Spatial trend assessment of saline intrusion in Igbokoda/Awoye Coastal Area of Ondo State, Southwestern Nigeria

Abstract

Access to safe drinking-water is a key water security issue, as it influences public health protection both in the developed and underdeveloped countries. This study assessed the spatial trend of water quality status of the coastal area of Ondo State, Southwestern Nigeria. Twenty-five samples were strategically collected between Igbokoda and Awoye, and analyzed to verify the water quality status. The data were subjected to statistical analysis (correlation) and geo-statistical analysis to create a spatial trend map of selected water quality parameters (salinity risk). Result showed that Temperature, pH, Turbidity and Electrical Conductivity ranged from 28.2-33.9°C, 8.08-9.48, 0.3- 34.6 NTU and 0.16 – 2.77 µS/cm, respectively. The total alkalinity and salinity ranged from 80- 415 mg/L and 0.08-1.29 mg/L, respectively. The major cations Ca+, Na+, and K+ have concentration range below detection level – 9.99 mg/L, 0.13- 1.13 mg/L, and 0.08-0.9 mg/L. The heavy metals with values above permissible limit in the groundwater samples are in the order of cadmium> lead> chromium> iron> copper> zinc. The geo-statistical analysis showed that Aiyetoro had a very high salinity, Awoye 1 has high salinity, Igbokoda, Ugbo-Nla, and Mahin had moderate salinity while Ilowo and Ilepete had the lowest salinity level. Generally, the result showed that 95% of the well sampled had salinity level above the permissible limit. Hence, the water is considered unfit for consumption without an appropriate treatment. Also, the high salinity level obtained from the result could be attributed to saline intrusion from the Atlantic Ocean and other anthropogenic activities such as agriculture and excessive groundwater withdrawal.