Promoter(s) : Prof. Dr. Eric Van Ranst (WE 13)

Tutor(s) : Ir. Johan Van de Wauw (WE13)

«Promotor_1» «Promotor_2»

Master dissertation submitted in partial fulfillment of the requirements for the degree of Master of Science in Physical Land Resources by Kanyangalazi Joseph Jones (Malawi)

Academic Year 2009-2010

INTERUNIVERSITY PROGRAMME IN

PHYSICAL LAND RESOURCES

Ghent University Vrije Universiteit Brussel

Belgium

Quality assessment of hot spring water for irrigation and domestic use in Malawi

I C E

This is an unpublished M.Sc dissertation and is not prepared for further distribution. The author and the promoter give the permission to use this Master dissertation for consultation and to copy parts of it for personal use. Every other use is subject to the copyright laws, more specifically the source must be extensively specified when using results from this Master dissertation.

Gent, The Promoter(s), The Author, E. Van Ranst (WE 13) Kanyangalazi Joseph Jones

i

Summary

Water quality refers to the characteristics of a water supply that will influence its

suitability for a specific use, i.e. how well the quality meets the needs of the user. This

study intended to evaluate the quality of hot spring water for irrigation and domestic

purposes in Malawi. Two types of samples were collected namely soil and water samples.

Water samples were collected from (1) four hot springs spread all over the country (2)

ground water from a soil profile at Malemia 2. Soil samples were collected from Malemia

2 area where irrigation using water from Namitukuta hot spring is being practiced. The

XRD analyses of the evaporites of the water from the four hot springs revealed that

burkeite (Na4(SO4)1.45(CO3)0.55), halite (NaCl), kogarkoite (Na3SO4F) and trona

(Na3H(CO3)2(H2O)2) are the salts present in all the hot springs. In addition to these salts,

Tambala hot spring has thernadite (Na2SO4). The dominant salts in the water from the hot

springs depend on the ratios of the solutes present in the water. The dominant salt in

water from Mphizi and Kumpalira 1 hot spring is halite, while water from Tambala is

dominated by halite and burkeite. Water from Namitukuta hot spring is dominated by

trona and burkeite. All the salts formed have Na+ as the cation since it is the only cation

present in high concentration. The chemical analyses of the salt evaporite from hot spring

water samples show that the quality of water from all the four hot springs is poor for

irrigation purposes due to the high SAR. Water with a high SAR if used for irrigation

poses a severe risk of reduction in rate of infiltration due to dispersion of surface soil

aggregates to much smaller particles which clog soil pores. In addition to the high SAR,

the water from Mphizi, Namitukuta and Kumpalira 1 have Na+ concentration above the

required limit (40 ppm) for irrigation water. Furthermore, Mphizi hot spring water has K+

and Cl- concentrations above the limits, 2 and 143 ppm respectively, required for

irrigation water. High concentrations of Na+ and Cl

- in the soil solution may depress

nutrient-ion activities and produce extreme ratios of Na+/Ca

2+, Na

+/K

+, Ca

2+/Mg

2+ and

Cl-/NO3

-. Chemical analysis of the ground water revealed that the water is not saline or

sodic. Therefore, salinity/sodicity problems due to ground water is not developed now at

Malemia 2. The chemical analyses of the soil samples indicate that the soil from Malemia

2 area is not saline/sodic. Furthermore, there is no evidence to suggest that there is a

ii

difference in salt accumulation along different slope positions due to use of water from

the hot spring for irrigation. The water from all the hot springs is not suitable for drinking

purposes due to the high content of F-, which is above the recommended maximum limit

in drinking water according to World Health Organization (WHO) and Malawi Bureau of

Standard (MBS) standards. However, the water can be used for other domestic purposes

like washing and bathing. Use of water with high concentration of F- causes dental and

skeletal fluorosis. The water can safely be used for drinking purposes if defluoridation

can be done.

iii

Dedication

I dedicate this thesis to my father, mother, grandfather, brothers (James, Albert, Lyton

and Wisdom), sisters (Hellena, Tinenenji, Martha and Regina), my wife (Gladys) and my

children (Jessica and Edward). I really appreciate your patience and support during the

period of my studies.

iv

Acknowledgements

I would like to thank the following institutions and individuals whom without their help

and support, the successful completion of my study would not have been possible:

The Government of Malawi, particularly the Ministry of Agriculture and Food Security,

for allowing me leave to study outside my country. Ghent University for the financial

support they gave me for the whole period of my study. Without this help it would not

have been possible for me to come all the way from Malawi and study at Ghent

University (Belgium).

I would like to thank Prof. Dr. Eric Van Ranst for his successful supervision of the

research and subsequent write-up of the thesis. I am so grateful for the advice and timely

help he offered. Many thanks to all the Professors, assistants and laboratory technicians

who were involved in one way or another, in the conduct of the course. Special thanks to

the staff in the Laboratory of Soil Science, Ms Nicole Vindevogel and Ms Veerle

Vandenhende, who helped in a way to the success of this work. I would like to especially

thank Johan Van de Wauw for his immense suggestions and ideas which are of valuable

help in furnishing the output of this thesis.

I wish to extend my sincere gratitude to Ministry of Agriculture staff from Rumphi,

Nkhotakota, Machinga and Zomba Districts for helping in locating the hot springs.

Special thanks to Mr Anderson Kawejere (Chief Land Resources Conservation Officer)

and Mr James Msangaambe (Land Resources Conservation Officer) from Machinga

Agricultural Development Division and Mr James Kanyangalazi (District Commissioner)

from Machinga District Assembly for assisting in soil sample collection.

Lastly, I thank God for enabling me complete my study successfully.

v

Table of contents

Summary ................................................................................................................................. i

Dedication ............................................................................................................................. iii

Acknowledgements .............................................................................................................. iv

Table of contents ................................................................................................................... v

List of Figures ...................................................................................................................... vii

List of Tables ........................................................................................................................ ix

Abbreviations and acronyms ............................................................................................... x

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

1.1 Background of the study and problem statement ...................................................... 1

1.2 Research significance ................................................................................................ 3

1.3 Objectives ................................................................................................................. 3

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

2.1 Characteristics of hot spring water ........................................................................... 5

2.2 Characteristics of irrigation water ............................................................................. 6

2.3 Effects of low quality irrigation water ...................................................................... 9

2.4 Safe drinking water ................................................................................................. 13

2.4 Relationship between slope position and soil properties ........................................ 16

3 MATERIALS AND METHODS .................................................................................... 18

3.1 Environmental setting of the study area.................................................................. 18

3.1.1 Location and climate ........................................................................................ 18

3.1.2 Geomorphology and geology ........................................................................... 20

3.2 Socio-economic information ................................................................................... 25

3.3 Field sampling ......................................................................................................... 28

3.4 Chemical and physical characterization.................................................................. 29

3.4.1 Physico-chemical analyses of soil and water ................................................... 29

3.4.2 Mineralogical analysis ..................................................................................... 31

4. RESULTS ........................................................................................................................ 32

4.1 Soil morphology and physical properties ............................................................... 32

4.2 Soil chemical properties .......................................................................................... 34

4.3 Mineralogical characteristics .................................................................................. 37

4.3.1 Mineralogy of the clay fraction of the soil and ground water sediment .......... 37

4.3.2 Mineralogy of the salts from hot spring water ................................................. 42

vi

4.4 Chemical composition of water samples ................................................................ 45

4.4.1 Groundwater from P3 ...................................................................................... 45

4.4.2 Water from hot springs .................................................................................... 45

5 DISCUSSION ................................................................................................................... 49

5.1 Characterization of dissolved salts.......................................................................... 49

5.2 Irrigation water quality ........................................................................................... 51

5.2.1 Salinity and sodium hazard .............................................................................. 51

5.2.2 Soil structure deterioration and infiltration ...................................................... 52

5.2.3 Specific ion toxicity ......................................................................................... 53

5.2.4 Irrigation at Malemia 2 .................................................................................... 54

5.2.5 Soil properties along the toposequence ............................................................ 55

5.3 Drinking water quality ............................................................................................ 56

6 GENERAL CONCLUSIONS ......................................................................................... 59

7 SUGGESTIONS FOR FURTHER RESEARCH .......................................................... 61

8 RFERENCES ................................................................................................................... 62

vii

List of Figures

Figure 1: Diagram of sodium adsorption ratio (SAR) and electrical conductivity (EC) for

the classification of water for irrigation purposes (Richards, 1954) .................. 9

Figure 2: Relative rate of water infiltration as affected by salinity and sodium adsorption

ratio (Ayers and Westcot, 1985) ....................................................................... 13

Figure 3: Location of sampled hot springs ....................................................................... 18

Figure 4: Rainfall distribution in Malawi (Source: Malawi Government, 2006) ............. 19

Figure 5: Climatic characteristics of Makoka Research Station, Zomba (Source: Malawi

Government, 2009) ........................................................................................... 20

Figure 6: General geology of Malawi (a) and major physiographic zones of Malawi (b)

(Source: Chilton and Smith-Carington, 1984) ................................................. 22

Figure 7: Villagers washing at Tambala (a) and Namitukuta (b), and villagers bathing at

Tambala (c) and Kumpalira 1 (d) ..................................................................... 27

Figure 8: Canal from hot spring to the dam (a), dam for storing water (b), fish pond (c)

and land prepared to be planted at Malemia 2 in Zomba district (d) ............... 28

Figure 9: Sketch of the toposequence showing the position of the hot spring, profiles and

elevation (meters above sea level) at Malemia 2 ............................................. 29

Figure 10: XRD patterns of the clay fraction of groundwater sediment from Profile 3; d-

values are in nm ................................................................................................ 37

Figure 11: XRD patterns of the clay fraction of Profile 1 (a) Na+-saturated for all

horizons and (b) Na+-saturated and Na

++glycol-saturated for horizon 25-50 cm;

d-values are in nm ............................................................................................ 38

Figure 12: XRD patterns of the clay fraction of Profile 2 (a) Na+-saturated for all

horizons and (b) Na+-saturated and Na

++glycol-saturated for horizon 25-50 cm;

d-values are in nm ............................................................................................ 39

Figure 13: XRD patterns of the clay fraction of Profile 3 (a) from 0-25 cm and (b) 25-50

cm; d-values are in nm ..................................................................................... 40

Figure 14: XRD patterns of the clay fraction of Profile 3 (a) from 50-75 cm and (b) 75-

100 cm; d-values are in nm .............................................................................. 41

Figure 15: XRD pattern of the salts from Mphizi hot spring water; d-values are in nm .. 42

Figure 16: XRD pattern of the salts from Tambala hot spring water; d-values are in nm 43

Figure 17: XRD pattern of the salts from Kumpalira 1 hot spring water; d-values are in

nm ..................................................................................................................... 43

Figure 18: XRD pattern of the salts from Namitukuta hot spring water; d-values are in nm

........................................................................................................................................... 44

Figure 19: Calculated percentages of ionic species concentration in Namitukuta,

Tambala, Kumpalira 1 and Mphizi hot spring water ........................................ 48

viii

Figure 20: Divisions for relative salt tolerance ratings of agricultural crops (Maas, 1984

as quoted by Ayers and Westcot, 1985) ........................................................... 55

ix

List of Tables

Table 1: Sodium hazard (permeability) guidelines of irrigation water based on SARw

(Richards, 1954; Carrow et al., 2001) ................................................................. 7

Table 2: Irrigation water classification guidelines based on ECw and TDS according to

Ayers and Westcot, and USSL (Carrow et al., 2001) .......................................... 9

Table 3: Classification of salt-affected soils (Horneck et al., 2007) ................................ 10

Table 4: Crop tolerance threshold values to irrigation water salinity (ECw) or soil salinity

(ECe) (adapted from Ayers and Westcot, 1985) ................................................ 11

Table 5: Quality guidelines for drinking water according to WHO (2008) and MBS

(2005) ................................................................................................................. 15

Table 6: Morphological and physical characteristics of the soils from Malemia 2 area .. 33

Table 7: Chemical characteristics of the soil solution extract (1:5) from Malemia 2 area 35

Table 8: Chemical characteristics of the soil from Malemia 2 area ................................. 36

Table 9: Salts present in hot spring water ......................................................................... 44

Table 10: Chemical characteristics of ground water from P3........................................... 45

Table 11: Chemical composition of water from hot springs............................................. 47

Table 12: Water quality classification based on EC according to Ayers and Westcot

(1985) and Richards (1954) ............................................................................... 52

x

Abbreviations and acronyms

µm micrometer

AAS Atomic Absorption Spectroscopy

CEC Cation Exchange Capacity

EC Electrical Conductivity

ECe Electrical Conductivity of saturation extract

ECw Electrical Conductivity of irrigation water

ESP Exchangeable Sodium Percentage

ETo Potential Evapotranspiration (reference)

FAO Food and Agricultural Organization (United Nations)

GDP Gross Domestic Product

Hg Mercury

masl meter above sea level

MBS Malawi Bureau of Standards

MDGs Millennium Development Goals

MPRS Malawi Poverty Reduction Strategy

nm nanometer

NSO National Statistical Office

ppm parts per million

SAR Sodium Adsorption Ratio

SARw Sodium Adsorption Ratio of irrigation water

SEM Scanning Electron Microscopy

TDS Total Dissolved Salts

UN United Nations

USDA United States Department of Agriculture

USSL United States Salinity Laboratory

UTM Universal Transverse Mercator

WHO World Health Organization

XRD X-Ray Diffraction

1

1 INTRODUCTION

1.1 Background of the study and problem statement

Population growth and economic development are driving significant increases in

agricultural and industrial demand for water. Agriculture accounts for more than two-

thirds of global water use, including 90% in developing countries (Morrison et al., 2009).

Due to climate change, there is increased water demand for agriculture, primarily for

irrigation, as a result of prolonged dry periods and severe drought. Rising water demand

coupled with lack of adequate sanitation facilities is a key reason to why almost 1.1

billion people worldwide lack access to safe drinking water (WHO, 2006a). Inadequate

water supply and sanitation remain one of the major challenges in the developing

countries (Njalam‟mano, 2007). In Sub-Saharan Africa, 42% of the population is still

without improved water sources (WHO, 2004) and over the period 1990-2004, the

number of people without access to safe drinking water increased by 23% (WHO,

2006a).

Irrigation has for a long time played a key role in feeding the expanding world population

and is still expected to play this greater role in the future. Although only approximately

17% of the world‟s crop land is irrigated, it produces more than a third of the food and

fiber harvested throughout the world (Hillel, 2000). It is a fact that irrigated agriculture

brings some benefits to the farmers as well as to the entire nation. However, it can bring

undesirable effects if not practiced sustainably. The most critical aspect for the success of

irrigated agriculture is the use and management of water in the irrigation schemes

(Mulwafu and Nkhoma, 2002). The major problem of irrigated agriculture is salinization

resulting from the application of irrigation water without proper management to control

salt accumulation.

