UNIVERSITI PUTRA MALAYSIA

EVALUATION OF TECHNIQUES FOR DETERMINATION OF SATURATED HYDRAULIC CONDUCTIVITY IN THE VADOSE ZONE

ABDOLHAKEM O MOHAMED.

FK 2004 53

EVALUATION OF TECHNIQUES FOR DETERMINATION OF SATURATED HYDRAULIC CONDUCTIVITY IN THE VADOSE ZONE

BY

ABDOLHAKEM 0 MOHAMED

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia in Fulfilment of the Requirements for the

Degree of Master of Science

June 2004

Abstract of thesis presented to the Senate of Univeresiti Putra Malaysia in fulfilment ofthe rcquirement for the d e s e e of Master of Sciencc

EVALUATION OF TECHNIQUES FOR DETERMINATION OF SATURATED HYDRAULIC CONDUCTIVITY

IN THE VADOSE ZONE

ABDOLHAKEM 0 MOHAMED

June 2004

Chairman: Professor Ir. Mohd. Amin Mohd. Soom, Ph.D.

Faculty: Engineering

Saturated hydraulic conductivity of a soil (Ks) is a measure of a soil's ability to

transmit water in a water-saturated state. Infiltration, drainage, and groundwater

pollution are strongly influenced by the magnitude and spatial distribution of the

vadose zone field saturated soil hydraulic conductivity (Kfs). There are numerous

methods of estimating K, rangmg from direct measurement in the laboratory or in

situ to models that use only basic soil data (e.g. soil textural classes, bulk density,

Db, organic matter, OM, or porosity, E,). However, the results from different

measuring techniques vary under different field conditions. In this study of

Serdang Series soils found in the Universiti Putra Malaysia (UPM) campus, soil K,

values were collected at different depths using three direct methods. Estimation of

K, were done using six empirical models. The direct methods were in situ

techniques of Guelph Permeameter (GP) and double ring infiltrometer (DRI), and

constant head pcrrneameters (SCHP), a laboratory technique on intact soil cores

extracted from the same site at different depths. Predictive models included models

of Cosby et al. ( 1 984); Brakensiek et al (1984); Saxton et a1 (1986); Vereccken et

al. (1990); Sabro (1992) and Amin et al. (1997). In this study of K, in the vadose

zone, the focus was towards comparison of measurements in the field to those of

extracted samples from the same site, but determined by laboratory testing, under

controlled condition, and those estimated from empirical models. In addition, a

model was developed for determining K, values based on seven basic soil

properties (sand, silt, clay, Db, moisture content (MC), E and OM). The results of

the comparison showed that the geometric mean of K, values obtained by the three

experimental methods varied from 7.333 x 1 o - ~ to 1.3 15 x 1 0-2 cm S - I (6.34 x 1 o-'

m I day to 11.36 m 1 day). The GP method yielded the widest range from 7.333 x

1 0-8 to 1.654 x 1 0-3 cm s-' while the SCHP yielded the narrowest range from 4.4 x

10" to 1.3 15 x cm s-'. Geometric mean K, values were 27 to 360 times greater

for the SCHP compared to the GP method and were significantly different at all

depths. Measurements of Ks for the soil under consideration indicate that the DRI

and GP methods provided reasonable similar values at the topsoil layer (0-1 5 cm).

While the geometric mean Ks values measured by the DRI method was statistically

different from those obtained by SCHP method at 0-1 5 cm depth.

The laboratory technique yielded greater standard deviation (SD) at the 30 cm and

60 cni depths. Some soil cores may have more macropores than others. whereas the

coefficient of variation values were greater for the GP method. The GP produced

in situ calculation of Kfs in a relatively short time (25 to 90 minutes for a single

measurement) compared to DRI (1 20-1 80 minutes) and SCHP (1 500-1 660

minutes).

