ABSTRACT

The study of the groundwater quality in Souza is of vital importance due to increased urbanization and agricultural activities. This study was undertaken to understand groundwater chemistry, recharge mechanisms and groundwater quality. Twenty five (25) groundwater samples (23 boreholes and 2 springs) were analysed for major cations, anions, some trace elements(Si, Al, B, Ba, Cu, Fe, Li, Mn, Ti, Zn) and stable environmental isotopes (Deuterium (δ²H) and Oxygen-18 (δ¹⁸O)). In-situ measurements were carried out for physico-chemical parameters including; temperature, pH, EC, TDS. The pH ranged from 3.75-5.60 with a mean of 4.41 indicating acidic water, TDS(6-173 mg/L) with a mean of 53.28 mg/L was generally less than 352 hence classified as fresh water. The relative abundance of major ions was in the order of Na⁺˃K⁺˃Ca²⁺˃Mg²⁺ and NO₃^–˃HCO₃^–˃Cl^–˃SO₄^2-. The water types were Ca-Mg-Cl (36%), Mg-HCO₃ (32%), Ca-Cl (16%), Na-Cl (8%), and Na-Ca-HCO₃ (8%). Groundwater ionic content was as a result of ion exchange, rock-weathering and atmospheric precipitation. Fe concentrations (0.05-0.13mg/L) in the samples were below the WHO guideline. Seven (7) samples recorded high values of Al (0.06-1.99mg/L) out of the WHO limit. Major ion concentrations were within the WHO guidelines, except NO₃^– with 44% samples above set limit. Water quality indices: SAR, PI, %Na and Wilcox diagram indicate that water in the study area is suitable for agricultural purposes. The δD and δ¹⁸O relationship revealed the slope of δD =8.5δ¹⁸O + 15.2, similar to the Global Meteoric Water Line which indicates that recharge is derived from precipitation into the phreatic aquifer.

CHAPTER ONE

INTRODUCTION

1.1 BACKGROUND TO THE STUDY

Groundwater is stored in geologic formations called aquifers and has been exploited for domestic, livestock and irrigation purposes since the earliest time (Clark, 1985; Bowers, 1997). A great majority of the world’s population depends on groundwater source like bore holes, wells and springs for daily needs (Kemper, 2004; Tamungang et al., 2016; Ketchemen et al., 2017). Its assessment on a spatial and temporal scale is imperative (Ako et al.,2012; Wirmvem et al.,2013; Kamtchueng et al.,2014). Inadequate supply of pipe-borne water pushes the population to depend on groundwater (Fonteh et al., 2017; Akoachere et al., 2019). The international atomic energy agency (IAHS) (1997) stipulates that we must be able to observe how water quality changes with time as a function of both natural and anthropogenic stresses (Wotany et al., 2013; Takem et al., 2015).

As a result of growing population, industrialization without adequate measures of waste disposal, agricultural activities, the groundwater environment is being polluted with an ever-increasing number of pollutants (Waheed et al., 2011, Wotany et al., 2013).

Currently, more than 300 million people in Africa do not have access to safe drinking water many of whom are among the poor. Increase reliable water supplies will depend on the community development of groundwater. Careful characterization of the resource is required to guide investment in water supply and to manage the resource to minimize environmental degradation and wide spread depletion (MacDonald et al., 2012).

According to Ako et al. (2009), in Sub-Saharan Africa, 42% of the population is still without improved water and sanitation coverage. 1.8 million People die every year from water borne diseases with 90% of whom are children under the age of 5, attributed to unsafe water supply, inadequate hygiene and sanitation. Geochemical studies from groundwater and surface water can provide a better understanding of a potential water quality variation due to geology and land use.

Groundwater quality is based on the behaviour of physical and chemical parameters that are influenced by geological formations, atmospheric precipitation, inland surface water, and geochemical processes as they are in contact with the rock and the various anthropogenic activities (Katte et al., 2003; Molua and Lambi, 2006; Wotany et al; 2013).