Salinization is the accumulation of water-soluble salts in the soil solum or regolith to a

level that impacts on agricultural production, environmental health and economic welfare

(Rengasamy, 2006). Salinity can occur naturally (primary salinity) or due to human

activities such as land clearing and over-irrigation (secondary salinity). It is estimated

that salt affected soils occupy 20% of irrigated land (Qadir and Oster, 2004) and globally

2

955 million ha of land are affected by salts (Pessarakli and Szabolcs, 1999). Increased

salinity in the root zone leads to decreased agricultural production from non-salt tolerant

cropping and pasture systems (Richardson and Narayan, 1995).

Malawi with a total population of 13,066,320 (NSO, 2008), relies heavily on agriculture

as this sector contributes about 34% of the country‟s GDP and employs about 81% of the

labour force (NSO, 2005). It also generates 90% of export earnings (FAO, 2000). The

relative importance of agriculture in Malawi‟s economy is further illustrated by the

amount of land under estate and customary tenure (7.43 million ha out of the total 9.4

million), the balance being occupied by protected areas, cities and other urban areas (Orr

et al., 1998). Almost 80% of total food production comes from smallholder farmers

(Malawi Government, 2008) most of whom rely on single harvest of maize for

consumption, but have a chronic lack of access to seed and fertilizer.

Agricultural development in the country has for a long time relied on rain fed farming.

Almost 95% of precipitation occurs during the warm–wet season between November and

April over most parts of the country. Recent droughts have adversely affected agricultural

production worsening the plight of the smallholder and affecting the economy as a whole.

Since there are limited opportunities under rain fed agriculture to produce sufficient food

at household and national levels, rain fed crop production has been supplemented through

irrigation. In countries with erratic or inadequate rainfall, irrigation provides the surest

and most efficient way of providing water for agricultural production (Mulwafu and

Nkhoma, 2002).

Access to safe drinking water is one of the Millennium Development Goals (MDGs) and

Malawi Poverty Reduction Strategy (MPRS) targets. It is estimated that 66.4% of

households in Malawi has access to safe-drinking water (NSO, 2005). The above estimate

assumes that all existing facilities are working but it may go as low as 40% due to non-

functionality of the facilities (Mkandawire, 2008).

In most parts of the country, water is a problem during the dry season as most of the

streams and shallow wells dry up. Malawi, as all countries located in the Great African

Rift Valley, has many hot springs spread across the country. Hot spring water usually

3

shows high concentrations of many elements and can be highly supersaturated with

respect to a variety of minerals (Fernandez-Turiel et al., 2005). Prolonged exposure to

such elements can bring adverse health effects to humans. One such element which is

usually in high concentration in hot spring water is fluoride which causes dental and

skeletal fluorosis (WHO, 2008).

With climate change, some sources of water which people rely on for irrigation and

domestic purposes, like rivers, boreholes and shallow wells dry up quickly after the rain

season ends. People are then forced to turn to other sources of water for irrigation as well

as domestic purposes. As of now, no known studies have been conducted in Malawi to

evaluate the suitability of hot spring water for irrigation or domestic use. It is against this

background that this study was conducted to assess the quality of hot spring water from

selected hot springs in Malawi.

1.2 Research significance

The chemical quality of groundwater in Malawi has been little documented (Water Aid,

2004). Knowing the characteristics of the hot spring water will provide some information

on the chemical quality of the ground water resources in Malawi. This will in turn assist

in assessing the suitability of the water for various purposes. Various government

ministries, departments and institutions will use the information for various programmes.

For instance the information will help the Ministries of Irrigation and Water

Development and Agriculture and Food Security in devising ways on how the irrigated

land can be sustainably managed. In addition, the Ministry of Health can use the

information to assess the effects of using hot spring water for drinking on the health of

the people.

1.3 Objectives

The overall objective of this study is to determine the suitability of hot spring water in

Malawi for irrigation and domestic purposes.

The specific objectives are:

1. to characterize the salts dissolved in different hot spring water in Malawi;

4

2. to assess the quality of hot spring water for irrigation and for domestic

purposes; and

3. to evaluate effect of toposequence position on salt concentration in the soil

due to irrigation using hot spring water.

The major question addressed in this study is: “Is the water of the selected hot springs

suitable for irrigation and domestic purposes?”

5

2 LITERATURE REVIEW

2.1 Characteristics of hot spring water

Hot springs are the surface manifestation of a large hydrothermal system. Numerous

thermal and cold springs are located in active volcanic regions all over the world, as a

result of eruptive events, as well as obvious manifestation of long-lived hydrothermal

system (Shakeri et al., 2008). Hot springs are also present in places with rift tectonic

activities. The East African Rift Valley is characterized by hot springs due to its special

geological conditions. The active rift appears to be ideal for evaporite formation because

these systems are often associated with geothermal anomalies that drive the convection of

hot brines (Ingebritsen et al., 2006).

Groundwater use is superior to surface water as it serves as a naturally occurring

reservoir less susceptible to evaporation losses, climate variability and anthropogenic

activities (Mor et al., 2009). However, groundwater from hot springs usually show high

concentrations of many elements and can be highly supersaturated with respect to a

variety of minerals (Fernandes-Turiel et al, 2005). The hot springs have various

compositions of salts usually encountered in inland salt accumulations. Some of the salts

usually encountered in hot spring water are thernadite (Na2SO4), kogarkoite (Na3SO4F),

trona (Na3H(CO3)2(H2O)2), thermonatrite (Na2CO3H2O), halite (NaCl), calcite (CaCO3),

pirsonnite (Na2Ca(CO3)22H2O) and natron (Na2CO3). Most of the mentioned salts are

found in different lakes which get all or part of their water from hot springs surrounding

these lakes. Such lakes as Pilkrolimni in Greece and Deep Springs Lake in California

(Dotsika et al., 2009); Natron in Tanzania, Magadi in Kenya and Katwe in Uganda

(Nielsen, 1999); and Otjivalunda East Pan in Northern Namibia (Mees, 2001). Other

places include Wadi Natrun in Egypt (Shortland, 2004; Shortland et al., 2006); El-Atrun

in Sudan (Nielsen, 1999); Choma District in Southern Province of Zambia (Van Ranst et

al., 2007); and Mt. Princeton Hot Springs along Chalk Creek in Chaffee County (Pabst

and Sharp, 1973).

6

Extensive occurrences of trona have been reported in lakes in East African countries of

Kenya, Tanzania, Uganda and Sudan and in these countries it is locally called magadi1

(Nanyaro et al., 1984; Nielsen, 1999; Nielsen and Dahi, 2002). In East, Central and West

African countries, trona is used as a tenderizer (for softening foods such as cowpeas,

meat, and bones), as a flavoring agent, and as a food preservative (Sodipo, 1993; Nielsen

and Dahi, 2002).

The suite of minerals to precipitate during the evaporation of a brine depends primarily

on its chemical composition (i.e., the ionic ratios of the solutes), which in turn depends

on the solutes supplied by the source water (Ingebritsen et al., 2006; Li et al., 2010).

Generally, regardless of water type, the sequence of minerals to precipitate is carbonates,

sulfates, and finally chlorides (Warren, 1989 as quoted by Li et al., 2010). Weathering

reactions on volcaniclastic sediments are typically invoked as the precondition for trona

deposition, because of the low ratio of Ca2+

to CO32-

(Earman et al., 2005).

2.2 Characteristics of irrigation water

The chemical characteristics of water govern its suitability for various activities, such as

domestic, irrigation and industrial use. Water quality refers to the characteristics of a

water supply that will influence its suitability for a specific use, i.e. how well the quality

meets the needs of the user. Water quality depends strongly on the water-rock interaction

processes and of course also on the anthropic activities (Fontana et al., 2009). Water

quality is determined according to the purpose for which it will be used and is assessed

using various physical, chemical and biological characteristics. Using water of low

quality for a specific purpose can bring adverse health or environmental effects.

Irrigation water contains relatively small but significant amounts of salts. These salts

originate from dissolution or weathering of the rocks and soil, including dissolution of

lime, gypsum and other slowly dissolved soil minerals. The most common cations in

water are sodium (Na+), magnesium (Mg

2+) and calcium (Ca

2+) and the anions are

chloride (Cl-), sulfate (SO4

2-), and bicarbonate (HCO3

-) (Grattan and Grieve, 1999).

1 The name magadi probably originated from the Masai word magad meaning bitter (Nielsen, 1999).

7

Potassium (K+), carbonate (CO3

2-) and nitrate (NO3

-) all exist in water supplies but

concentrations of these constituents are comparatively low.

According to Richards (1954), the characteristics of irrigation water that appear to be

most important in determining its quality are: (1) Total concentration of soluble salts; (2)

relative proportion of sodium to other cations; (3) concentration of boron or other

elements that may be toxic; and (4) under some conditions, the bicarbonate concentration

as related to the concentration of calcium plus magnesium. There are a number of

guidelines used to assess the quality of irrigation water under different conditions.

However, the most commonly used methods take into account the electrical conductivity

(EC) and sodium adsorption ratio (SAR) (Tables 1 and 2, and Figure 1). Salinity and

sodicity are the principal water quality concerns in irrigated areas of arid and semi-arid

regions using poor water quality for irrigation (Jalali, 2007). According to Wilcox

classification diagram for classification of irrigation water (Richards, 1954), the water

falling in the left bottom corner is of good quality and the quality decreases as one moves

towards the right top corner (Figure 1).

Table 1: Sodium hazard (permeability) guidelines of irrigation water based on SARw

(Richards, 1954; Carrow et al., 2001)

Na+ hazard

classification SARw Comments on Na

+ hazard

Low <10 Can be used to irrigate almost all soils without structure

deterioration. Na+ sensitive plants may be affected.

Medium 10–18 Appreciable Na+ permeability hazard on fine-textured soils

with high CEC. Best used on coarse-textured soils with

good drainage.

High 18–26 Harmful levels of Na+ accumulation on most soils. Will

require intensive management, drainage, leaching.

Very high >26 Generally not suitable for irrigation except at low to

medium soil salinity levels. Requires intensive

management.

Table 2: Irrigation water classification guidelines based on ECw and TDS according to Ayers and Westcot, and USSL (Carrow

et al., 2001)

Salinity

Hazard

Comments

Ayers and Westcot USSL

ECw

(dS m-1

)

TDS

(ppm)

ECw

(dS m-1

)

TDS

(ppm)

Low Low salinity hazard, no detrimental effects on

plants or soil build up are expected.

<0.75 <500 <0.25 <160

Medium Sensitive plants may show salt stress; moderate

leaching prevents soil salt accumulation.

0.75–1.50 500-1000 0.25–0.75 160-500

High Salinity will adversely affect most plants. Requires

selection of salt tolerant plants, careful irrigation,

good drainage and leaching. Salt amendments such

as gypsum may be necessary.

1.50–3.00 1000-2000 0.75–2.25 500-1500

Very

high

Generally unacceptable except for very salt tolerant

plants, good drainage, frequent leaching and use of

amendments.

˃3.00 ˃2000 ˃2.25 ˃1500

8

9

Figure 1: Diagram of sodium adsorption ratio (SAR) and electrical conductivity (EC) for

the classification of water for irrigation purposes (Richards, 1954)

2.3 Effects of low quality irrigation water

Accumulation of salts and Na+ in salt-affected soils originates either through the

weathering of parent minerals (causing fossil or primary salinity/sodicity) (Qadir and

Oster, 2004), or from anthropogenic activities involving the inappropriate management of

land and waters (contributing to management or secondary salinity/sodicity) (Qadir and

Oster, 2004; Luedeling et al., 2005). The main cause of secondary salinization in arid

10

regions is irrigation with saline waters (Szabolcs, 1994 as quoted by Crescimanno and

Garofalo, 2006). Salts accumulate in the root zone by two processes: the upward

movement of a shallow saline water table and salts left in the soil due to insufficient

leaching. Soil salinity is a major problem in all the countries where climate is arid to

semi-arid and where the average rainfall is less than the evapotranspiration (Javed, 2003).

Irrigated agriculture in semi-arid and arid areas should take into account the risk of

progressive salinization of soils due to solute accumulation from irrigation water (Jalali,

2007). To avoid accumulation of salts in the root zone, excess irrigation water must be

applied to leach the salts out of the root zone (Beltrẚn, 1999; Bouwer, 2000). Jalali (2007)

believes that an understanding of the quality of water used for irrigation and its potential

negative impacts on crop growth is essential to avoid problems and to minimize

production.

The composition of the saturation extract is used to classify soils into normal, saline,

sodic and saline-sodic categories. The major criteria used to classify salt-affected soils

are:

the salinity of the saturation extract as measured by the ECe at 25°C; and

the exchangeable sodium percentage (ESP) and the SAR.

The limits for the various classes of salts in terms of EC, ESP and SAR are given in Table

3.

Table 3: Classification of salt-affected soils (Horneck et al., 2007)

Criteria Normal (non-

saline/non-sodic) Saline Sodic

Saline-

Sodic

EC (mS cm-1

) < 4 > 4 < 4 > 4

SAR < 13 < 13 > 13 > 13

ESP < 15 < 15 > 15 > 15

11

A soil is considered saline if the electrical conductivity of its saturation extract (ECe)

is

above 4 dS m–1

. However, the threshold value above which deleterious effects occur can

vary depending on several factors including plant type, soil-water regime and climatic

conditions (Maas, 1986). Different crops have different threshold level of salinity (i.e. the

maximum salinity above which yield reduction occurs). Even when salts are below the

threshold values as listed in Table 4, some crop yield or quality loss may occur if the

plants are stressed by other factors like drought, extreme weather and herbicides

(Horneck et al., 2007).