The results of the multiplc regression analysis indicated that the significant Inter-

correlations limitcd the numbcr of useful functional relationships that could be

der~ved from the seven variables (Textural classes, Dh, MC, E, and OM). The

results of regress~on for full data set showed that only simple function based on silt

content and OM gave a si~gnificant relationship with K, at 0.05 level, but only 10.5

n/o of variability in K1, was explained by those variables. There was a sipificant

relationship between K, and the input variables at each depth. These relationships

however were different at each depth. The best models found from this study at

depth of 0- 15 cm, have silt. sand, E, and MC; at depths of 15-30 cm have silt. sand,

and E; at depths of 30-60 cm have clay, sand, OM, and MC: and at depths of 60-90

cm silt. Db and E with values of R'= 0.57, 0.50, 0.41 and 0.74, respectively.

In this study the geometric mean error ratio (GMER) and geometric standard

deviation error ratio (GSDER) were used to evaluate the applicability of the

selected empirical models. The results showed that model of Amin et a1 (1997)

produced noticeably best results with GMER closest to 1 (0.54) and the lowest

GSDER (7.64) of the models tested here. This is followed by the Jabro (1992)

model with GMER (0.43) and GSDER (10.22), then Brakensiek et a1 (1984) with

GMER (0.43) and GSDER (15.6). It consequently appeared, at least for this soil

(Serdang Series), that of the six models compared in this study. the Amin et a1

model was the model of choice for the prediction of K,. The second best model was

labro model whereas the model of Brakensiek et al. ranked third.

%fif'USTAKAAN U T A F I WVE4lW WTRA LUUW

Comparison between the methods was hampered by a number of factors. It was

difficult to discriminate between spatial variables of Ks and errors related to the

methods. Different sample volumes and sample numbers were used. Comparisons

made between different K, measurements in the field are subject to natural soil

variations that may be larger than the differences between methods. Findings of

this study can be used as a guideline for application of these methods particularly

to the same soil type and depth setup. The correct use of any of these methods for

one of the most extensive and productive soils in Selangor (Serdang Series) could

be highly beneficial to the agricultural sector.

Abstrak tesis yang dikcmukakan kepada Senat Universiti I'utra Malaysia sebagai memenuhi keperluan untuk 1-jazah Master Sains

PENINAIAN TEKNIK UNTUK MENENTUKAN KEBERKONDUKAN HIDRAUL TEPU DALAM ZON VADOS

Oleh

ARDOLHAKEM O MOHAMED

Jun 2004

Pengurusi: Profesor Ir. Mohad. Amin Mohd. Soom, Ph.D.

Fakulti: Kejuruteraan

Ketertelapan tepu tanah (K,) adalah ukuran kemampuan tanah untuk mengalirkan

air dalam keadaan tepu. Penyerapan, saliran dan pencemaran air bawah tanah

sangat dipengaruhi oleh magnitud dan taburan spatial dilapaugan ketertelapan tepu

tanah (K,,) dalam zon vados. Ada beberapa kaedah bagi menganggarkan K,

antaranya ukuran terus dalam makmal atau di situ dan menggunakan data asas

tanah seperti tekstur, ketumpatan (Db), bahan organik (OM) dan Keliangan tanah

(E). Walau bagaimanapun. keputusan yang diperolehi adalah berbeza hasil

daripada perbezaan teknik pengukuran dan perbezaan keadaan lapangan. Dalam

kajian ini, ujikaji dan ramalan K, siri tanah Serdang yang terletak di kampus UPM

telah dibuat mengikut kedalaman tiga kaedah term dan enam model ramalan.

Kaedah terus n~engikut Guelph permeameter (GP), infiltrometer gegelung kembar

(DRI) suatu teknik di situ, dan permeameter turus tetap (SCHP), suatu teknik

makmal ke atas teras tanah jrang tidak diganggu dan diperolehi di kawasan yang

sama pada kedalaman yang berbeza. Sementara model ramalan termasuk model

Cosby et al. (1984), Brakensiek et a]. (1984), Saxton et al. (1986), Vereecken ct al.

