DETERMINATION OF THE HYDRAULIC CONDUCTIVITY AND INFILTRATION CAPACITY OF THE FEDRAL UNVERSITY OF TECHNOLOGY OWERRI (FUTO) FARM

ABSTRACT

This thesis describes the in situ methods of the determination of both the hydraulic conductivity and infiltration capacity of the Federal University of Technology, Owerri (FUTO) farm soil. The inverse anger hole method was chosen to determine the hydraulic conductivity   due to its simplicity and effectiveness. Cognizance was taken of the factors as presented in the project report that affect the results determined. Also the various methods of determining the two parameters were reviewed. The importance of the data gotten from the use of these methods both in Agricultural and other fields have also been stressed in various sections of the project report. Finally, both tests and results were done and presented under the standard recommended procedures. From these, it was found out that the soil has a basic infiltration rate of about 7.45cm/hr and based on average values the hydraulic conductivity is about 9.2 x 10^-3 cm/sec and infiltration rate of about 19.70cm/hr. This implies that the soil has a medium value of hydraulic conductivity and a moderately high rate of infiltration, therefore sprinkler irrigation system is recommended. Keywords: Hydraulic conductivity and infiltration capacity

Table of contents

Contents                                                                                                   Page

Title Page                                                                                                      i

Certification                                                                                                  ii

Dedication                                                                                                    iii

Acknowledgement                                                                                        iv

Abstract                                                                                                          v

Table of contents                                                                                          vi

List of tables                                                                                               xii

List of appendixes                                                                                      xiii

List of figures                                                                                             xiv

Chapter One

Introduction

1.1      Background                                                                                    1

1.2      Statement of Problem                                                                     3

1.3      Objectives                                                                                       4

1.4      Justification                                                                                    4

1.5      Scope                                                                                              5

Chapter Two

Literature Review

2.1    Hydraulic Conductivity                                                                        7

2.1.1 Factors that Affect Permeability                                                           7

2.1.2 Methods of Determining Hydraulic Conductivity                               9

2.1.3 Saturated Hydraulic Conductivity                                                      10

2.1.3.1 Auger Hole Method                                                                         10

2.1.4  Unsaturated Hydraulic Conductivity                                                12

2.1.4.1 Laboratory Methods                                                                        12

2.1.4.2 Field Methods                                                                                 13

2.2  Infiltration Rate                                                                                    14

2.2.1 Factors Affecting Infiltration Rate                                                     15

2.2.2 Methods of Determining Infiltration Rate                                          16

Chapter Three

Materials and methods

3.1  Study Area                                                                                            19

3.2 Materials                                                                                                19

3.2.1 Moisture  Content                                                                               19

3.2.2 Infiltration Capacity                                                                            19

3.2.3 Hydraulic Conductivity                                                                      19

3.3 Methods                                                                                                 20

3.3.1 Determination of Moisture Content                                                   20

3.3.2 Determination of Infiltration Capacity                                               20

3.3.3 Determination of Hydraulic Conductivity                                         21

Chapter four

Results and Discussion

4.1  Results                                                                                                24

4.2 Discussion                                                                                            33

4.2.1 Infiltration                                                                                        35

4.2.2 Hydraulic Conductivity                                                                     34

4.2.3 General Comments                                                                            34

Chapter five

Conclusion

5.1   Conclusion                                                                                           36

5.2   Recommendation                                                                                 37

References                                                                                                   38

CHAPTER ONE

INTRODUCTION

1.1       BACKGROUND

The voids in a soil mass are not isolated cavities that hold water like storage reservoirs but are interconnected, small, irregular passage ways through which water can flow in the same way as it flows through other conduits.

Thus any material with voids are interconnected and thus possesses permeability.

Thus rock, concrete, soil, and many other materials are both porous and permeable (Peters, 2001),

The term hydraulic conductivity (K) or Coefficient of permeability is used to indicate the easiness or difficulty that a particular fluid will encounter when flowing through a permeable material.

The permeability of a soil mass is important in various fields including agriculture. It is one of the most important characteristics in evaluating drainage problems as well as evaluating the amount of seepage through or beneath dams and levees and flow into water wells.

It also plays an important role in evaluating the uplift or seepage forces beneath hydraulic structures for stability analysis. The devices used for determining the hydraulic conductivity in the laboratory are called permeameters. Also there are several methods for determining the hydraulic conductivity in the field.

On the other hand, when water is supplied to the soil surface, whether by precipitation or irrigation, some of the water penetrates the surface and is absorbed into the soil, while some may fail to penetrate but instead accrue at the surface or flow over it.

Infiltration is the term applied to the process of water entry into the soil generally by downward flow through all or part of the soil surface.