Irrigation with waters that have high concentrations of Na+ relative to divalent cations

may cause an accumulation of exchangeable Na+ on soil colloids (Jalali and Merrikhpour,

2008). The detrimental effect of adsorbed sodium on the physical properties of soils

results in low water infiltration rate, low permeability to water and gases, increase of

osmotic pressure of the soil, and poor soil structure. Excessive sodium in irrigation water

promotes soil dispersion and structural breakdown only if sodium exceeds calcium by

Table 4: Crop tolerance threshold values to irrigation water salinity (ECw) or soil salinity

(ECe) (adapted from Ayers and Westcot, 1985)

Crop ECe ECw

(dS m

-1)

Sugarcane (Saccharum officinarum) 1.7 1.1

Corn (maize) (Zea mays) 1.7 1.1

Bean (Phaseolus vulgaris) 1.0 0.7

Tomato (Lycopersicon esculentum) 2.5 1.7

Spinach (Spinacia oleracea) 2.0 1.3

Cabbage (Brassica oleracea capitata) 1.8 1.2

Potato (Solanum tuberosum) 1.7 1.1

Sweet potato (Ipomoea batatas) 1.5 1.0

Pepper (Capsicum annuum) 1.5 1.0

Lettuce (Lactuca sativa) 1.3 0.9

Onion (Allium cepa) 1.2 0.8

12

more than a ratio of about 3:1 (Ayers and Westcot, 1985). Another factor affecting rate of

infiltration is irrigation with low salinity water. Very low salinity water with relatively

high proportions of Na+ salts adversely affects permeability (Rhoads et al., 1992). In

addition, low salinity water (less than 0.5 dS m-1

and especially below 0.2 dS m-1

) is

corrosive and tends to leach surface soils free of soluble minerals and salts, especially

calcium, reducing their strong stabilizing influence on soil aggregates and soil structure

(Ayers and Westcot, 1985). This is due to lack of sufficient calcium to counter the

dispersing effects of the sodium. Without salts and without calcium, the soil disperses

and the dispersed finer soil particles fill many of the smaller pore spaces, sealing the

surface and greatly reducing the rate at which water infiltrates the soil surface. Other

problems such as lack of aeration and soil crusting may appear, in addition to a reduction

in the amount of water that will enter the soil in a given amount of time and which may

ultimately cause water stress between irrigations. Very low salinity water (less than ECw

= 0.2 dS m-1

) almost invariably results in water infiltration problems, regardless of the

relative sodium adsorption ratio (Figure 2). The low salt water dissolves and leaches most

of the soluble minerals, including calcium, from the surface soil (Ayers and Westcot,

1985).

A number of studies have been conducted in various places to evaluate the impact of

using saline-sodic water for irrigation. Mandal et al. (2008) found that over the years, a

substantial decrease in the yield of irrigated crops has been noted in the Bet She‟an

Valley. The decrease was ascribed partly to deterioration in soil structure and its

hydraulic properties caused by the high sodicity and salinity of the irrigation water. Jamil

et al. (2006) conducted an experiment of salt stress on germination and early seedling

growth of four vegetables species namely sugar beet (Beta vulgaris), cabbage (Brassica

oleracea capitata L.), amaranth (Amaranthus paniculatus) and pak-choi (Brassica

compestris). Results indicated that salinity caused significant reduction in germination

percentage, germination rate, root and shoot lengths and fresh root and shoot weights in

all the four vegetables.

13

Figure 2: Relative rate of water infiltration as affected by salinity and sodium adsorption

ratio (Ayers and Westcot, 1985)

2.4 Safe drinking water

Access to safe drinking-water is important as a health and development issue at

international as well as national levels. That is why it has been reflected in the outcomes

of a series of international policy forums. Such conferences include the 1977 World

Water Conference in Mar del Plata, Argentina, which launched the water supply and

sanitation decade of 1981–1990, as well as the Millennium Development Goals (MDGs)

adopted by the General Assembly of the United Nations (UN) in 2000 and the outcome

of the Johannesburg World Summit for Sustainable Development in 2002 (WHO, 2008).

14

At national level the Malawi government has put this issue as one of its priority areas as

evidenced by its inclusion in the Malawi Poverty Reduction Strategy (MPRS) targets.

Water of poor quality can cause social and economic damages through water related

epidemics such as cholera which in turn increases medical treatment costs (Pritchard et

al., 2007). Safe-drinking water is the water that does not represent any significant risk to

health over a lifetime of consumption, including different sensitivities that may occur

between life stages (WHO, 2008). The water should also be clear, non-saline, and free

from compounds that can cause colour, taste and odour (Pritchard et al., 2007). Safe-

drinking water is suitable for all usual domestic purposes, including personal hygiene

(WHO, 2008).

At international level, the World Health Organization (WHO) has developed guidelines

for safe-drinking water. At national as well as at local level, guidelines for safe-drinking

water are also provided by some national or local institutions. For instance, in Malawi,

the Malawi Bureau of Standards (MBS) and the Ministry of Irrigation and Water

Development provides the standard guidelines for safe drinking water. Table 5 below

gives the limits for some of the parameters for drinking water according to WHO

guidelines (WHO, 2008) and also those for Malawi Bureau of Standards (MBS, 2005).

A number of chemical contaminants have been shown to cause adverse health effects in

humans as a consequence of prolonged exposure through drinking water. One of the

elements of major health concern found in high concentration is fluoride (F-). A high

concentration of F- in drinking water causes dental and skeletal fluorosis in humans as

well as animals. Over 26 million people in China suffer from dental fluorosis due to

elevated F- in their drinking water (WHO, 2004). In a study to investigate the high

incidence of mottled teeth of residents of Choma District in Southern Province of

Zambia, Shitumbanuma et al. (2007) found that all pupils who drank water from hot

springs during the period of formation of their permanent teeth had clinical symptoms

associated with dental fluorosis. In a study on endemic fluorosis in domestic animals in

Southern Rajasthan (India), Choubisa (1999) found that at a F- concentration in the water

of 4.0 ppm, 100% of calves, 65.6% of buffaloes and 61.0% of cattle were found to be

affected with dental fluorosis to varying degrees.

15

Table 5: Quality guidelines for drinking water according to WHO (2008) and MBS

(2005)

Water parameter WHO MBS

pH 6.5-9.2 6.5-8.5

Na+ (ppm) 200 200

K+(ppm) 200 -

Mg2+

(ppm) 50 150

Ca2+

(ppm) 105 200

F- (ppm) 1.5 2.0

Cl- (ppm) 250 600

SO42-

(ppm) 200 400

CO32-

(ppm)

75 -

HCO3- (ppm)

150 -

NO3- (ppm) 50 10

The most important source of F- is groundwater and the secondary sources are related to

pollution from industries (ceramic factories, coal burning) and agricultural activities,

particularly the use of phosphatic fertilizers (Tekle-Haimanot, 2006). The concentration

of F- in groundwater is varied and it depends in the geological formations traversed by

water, temperature, pH, solubility of F- bearing minerals and the presence or absence of

other precipitating or complexing ions (Parkhurst et al., 1996). A very high

F- concentration in the groundwater is a very acute problem in the countries along the

African Rift Valley System. In Tanzania, Mjengera and Mkongo (2003) found that F- in

drinking water exceeds WHO guidelines of 1.5 ppm in some of the groundwater supplies

in most parts of the North East of the country. Groundwater from Shinyanga area in

Tanzania has F- content in the range of 110-250 ppm. This high F

- content is attributed to

some geological processes such as volcanic activities, thermal springs and presence of

minerals such as fluorite and apatite (Mjengera and Mkongo, 2003). In a study of

F- distribution in Ethiopia, Tekle-Haimanot et al. (2006) found that 90% of water from

the 232 hot springs they sampled had F- concentration exceeding 1.5 ppm. Shitumbanuma

et al. (2007) found F- concentrations in water from hot springs in Choma District in

16

Zambia to range from 5.95 to 10.09 ppm. Water with high F- can be made suitable for

drinking if excess F- is removed. A number of defluoridation techniques exist. However,

due to various reasons, the method that can work in one community may not work in

another community (WHO, 2006b).

Exposure to high concentrations of NO3- in drinking water is related to

methemoglobinemia or blue baby syndrome. Infants are particularly susceptible to the

condition during their first six months of life because they have low amounts of

methemoglobin reductase (Knobeloch et al., 2000). NO3- can reach both surface and

groundwater as a consequence of agricultural activities (including excess application of

inorganic nitrogenous fertilizers and manures), from wastewater treatment and from

oxidation of nitrogenous waste products in human and animal excreta, including septic

tanks (WHO, 2007).

The other element of health concern is SO42-

and it is of importance in public water

supplies due to its cathartic effect upon humans when it is present in disproportionate

amounts (Venkatesan and Swaminathan, 2009). SO42-

content of more than 200 ppm

causes gastro-intestinal irritation (Mor et al., 2009). Furthermore, high concentrations

(˃400 mg L-1

) may cause water unpleasant to drink (WHO, 1996). SO42-

may find its

way in groundwater through natural processes as well as anthropogenic processes.

Cl- toxicity has not been observed in humans except in the special case of impaired

sodium chloride metabolism, e.g. in congestive heart failure (WHO, 2003a). In many

areas of the world where water supplies are scarce, sources containing as much as 2,000

mg L-1

of Cl- are used for domestic purpose, once the human system becomes adapted to

the water (Venkatesan and Swaminathan, 2009). Healthy individuals can tolerate the

intake of large quantities of Cl- provided that there is a concomitant intake of fresh water

(WHO, 2003a). Cl- coupled with Na

+ bring to bear salty taste, when its concentration is

more than 250 mg L-1

(Venkatesan and Swaminathan, 2009).

2.4 Relationship between slope position and soil properties

The variation of soil properties is significantly influenced by factors such as climate,

topography, parent materials, vegetation, time and disturbance due to human activity

17

(Jenny, 1994). Parent material, climate and geological history are of major importance to

affect soil properties on regional and continental scale. However, landscape position and

land use may be the dominant factors influencing soil properties under a hill slope and

small catchment scale (Wang et al., 2001). Among other factors, landscape positions

influences runoff, drainage and soil erosion (Hairston and Grigal, 1994; Tsui et al., 2004;

Babalola et al., 2007) thereby controlling the distribution of water and soluble materials

from higher to lower elevation (Pennock et al., 1987).

In their study of relationship between soil properties and slope position, Wang et al.

(2001) found that soil physical properties such as clay content distribution with depth,

sand content and pH have been shown to be highly correlated with landscape position. In

Ethiopia, Wolde et al. (2007) found that upslope areas had lower nutrient concentrations

than lower areas as a result of erosion of top soil and subsequent deposition on lower

slope positions. Tsui et al. (2004) found that exchangeable Ca2+

and Mg2+

were

significantly higher on the foot slope at 0-20 cm depth soils than on the summit while the

reverse was true for available K+ and exchangeable Na

+. They attributed the higher

concentration of exchangeable Ca2+

and Mg2+

to stronger leaching from the upper slope

and deposition on the foot slope position where leaching is weaker and soil enrichment is

stronger. Other studies have found no relationship between slope position and nutrient

concentration. In spite of the leaching process, Dölarslan and Göl (2008) found that upper

slope soils contained higher Ca2+

concentration than lower slope soils due to their parent

materials which are gypsiferous rocks. Anderson (1982) found that hill slope topography

was unimportant for soil water movement on slopes of less than 10o.

18

3 MATERIALS AND METHODS

3.1 Environmental setting of the study area

3.1.1 Location and climate

Malawi lies in south-eastern Africa between latitudes 9° 22' and 17° 03' S and longitude

33° 40' and 35° 55' E. The country is divided into three major administrative regions.

Four hot springs have been sampled namely Mphizi in the Northern Region (Uzumara

area), Tambala in the Central Region (Nkhotakota-Benga area) and Kumpalira 1 and

Namitukuta in the Southern Region (Zomba area). The coordinates for Mphizi hot spring

are 0629671 (E), 8818601 (N); for Tambala 0640226 (E), 8568488 (N); for Kumpalira 1

0737978 (E), 8332972 (N); and for Namitukuta 0753573 (E), 8312720 (N). Plotting these

points on a base map with UTM projection (Arc 1950, Zone 36 S) gives the location of

the hot springs as indicated in Figure 3.

Figure 3: Location of sampled hot springs

19

Malawi has a relatively dry and strongly seasonal climate. Almost 95% of the

precipitation occurs during the warm–wet season between November and April over most

parts of the country. Annual average rainfall varies from 725 to 2,500 mm with Lilongwe

(Central Region) having an average of 900 mm, Chileka in Blantyre (Southern Region)

having 1,127 mm and Mzuzu (Northern Region) 1,289 mm (Figure 4). The mean annual

temperatures for Malawi range from 12 to 32 oC (Malawi Government, 2002). The

highest temperatures occur at the end of October or early November. The coldest months

are June and July. Humidity ranges from 50 to 87% for the drier months of

September/October and wetter months of January/February, respectively (Malawi

Government, 2006).

Figure 4: Rainfall distribution in Malawi (Source: Malawi Government, 2006)

20

Tambala hot spring is located in an area with annual rainfall between 1,401-1,600 mm;

Kumpalira 1 in an area with annual rainfall between 801-1,000 mm, while Namitukuta

and Mphizi hot springs are located in areas which receive annual rainfall between 1,201-

1,400 mm. The potential evapotranspiration of Zomba area (Namitukuta hot spring) is

1,942 mm per year as measured at Makoka Research Station (Figure 5). The length of

growing period in the area varies between 120 and 180 days (Venema, 1992).

Figure 5: Climatic characteristics of Makoka Research Station, Zomba (Source: Malawi

Government, 2009)

3.1.2 Geomorphology and geology

The sampled hot springs are located in the Malawi Rift. This Rift belongs to the Western

branch of the East African Rift system and extends over 900 km from the Rungwe

volcanic province in the North (Southern Tanzania) to the Uremba graben in the South

(Mozambique) (Ring et al., 1992).

Most parts of the country are underlain by „Basement Complex,‟ composed of

Precambrian to Lower Palaeozoic crystalline metamorphic and igneous rocks (Figure 6a).

The Precambrian of Malawi consists of various Proterozoic lithologies and structures:

0

50

100

150

200

250

Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun

Wate

r su

pp

ly/d

em

an

d (

mm

)

Time (month)

Eto/2

Eto

Rainfall

21

paragneisses, quartzites and marbles of the Neoproterozoic Mozambique Belt, rock

sequences of the Mesoproterozoic Irumide Belt, including granulite facies rocks in

Southern Malawi (Daly, 1986), and Northwest-striking rocks of the Paleoproterozoic

Ubendian Belt in Northern Malawi (Fitches, 1970; Schluter and Trauth, 2006).

Sedimentary rocks and basalts of the Permian to Jurassic Karroo System occur in the far

North and far South of the country. Several carbonatite intrusions are known from

southern and South-central Malawi. Quaternary to recent alluvial and lacustrine

sediments are found along the shores of Lake Malawi and in the Shire Valley.

Uzumara area

Uzumara area lies in the Northern region of Malawi. The Nyika, highest and most

extensive of the high altitude plateaus, is the major feature in this area and is bounded by

steep scarps on all sides (Figure 6b). The geomorphology of the area is a result of

extensive faulting which has led to the formation of the Great African Rift Valley and

expresses various stages in the break-up of the Jurassic continent by rift faulting.

Different erosion surfaces can be recognized in the area. According to Kemp (1975) and

Chilton and Smith-Carington (1984), the erosion surfaces which can be recognized in the

area are the Post Gondwana surface (early and mid-Cretaceous) with Gondwana

residuals; the African surface (late-Cretaceous to early-Miocene); the Post-African

surface (late-Miocene and Pliocene); and the Quaternary erosion and deposition surface.

The Gondwana erosion cycle was initiated by the uplift and faulting in the Jurassic times.