( 1990), Jabro et a]. ( 1992) dan Amin et al. ( 1997). Objektif utama kajian kc dalam

zon vados ini ialah untuk membandingkan K, di lapangan yang disctkan dcngan

sampcl yang diperolehi di lapangan yang sama, tctapi ditentukan oleh u-jian

makmal, dan juga ramalan model cmpirikal. Selain daripada itu. untuk

membangunkan sebuah model bagi rnenentukan nilai K, berdasarkan tujuh data

asas tanah (pasir. kelodak, tanah liat, ketumpatan pukal, kandungan kelembapan,

keliangan dan bahan organik). Keputusan perbandingan uj i kaji menunjukkan nilai

purata geometrik K, oleh tiga kaedah eksperimen berbeza dari 7.333 x hingga

1.3 15 x 10 ' sm s-' (6.34 x 10" m/hari hingga 1 1.36 mlhari). Kaedah GP pula

menghasilkan jarak nilai paling kecil iaitu 7.33 x lo-' hingga 1.654 x 1 o4 sm s",

sementara SCHP jarak nilai paling besar iaitu dari 4.4 x 10" hingga 1 . 3 1 5 x 10 ' sm s-I. Purata nilai geometrik Ks adalah 27 hingga 360 kali lebih besar bagi SCHP

berbanding kaedah GP dan adalah berbeza secara bererti untuk semua kedalaman.

Kajian ini juga menunjukkan nilai K, yang diukur oleh kaedah DRI adalah tidak

berbeza secara statistik dengan nilai yang diperolehi oleh kaedah GP pada

kedalamam 0- 15 sm tetapi berbeza secara statistik dengan yang diperolehi daripada

kaedah SCHP.

Teknik makmal menghasilkan sisihan piawai (SD) yang lebih besar pada

kedalaman 30 dan 60 sm. Kemungkinan ada teras tanah mempunyai lebih banyak

rongga daripada yang lain, sebaliknya nilai pekali perbezaan (CV) adalah lebih

besar untuk kaedah GP. Kaedah GP menghasilkan anggaran pengiraan Kl., di situ

dalam masa yang singkat secara relatif (35 hingga 90 ininit untuk satu

pengwkuran) berbanding dengan DRI ( 1 20- 1 80 minit) dan SCHP ( 1 500- 1660

minit).

Kcputusan analisis lebi h daripada satu regresi lnenunjukkan keberertian saling

pcrhubungan rnenghadkan nilai fungsi perhubungan yang mungkin timbul daripada

tujuh pembolehubah (kelas tekstur, Dh, MC, E, dan OM). Keputusan regresi untuk

semua set data menunjukkan hanya satu fungsi mudah berdasarkan kandungan

kelodak memberikan hubungan bererti dengan Ks pada tahap 0.05 tetapi hanya

10.5 % daripada keberubahan dalam Kl., yang diperihalkan oleh keberubahan itu.

Keputusan analisis regresi juga menunjukkan ada keberertian perhubungan antara

K, dan input keberubahan setiap kedalaman. Perhubungan ini walau bagaimanapun

adalah berbeza inengikut kedalaman. Model terbaik yang ditemui dalan kajian ini

pada kedalaman 0-15 sm, mempunyai kelodak, pasir, E dan MC; pada kedalaman

15-30 sm mempunyai kelodak, pasir, dan E, pada kedalaman 30-60 sm mempunyai

tanah hat, pasir, OM, dan MC;pada kedalaman 60-90 sm mempunyai kelodak, Db

dan E dengan masing-masing nilai ~ '=0 .57 , 0.50, 0.41 dan 0.74.

