ABSTRACT:

Seasonal variation of groundwater quality in Jimeta-Yola area was investigated using selected chemical
contaminants. The results indicated that pollutant loading occurred in the dry and rainy seasons. The groundwater is
fresh and varied from slightly acidic to alkaline in both the dry and rainy seasons. The mean values of BOD, COD and
chloride exceeded the recommended standards of drinking water quality in the rainy season from the shallow and
deep aquifers (hand-dug wells and boreholes). Nitrate and ammonium ion mean values in both seasons in shallow
and deep aquifers exceeded the recommended limit of WHO. The mean coliform number counts exceeded the WHO
recommended limit in both seasons in shallow and deep aquifers. The spatial distribution of EC and TDS reveal that
the leachates from the dumpsites are significant source of groundwater contamination. The variation in contaminant
distribution is influenced by depth to water and well depth. There were increase in COD, BOD, nitrate, phosphate and
chloride, and decrease in ammonium ion and coliform with water depth in shallow aquifer in the dry season, and COD,
nitrate, ammonium ion, phosphate and chloride increase with water depth, and decrease in BOD and coliform in the
rainy season. COD, ammonium ion and chloride increase with well depth, and decrease in COD, BOD, nitrate,
phosphate and coliform in deep aquifer in the dry season while COD, BOD, nitrate, ammonium ion, phosphate and