The major river courses draining the area date from late-Cretaceous to early-Miocene,

while the consequent rivers date from late-Pliocene to present (Kemp, 1975).

Generally, the rocks in the western and southern parts of the area are mainly gneiss and

schists of the Precambrian to Lower Palaeozoic Basement Complex. The northern and

eastern parts of the area are overlain to a large extent by sediments of the Karroo System.

These sediments are as a result of a very long period of erosion of the gneisses followed

by deposition, mainly in the Permian and Triassic times. According to the geological map

of the area, a third of the southern part is underlain by the cordierite-gneisses. In this area,

Figure 6: General geology of Malawi (a) and major physiographic zones of Malawi (b) (Source: Chilton and Smith-Carington,

1984)

(a)

(b) KEY

Quaternary alluvium

Cretaceous-Pleistocene sediments

Mesozoic Chilwa Alkaline Province

Jurassic Karoo Volcanics

Perma-Trias Karoo sediments

Precambrian-Palaeozoic Metamorphic Basement Complex

Basement Complex igneous intrusions

KEY Rift valley plains

Plateau areas

Rift valley escarpment

Highland areas

22

23

a Ubendian event comprising two main episodes of folding was preceded by widespread

migmatization in the high grade rocks, with the development of cordierite (Kemp, 1975).

These rocks range from finely-banded grey and pink gneisses to massive pinkish-brown

granitoid rocks. The dominant rocks in the northern third of the area are biotite gneisses,

some with garnet, sillimanite and hornblende. In some parts, the biotite gneisses are

intruded by alkaline granite-gneisses and a few scattered dykes of metagabbro, dolerite,

pegmatite, microgranite and microsyenite.

Uzumara area‟s altitude ranges from 474 m at the shore of Lake Malawi in the East to

2,425 m at the Eastern escarpment of the Nyika Plateau to the West. The sampled hot

spring, at an elevation of 482 m above sea level, lies within the transitional zone between

the African and post-African surface. The hot spring is located along Mphizi stream near

the mouth of North Rumphi River in the Lakeshore Escarpment. This stream flows at the

edge and parallel to Chombe hill which is part of the Livingstonia hills. At the point of

issue, the hot spring emits steam and strong sulphurous gas. The area is characterized by

sedimentary rocks of the Karroo System of Permian and Triassic age and recent

unconsolidated fluvial and colluvial sediments (Kemp, 1975; Lorkeers, 1992) surrounded

by transitional zone of tectonically-derived schists with muscovite and chlorite or biotite,

and muscovite-biotite gneisses with cataclastic textures (Kemp, 1975).

Nkhotakota-Benga area

This area is located along the western boundary of the Malawi Rift Valley in the Central

region of the country. Like the Uzumara area, much of the topography is the result of the

faulting which occurred during the Mesozoic and Tertiary eras. Notable structural

features are the predominant N-S faults. The area has two major physiographic units: the

Rift Valley fault scarp zone in the West and the Lakeshore Plain in the East. Generally,

the rocks in the Western part are part of the Malawi Basement Complex of Precambrian

to Lower Palaeozoic age are usually biotite and hornblende-bearing gneisses. The

Lakeshore Plain is underlain by Basement Complex rocks of Precambrian and Cambrian

age, consisting of mainly paragneisses, schists, igneous and metaigneous rocks (Harrison

and Chapusa, 1975; Lorkeers, 1992). These rocks are largely obscured by alluvial and

colluvial deposits believed to be of Cretaceous or Tertiary age. The rocks crop out locally

24

as a consequence of faulting which took place during Mesozoic and Tertiary eras. The

effects of two erosion cycles can be recognized namely the dissection and erosion within

the fault scarp zone which occurred in the late Miocene and Pliocene, and Quaternary

erosion along the valleys (Lister, 1967).

The elevation of the area ranges from 474 m above sea level at the shores of Lake

Malawi in the East to 1,705 m above sea level on Ntchisi Mountain to the West. The

West is characterized by deep major river gorges and short tributaries flowing down

steep-sided gullies while the East has a dendritic drainage pattern and is less incised.

Tambala hot spring is located in the Lake Shore Plain at an elevation of 483 m above sea

level. This hot spring is among four hot springs along the Chandiya stream. In this area,

hot springs are associated with the Rift Valley faulting (Harison and Chapusa, 1975).

Zomba area

Zomba area is located in the Southern Region of the country. One third of the area is

covered by outcrops of the Basement Complex paragneisses and charnockitic granulites

(Precambrian to late-Palaeozoic age), while another third of the area is underlain by the

same. The complexes are thought to have been formed by the synkinematic intrusion of

pipe-like plutons of utrabasic rock into geosynclinal metasediments which underwent

horizontal compression (Bloomfield, 1965). Rocks of the Chilwa Alkaline Province form

an East-West line of neptheline-syenite ring complexes (Chinduzi, Mongolowe, Chaone

and Chikala mountains), the great syenogranitic Zomba-Malosa massif and a number of

small agglomerate and carbonatite vents.

The central feature of the area is the Zomba-Malosa massif characterized by a more

heterogeneous mixture of syenitic and granitic rocks. Quartz-syenite rock types are more

prevalent with local patches of granitic composition. In many places, the syenites are

intersected by narrow dykes of microgranite and microsyenite. The syenites contain

varying amounts of pyroxene, hornblende and olivine. The area also has small quantities

of radioactive elements like thorium, niobium and uranium (Bloomfield, 1965).

25

The dominant structural feature in the area is the great NE-trending fault which forms the

Eastern side of the Rift Valley. The main phase of the faulting was in late Cretaceous or

early Tertiary times followed by renewed movement in the late Tertiary and the

Quaternary (Kemp, 1975). The Shire River, which connects Lake Malawi with the

Zambezi River passes through the area. The crest of the Rift Valley escarpment is the

principal watershed in the area and streams flow from this crest to the West into the Shire

River and to the East into inland Lake Chilwa.

The elevation in the Zomba area ranges from 470 m in the Shire Plain in the West and

about 680 m at the shore of Lake Chilwa in the East to 2,087 m at Zomba Mountain. The

area has several more or less distinct physiographic units most of which are separated by

escarpments or terrace-features. Well known hot springs are located in the Shire Plain,

Shire Highlands and Lake Chilwa Plain. The two sampled hot springs, Kumpalira 1 and

Namitukuta, are located in the Shire Plain and Shire Highlands, respectively.

Kumpalira 1, at an elevation of 470 m above sea level, is located along the Shire River in

the Shire Plain. According to the geological map of Zomba area, the spring occurs along

a fault zone (Bloomfield, 1965). Most parts of the Shire Plain are covered by black sandy

clay with minor outcrops of calc-silicate gneisses and granulites of Upper Jurassic to

Lower Cretaceous age. The area has also biotite-quartz-feldspar-gneiss of Precambrian

age. All the three hot springs emit bubbling water with sulphurous smell.

Namitukuta hot spring, at an elevation of 902 m above sea level, lies in the Shire

Highlands specifically below the North-Eastern side of Malosa Mountain. According to

Bloomfield (1965) this area has faults trending in the East-West direction and displaces

laterally both the syenite and the main Rift Valley fault.

3.2 Socio-economic information

The hot springs are locally known as mawira2 in Malawi. The sampled hot springs are

located in the rural areas of Malawi. About 84.7% of Malawi‟s population lives in rural

areas (NSO, 2008). Very few villages have access to tap water. The majority of the

households in villages rely on shallow wells, lakes, rivers and springs for their source of

2 Noun from verb wira meaning „boil‟.

26

water which makes them prone to water-related diseases. Reports indicate that in Malawi,

nearly 50% of all illnesses are related to water borne diseases (Kalua and Chipeta, 2005).

The 2004-05 household survey showed that about 52.4% of the population lived below

the poverty line (NSO, 2005). The majority of people in Malawi rely on farming for their

livelihood. Estimates indicate that 55% of smallholder farmers have less than 1 hectare of

cultivable land (Malawi Government, 2002). Alwang and Siegel (1999) estimated that

70% of Malawian smallholder farmers cultivate 1.0 hectare with the median area

cultivated being 0.6 hectares, and devote 70% of the land to maize, the main staple food.

These land holding sizes have now decreased tremendously due to increase in population.

These small holdings cannot adequately support many households who have an average

of 4.4 members (NSO, 2005 and 2008). To supplement to rain fed farming, more farmers

are venturing into irrigation farming. Kaluwa et al. (1997) reported that the total area of

irrigated land in Malawi is estimated at 57,040 hectares, versus 24,048 hectares in 1994.

The most commonly grown crops under irrigation include maize, rice, sugarcane and

various types of vegetables.

In the four sampled areas, water is currently being used for bathing and washing (Figure

7). At Tambala, Namitukuta and Kumpalira 1, people go to the hot springs to bath or

wash at the point of issue. However, at Mphizi people draw the water and take it home

where it is used after cooling to a reasonable temperature since the temperature is too

high for the water to be used directly at the point of issue. At Mphizi the water is also

used at one stage of processing cassava into flour used for cooking nsima3. According to

the local people, the nsima made using hot spring water is more palatable than when it is

used with water from other sources. In Malemia 2 village, the water from Namitukuta hot

spring is largely used for irrigation, although fish ponds and livestock drinking also

feature high on the uses (Figure 8). Earth canals have been constructed to direct water

from the hot spring to the dam. The dam was constructed in 2006-07 period with

assistance from the Government of Malawi and the European Union but irrigation

activities started in 2004-05 season at a smaller scale since there was no water storage

facility. There are four groups of farmers with a total of about 150 farmers who use the

3 Local name for thick porridge made from maize or cassava flour.

27

Figure 7: Villagers washing at Tambala (a) and Namitukuta (b), and villagers bathing at

Tambala (c) and Kumpalira 1 (d)

water from the hot spring to irrigate a total of 11 hectares. The major problem

encountered is loss of water due to seepage since they use earth canals to distribute the

water. The other problem is evaporation losses since the temperatures are usually high

during the dry season when water demand for crops is high. Farmers in the area grow

crops such as bananas, sugarcane, maize and various vegetables. The farmers apply

compost and farmyard manure in addition to chemical fertilizers. The plots irrigated are

located in a sloping to gently sloping land. The same pieces of land are also used for

rainfed cultivation. According to the FAO classification system, the soils in the area are

Eutric Cambisol (Venema, 1992).

28

Figure 8: Canal from hot spring to the dam (a), dam for storing water (b), fish pond (c)

and land prepared to be planted at Malemia 2 in Zomba district (d)

3.3 Field sampling

Two types of samples were collected namely: soil and water samples. Soil samples were

collected from three profiles in the field at Malemia 2 village where hot spring water is

used for irrigation. The profiles were along a transect from the hot spring to the plot on

the lowest slope position (Figure 9). Water samples were collected from four different hot

springs from different areas across the country and one water sample was collected from

underground water from profile no. 3 which is located at the lowest elevation in the

irrigated field. The profiles were dug to a depth of 100 cm and soil samples were

collected in layers of 25 cm thick from all the three profiles. The soil samples collected

were stored in black plastics bags. Before any soil analysis was conducted the soil

samples were air-dried and then crushed in a ceramic mortar and passed through a 2 mm

29

sieve in the laboratory. A water sample from profile no 3 was collected at a depth of 55

cm, which was the level of the groundwater table at the time of sampling. The samples

were collected in a plastic container and taken to the laboratory. Immediately upon arrival

in the laboratory from the field, the sample was kept cold (4°C) and in the dark. The hot

spring water samples were taken to Chitedze Research Station where they were

evaporated and only the salts were taken to Ghent University for analysis.

Figure 9: Sketch of the toposequence showing the position of the hot spring, profiles and

elevation (meters above sea level) at Malemia 2

3.4 Chemical and physical characterization

3.4.1 Physico-chemical analyses of soil and water

The routine physico-chemical analyses were carried out according to the standard

methods described in „Procedures for soil analyses‟ (Van Reeuwijk, 1987) and „Manual

for the soil chemistry and fertility laboratory‟ (Van Ranst et al., 1999). All analyses were

performed on the fine earth fraction (< 2 mm). The physical-chemical analyses were

30

carried out in the Laboratory of Soil Science at Ghent University. A brief description of

the used methods is given below. For more details, see the above mentioned references.

Particle size distribution: Texture was determined by successive sedimentation.

Percentages of particle sizes were calculated on the dry weight basis. Textural

classes were identified according to the USDA textural triangle.

pH: the pH for soil was measured in H2O in a ratio 1:2.5, and the pH of the

underground water was measured using a Chemtrix pH meter. The pH of the hot

spring water was measured using an Alpha 600 ion meter.

Temperature: temperature of the hot spring water was measured using a Hg

thermometer.

CEC and exchangeable basic cations: CEC was determined by leaching the soil

with 1M NH4OAc which was removed with 95% ethylalcohol. The total amount

of NH4+ retained by the soil was regarded as a measure of CEC and the

ammonical N was determined by direct distillation of the sample (Vapodest 3

equipment). The distillate was titrated with a 0.05M HCl solution. The

exchangeable basic cations (Ca2+

, Mg2+

, Na+ and K

+) were determined by AAS

(Varian 250) in the exchanging solution of NH4OAc. Values for both CEC and

exchangeable basic cations are expressed in cmol(+) kg-1

soil.

Ions in the water samples were measured using ion chromatography.

Some soil characteristics are derived from the analytical data:

[

] x 100

√

[

]

EC: EC for hot spring water sample was not measured and it was estimated by

using the relationship between EC and concentration of the salts. The estimated

EC was used in assessing the quality of water for irrigation.

(Carrow et al., 2001; Gabriels, 2009)

31

3.4.2 Mineralogical analysis

Mineralogical analyses were carried out on soil, sediment from groundwater and salt

samples.

The following protocol was used for soil and ground water sediment:

Destruction of carbonates and organic matter:

- the carbonates were destroyed with a solution of NaOAc, buffered at pH 5.

- the organic matter was destroyed with H2O2 (30%).

Particle size separation by successive sedimentation: the fine earth was sieved on

a 63 μm sieve for separation of the sand fraction. The clay and silt fractions were

then separated by successive sedimentation after dispersion with a solution of

Na2CO3 (2%) at pH 9.5. The clay fraction was siphoned after 8 hours and 35

minutes. Flocculation of the clay was obtained by adding NaCl. The collected

clay and silt fractions were washed with alcohol and acetone until free of

chlorides.

X-ray diffraction (XRD): XRD patterns were collected on a Philips X'PERT

SYSTEM with a PW 3710 based diffractometer (Laboratory of Soil Science),

equipped with a Cu tube anode, a secondary graphite beam monochromotor, a

proportional xenon filled detector, and a 35 position multiple sample changer. The

incident beam was automatically collimated. The irradiated length was 12 mm.