Dalam kajian ini purata kadar ralat geometri (GMER) d m kadar ralat sisihan

piawai (GSDER) digunakan untuk inenilai kebolehgunaan kaedah model ramalan

yang telah dipilih. Keputusan kajian ini menunjukkan model Amin et al. (1997)

menghasilkan keputusan terbaik dengan GMER menghampiri 1 (0.54) dan GSDER

(7.64) terendah diikuti oleh model Jabro (1992) dengan GMER (0.43) dan GSDER

(1 0.22) dan seterusnya Brakensiek et al. ( 1 984) dengan GMER (0.43) dan GSDER

(15.6). Dalan kajian ini setelah perbandingan dibuat ke atas enam model untuk

tanah siri Serdang, model Amin adalah model yang dipilih untuk menganggarkan

nilai K,. Model kedua terbaik adalah model Jabro sementara model Brakensiek

adalah yang kctiga.

Pcrbandingan antara kaedah tclah dihalang oleh beberapa factor. Adalah susah

untuk mernbezakan keberubahan K, secara spatial dan ralat yang berkait dengan

kaedah yang digunakan dan perbezaan isipadu sampcl serta bilangan sampel.

Perbandingan dibuat antara perbezaan ukuran dalam lapangan adalah bergantung

kepada perbezaan semulajadi tanah yang mungkin lebih besar daripada perbezaan

antara kaedah. Keputusan daripada kajian ini memberikan panduan awal

menggunakan kaedah-kaedah tersebut khasnya pada tanah yang sama dan

kedalaman yang ditentukan. Kaedah yang paling sesuai untuk menentukan K, bagi

sejenis tanah yang paling prodiktif di sekitar Sin Serdang amatlah berguna kepada

sektor pertanian.

ACKNOWLEDGEMENTS

First and foremost, all praise be directed to Allah (SWT) for making all

things possible, Alhamdulillah.

I would like to express my sincerest thanks to my supervisor, Professor Ir.

Dr. Mohd. Amin Mohd. Soom, for his invaluable help, guidance, advice, support

and encouragement throughout this work. I also wish to thank Dr. Abdul Aziz

Zakaria and Associate Professor Kwok Chee Yan for serving as members of the

supervisory committee and for their guidance and valuable suggestions.

Special thanks are extended to Mr. Ghazali Kassium (technicians of Soil

and Water lab) for his constant assistance. I wish to express my gratitude to my

friends in the faculty of engineering for their help and support, especially

Associated Prof. Dr. Abdel Maged Hamuda , Mr Meh Awang, Mr. Johari , and

Mr Tajul Ariffin Tajuddin . Special thanks are extended to my best friends Dr.

Radim Dadang and Dr. Ahmed Ganfoud for their support.

I am grateful to the People of Libyan Arab Jamahiriya and Omer Al-

mukhtar University who provided me the scholarship for pursuing the Master

degree at Universiti Putra Malaysia. Also, I would like to express my gratitude to

Univeristi Putra Malaysia for some financial support to the study.

I would like to express my heartfelt thanks to all members of my family for

their encouragement and overwhelming support to complete this study.

I certify that an Examination Committee met on 14Ih June 2004 to conduct the final examination of Abdolhakem 0. Mohamed on his Master of Science thesis entitled "Evaluation of Techniques for Determination of Saturated Hydraulic Conductivity in the Vadose Zone" in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

Ir. Lee Teang Shui, Ph.D. Associate Professor Faculty of Engineering Universiti Putra Malaysia (Chairman)

Ir. Mohd. Amin Mohd. Soom, Ph.D. Professor Faculty of Engineering Universiti Putra Malaysia (Member)

Abdul Aziz Zakaria, Ph.D. Faculty of Engineering Universiti Putra Malaysia (Member)

Kwok Chee Yan Associate Professor Faculty of Engineering Universiti Putra Malaysia (Member)

ProfessodDeputy ~ e g n School of Graduate Studies Universiti Putra Malaysia

Date: 2 6 AUG 2004

This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirements for the degree of Master of Science. The members of the Supervisory Committee are as follows:

Ir. Mohd. Amin Mohd. Soom, Ph.D Professor Faculty of Engineering Universiti Putra Malaysia (Chairman)

Abdul Aziz Zakaria ,Ph.D. Senior Lecturer Faculty of Engineering Universiti Putra Malaysia (Member)

Kwok Chee Yan Associate Professor Faculty of Engineering Universiti Putra Malaysia (Member)

AIM IDERIS, Ph.D. Professor 1 Dean School of Graduate Studies Universiti Putra Malaysia

Date: 1 0 SEP 2004

xii

DECLARATION

I hercby declare that the thesis is based on my original work exccpt for quotations and citations which have been duly acknowledged. I also dcclarc that i t has not bccn previously or currently submitted for any other degce at Univcrsiti Putra Malaysia or othcr institutions.

