The Impact of Climate Change on the Water Quality of Ground Water in Limbe-Cameroon

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The Impact of Climate Change on the Water Quality of Ground Water in Limbe-Cameroon

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Fonteh Mathias Fru1 and Motchemien Rigobert2*

1 College of Technology, The University of Bamenda, Box 39, Bambilli, Mezam Division, NW Region, Cameroon.

2 Department of Rural Engineering, National Advanced School of Public Works Buea, Box 324 Buea, SW Region, Cameroon.

Abstract:- A significant proportion of the population of Limbe, a coastal town in Cameroon, relies on ground water (gw) to satisfy their drinking water needs. The coastal aquifer is threatened by pollution from sea water intrusion and hence the aim of this study was to determine the suitability of the water. Physico-chemical analysis were carried out on samples collected from the study area and the Revelle Index was calculated and used to determine the extent of pollution from seawater intrusion. The water quality index (WQI) was calculated using values of the pH, bicarbonate, chloride, total dissolved solids and the electrical conductivity. The results showed that the sea level rise is projected to rise by 32 cm in 2050 and 82 cm in 2100 due to climate change from 2018; the base year. About 23% of the groundwater in the study area is currently slightly polluted by seawater intrusion. By 2050, this is projected to increase to 30.8 % and to 42.31 % in 2100 due to sea level rise resulting from climate change. About 34.4 % of the ground water in the study area is currently good for drinking while 65.6 % is either poor, very poor or unsuitable for drinking. By 2050, it is projected that the proportion of the ground water considered to be good for drinking will reduce to 26.92 % and down to 17.86 % in 2100. In order to reduce the intrusion of sea water into the aquifer, a halophyte plant like mangrove should be planted at the mouth of the main river in Limbe.

Keywords: Coastal aquifer, pollution, Revelle Index, salinity, sea level rise, seawater intrusion, water quality index.

I. INTRODUCTION

In the last few decades, there has been a tremendous increase in the demand for fresh water in the world due to the rapid growth of the population and the accelerated pace of industrialization [1]. Limbe, a coastal town in Cameroon on the Atlantic Ocean has a demand for domestic water supply that the water utility company cannot satisfy and hence a significant proportion of the population relies on ground water (gw) to meet their domestic water demands.

Under natural conditions, coastal aquifers are recharged by rainfall, and the gw flows towards the ocean, preventing salt water intrusion into the freshwater. The global mean sea level (GMSL) increased by an average rate of 1.8 mm/year during the 20th century [2] and the IPCC reported with a high confidence that this rate has been increasing [3]. Reference [4] estimated that the GMSL increased by 3.1 mm/year from 1993 to 2003, but this change is not spatially uniform worldwide. Reference [5] estimated a GMSL rise of approximately 3.3 mm/year for the period 1992 to 2010.

He [6] estimated on the basis of data obtained from the tide gauge installed in Limbe, a rise in the mean sea level of the Atlantic Ocean in the lower part of the Gulf of Guinea of about 10 mm / year. One effect of such an increase is sea water intrusion into coastal aquifers [7]. Salt water intrusion is a serious problem because about 80% of the worlds population lives along the coast and utilize coastal aquifers for domestic water supply. In addition, over exploitation of coastal aquifers has resulted in falling groundwater levels (gwl). Sea level rise and falling gwl have resulted in increased pollution of gw due to sea water intrusion. This has caused wells previously used for domestic water supply to be abandoned. For example, in New Jersey, more than 120 wells were abandoned because of salt water contamination [8]. In the study area, about 250 wells have been abandoned because the water has become salty [6].

Variations in the sea level and the associated wedge movement can influence the near-shore and/or large-scale submarine discharge patterns and impact nutrient loading levels across the aquifer-ocean interface [9]. While anthropogenic activities, such as over pumping and felling of trees in urbanized coastal areas, are the major causes of salt water intrusion, it is projected that increases in the sea level due to climate change (CC) would aggravate the problem [9]. Reference [10] modelled the impacts of climate change and changes in land use patterns on the salt distribution in a coastal aquifer and concluded that rising sea level could induce rapid progression of salt water intrusion.

Excessive groundwater withdrawals have been reported to result in changes in the physical, chemical and microbiological water quality; drop in the water table level; reverse hydraulic gradient and consequently water quality deterioration in coastal areas [11]. Poor water quality results in incidences of water borne diseases and consequently reduces the life expectancy of the population [12]. Thus, concern for clean and safe drinking water and protection from contamination is justified because a large proportion of the population in the study area depends on ground water for domestic purposes.

Water quality evaluation is based on the physical, chemical and biological parameters ascertaining the suitability for various uses such as domestic consumption, agricultural, recreational and industrial use [13]. The traditional assessment of water quality consists of comparing the point values of water quality parameters levels with their guideline or standard values based on allocated water use or uses. This type of assessment does not provide an overall assessment of water quality of a water body which is important for managers and decision-makers. To resolve this decision-making problem, several water quality indices have been developed to transform point value water quality parameters into integrated indicator values. Many studies have demonstrated the usefulness of assessing the water quality of gw using a water quality index (WQI). Examples are presented by: [14]; [15]; [16]; [17]; [18]; [19]; [20]; and [21].

The aim of this study was to assess the suitability of the gw in Limbe for domestic use in a changing climate specifically to determine the effect of climate change on the sea water intrusion in Limbe; evaluate the change in the extent of sea water intrusion into the aquifer due to climate change; determine the change in the proportion of the gw suitable for drinking due to climate change and propose a solution to reduce the impact of sea water intrusion on the gw quality in the coastal aquifer.

II. MATERIALS AND METHODS

A. The study area(i) Location(ii) Climate(iii) Geomorphology and HydrogeologyB. Data collection and analysisC. Effect of CC on sea water intrusionA. Effect of CC on sea water intrusion in LimbeB. Extent of sea water intrusion in the coastal aquifer in a changing a climateC. Extent of the gw suitable for drinkingD. Measures to reduce sea water intrusion

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