The secondary beam side comprised a 0.1 mm receiving slit, a soller slit, and a 1°

anti-scanner slit. The tube was operated at 40 kV and 30 mA, and the XRD data

were collected in a theta, 2-theta geometry from 3.00' onwards, at a step of 0.020°

2-theta, and a count time of 1 sec. per step. The clay fraction (0-2 µm) was first

used without any further treatment and was therefore Na+ saturated. XRD patterns

of powdered and oriented samples on glass slides were recorded. Glycol treated

clay samples were also run. Glycol solvation of the Mg2+

saturated samples was

carried out in vacuum with glycol vapour during 24 hours.

32

4. RESULTS

4.1 Soil morphology and physical properties

The selected morphological and physical characteristics of the three profiles from

Malemia 2 area are summarized in Table 6. In profile 1 (upper mid slope), the top soil (0-

25 cm) has a dark reddish brown (5YR 3/4) colour (dry) and the subsoil from 25-50 cm is

reddish brown (2.5YR 4/4) in colour (dry). In the lower horizon (50-75 cm) the soil is

light dark red (2.5Y 2/6) in colour (moist). In the lowest horizon (75-100 cm) the soil is

brown (7.5YR 4/4) in colour (moist). According to the USDA texture triangle, the profile

has clay loam soil texture throughout. Clay content is below 40% throughout the profile.

For profile 2 (lower mid slope), the surface horizon (0-25 cm) consists of dark brown soil

(7.5Y 3/2) in colour (dry), while the horizon from 25-50 cm is reddish brown (5YR 4/3)

in colour (dry). The last two lower horizons (50-75 and 75-100 cm) consist of dark

reddish brown soils (2.5YR 3/4 and 2.5YR 2/4). From 25-75 cm, the texture is sandy clay

loam, while the last horizon (75-100 cm) has clay loam texture. The clay content is below

40% for the whole profile. At the time of soil sampling, the water table in profile 1 and 2

was at a depth of more than 100 cm.

In profile 3 (lower slope), the horizon from 0-25 cm has a clay loam texture with dark

brown (7.5YR 3/2) colour (dry) while the horizon from 25-50 cm has clay loam texture

with a yellowish brown (10YR 5/8) colour (moist). The horizon from 50-75 cm has a

sandy clay loam texture with brown (10YR 5/3) colour (moist) and 75-100 cm horizon

has clay loam texture with pale brown (10YR 6/3) colour (moist). The clay content is

below 40% while sand content is above 40% throughout the profile.

The physical characteristics of the profiles do not differ very much along the

toposequence. In general, sand content is high in all the profiles except for horizon 50-75

cm depth of profile 1 which has a high content of silt (42%). The clay content of profile 1

and 2 is increasing with depth while there is an irregular trend in profile 3. The irregular

trend in the lower profile can be attributed to the irregular deposition of sediments from

uplands.

33

Table 6: Morphological and physical characteristics of the soils from Malemia 2 area

Depth Munsell Colour Particle size (%) Texture

(cm) code (moist)

(µm)

Class

< 2 2 - 63 63 - 2000 (USDA)

Profile no. 1 (upper mid slope)

0-25 5YR 3/4 dark reddish browna 32 31 37 CL

25-50 2.5YR 4/4 reddish browna 34 29 37 CL

50-75 2.5YR 2/6 dark red 31 42 27 CL

75-100 7.5YR 4/4 brown 35 28 37 CL

Profile no. 2 (lower mid slope)

0-25 7.5YR 3/2 dark browna 20 28 52 SCL

25-50 5YR 4/3 reddish browna 27 24 49 SCL

50-75 2.5YR 3/4 dark reddish brown 29 20 51 SCL

75-100 2.5YR 2/4 dark reddish brown 29 27 44 CL

Profile no. 3 (lower slope)

0-25 7.5YR 3/2 dark browna 32 27 41 CL

25-50 10YR 5/8 yellowish brown 37 18 45 CL

50-75 10YR 5/3 brown 28 20 51 SCL

75-100 10YR 6/3 pale brown 36 20 44 CL

aColour dry

C = Clay

CL = Clay loam

SL = Sandy loam

SCL = Sandy clay loam

34

4.2 Soil chemical properties

Different chemical characteristics were determined in solution extracts (1:5) from all the

samples from all the three profiles. The results of the analyses are summarized in Table 7.

The soils are slightly acidic to neutral with pHwater ranging from 6.39 to 7.12. In general,

the pH is increasing with depth in all the horizons. The SO42-

content concentration is

generally lower in profile 3 compared to profile 1 and 2. Profile 1 and 3 show higher

concentration of Cl- in the surface horizon compared to the subsurface horizons. The

concentrations of Na+, Cl

- and F

- are generally higher in all the profiles compared to other

ions with Na+ being lower in the surface horizon than in the subsurface horizon. The

other chemical parameters show an irregular trend in concentration of the ions within the

profiles and across the different slope positions. The highest sodium adsorption ratio

(SAR) is 3.6 mmol L-1

, while the lowest is 1.8 mmol L-1

.

Exchangeable cations were determined on the soil samples from all the three profiles

from Malemia 2 area and the results of the analysis are presented in Table 8. In general,

the base saturation is higher in profile 3 compared to the other two profiles from mid

slope position. Base saturation of over 100% is calculated for the sample at 75-100 cm

depth (103%) of profile 3. The CEC is also relatively high (25.44-32.53 cmolc kg-1

) in

profile 3 compared to the other two profiles (15.59-26.41 cmolc kg-1

). Exchangeable

Sodium Percentage (ESP) is very low in all the soil profiles with the highest value being

3.1% for the 50-75 cm horizon of profile 1 and the lowest being 0.5% for the 0-25 cm

horizon of the same profile. The ESP is low because exchangeable Na+ concentration is

very low in all the three profiles. The concentrations of exchangeable Ca2+

and Mg2+

are

higher in profile 3 than in profile 1 and 2. In general, the concentration of exchangeable

K+ and exchangeable Na

+ is decreasing with slope. Based on the measured electrical

conductivity (EC), calculated SAR and ESP, the soils from all the three profiles can be

classified as normal soils. Normal soils have EC of less than 4 mS cm-1

, a SAR of less

than 13 mmol L-1

and an ESP of less than 15%.

Table 7: Chemical characteristics of the soil solution extract (1:5) from Malemia 2 area

Depth pH EC 25°C alkalinity alkalinity Ca2+

Mg2+

K+ Na

+ Cl

- SO4

2- NO3

- F

- SAR

(cm)

(dS m-1

) (meq L-1

) (cmolc kg-1

) (ppm) (mmol L-1

)

Profile no. 1 (mid upper slope)

0-25 6.5 0.06 0.21 0.12 15 4 11 40 55 20 <0.1 40 2.4

25-50 6.8 0.09 0.32 0.16 39 11 11 50 45 12 <0.1 49 1.8

50-75 6.9 0.08 0.26 0.13 17 7 7 59 15 6 <0.1 55 3.1

75-100 6.9 0.07 0.22 0.11 15 5 7 54 36 10 <0.1 59 3.1

Profile no. 2 (lower mid slope)

0-25 6.4 0.08 0.17 0.08 16 5 8 50 36 43 <0.1 49 2.8

25-50 6.9 0.08 0.25 0.13 23 5 21 56 30 12 <0.1 54 2.8

50-75 6.5 0.07 0.31 0.15 12 3 19 50 40 5 <0.1 52 3.4

75-100 6.8 0.07 0.24 0.12 16 7 9 57 45 10 <0.1 49 3.0

Profile no. 3 (lower slope)

0-25 6.6 0.07 0.36 0.18 22 5 6 44 55 3 <0.1 33 2.2

25-50 6.7 0.07 0.24 0.12 16 4 4 53 25 5 <0.1 46 3.0

50-75 6.7 0.07 0.18 0.09 11 2 2 51 35 3 <0.1 45 3.6

75-100 7.1 0.08 0.33 0.17 18 4 3 54 50 10 <0.1 57 3.0

35

36

Table 8: Chemical characteristics of the soil from Malemia 2 area

Depth NH4OAc extraction pH 7 Base Sat. ESP

(cm) Exchange complex (cmolc kg-1

) (%) (%)

Ca2+

Mg2+

K+ Na

+ CEC

Profile no 1 (upper mid slope)

0-25 18.26 1.38 0.64 0.13 26.41 77 0.5

25-50 16.79 1.46 0.32 0.24 23.75 79 1.0

50-75 13.73 1.15 0.32 0.64 20.58 77 3.1

75-100 16.16 1.75 0.19 0.44 22.62 82 1.9

Profile no. 2 (lower mid slope)

0-25 14.49 0.79 0.33 0.33 19.21 83 1.7

25-50 12.01 0.77 0.33 0.33 17.02 79 1.9

50-75 10.53 0.80 0.30 0.34 16.82 71 2.0

75-100 9.63 0.75 0.31 0.37 15.59 71 2.4

Profile no. 3 (lower slope)

0-25 23.37 3.36 0.29 0.20 30.28 90 0.7

25-50 25.33 3.79 0.22 0.36 31.36 95 1.2

50-75 21.52 2.94 0.12 0.29 25.44 98 1.2

75-100 28.44 4.49 0.18 0.43 32.53 103 1.3

37

4.3 Mineralogical characteristics

4.3.1 Mineralogy of the clay fraction of the soil and ground water sediment

Clay mineralogical analysis was carried out on the Na+-saturated clay fraction of the soil

samples from the three profiles and the sediment from the ground water sample. The X-

ray diffraction patterns for the clay from groundwater sediment show the presence of

smectite, kaolinite, mica and feldspar (Figure 10). The X-ray diffraction (XRD) patterns

of the clay from all the profiles are almost similar and show the presence of smectite,

mica, kaolinite and goethite (Figures 11 to 14). There is also feldspar in profile 2 and 3.

Mica was characterized by its diffraction peaks at 1.0, 0.50, 0.333, 0.250 and 0.200 nm

while kaolinite was characterized by its diffraction peaks at 0.72, 0.356, 0.238 and 0.180

nm. Smectite clay was characterized by peaks at 1.265 to 1.489 nm for the first order

which shifted to 1.691 to 1.711 after glycolation. On the other hand, feldspar was

characterized by its diffraction peak at 0.324 nm and goethite by its diffraction peak at

0.418 and 0.268 nm. The dominant clay mineral in profile 1 and 2 is kaolinite while

smectite is dominant in profile 3.

Figure 10: XRD patterns of the clay fraction of groundwater sediment from Profile 3; d-

values are in nm

38

Figure 11: XRD patterns of the clay fraction of Profile 1 (a) Na+-saturated for all

horizons and (b) Na+-saturated and Na

++glycol-saturated for horizon 25-50 cm; d-values

are in nm

(a)

(b)

39

Figure 12: XRD patterns of the clay fraction of Profile 2 (a) Na+-saturated for all

horizons and (b) Na+-saturated and Na

++glycol-saturated for horizon 25-50 cm; d-values

are in nm

(b)

(a)

40

Figure 13: XRD patterns of the clay fraction of Profile 3 (a) from 0-25 cm and (b) 25-50

cm; d-values are in nm

(b)

(a)

41

Figure 14: XRD patterns of the clay fraction of Profile 3 (a) from 50-75 cm and (b) 75-

100 cm; d-values are in nm

(b)

(a)

42

4.3.2 Mineralogy of the salts from hot spring water

Mineralogical analysis was carried out on all the salt powder samples from the water

from all the hot springs. The XRD patterns of the non-oriented powders (Figures 15 to

18) of the salts show presence of halite (NaCl), burkeite (Na4(SO4)1.45(CO3)0.55),

kogarkoite (Na3SO4F), trona (Na3H(CO3)2(H2O)2) and thernadite (Na2SO4). Halite was

characterized by its diffraction peaks at 0.326, 0.282, 0.200 and 0.163 nm, while burkeite

was characterized by its diffraction peaks at 0.381, 0.353, 0.259 and 0.230 nm.

Kogarkoite was characterized by peaks at 0.381, 0.300 and 0.272 nm. Thernadite was

characterized by its diffraction peak at 0.265 nm and trona by its diffraction peaks at

0.308, 0.276, 0.265 and 0.200 nm.

Figure 15: XRD pattern of the salts from Mphizi hot spring water; d-values are in nm

43

Figure 16: XRD pattern of the salts from Tambala hot spring water; d-values are in nm

Figure 17: XRD pattern of the salts from Kumpalira 1 hot spring water; d-values are in

nm

44

Figure 18: XRD pattern of the salts from Namitukuta hot spring water; d-values are in nm

Salts identified in the evaporite from the various hot springs are given in Table 9.

Thernadite is present in the water from Tambala hot spring only and it is the only water

which has a ratio of SO42-

to Na+ of more than one. The dominant salt in water from

Mphizi and Kumpalira 1 hot spring is halite, while the evaporite from Tambala is

dominated by halite and burkeite. Water from Namitukuta hot spring is dominated by

trona, but burkeite is also in appreciable amounts.

Table 9: Salts present in hot spring water

Hot spring Salt minerals

burkeite halite kogarkoite trona thernadite

Mphizi + ++ + +

Tambala ++ ++ + + +

Kumpalira 1 + ++ + +

Namitukuta + + + ++

+ Present

++ Dominant

45

4.4 Chemical composition of water samples

4.4.1 Groundwater from P3

The quality parameters of groundwater from profile 3 are presented in Table 10. The

dominant ions in the ground water are Na+ and Ca

2+. The pH is neutral and the calculated

SAR is 1.1 mmol L-1

.

Table 10: Chemical characteristics of ground water from P3

pH EC 25oC Alkalinity Ca

2+ Mg

2+ K

+ Na

+ Cl

- SO4

2- NO3

- F

- SAR

(µS cm

-1) (meq L

-1) (ppm) (mmol L

-1)

7.2 151 1.2 13 2 1 16 4 3 1 3 1.1

4.4.2 Water from hot springs

Mphizi is the hottest of the four hot springs with a temperature of 77 oC while Kumpalira

has the lowest temperature of 34 oC. The pH of water from all the hot springs is slightly

alkaline with the lowest pH being 7.74 and the highest being 7.94 for Namitukuta and

Tambala respectively. Total Dissolved Salts (TDS) range from 195 to 1,194 mg L-1

with

Namitukuta having the lowest value and Mphizi having the highest. The EC value range

from 0.30 to 1.87 dS m-1

with Namitukuta having the lowest value and Mphizi having the

highest value. Visual analysis and interpretation of relationship between temperature and

ionic concentration reveals a linear relationship between them. An increase in

temperature leads directly to an increase in concentration of the ions in water. From

Table 11 and Figure 19, it is evident that Na+ is the dominant cation in the water from all

the four hot springs with the concentrations ranging from 30 to 383 ppm. SO42-

is the

dominant anionic species in the water from Tambala and Kumpalira 1 but it is Mphizi

which has the highest concentration of 285 ppm. The dominant anion in Mphizi hot

spring water is Cl- with a concentration of 366 ppm while the dominant anion in water

from Namitukuta hot spring is CO32-

(+ HCO3-) with a total concentration of 28 ppm. The

concentration of other major ions is low, with Mg2+

and Ca2+

contents less than 2 ppm.

