.

Members of the Thesis Examination committee were as follows:

Professor

Faculty of

Universiti Putra Malaysia

(Chairman)

Professor

Faculty of

Universiti Putra Malaysia

(Internal Examiner)

Professor

Faculty of

Universiti Putra Malaysia

(Internal Examiner)

Professor

Faculty of

University

(External Examiner)

_________________________

SEOW HENG FONG, PhD

Professor and Deputy Dean

School of Graduate Studies

Universiti Putra Malaysia

Date:

© COPYRIG

HT UPM

xi

This thesis was submitted to the Senate of Universiti Putra Malaysia and has been

accepted as fulfillment of the requirement for the degree of Doctor of Philosophy.

The members of the supervisory committee were as follows:

Lee Teang Shui, PhD, Ir

Professor

Faculty of Engineering

Universiti Putra Malaysia

(Chairman)

Desa Ahmad, PhD, Ir

Professor

Faculty of Engineering

Universiti Putra Malaysia

(Member)

______________________________

BUJANG BIN KIM HUAT, PhD

Professor and Dean

School of Graduate Studies

Universiti Putra Malaysia

Date:

© COPYRIG

HT UPM

xii

DECLARATION

I declare that the thesis is my original work except for quotations and citations which

have been duly acknowledged. I also declare that it has not been previously, and is

not currently, submitted for any other degree at Universiti Putra Malaysia or at any

other institution.

_________________________

ABDUL SAMAD CHANDIO

Date: 10 January 2012

© COPYRIG

HT UPM

xiii

TABLE OF CONTENTS

Page

DEDICATION ii

ABSTRACT iii

ABSTRAK vi

ACKNOWLEDGEMENTS ix

APPROVAL x

DECLARATION xii

LIST OF TABLES xvi

LIST OF FIGURES xvii

LIST OF NOTATIONS xxiii

CHAPTER

1 INTRODUCTION

1.1 General 1

1.2 Statement of the Problem 4

1.3 Objectives of the Study 7

1.4 Scope of the Study 8

2 LITERATURE REVIEW

2.1 General 11

2.2 Groundwater Development 12

2.3 Groundwater Modeling 17

2.4 Numerical Methods 22

2.5 Mathematical Formulation 24

2.5.1 Groundwater Flow and Mass Transport Equations 24

2.5.2 Initial and Boundary Conditions 27

2.5.3 Discretization of Time Domain 30

2.5.4 Free Surface Boundary 31

2.6 Finite Element Method 31

© COPYRIG

HT UPM

xiv

2.7 Summary 33

3 METHODOLOGY

3.1 Description of the Study Area 36

3.2 Finite Element Formulations` 38

3.2.1 Conceptual Model 39

3.2.2 Galerkin Weighted Residual Method 43

3.2.3 Coordinate Transformation 44

3.2.4 Transformation of Integer 46

3.2.5 Representing the Pumping/Injection Well 50

3.3 Development of 3D Finite Element Model 51

3.4 Field Investigations 60

3.4.1 Pumping Test 60

3.4.2 Installation of Observation Wells 61

3.4.3 Soil Lithology and Groundwater Salinity Profile 64

3.5 Domain Discretization 65

3.6 Model Calibration and Verification 67

3.7 Model Performance Criteria 68

3.8 Variables Affecting Model Efficiency and Stability 70

4 RESULTS AND DISCUSSIONS 71

4.1 General 71

4.2 Model Calibration and Validation 72

4.2.1 Model Calibration for Steady Flow 72

4.2.2 Model Calibration for Transient Flow 75

4.2.3 Model Calibration for Solute Transport 79

4.2.4 Statistical Analysis 82

4.2.5 Evaluation of the Time Marching Scheme 84

4.3 Application of FEMGWST model for Assessing

Groundwater Quality 87

4.3.1 Impacts of Well Discharges and Number of Well

Strainers on Pumping Water Quality 88

© COPYRIG

HT UPM

xv

4.3.2 Impact of Well Discharge on Groundwater Quality at

the Bottom of the Single Strainer Well 96

4.3.3 Impact of Well Discharge on Groundwater Quality at

the Bottom of the Multi Strainer Well 100

4.3.4 Impact of Intermittent Pumping on Groundwater

Quality at the Bottom of the Well 102

4.3.5 Impact of Fresh Saline Water Interface 109

4.3.6 Impact of Well Strainer Spacing on Groundwater

Quality 122

4.3.7 Simulation for Waterlogging Control in the Study

Area 126

5 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 139

5.1 General 139

5.2 Limitations of the Study 141

5.3 Conclusions 141

5.4 Recommendations 144

REFERENCES 145

APPENDICES 156

BIODATA OF STUDENT 191

LIST OF PUBLICATIONS 192