Cameroon is richly blessed with large amount of water resources. It is currently considered as a country with the second highest volume of water in Africa after the Democratic Republic of Congo (Ako, 2011). Groundwater constitutes 21.5% (57 billion m³) of this resource and plays a very important role in socio-economic life of the country. In developing countries including Cameroon where ground water has become the main source of drinking water, they are faced with the issue of sustainability and maintenance.

Trace elements are environmentally hazardous substances that pollute and are principally of concern due to their persistence toxicity and bioaccumulation setbacks since they cannot be degraded or destroyed (Deruibe et al., 2007; Akoachere et al., 2019; Ntube et al., 2022).

In other to utilize and protect valuable water resources effectively and predict the change in groundwater environments, it’s necessary to understand the characteristics of the groundwater and its evolution under natural water circulation processes (Edmunds and Ma, 2006; Fantong et al., 2016; Ngoupayou et al., 2019).

1.2 PROBLEM STATEMENT

WHO (1997) estimates that 80% of diseases affecting the population of the planet are directly or indirectly related to water. Groundwater has been recognized as an important source of water for domestic, agricultural and industrial uses and its contamination is one of the most serious problems faced by the population of Cameroon (Ako et al., 2011).

The Douala-basin has vulnerable water resources owing to its unconsolidated alluvial deposits and largest urban population in the country that host majority of the country’s industries (Fonteh et al., 2017).

The population of Souza is made up of mostly low income subsistence farmers who are very dependent on groundwater for drinking and domestic activities.  The rapid population growth, unplanned urbanization and the shortage of pipe borne water have led to groundwater pressure with limited data on hydrogeochemistry. Monitoring the groundwater quality is necessary in the practice of groundwater quality assessment and resource management. In this respect, an effort to reduce the risks associated with the consumption of unsafe water in this study area is important for the development of and management of the water resources.

1.3 RESEARCH OBJECTIVES

1.3.1 Main Objective

The main objective of the study was to determine the physico-chemical characteristics and quality of the groundwater sources of the study area.

1.3.2 Specific Objectives

The specific objectives where;

1. To determine the Physical parameters (pH, TDS, EC and temperature) and major ions of the groundwater sources.
2. To determine the factors influencing the chemical composition of groundwater.

• To assess the suitability of water for domestic and agricultural purposes.

1. To determine the trace element distribution.
2. To determine the isotopic composition, origin and recharge mechanisms of the groundwater sources.

1.4 RESEARCH QUESTIONS

The following questions will aid in a better understanding of the research work.

1. What factor controls the physico-chemical characteristics of groundwater in the area?
2. Does water-rock interaction have an impact on the groundwater quality in the area?

• What is the suitability of groundwater in the study area for domestic and agricultural use?

1. What are the trace element distributions in the study area?
2. What are the origin and recharge mechanisms of groundwater in the study area?

1.5 RATIONAL OF THE STUDY

Groundwater and surface water geochemical studies can provide a better understanding of potential water quality variations as a factor of the geology and land use practices (Edmunds and Smedley 1996; Deutsch, 1997; Appelo and Postma, 2005; Ramesh and Elango, 2012).

Due to the rapidly increasing population and high demand for groundwater in this area, it is therefore important to characterize the quality of groundwater in Souza. Water quality assessment provides a base line information on water safety. Since water quality in any source of water and at the point of use can change with time and other factors, continuous monitoring of water is essential (Tamungang et al., 2016). This study will provide;

1. Suitability of water for human use.
2. A water management tool for the government and the community.

• Produce a hydrogeochemical data.

1. Great input to knowledge on groundwater resources in Cameroon.

1.6 LOCATION OF STUDY AREA

Geographically, the study area is located in the Littoral region of Cameroon, precisely in the Bonalea subdivision. Souza extends from latitude N 04⁰ 13’ 549’’ to N 04⁰ 15’ 397’’ of the equator and from longitude E 009⁰ 36’ 471’’ to E 009⁰ 36’ 227’’ and lies at an attitude of about 98 m above the sea level. The study area is located within the Douala sedimentary basin.