46

The K+ and NO3

- concentration is also very low in all the hot springs with an exception of

Mphizi which has 6 ppm of K+. In all the hot springs, F

- content is over 1.5 ppm which is

the recommended concentration for drinking water according to WHO guidelines. The

order of abundance of the anions in the hot spring water is Cl- > SO4

2- > CO3

2- > HCO3

- >

F- > NO3

- for Mphizi; SO4

2- > CO3

2- > Cl

- > F

- > NO3

- for Tambala; SO4

2- > CO3

2- > Cl

- >

HCO3- > F

- > NO3

- for Kumpalira 1; and CO3

2- > HCO3

- > F

- > Cl

- > SO4

2- > NO3

- for

Namitukuta.

The concentration of ions is generally high in water from Mphizi hot spring and it is low

in water from Namitukuta hot spring. The few exceptions are the highest concentration of

F- in Tambala hot spring and CO3

2- in Kumpalira 1 hot spring. The SAR of the water

from all the hot springs is excessively high, due to the low concentrations of Mg2+

and

Ca2+

and the very high Na+ concentration, indicating sodium hazard. The ratio of SO4

2- to

Na+ for Tambala hot spring water is more than 1, while it is equal to or less than 1 for the

other three hot spring water. While all the hot springs have almost similar ionic species in

common, there are some differences in calculated percentages of these species among the

hot springs (Figure 19). For example, Namitukuta has a total of 36% of

HCO3-+CO3

2- while for Mphizi it is only 4%. Mphizi contain 33% of Cl

- while Tambala

contains only 4% of Cl-. Namitukuta contains 9% of F

- while Mphizi and Kumpalira

contain only 1% each and Tambala contain 4%.

47

Table 11: Chemical composition of water from hot springs

Measured parameters Hot spring

Mphizi Tambala Kumpalira 1 Namitukuta

Temperature (oC) 77 43 42 34

pH 7.92 7.94 7.86 7.74

EC (dS m-1

) 1.87 0.59 0.74 0.30

TDS (mg L-1

) 1194 378 472 195

Na+ (ppm) 383 112 147 30

K +(ppm) 6 0.52 0.36 0.63

Mg2+

(ppm) <0.1 <0.1 <0.1 <0.1

Ca2+

(ppm) <0.1 <0.1 <0.1 <0.1

F- (ppm) 10 14 6 7

Cl- (ppm) 366 15 48 6

SO42-

(ppm) 285 140 146 5

NO3- (ppm) 1 0.2 1 0.2

CO32-

(ppm) 35 26 50 20

HCO3- (ppm) 12 11 20 8

SAR(mmol L-1

) 470 518 651 217

48

Figure 19: Calculated percentages of ionic species concentration in Namitukuta,

Tambala, Kumpalira 1 and Mphizi hot spring water

49

5 DISCUSSION

5.1 Characterization of dissolved salts

The water from Mphizi hot spring is mineralized water (TDS > 1,000 mg L-1

) while water

from the other three hot springs is not mineralized (TDS < 1,000 mg L-1

). Such a wide

range in the TDS value suggests the presence of hydrological circuits having different

length and/or residence times (Fontana et al., 2009). High TDS can be due to longer

residence time in the aquifer (Fontana et al., 2009). In addition, high TDS can be due to

high temperature since temperature affect solubility of minerals. The results indicate that

the hot spring with the highest temperature has the highest concentration of TDS while

the hot spring with the lowest temperature has the lowest concentration. The ionic

concentration ratios are different among the various hot spring waters. Possible causes of

such differences may be local variations in the mineralogical nature of the groundwater

reservoir and/or to geochemical processes occurring in the aquifer (Njitchoua et al.,

1997). Based on the dominant cations and anions, Namitukuta is the Na-CO3 (+HCO3)

type with these ions comprising 75% of all ions in the solution while Tambala is Na-

SO42-

type with these ions comprising 79% and Mphizi is Na-Cl-SO4 type with these ions

comprising 94%. Kumpalira 1 is Na-SO4-(CO3+HCO3) with these ions comprising 87%.

Mphizi hot spring water has almost similar percentage ionic composition to that of the

water from Nhambita hot spring in Mozambique, also within the African Rift Valley.

Steinbruch and Merkel (2008) found that 89% of the ions in water from Nhambita hot

spring were Na-Cl-SO4.

Different hot spring waters have different salts which are dominant depending on the

ionic ratios of the solutes. However, all the identified salts have Na+ as the dominant

cation since the concentration of other cations is very low. The relatively high proportion

of CO32-

and HCO3- in water from Namitukuta and Kumpalira 1 hot spring could be

attributed to the presence of carbonatite vents present in these areas. The

dissolution/precipitation of carbonate mineral is a common control of HCO3- contents in

groundwater (Dotsika et al., 2009). In areas of noncarbonated rocks, the HCO3- and

CO32-

originate entirely from the atmosphere and soil CO2, whereas in areas of carbonate

rocks, the rock itself contribute approximately 50% of the carbonate and bicarbonate

50

present (WHO, 1996). The dominance of trona in Namitukuta can be attributed to the

relatively high CO32-

and HCO3- concentration. Trona deposits formation is dictated by

the evaporative concentration of waters that have high proportions of Na+ and

HCO3- (Earman et al., 2005; Dotsika et al., 2009). Weathering of granitic and rhyolitic

rocks (or sediments derived from them) is a common means of producing Na-HCO3- type

waters as these rocks are composed primarily of K-feldspar, quartz, and Na-plagioclase,

with generally little Ca2+

(Earman et al., 2005). The results from this study indicates very

low amounts of Ca2+

and Mg2+

in the water from all the hot springs providing a suitable

environment for the formation of trona.

SO42-

is one of the dominant anions in the water from all the hot springs except

Namitukuta. According to the geology of Malawi, most parts of the country are underlain

by „Basement Complex‟ (Chilton and Smith-Carington, 1984) and pyrite and pyhrrotite

occur in these rocks (Bloomfield, 1965; Harrison and Chapusa, 1975; Kemp, 1975). The

high SO42-

levels may thus be the result of progressive oxidation of S2-

rich parent

material, with one of the products being sulphuric acid (Chilton and Smith-Carington,

1984). The other possible source of SO42-

in groundwater is the use of chemical fertilizers

in the gardens (Mkandawire, 2008). However, contribution of fertilizer use in Malawi is

very minimal since very few farmers apply fertilizers in their gardens. Apart from the

above factors affecting concentration of ions in groundwater, the high concentration of

SO42-

in water from Mphizi hot spring could be attributed to the depth of source water

and also coal mining activities taking place in the area. In a study of groundwater

supplies in Dowa West (Malawi), Chilton and Smith-Carington (1984) found that

sulphate concentration in groundwater often increases with depth. The water from

Tambala hot spring is the only water with a SO42-

to Na+ ratio of more than 1 and it is the

only water where thernadite has been identified.

The East African Rift Valley is well recognized as a high-fluoride province and many

countries in the region have significant fluoride groundwater problems. Sources of F- in

groundwater may be from dissolution of F- bearing rocks or pollution activities. Pollution

activities include:- runoff and infiltration of chemical fertilizers in agricultural areas;

septic and sewage treatment system discharges in communities with fluoridated water

51

supplies; and liquid waste from industrial sources. Significant concentrations of F- have

been found in Precambrian rocks (Tekle-Haimanot et al., 2006). Malawi‟s geology is

largely covered by Precambrian rocks (Chilton and Smith-Carington, 1984) where

occurrences of gneisses, biotite, hornblende, fluorite and amphibole have been reported

(Bloomfield, 1965; Harrison and Chapusa, 1975; Kemp, 1975). Differences in

concentration may be attributed to localized occurrence of fluoride-bearing minerals.

High fluoride concentrations tend to occur where the element is most abundant in host

rocks. F- is present in the evaporite of hot spring water as kogarkoite.

Mphizi and Kumpalira 1 are dominated by halite. This is because these hot springs have

relatively high percentage concentrations of Cl- compared to the other two hot springs.

Given that the sequence of salts to precipitate from a solution, regardless of water type, is

carbonates, sulfates, and finally chlorides (Li et al., 2010), the sequence of minerals to

precipitate for studied hot springs would start with trona and ends with halite while

burkeite, kogarkoite and thernadite are intermediate.

5.2 Irrigation water quality

5.2.1 Salinity and sodium hazard

Irrigation water quality is usually assessed in terms of salinity, sodicity and element

toxicities. While the ionic species composition of the water from the four hot springs is

almost similar, the concentration of the ions is different among the hot springs. This

indicates that the water have different quality ratings for irrigation.

All the measured chemical composition parameters of water from Namitukuta hot spring

are within the recommended limit for the composition of irrigation water while Mphizi,

Tambala and Kumpalira 1 have Na+ exceeding the required limit of 40 ppm. In addition,

the high concentration of Na+ relative to Ca

2+ and Mg

2+ in the water from all the four hot

springs, gives a very high value for SAR. According to Ayers and Westcot (1985), SAR

of greater than 9 meq L-1

has severe degree of restriction on use for surface irrigation,

which is the most common form of irrigation in Malawi. High Na+ content in irrigation

water is the primary cause in development of sodic or saline-sodic soils in irrigated sites

(Carrow et al., 2001).

52

According to Wilcox classification diagram for classification of irrigation water

(Richards, 1954), the water from the hot springs fall in different categories. The water

from Namitukuta, Tambala and Kumpalira 1 hot springs are in category C2-S4. This

indicates a very high sodium hazard and a medium salinity hazard. On the other hand, the

water from Mphizi is within category C3-S4, indicating a very high sodium hazard and

high salinity hazard. The medium level of salinity in Namitukuta, Tambala and

Kumpalira 1 hot spring water means that sensitive plants may show salt stress. Table 12

below gives water quality classification based on EC. According to Ayers and Westcot

(1985) guidelines, which use the EC, the level of salinity in Namitukuta, Tambala and

Kumpalira 1 hot springs is low and no detrimental effects on plants or soil build up are

expected while the water from Mphizi hot spring has high salinity level that can

adversely affect most plants. Successful use of the water from Mphizi hot spring requires

selection of salt tolerant plants, good drainage and leaching. The water from Mphizi hot

spring is unsuitable for some crops like maize, beans, peas, onions and carrots. Using the

water to irrigate the mentioned crops will result in reduced yields.

Table 12: Water quality classification based on EC according to Ayers and Westcot

(1985) and Richards (1954)

Water source Ayers and Westcot Richards

Mphizi High High

Tambala Low Medium

Kumpalira 1 Low Medium

Namitukuta Low Medium

5.2.2 Soil structure deterioration and infiltration

EC and SAR are the two most common water quality factors which influence the normal

infiltration rate. Low salinity water or water with high sodium to calcium ratio has a

severe reduction in rate of infiltration (Figure 2). When a soil is irrigated with high

sodium water, a high sodium surface soil develops which weakens soil structure. The

surface soil aggregates then disperse to much smaller particles which clog soil pores

53

(Ayers and Westcot, 1985). According to Carrow et al. (2001) and Richards (1954), the

water from all the hot springs has a very high Na+ hazard. This means the water from all

the hot springs is generally not suitable for irrigation. However, the water can be used for

irrigation if the soils can have low to medium salinity levels and intensive management

will be required. When the concentration of sodium is high in irrigation water, sodium

ions tend to be absorbed by clay particles, displacing Mg2+

and Ca2+

ions (Kumar et al.,

2007). Where HCO3- or CO3

2- concentrations in irrigation water are relatively high, as is

the case with Kumpalira 1 and Namitukuta hot springs, these ions can react with Ca2+

and

Mg2+

from the soil to precipitate CaCO3 or MgCO3, thereby leaving Na+ to dominate.

While Na2CO3 can form, it is much more soluble than CaCO3 or MgCO3 and leaves

soluble Na+ to interfere with soil physical conditions (Carrow et al., 2001).

5.2.3 Specific ion toxicity

Toxicity problems occur if certain constituents (ions) in the soil or water are taken up by

the plant and accumulate to concentrations high enough to cause crop damage or reduced

yields (Ayers and Westcot, 1985). On the measured chemical composition of the water,

Na+ is above the maximum recommended limit in irrigation water of 40 ppm in the water

from all the hot springs except Namitukuta hot spring. In addition to Na+, Mphizi hot

spring has K+ and Cl

- levels above the recommended limits of 2 and 143 ppm

respectively. Therefore, use of the water from these hot springs for irrigation will cause

the concentration of Na+, K

+ and Cl

- to increase in the soil relative to other ions. High

concentrations of Na+ and Cl

- in the soil solution may depress nutrient-ion activities and

produce extreme ratios of Na+/Ca

2+, Na

+/K

+, Ca

2+/Mg

2+ and Cl

-/NO3

- (Grattan and

Grieve, 1999). Salinity dominated by Na+ salts not only reduces Ca

2+ availability but

reduces Ca2+

transport and mobility to growing regions of the plant (Grattan and Grieve,

1999). Cl- concentration in irrigation water of more than 10 meq L

-1 has a severe degree

of restriction for surface irrigation (Ayers and Westcot, 1985). This is because Cl- is not

adsorbed or held back by soils, therefore it moves readily with the soil-water, is taken up

by the crop, moves in the transpiration stream, and accumulates in the leaves (Ayers and

Westcot, 1985). This may make plants susceptible to osmotic and specific ion injury as

54

well as to nutritional disorders that may result in reduced crop yield or quality (Grattan

and Grieve, 1999).

5.2.4 Irrigation at Malemia 2

Water quality for irrigation is also evaluated together with soil parameters of the land

where the water is to be used. By looking at the chemical composition of soil at Malemia

2 area (Tables 2 and 3), the soil is classified as normal soil (non-saline/non-sodic)

because the EC, SAR and ESP are very much less than 4 mS cm-1

, 13 mmol L-1

and 15%

respectively. This indicates that the soil can effectively be used for irrigation without any

problem if the water can be of good quality. However, the water from the hot spring

currently being used has a very high SAR. Since the area currently being irrigated is well

drained (Venema, 1992), leaching of the excess Na+ can be accomplished provided

enough water is applied during irrigation to take into account the leaching requirement.

However, the problem may appear where the groundwater level is shallow like profile 3

or when the level becomes shallow due to irrigation activities. Since irrigation has just

started using this water, the effects of high sodium may not be reflected in the soil now.