Date: 56

TABLE OF CONTENTS

Page

ABSTRACT ABSTRAK ACKNOWLEDGEMEKTS APPROVAL DECLARATION LIST OF TABLES LIST OF FIGURES LIST OF PLATES LIST OF SYMBOLES

CHAPTER

INTRODUCTION General Statement of the Problem Objectives of the Study Thesis Organisation

LITERATURE REVIEW Introduction In Situ Vadose Zone Methods Guelph Perrneameter Double Ring Infiltrometer, DRI Laboratory Method, SCHP Comparison of Methods Empirical Models Theoretical considerations of the SCHP, DRI, and GP methods

Laboratory method using SCHP Ring Infiltrometer method, DRI Guelph Permeameter method, GP

Factors Affecting Soil K- Values Soil Texture and Structure Soil Heterogeneity Smearing, remolding and siltation Air Entrapment Capillarity Solution analysis methods

Summary

x xi

. . . X l l l

xvii xix xxi xxii

I11 MATERIALS AND METHOD Site Description Experimental Design Determination of Soil Properties

Determination of Soil Water Moisture Content Soil Texture Bulk Density Calculation of Total Soil Porosity Determination of Organic Matter (OM)

Determination of Saturated Hydraulic Conductivity Guelph Permeameter (GP) Double Ring Infiltrometer (DRI) Determination of Ks Using SC-HP Ks Estimation Methods

Jabro Model Saxton et a1 Equation Vereecken et a1 Equation Cosby et a1 Equation Brakensiek et a1 Equation Amin et a1 Equation

Statistical Analysis Statistical Distribution Comparison Method

RESULTS AND DISCUSSION Field Site Characteristics Results of Soil Properties and Infiltration Rate

Soil Moisture Content Organic matter Bulk Density Porosity Sand Silt Clay Soil Texture Infiltration Rate

Results of Soil Saturated Hydraulic Conductivity, Ks, Model Analysis and empirical Models Evaluation Soil saturated hydraulic conductivity

Statistical Distribution of Ks parameter Double Ring Infiltrometer Constant Head Method Guelph permeameter Failure and Time Requirement Comparison of the Methods

K, Model Analysis Empirical Models Evaluation

V1 SUMMARY AND CONCLUSION

REFERENCES APPENDICES BIODATA OF THE AUTHOR

xvi

LIST OF TABLES

Table

2.1 Brief description ol'method for measuring the soil satusatod hydraulic conductivity. l'ypc. applicability. main direction o l ' h measurement and approximate sample volume.

2.2 Hydraulic conductivity values of sat~lrated soils.

2.3 Classification of soil hydraulic conductivity values.

2.4 Approximate relationships between texture. structure. and hydraulic Conductivity.

3.1 Porous media categories used for estimating a* in the single-head well permeameter analysis.

4. 1 Soil physical properties of the study area. OM organic matte. MC moisture content, E porosity and Db bulk density

4.2 Physical properties of Serdang Series soil at the experimental site across at each depth

Results of Infiltrometer measurement and predictioli

4.4 Equations of infiltration rates and cumulative infiltration

4.5 Descriptive statistics of parameters of Serdang Series soil measured at the experimental site across all depths.

4.6 The total numbel- of observation. percentage of f a i l~~re ratio (FR), percentage of negative KI, values and time requircnient to complete one set of measurement

4.7 Comparison of K, measurements obtained using the double sing 148 infiltrometer (DRI). Guelph permeanieter GP). and intact soil corc (SCHP) methods K\Gnl is geometric mean K, valuc: K,I\IIIl i 4 the

mininiuni K, value. K,M,I, is the ~ i i a x i m ~ ~ m K, \ al~le: SD 1s tlic standard deviation: CV is the coefficient of variation. ncgatibc value . and N is the nuniber of mcas~~rements.

