GEO-ENVIRONMENTAL INFLUENCE ON GROUNDWATER QUALITY IN NDELE,SOUTHERN NIGERIA

摘要

Groundwater contamination has been a growing issue in recent times as a result of population growth, urbanization and industrialization. Groundwater is highly susceptible to impacts associated with anthropogenic activities such as the release of wastematerials to the environment. The groundwater vulnerability of an area is a function of the geologic and environmental factors of the area. The purpose of the study was to determine the impact of geological and environmental factors on groundwater quality in the Ndele Area of Southern Nigeria. Estimations of groundwater flow direction and overlandflow direction in the study area were used to establish the likely groundwater vulnerable areas. The water quality index of groundwater sourced from hand-dugwells and boreholes in the study area was used to appraise the groundwater quality of different locations in the area. Water Quality Index is a means of summarizing and reporting water quality in a consistent manner. The mean values of water quality index parameters evaluated revealed that the WQIof water samples sourcedfrom hand dug wells in the lower altitudes and hydraulc head areas (mini-watershed area) were found to be 101.5, which is categorised to be "unsafe for drinking, "while those of the twocontrol locations with higher altitudes and hydraulic heads were 69.0 and 67.2, respectively, and are categorised to be "poor water quality." Water samples sourced from boreholes with average depths of 40m in the lower altitudes and hydraulic head areas(mini-watershed areas) and two control areas were found to be 39.0, 44.3, and 41.2 m respectively and categorized to be "good water quality". Thus, based on some environmental ill practices such as the use of open pit toilets, discharge of suckaway to flow with surface runoffs, and improper disposal of domestic wastes in the area, this study has revealed that groundwater at the locations with lower hydraulic heads and altitudes (mini-watershed area) is highly vulnerable. This may be attributed to the fact that lower lands and hydraulic head areas are susceptible to overland and groundwater flow; hence, infiltration and water table recharge by water from higher altitudes that contaminate groundwater in such areas.