The effects may be evident after a long period of time as salinity problems effects rarely

show up within short periods unless the water is very saline. Crop performance of all the

crops that are currently being grown at Malemia 2 cannot be affected by using the hot

spring water since irrigation water salinity and soil salinity values are well below crop

tolerance threshold values to irrigation water salinity and soil salinity. With reference to

Table 3 and Figure 20, yield of even sensitive crops cannot be affected since the ECw and

ECe are low. For sensitive crops, yield loss begins at less than 1.3 dS m-1

while for

tolerant crops it begins at 6-10 dS m-1

.

In the long term, sodicity problems may arise because of the relatively high concentration

of Na+ in the irrigation water as well as in the soil only if drainage can be impeded. EC

and SAR of the groundwater from Malemia 2 area indicate that the water is not saline or

sodic. Since in irrigated areas, salinity often originates from a saline, high water table or

from salts in the applied water, chances of groundwater induced salinity at Malemia 2 are

low in the meantime. Irrigation with this water can affect the soil physical properties in

some parts of the irrigated land which have smectite as dominant clay, like profile 3.

55

There is consistent agreement that sodicity, as reflected in the SAR, is a source of

significant impairment of many soils, particularly irrigated soils in arid or semi-arid zone

conditions and montmorillonitic or 2:1 expanding lattice clay (Oster and Shainberg,

2001).

Figure 20: Divisions for relative salt tolerance ratings of agricultural crops (Maas, 1984

as quoted by Ayers and Westcot, 1985)

5.2.5 Soil properties along the toposequence

In general, the analysis of the three soil profiles does not indicate any significant

difference in properties among the profiles. The chemical as well as the physical

characteristics of the soil show that there is little profile development. The soil has good

56

natural fertility and is suitable for agriculture. Profile 3 which is dominated by smectite

clay has high CEC and high base saturation compared to the other two profiles which are

dominated by kaolinite. This can be attributed to the high CEC of smectite clay as

opposed to kaolinite clay which has a low CEC. Soil texture of profile 1 and 3 is optimal

for surface irrigation which is the type of irrigation being practiced at Malemia 2 while

the texture for profile 2 is marginal for surface irrigation.

The results of the comparison between hot spring water from Namitukuta hot spring

which is currently being used for irrigation and groundwater from profile 3 show higher

concentrations of Ca2+

, Mg2+

, K+ and NO3

- in groundwater while the concentration of

Na+, Cl

-, SO4

2- and F

- is higher in irrigation water. The concentration of the same ions

whose concentration is high in irrigation water (Na+, Cl

-, SO4

2- and F

-) is also high

compared to other ions in the soil. The low concentration of F- in groundwater compared

to irrigation water may be attributed to the relatively high concentration of Ca2+

in

groundwater. According to WHO (2006b), it is the absence of calcium in solution which

allows higher concentrations of F- to be stable.

Although there is documented information that landscape positions influences runoff,

drainage and soil erosion (Hairston and Grigal, 1994; Tsui et al., 2004; Babalola et al.,

2007) thereby controlling the distribution of water and soluble materials from higher to

lower elevation (Pennock et al., 1987), the EC of all the three profiles which ranges from

0.06 to 0.09 dS m-1

across the profiles indicate that there is no difference in salt

concentration among the profiles. Generally, the distribution of the ions is fluctuating

across the profiles and within the profile. This could indicate little movement of soil

materials from upslope positions to low slope positions. Some studies have shown that

hill slope topography was unimportant for soil water movement on slopes of less than 10o

(Anderson, 1982). Since Malemia 2 fields are in an area with slope ranging from 1.1 to

3.4o (Venema, 1992), it is possible that movement of water and soil materials is minimal.

5.3 Drinking water quality

The quality of water and its potential use as drinking water has been evaluated on the

basis of chemical analyses. To evaluate whether or not the water could be used for

57

drinking purposes, the chemical data was compared with the maximum permissible

concentrations indicated in the WHO guidelines (WHO, 2008) and the MBS guidelines

(MBS, 2005) as presented in Table 4. According to WHO (2008), safe-drinking water is

suitable for all usual domestic purposes, including personal hygiene.

A small quantity of F- is required for healthy growth of teeth and prevention of dental

carries. F- concentrations between 0.5 and 1.5 ppm in drinking water promotes dental

health while concentrations of less than 0.5 ppm leads to dental carries (WHO, 2009). On

the other hand, F- content of more than 1.5 ppm in drinking water leads to dental fluorosis

while concentrations greater than 10 ppm leads to crippling skeletal fluorosis (WHO,

2006b). The water from all the four hot springs has F- concentration above 1.5 and 2 ppm

which are the recommended levels of F- in drinking water according to WHO and MBS

respectively. The water from all the four hot springs poses a risk of dental fluorosis while

the water from Mphizi and Tambala poses a further risk of crippling skeletal fluorosis for

the population consuming the water over a long period of time. The most vulnerable

category of individuals to dental fluorosis is children below seven years of age. For

drinking purposes, the water from all the hot springs is not suitable with respect to

F- concentration. However, the water from Namitukuta, Tambala and Kumpalira 1 hot

springs can be made suitable for drinking if defluoridation measures can be put in place.

SO42-

content of more than 200 ppm is objectionable for domestic purposes and

concentration beyond this limit causes gastro-intestinal irritation (Mor et al., 2009).

Water from Mphizi hot spring is the only water with concentration beyond the limit by

WHO, while according to MBS, water from all hot springs have SO42-

below the

maximum permissible limit of less than 400 ppm. Waters with high SO42-

content,

especially when in combination with high Mg2+

are unsuitable for human consumption

because of their laxative effect (Chilton and Smith-Carington, 1984). NO3- concentration

in the water from all the hot springs is also below the recommended concentration by

both standards. Documented nitrate concentration of groundwater in Malawi show low

concentrations. For example the concentration of NO3- in Nkhotakota district where

Tambala hot spring is located ranged from <0.2 to 6.1 ppm while in Rumphi district

where Mphizi hot spring is located ranged from 0.02 to 9.9 ppm (Bath, 1980). These

58

results imply minimal pollution inputs in the ground water resources. High NO3- contents

in groundwater have to be related to anthropic pollution (Njitchoua et al., 1997; Fontana

et al., 2009).

Mphizi is the only hot spring which has Cl- and Na

+ concentration above the WHO

guideline limit of 250 and 200 ppm, respectively, while according to MBS standards it is

only Na+ which is above the limit. Cl

- coupled with Na

+ bring to bear salty taste, when its

concentration is more than 250 ppm (Venkatesan and Swaminathan, 2009). High content

of Cl- in water can corrode pipes, pumps and plumbing fixtures while high concentration

of Na+ in drinking water may cause heart problems (Mor et al., 2009). Ca

2+ and Mg

2+ are

the two principal ions responsible for water hardness (WHO, 2009). The very low

concentrations of these ions in water from all the four hot springs indicate that the water

is not hard. This means the water can be used for washing purposes without any problem.

The pH values are within the range recommended for drinking water according to both

guidelines. In humans, exposure to extreme pH values results in irritation to the eyes,

skin and mucous membranes (WHO, 2003b).

59

6 GENERAL CONCLUSIONS

The XRD patterns of the evaporites of the water from the four hot springs revealed that

burkeite, halite, kogarkoite and trona are the salts present in the water from all the hot

springs. In addition to these salts, Tambala hot spring has thernadite. The salts formed

from the water from each hot spring depend on the ratios of the solutes present in the

water. The dominant salt in water from Mphizi and Kumpalira 1 hot spring is halite,

while water from Tambala is dominated by halite and burkeite. Water from Namitukuta

hot spring is dominated by trona. All the salts formed have Na+ as the cation.

The chemical properties of water from the four hot springs show a poor quality for

irrigation. The water from Namitukuta, Tambala and Kumpalira 1 hot springs are in

category C2-S4 while water from Mphizi hot spring is in category C3-S4 according to

Wilcox classification diagram, indicating medium salinity and very high sodium and high

salinity and very high sodium hazard respectively. The quality of groundwater at

Malemia 2 and the soil characteristics revealed that neither is saline nor sodic.

Furthermore, the irrigated land is generally well drained with a few portions where

groundwater level is shallow. This means that the water from Namitukuta hot spring can

be used for irrigation, although it has a sodicity problem, provided good drainage is

improved and maintained. From the chemical characteristics of the soil profiles along the

toposequence at Malemia 2, it can be concluded that use of irrigation water from

Namitukuta hot spring has no effect on the salt accumulation across the different slope

positions.

The chemical properties of the water from all the four hot springs indicate that the water

does not meet the requirements for drinking purposes but can be used for other domestic

purposes like washing and bathing. The ion limiting the use of water for drinking

purposes is F- which is above the maximum limit for drinking water of 1.5 and 2 ppm

according to WHO and MBS standards respectively. In addition to high F- concentration,

Mphizi hot spring water has Na+ and Cl

- concentration above the maximum limit for

drinking water according to WHO standards.

60

Recommendations

Defluoridation: With scarcity of water problem on the increase due to factors like climate

change, the government through various ministries involved in water and health related

issues should explore simple ways of water defluoridation so as to make the water from

some hot springs safe for drinking since F- is the major limiting factor in the safety of the

water from the hot springs.

Irrigation at Malemia 2: Since good drainage can assist to prevent the water table to rise

in the irrigated fields, it is imperative that care should be taken so that adequate drainage

is maintained and improved at Malemia 2. Irrigation and agriculture officials in the area

should make sure that farmers are adequately trained in issues to do with irrigation and

drainage so that problems of salinity and sodicity are avoided.

61

7 SUGGESTIONS FOR FURTHER RESEARCH

I suggest that a larger scale study of the hot springs and soils in areas adjacent to these

hot springs which can be used for irrigation purposes be undertaken so as to evaluate the

quality of irrigation water for irrigation in different parts of the country.

Since F- is the major chemical element contributing to unsuitability of water for drinking

purposes, a study should be conducted to evaluate which methods of defluoridation can

be effectively used in different parts of the country.

62

8 RFERENCES

Alwang, J., Siegel, P.B., 1999. Labour shortages on small land holdings in Malawi:

Implications for Policy Reforms. World Development 27, 1461-1475.

Anderson, M.G., 1982. Modelling hillslope soil water status during drainage.

Transactions of the Institute of British Geographers 7, 337-353.

Ayers, R.S., Westcot, D.W., 1985. Water quality for agriculture. FAO Irrigation and

Drainage Paper No. 29, Rome, 174 pp.

Babalola, T.S., Fasina, A.S., Peter, T., 2007. Relationship between soil properties and

slope position in a humid forest of South Western Nigeria. Agricultural Journal 2,

370-374.

Bath, A.H., 1980. Hydrochemistry in grounwater development: report on advisory visit to

Malawi. British Geological Survey Report, WD/OS/80/20.

Beltrẚn, J.M., 1999. Irrigation with saline water: benefits and environmental impact.

Agricultural Water Management 40, 183-194.

Bloomfield, K., 1965. The geology of the Zomba area. Geological Survey of Malawi

Bulletin no. 16. Zomba, Malawi.

Bouwer, H., 2000. Intergrated water management: emerging isssues and challenges.

Agricultural Water Management 45, 217-228.

Carrow, R.N., Waddington, D.V., Rieke, P.E., 2001. Turfgrass soil fertility and chemical

problems: assessment and management. John Wiley & Sons, Inc., Hoboken, New

Jersey, USA.

Chilton, P.J., Smith-Carington, A., 1984. Characteristics of the weathered basement

aquifer in Malawi in relation to rural water supplies. Challenges in African

Hydrology and Water Resources (Proceedings of the Harare Symposium). IAHS

Publ. no. 144. Hydrogeology Group, British Geological Survey (BGS),

Wallingford, Oxfordshire OXIO 8BB, UK

Choubisa, S.L., 1999. Some obeservations on endemic fluorisis in domestic animals in

Southern Rajasthan (India). Veterinary Research Communications 23, 457-465.

Crescimanno, G., Garofalo, P., 2006. Management of irrigation with saline water in

cracking clay soils. Soil Sci. Soc. Am. J. 70, 1774-1787.

63

Daly, M.C., 1986. The intracratonic Irumide Belt of Zambia and its bearing on collision

orogeny during the Proterozoic of Africa. In: Coward M.P. and A.C. Ries (eds.)

Collision Tectonics. Geol. Soc. Spec. Publ 19, 321-328.

Dölarslan, M., Göl, C., 2008. An investigation on the relationship between saline soil and

halophytic plants in semi-arid region (Aciҫay Stream). International Meeting on

Soil Fertility Land Management and Agroclimatology, Turkey, 2008. pp 83-93.

Dotsika, E., Poutoukis, D., Tzavidopoulos, I., Maniatis, Y., Ignatiadou, D., Raco, B.,

2009. A natron source at Pikrolimni Lake in Greece? Geochemical evidence.

Journal of Geochemical Exploration 103, 133-143.

Earman, S., Phillips, F.M., McPherson, B.J., 2005. The role of “excess” CO2 in the

formation of trona deposits. Applied Geochemistry 20, 2217-2232

FAO. 2000. Agriculture-Malawi. Food and Agricultural Organization of the United

Nations, Rome, Italy.

Fernandez-Turiel, J.L., Garcia-Valles, M., Gimeno-Torrente, D., Saavedra-Alonso, J.,

Martinez-Manent, S., 2005. The hot spring and geyser sinters of El Tatio, Northern

Chile. Sedimentary Geology 180, 125–147

Fitches, W.R., 1970. A part of the Ubendian Orogenic Belt in Northern Malawi and

Zambia. Geol. Rdsch. 59, 444-458.

Fontana, M., Grassa, F., Cusimano, G., Favara, R., Hauser, S., Scaletta, C., 2009.

Geochemistry and potential use of groundwater in the Rocca Busambra area (Sicily,

Italy). Environ Geol 57, 885-898.

Gabriels, D., 2009. Soil Degradation lecture notes for Physical Land Resources Master

Programme 2009/10. Ghent University, Belgium.

Grattan, S.R., Grieve, C.M., 1999. Salinity-mineral nutrient relations in horticultural

crops. Scientia Horticulturae 78, 127-157.

Hairston, A.B., Grigal, D.F., 1994. Topographical variation in soil water and nitrogen for

two forested landforms in Minnesota, USA. Geoderma 64, 125-138

Harrison, D., Chapusa, F., 1975. The geology of the Nkhotakota-Benga area. Geological

Survey of Malawi Bulletin No. 32. Zomba, Malawi.

64

Hillel, D., 2000. Salinity management for sustainable irrigation: integrating science,

environment, and economics. Washington, DC: The World Bank, 2000.

Horneck, D.A., Ellsworth, J.W., Hopkins, B.G., Sullivan, D.M., Stevens, R.G., 2007.

Managing salt-affected soils for crop production. A Pacific Northwest Extension

publication. Oregon State University Extension Service, Washington State

University Extension, University of Idaho Cooperative Extension System, and the

U.S. Department of Agriculture Cooperating.

