TITLE:
Groundwater Evolution, Hydrochemical Facies and Quality Evaluation for Irrigation Use in Akure, Ondo State, Nigeria
AUTHORS:
Olumuyiwa Olusola Falowo, Moses Bamidele Amodu, Victor Oluwasegunfunmi, Adekunle Aliu, Moses Philip Otuaga
KEYWORDS:
Wilcox Diagram, Piper Plot, Geochemical Signature, Groundwater Evolution, Salinity Hazard, Irrigation, Groundwater
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.7 No.8,
August
19,
2019
ABSTRACT: Hydrochemical facies, groundwater evolution, and
physicochemical reactions between soil or rock and water are of considerable importance
when evaluating or predicting the nature of anthropogenic impacts on
groundwater quality. In this respect a total of 67 ground water samples were
collected randomly in Akure, southwestern, Nigeria from hand pump/dug wells and
analyzed for major cations and anions. The domination of cations and anions was
in the order of Ca2+ > K+ > Na+ > Mg2+ and > Cl- > > respectively.
The pH and Eh of the water samples show an acidic condition, with low salinity
hazard (generally less than 250 μS/cm). The Piper
classification for hydrogeochemical facies indicates carbonate hardness
(secondary alkalinity) exceeds 50% that is by alkaline earths and weak acids,
with Ca2+ + Mg2+ + water-type. This also suggests a meteoric
origin of water quality caused by rock-water interaction.
The ratio of and Cl- is greater than 1 and implies recharge area or upper water flow course of
carbonate rocks (interaction of water with aquifer material). The Na+:Cl- is less than 0.7 signifying loss of Na+ through precipitation of
evaporating water; the water is Ca2+ rich and Na+ depleted
with Mg2+:Ca2+ less than 0.5 and Na+:K+ less than 15. The Na+:Ca2+ (2+:+ for the
samples is less than 1.0 suggestive of flow of water through the normal
hydrological cycle. The calculated range of values of sodium absorption ratio
(1.89 - 26.42), permeability index (42.67 - 170.24), residue sodium carbonate (-1 to
5), magnesium ratio (4 - 53), Kelly ratio
(0.04 - 0.84), percent sodium (0.41 - 3.45) suggest good water suitable for irrigation purposes. In addition,
the Wilcox plot shows that 98% of the water
samples belong to “good to permissible category” for irrigation use.