4.8 Correlation n~atsis of parameter nieas~~red at study area

4 . Derived regression models where Ks- Kli in cni s" arc measuscd 102

saturated hydraulic conductivity using constant head pern1canictcr (SCI-II') and Guelpli ermeametcr (GP) methods respectively. Dl, ! bulk density in g cm- . I=, porosity %I. MC moisture content %,

4.10 Summary of'statistics ol'saturated hydraulic conductivity for Serdang Series. sandy clay loam soil. obtained bl threc methods and predicted by the six selected modcls mcasurc

4.1 1 Geometric mean crror (GMER) and geometric standard deviation 170 of error ratio (GSDER) calculated with six selected models using the data set of the Serdang Series soil of study area comparcd to measurements val ucs.

svi i i

LIST O F FIGURES

2.1 Inliltration ratc ol'dry and wet soil.

2.2 Schematic tcst setup for constant head and lalling head lest.\;

2.3 Approximation of steady state flow out of a well situutcd i n a homogenous isotropic porous medium.

2.4 Illustrates the constant head borehole test (GP) in vaciose (~lnsaturated) zone using two heads. 14 1 and H2. Whcre. a is radius of the well and G P represents Guelph Permearnetel-.

3.1 Soil map showing the location of Serdang series at UPM campus.

3.2 Contour map of the Field Research Area Faculty of Engineering showing the stud!. area (Basin irrigation area)

3.3 Syninietric plan showing the location of saturated hydraulic conductivity test and samples collection.

3.4 Shape factors (C) for use in the constant-head well pernieameter method.

3.5 The components of laboratory constant head permeameter.

4.1 Textural distribution for study area data set

3.2 Soil profiles description of study area located at Facult! of engineering research area DBAE Field Station

4.3 Textural distributions fbr the data set at each depth.

3.4 Infiltration rate and cumulative infiltration versus elapsed time for point No. Serdang series soil

4.5 A log-log of infiltration rate and cun~ulative infiltration versus elapscd time for point 110.7 Serdang series soil

4.6 Frecluency histogram and fitted distribution f~~nct ions l'or laboratory evaluated saturated hydraulic conductivity (K, ) using constant head (SCI-1P) method

4.7 Frequency histograni and fitted distribution functions Ihr field cvaluatcd saturated hydraulic conductivity (I(,)

using Guelph pcrn~camcter (GP) method.

Normal probability plot for field-evaluation logarithmic saturated hydraulic conductivity (Kt,) values for sand) clay loam soil

4.9 Normal probability plot for lab-evaluation logarithmic saturated hydraulic conductivity (K,) values for sandy clay loam soil

4.1 0 Linear regression betwecn field (GP) and laboratory (SCI 11') evaluated saturate l~ydraulic cond~~ctivity (K,) values li)r Serdang series sandy

clay loam soil.

4.1 1 Measured Ks vs. predicted for coniplete date set of the stud) area. 160

4.12 Saturated hydraulic conductivity. measured vs. estimated results for the models with the best fit for Serdang Series soil at each depth

4.13 Measured versus estimated Ks for the six niodels tested li,r ;I

sandy clay loam soil.

LIST OF PLATES

J'late 1';1gc

3.1 The study area at DBAE Field Station. UPM X 4

3.2 Guelph Permeanleter ((31') kit and GP Set up in the s t ~ ~ d y ill.eil. 01

? ? 3 . 3 Infiltration rate measurement using double ring in f i l t~ .o~ i i~ t~~ . .