Ingebritsen, S., Sanford, W., Neuzil, C., 2006. Groundwater in geologic processes. 2nd

ed.

Cambridge University Press, Cambridge CB2 2RU, UK.

Jalali, M., 2007. Salinization of groundwater in arid and semi-arid zones: an example

from Tajarak, Western Iran. Environ Geol. 52, 1133–1149.

Jalali, M., Merrikhpour, H., 2008. Effects of poor quality irrigation water on the nutrient

leaching and groundwater quality from sandy soil. Environ Geol 53, 1289–1298.

Jamil, M., Lee, D.B., Jung, K.Y., Muhammad, A., Lee, S.C., Rha, E.S., 2006. Effect of

salt (NaCl) stress on germination and early seedling growth of four vegetable

species. Journal of Central European Agriculture 2, 273-282.

Javed, A., 2003. Effects on some physico-chemical and mineralogical characteristics of

salt affected soil by growing Kallar grass using saline water. Ph.D. thesis.

University of Punjab, pp. 30-32.

Jenny, H., 1994. Factors of soil formation-A system of quantitative Pedology. Dover

Publications, New York.

Kalua, P.W.R., Chipeta, W.P.C., 2005. A situation analysis of water sector in Malawi. In:

A Paper Presented at the Workshop on Situation Analysis of Water Sector in

Malawi, September, 2005.

Kaluwa, P., Mtambo, F., Fachi, R., 1997. The Country Situation Report on Water

Resources in Malawi (Lilongwe: UNDP/SADC Water Initiative, 1997).

Kemp, J., 1975. The geology of the Uzumara area. Geological Survey of Malawi Bulletin

No. 41. Zomba, Malawi.

Knobeloch, L., Salna, B., Hogan, A., Postle, J., Anderson, H., 2000. Blue babies and

nitrate-contaminated water. Environmental Health Perspectives 108, 675-678

65

Kumar, M., Kumari, K., Ramanathan, A.L., Saxena, R., 2007. A comparative evaluation

of groundwater suitability for irrigation and drinking purposes in two intensively

cultivated districts of Punjab, India. Environ. Geol. 53, 553-574.

Li, M., Fang, X., Yi, C., Gao, S., Zhang, W., Galy, A., 2010. Evaporite minerals and

geochemistry of the upper 400 m sediments in a core from the Western Qaidam

Basin, Tibet. Quaternary International 218, 176-189.

Lister. L., 1967. Erosion surfaces in Malawi. Rec. Geological Survey of Malawi 7.

Zomba, Malawi.

Lorkeers, A., 1992. Land Resources Appraisal of Salima ADD. Ministry of Agriculture,

Malawi. MOA/UNDP/FAO, MLW/85/011, Field Document No. 25.

Luedeling, E., Nagieb, M., Wichern, F., Brandt, M., Deurer, M., Buerkert, A., 2005.

Drainage, salt leaching and physico-chemical properties of irrigated man-made

terrace soils in a mountain oasis of northern Oman. Geoderma 125, 273–285.

Maas, E.V., 1984. Salt tolerance of plants. In: The Handbook of Plant Science in

Agriculture. B.R. Christie (ed). CRC Press, Boca Raton, Florida.

Maas, E.V., 1986. Salt tolerance of plants. Applied Agricultural Research 1, 12–25.

Malawi Buruea of Standards (MBS), 2005. Malawi Standard; Drinking water-

Specification, Malawi Standard Board: MS 214:2005, ICS 13.030.40 (First

Revision).

Malawi Government, 2002. State of Environment Report for Malawi. Environmental

Affairs Department, Lilongwe, Malawi.

Malawi Government, 2006. Climate of Malawi. Ministry of Natural Resources, Energy

and Environment, Department of Climate Change and Meteorological Services.

Blantyre, Malawi.

Malawi Government, 2009. Time series climate data for Malawi. Ministry of Natural

Resources, Energy and Environment, Department of Climate Change and

Meteorological Services. Blantyre, Malawi.

Malawi Government. 2008. African Development Fund-Mwanza Rural Development

Project. Project Completion Report. Malawi.

66

Mandal, U.K., Warrington, D.N., Bhardwaj, A.K., Bar-Tal, A., Kautsky, L., Minz, D.,

Levy, G.J., 2008. Evaluating impact of irrigation water on a calcareous clay soil

using principal component analysis. Geoderma 144, 189-197.

Mees. F., 2001. The development of a burkeite-dominated salt crust - an example of

evaporite sedimentation in a saline pan with non-monomineralic deposits.

Sedimentology 48, 1225-1233.

Mjengera, H., Mkongo, G., 2002. Appropriate technology for use in fluoritic areas in

Tanzania, 3rd Waternet/WARFSA Symposium on Water Demand Management for

Sustainable Use of Water Resources, University of Dar Es Salaam, Tanzania.

Mkandawire, T., 2008. Quality of groundwater from shallow wells of selected villages in

Blantyre District, Malawi. Physics and Chemistry of the Earth 33, 807-811.

Mor, S., Singh, S., Yadav, P., Rani, V., Rani, P., Sheoran, M., Singh, G., Ravindra, K.,

2009. Appraisal of salinity and fluoride in semi-arid region of India using statistical

and multivariate techniques. Environ Geochem Health 31, 643-655.

Morrison, J., Morikawa, M., Murphy, M., Schulte, P., 2009. Water Scarcity and Climate

Change: Growing Risks for Businesses and Investors. Pacific Institute, Oakland,

CA 94612.

Mulwafu, W.O., Nkhoma, B.G., 2002. The use and management of water in the

Likangala Irrigation Scheme Complex in Southern Malawi. Physics and Chemistry

of the Earth 27, 839–844.

Nanyaro, J.T., Aswathanarayana, U., Mungure, J.S., Lahermo, P.W., 1984. A

geochemical model for the abnormal fluoride concentrations in northern parts of

Tanzania. Journal of African Earth Sciences 2, 129-140.

National Statistical Office (NSO), 2005. Integrated Household Survey 2004-2005.

Government Printer, Zomba, Malawi.

National Statistical Office (NSO), 2008. Population and Housing Census - 2008.

Government Printer, Zomba, Malawi.

Nielsen, J.M, Dahi, E., 2002. Fluoride exposure of East African consumers using alkaline

salt deposits known as magadi (trona) as a food preparation aid. Food Additives and

Contaminants 19, 709-714.

67

Nielsen, J.M., 1999. East African magadi (trona): fluoride concentration and

mineralogical composition. Journal of Afican Earth Sciences 29, 423-428.

Njalam‟mano, J., 2007. Current status and management of hand pump equipped water

facilities in Blantyre Rural District, Malawi. Thesis Master of Science in Water

Resources and Livelihood Security at the Department of Water and Environmental

Studies, Institute of Thematic Studies, Linkoping University, Sweden.

Njitchoua, R., Dever, L., Fontes, J.C.H., Naah, E., 1997. Geochemistry, origin and

recharge mechanisms of groundwaters from the Garoua sandstone aquifer, northern

Cameroon. Journal of Hydrology 190, 123–140.

Orr, B., Eiswerth, B., Finan, T., Malembo, L., 1998. Malawi Public Lands Utilization

Study, Final Report. University of Arizona and the Forestry Research Institute of

Malawi, Tucson, Arizona.

Oster, J.D., Shainberg, I., 2001. Soil responses to sodicity and salinity: challenges and

opportunities. Australian Journal of Soil Research 39, 1219-1224.

Pabst, A., Sharp, W.N., 1973. Kogarkoite, a new natural phase in the system Na2SO4-

NaF-NaCl. Ameircan Mineralogist 58, 116-127.

Parkhurst, D.L., Scott, C., George, N.B., 1996. Groundwater quality assessment of the

Central Oklahoma aquifer, Oklahoma-Geochemical and Geological investigations.

United States Geological Survey, Water supply paper 2357 United States of

America.

Pennock, D.J., Zebarth, B.J., de Jone, E., 1987. Landform classification and soil

distribution in hummocky terrain Saskatchewan, Canada. Geoderma 40, 297–315.

Pessarakli, M., Szabolcs, I., 1999. Soils salinity and sodicity as particular plant/crop

stress factors. In: M. Pessarakli, ed. Handbook of Plant and Crop Stress. Marcell

Dekker Inc., New York, NY, USA.

Pritchard, M., Mkandawire, T., O‟Neill, J.G., 2007. Biological, chemical and physical

drinking water quality from shallow wells in Malawi: Case study of Blantyre,

Chiradzulu and Mulanje. Physics and Chemistry of the Earth 32, 1167–1177.

68

Qadir, M., Oster, J.D., 2004. Crop and irrigation management strategies for saline-sodic

soils and waters aimed at environmentally sustainable agriculture. Science of the

Total Environment 323, 1-19.

Rengasamy, P., 2006. World salinization with emphasis on Australia. Plants and Salinity

Special Issue 57, 1017-1023.

Rhoads, J.D., Kandiah, A., Mashali, A.M., 1992. The use of saline waters for crop

production. FAO Irrigation and Drainage Paper No. 48, Rome.

Richards, L.A. 1954. Diagnosis and improvement of saline and alkali soils. United States

Salinity Laboratory Staff. Agriculture Handbook Number 60, United States

Department of Agricultue, Washington, D.C., pp 160.

Richardson, S., Narayan, K., 1995. The effectiveness of management options for dry

land salinity control at Wanilla, South Australia. Agricultural Water Management

29, 63-83.

Ring, U., Betzler, C., Delvaux, D., 1992. Normal vs. strike-slip faulting during rift

development in East Africa: The Malawi rift. Geology 20, 1015-1018.

Schluter, T., Trauth, M., 2006. Geological Atlas of Africa: with notes on stratigraphy,

tectonics, economic geology, geohazards and geosites of each country. Springer.

Shakeri, A., Moore, F., Kompan-Zare, M., 2008. Geochemistry of the thermal springs of

Mount Teftan, southeastern Iran. Journal of Volcanology and Geothermal Research

178, 829-836.

Shitumbanuma, V., Tembo, F., Tembo, J.M., Chilala, S.,Van Ranst, E., 2007. Dental

fluorisis associated with drinking water from hot springs in Choma District in

southern province, Zambia. Environ. Geochem. Health 29, 51-58.

Shortland, A., 2004. Evaporites of the Wadi Natrun: seasonal and annual variation and its

implication for ancient exploitation. Archaeometry 46, 497-516.

Shortland, A., Schachner, L., Freestone, I., Tite, M., 2006. Natron as a flux in the early

vitreous material industry: sources, beginnings and reasons for decline. Journal of

Archaeological Science 33, 521-530.

Sodipo, O.A., 1993. How safe is the consumption of trona? (letter). American Journal of

Public Health 83, 1181-1181.

69

Steinbruch, F., Merkel, B.J., 2008. Characterization of a Pleistocene thermal spring in

Mozambique. Hydrology Journal 16, 1655-1668.

Szabolcs, I., 1994. Prospects of soil salinity for the 21st century. 15

th International

Congress of Soil Science, Acapulco, Mexico.

Tekle-Haimanot, R., Melaku, Z., Kloos, H., Reimann, C., Fantaye, W., Zerihun, L.,

Bjorvatn, K., 2006. The geographic distribution of fluoride in surface and

groundwater in Ethiopia with an emphasis on the Rift Valley. Science of the Total

Environment 367, 182–190.

Tsui, C., Chen, Z., Hsieh, C., 2004. Relationship between soil properties and slope

position in a lowland rain forest of southern Taiwan. Geoderma 123, 131-142.

Van Ranst, E., Shitumbanuma, V., Tembo, F., Mees, F., 2007. Soil salinization and

dental fluorisis as a result of water use in Zambia. Bull. Seanc. Acad. R. Sci. Outre-

Mer 53, 431-446.

Van Ranst, E., Verloo, M., Demeyer, A., Pauwels, J.M., 1999. Manual for the Soil

Chemistry and Fertiliy Laboratory. Analytical methods for soils and plants

equipment and management of consumables. University of Ghent.

Van Reeuwijk, L.P., 1987. Procedures for soil analysis. Second edition. Technical paper

No. 9. ISRIC, Wageningen.

Venema, J.H., 1992. Land Resources Appraisal of Machinga ADD. Ministry of

Agriculture, Malawi. MOA/UNDP/FAO, MLW/85/011, Field Document No. 23.

Venkatesan, G., Swaminathan, G., 2009. Review of chloride and sulphate attenuation in

groundwater nearby solid-waste landfill sites. Journal of Environmental

Engineering and Landscape Management 17, Ia–Ig

Wang, J., Fu, B., Qui, Y., Chen, L., 2001. Soil nutrients in relation to land use and

landscape position in the semi-arid small catchment on the loess plateau in China.

Journal of Arid Environments 48, 537-550

Warren, J.K., 1989. Evaporite Sedimentology: Importance in Hydrocarbon

Accumulation. Prentice Hall, Englewood Cliffs, N.J, pp.1-37.

WaterAid, 2004. Groundwater quality: Malawi. British Council Geological Survey.

70

WHO, 1996. Water Quality Assessments - A Guide to Use of Biota, Sediments and

Water in Environmental Monitoring - Second Edition. World Health Organization,

Geneva.

WHO, 2003a. Chloride in Drinking-water. Background document for development of

WHO Guidelines for Drinking-water Quality. World Health Organization, Geneva.

WHO, 2003b. pH in Drinking-water. Background document for development of WHO

Guidelines for Drinking-water Quality. World Health Organization, Geneva.

WHO, 2004. Water, Sanitation and Hygiene Links to Health, Facts and Figures.

http://www.who.int/water_sanitation_health/factsfigures2005.pdf. Accessed 22nd

February, 2010.

WHO, 2006a. Meeting the MDG drinking water and sanitation target: the urban and rural

challenge of the decade. World Health Organization, Geneva.

WHO, 2006b. Fluoride in Drinking-water. Ed. Fawell, J., Bailey, K., Chilton, J., Dahi, E.,

Fewtrell, L., Magara, Y. IWA Publishing, London, UK.

WHO, 2007. Nitrate and nitrite in drinking-water. Background document for

development of WHO Guidelines for Drinking-water Quality. World Health

Organization, Geneva.

WHO, 2008. Guidelines for Drinking Water Quality. 3rd

ed. Incorporating the first and

second addenda, Vol.1, Recommendations. World Health Organization, Geneva.

WHO, 2009. Hardness in drinking-water. Background document for development of

WHO Guidelines for Drinking-water Quality. World Health Organization, Geneva.

Wolde, M., Veldkamp, E., Mitiku, H., Nyssen, J., Muys, B., Kindeya, G., 2007.

Effectiveness of exclosures to restore degraded soils as a result of overgrazing in

Tigray, Ethiopia. J. Arid Environ. 69, 270–284.