THE DYNAMICS OF GROUNDWATER SALINITY: DIRECTIONS AND SUSCEPTIBILITY OF AQUIFERS IN THE COASTAL AREAS, RIVERS STATE, SOUTHERN NIGERIA.

Ibim, D.F.

Department of Physics

Ignatius Ajuru University of Education, Rumuolumeni, Port Harcourt, Rivers State, Nigeria

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ABSTRACT

Assessment of the dynamics of groundwater salinity, trends and susceptibility of aquifers in the coastal areas of Rivers State in the southern Nigeria was carried out. Twenty seven (27) borehole samples from the study area were collected and the salinity measured in mg/L based on TDS was analysed. The study revealed that the salinity values range from 10.74 mg/l at Abalama to 700.00 mg/l at Krakrama. The study also revealed that the borehole depth values range from 9.24 m at Abonnema to 281.00 m at Kalibiama. Salinity tends to increase in a southerly direction. Least values of salinity are more common in the hinterland (remote and underdeveloped area). By WHO 2018 standard, the salinity values of groundwater in the study area seem to be generally acceptable. The salinity depths in deep boreholes could suggest saltwater intrusion into submarine freshwater aquifers. Extravagant abstraction of groundwater seems to have resulted in a reduced seaward flow of fresh groundwater making saline water to enter and permeate inland through submarine outcrops. Deep salinity depths in deep boreholes in the coastal locations could be evidence of groundwater quality degradation resulting from saline water intrusion into freshwater aquifers (Adepelumi et al., 2001). Boreholes in deeper aquifers are expected to be safe and free from pollution with little or no vulnerability ensuring exploitation of potable freshwater, but this could not be in the coastal areas.

Key Words: Dynamics, Salinity, Susceptibility, Aquifers, Total dissolved solids.

 

INTRODUCTION

Salinization of groundwater is considered a special category of pollution that threatens groundwater resources, because mixing a small quantity of saltwater with groundwater makes freshwater unsuitable and can result in abandonment of freshwater supply. Salinity in this context is defined as the total solids in water after all carbonates have been converted to oxides, all bromide and iodine have been replaced by chloride and all organic matter has been oxidized (Todd, 1980). It is numerically smaller than the total dissolved solids and usually reported as grams per kilogram. In its simple term, it is the concentration of dissolved salt in a given volume of water. Salinity is an important parameter in the analysis of groundwater. It is caused either by sea water intrusion or when the water in the aquifer comes into contact with salt deposits under-ground.

Population growth and continuous development require larger quantities of water, especially in the coastal regions where about 70% of the world population dwell (Nwankwoala and Udom, 2011). It is a great challenge to supply the required water, while the available water resources are nearly constant, requiring practical measures to protect the available resources from pollution, saltwater intrusion and other contaminants that deplete the current resources. Saltwater intrusion is a major problem in coastal regions all over the world. In coastal areas the aquifers are in hydraulic contact with the sea. Under normal conditions the freshwater flows into the sea. However, over-pumping and exploitation may result in inversion of the groundwater flow from the sea towards the inland causing saltwater intrusion (Scheidleger et al., 2004; Nwankwoala, 2011). Also the rise in sea level will accelerate the saltwater intrusion. 

Water moving through the ground will react to varying degrees with the surrounding minerals (and other components), and it is these rock-water interactions that give the water its characteristic chemistry. As already noted, the silicate minerals that comprise most rocks do not react readily with most groundwaters. On the other hand, carbonate minerals do react quite readily with water, and they play an important role in the evolution of many groundwaters (Ngah, 2009). >>>read more>>>

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