3.4 View of undisturbed soil core samples collected for bull, density and saturated hydraulic i n the laboratory.

4.1 Plate 4.1 through 4.4 show soil profiles at the study area

SSI

LIST O F SYMBOLS

Description

Bulk Density Real Density Liquid density Dynamic viscosity Steady Discharge Steady Discharge at hydraulic head (HI ) Steady Discharge at hydraulic head (Hz) Hydraulic conductivity Intrinsic permeability Saturated hydraulic conductivity Field Saturated Hydraulic Conductivity Geometric mean saturated hydraulic conductivity Maximum saturated hydraulic conductivity Minimum saturated hydraulic conductivity Horizontal saturated hydraulic conductivity Vertical saturated hydraulic conductivity The hydraulic or potential gradient Acceleration due to gravity Sorptive number Matric flux potential Infiltration flux through (x, y, and z) directions Depth of water level in the borehole Hydraulic Head Depth of water ponded at soil core surface Infiltration Rate Final infiltration rate Measured cunlulative infiltration Organic Mattes Soil moisture content Porosity Number of samples or observations Length of the intact sample Cross-section area of the core or brass ring Internal diameter of the brass ring Radius of the brass ring Volume of the cylindrical core length of the cylindrical core Time Weight of the air dry soil Rate of fall of' water level in GI' rcservois Coefficient of \,ariation Standard deviation

unit

- i g C l l l

g c m - ' g c111-' poisc c111.; s-

; - I en1 s ; - I cn1- s

c m s - ' 3

e m - em s - '

- I cm s

C l l l s- I

cm- em's-'

- I C l l l s

c ni

c I l l

c I l l

ssii

R?

r v S S i C' SE SI-I GI1 C1-1 WP SCHP AH DRI RI I PM DTM WP SWPT S I TI F I G1 PM PTF H z 0 2 GMER GSDER PSD RMSE RMSR RMSD UPM FA0 USBR LJSDA

Coefficient of n~ultiple dcterniination Correlation cocl'ficient variance Sand Silt Clay Simultaneous 1:quation analysis Single Head analysis Guclph permeameter method Constant Head Well Perniean~eter method Constant Head I'ernieametcr method Auger hole method Double Ring Inliltrometer method Ring Infiltronieter I~istantaneous profile method Double Tube Method Wcll Permeameter Shallow Water Pernieameter Technique Sprinkler infiltrometer Tension infiltrometer Furrow infiltrometer Guclpl~ infiltrometer Predictive Model Pedotransfer function H! drogen peroxide % Gcometric mean error ratio Gcometric standard deviation of error ratio Pal-iicle-size distribution Root mean squared error Root mean squared of residuals Root mean squared deviations Ll~liversiti Putra Malaysia. Food Agricultural Organization U~litcd States Bureau of Reclamation llliitcd States Department of Agriculture

ssiii

CHAPTER 1

INTRODUCTION

General

Water movement in soils whether under the saturated or unsaturated

conditions is highly dependent on the hydraulic conductivity (K) of the soil. For a

given soil, K is defined as a constant that relates the rate of water transport in that

soil to the hydraulic gradient or driving force causing water to move. Under

saturated c ondition it i s called saturated hydraulic conductivity and generally is

denoted by Ks, or while under unsaturated condition it is referred to as

unsaturated hydraulic conductivity. Qualitatively, K is the ability of the soil to

transmit water and generally speaking, is a maximum at saturation but under

unsaturated condition its value however, have been found to decrease dramatically

with decreasing water content.

Vadose zone soil saturated hydraulic conductivity, K,, is the volume of

water, which will pass through a unit cross-sectional area of a soil above the water

table in unit time, given a unit difference in water potential. Its behavior plays a

crucial role in modeling water flow and chemical transport in the saturated media.

It is perhaps one of the most important hydraulic properties used by hydrologist,

water resources engineers, and environmental soil scientists to solve many

agricultural and hydrological and environmental problems. Soil's K, values have

an important application in areas ranging from the analysis of any saturated-soil