The Infiltration rate is the soil characteristic determining the maximum rate at which water can enter the soil under specific conditions including the presence of water (Micheal, 2001).  It is defined as the volume of water passing into a unit area of soil per unit time (or dimensions of velocity). The actual rate at which water is entering the soil at any given time is termed the infiltration velocity. The infiltration capacity of a soil is the infiltration rate which it will allow. The infiltration decreases during irrigation or water application. The rate of decrease is rapid initially and the infiltration rate tends to approach a constant value. The nearly constant rate that develops after some time has elapsed from the start of irrigation is called the basic infiltration rate. Accumulated infiltration also called cumulative infiltration is the total quantity of water that enters the soil in a given time. Infiltration rate and accumulated infiltration are the two parameters commonly used in evaluating the infiltration characteristics of soil.

Infiltration may involve one dimensional, vertical soil water movement such as occurs during sprinkler or flood irrigation, water movement in two dimensions such as flows from an irrigation furrow; or in three dimensions such as from a drip irrigation emitter (Jensen, 2005).

The rate of this process relative to the rate of water supply, determines how much water will enter the root zones, and how much if any will run off. Hence the rate of infiltration affects not only the water economy of plant communities, but also the amount of surface runoff and its attendant danger of soil erosion. Where the rate of infiltration is restricted plants may be denied sufficient moisture while the amount of erosion increases.

Knowledge of the infiltration process as it is affected by the soils properties and transient conditions, and by the mode of water supply is therefore prerequisite for efficient water management.

The term co-efficient of permeability, K, is used for designating flow through in any direction while the infiltration rate relates more to the vertical movement of water. The rate at which water moves in soil is directly proportional to its hydraulic conductivity. Both hydraulic conductivity and the infiltration rate has the same dimensions of velocity and the determination of both can be carried out either in the field or in the laboratory.

1.2    STATEMENT OF PROBLEM

Soil factor is a determining factor in crop production. The soil structure, texture etc are all dependent on the Hydraulic conductivity and infiltration rate. The idea of this work is to have the idea of these and be able to know precisely the type of crops to plant and also Agricultural practice to use for effective crop yield.

 

1.3          OBJECTIVES

The objectives of this project are:

1,  The determination of the hydraulic conductivity of the soil.

2,  The determination of the filtration capacity of the farm soil to make data available     for future irrigation and water conservation.

1.4         JUSTIFICATION

In general, there are numerous types of problems in connection with engineering projects which will require knowledge of the hydraulic conductivity characteristics of the soil concerned such as computations of seepage through earth dams and losses from irrigation ditches, selection of appropriate irrigation systems, erosion and drainage problems; discharge from wells or the rate of draw down.

This project is therefore chosen to help find a solution to some of these problems which affect the productivity of the college farm.

The values for saturated hydraulic conductivity are used in the design of drainage systems e.g. depth and spacing of under drains for lowering the water table under a road for draining waterlogged agricultural land. It is intended to irrigate the college farm. Hence, knowledge of the soil hydraulic conductivity is essential for computing water conveyance and application efficiencies as well as the design of the drainage system.

In general, soil hydraulic conductivity is a major factor in determining the use to which a soil can be put, stability of roads and building foundations, crop production potential, and growth of trees, shrubs and grasses are all affected to some degree by the ease or difficulty with which the soils drain.

In order words, soil hydraulic conductivity, K, enters all problems involving flow of water through soils such as seepage under dams, the drainage of a sub-grade, backfills and agricultural lands. From the above, it could be seen that the values of, K, determined is also applied to other fields other than agriculture which goes further to justify this project.

As regards to soil infiltration capacity, infiltration measurements are usually made to determine the infiltration rate, which is significant in irrigation designs and the type of soil management to be practiced in a given piece of land for optimum crop production.

Knowledge of infiltration capacity is important since it helps in determining the quantity of water to be applied to avoid waste due to deep percolation and danger of erosion due to runoff which might be disastrous to both the crops in the field and human life.

With the hydraulic conductivity and the infiltration capacity values of the school farm obtained, the college farm could now be properly irrigated and this will improve the productivity of the school farm.

Again for surface irrigation, the most efficient furrow or border length depends on the infiltration capacity, (Peters, 2001). Failure to adequately consider the infiltration process may result in poor water application in the field. Many of the soil related factors that control infiltration also govern soil water movement and distribution during and after the infiltration process. Hence, an understanding of infiltration and the factors affecting it is important to the design and operation of efficient irrigation systems

1.5  SCOPE

The study focused on the determination of the hydraulic conductivity and infiltration capacity of the soil in Federal University of Technology Owerri (FUTO) farm.

DETERMINATION OF THE HYDRAULIC CONDUCTIVITY AND INFILTRATION CAPACITY OF THE FEDRAL UNVERSITY OF TECHNOLOGY OWERRI (FUTO) FARM

 

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