GROUNDWATER VULNERALITY ASSESSMENT USING ELECTRICAL RESISTIVITY METHOD IN PARTS OF ETCHE LOCAL GOVERNMENT AREA, RIVERS STATE

Abstract

Potable  water is  essential for  survival of  both  mankind and   the  environment.  Groundwater  is  described  by  (Otutu  and  Oviri,   2010) as  water  that  occupied the  saturated  layers of  soil and rocks  (which  are  referred to  as  aquifers).  While  Ajuwai, (2013) emphasized  the  global  rise in development of  groundwater  sources  as  a result of  increased  demands  for  drinking  water, as  it  appears  to be  a more  reliable  source  as  reported  by  (Alibi, et al, 2010).  Aquifer  vulnerability  descried  the  comparative  assessment of  the  potential  exposure of  groundwater  as  a  result  of  anthropogenic  activities  to  contamination  (Thriumalaivesan,  et al., 2003) further   describes  it  as  a  qualitative  reflection of   the  natural  tendency  for  an aquifer to  be  affected by human  activities  from surfaces  such as   chemicals, dumpsites and  wastewater  discharge.   (Todd, 1980) further elucidates the extreme  difficulty in detecting and  controlling  subsurface  water   pollution.    Thus, aquifer   vulnerability  assessment  comes  in handy for  recognizing  and  mapping  areas  that  are  susceptible to  contamination resulting  from human  activities  (Eke,  et al., 2015).  

The  information  in  groundwater  vulnerability  is  required  for  groundwater  protection and management. Vulnerability of aquifer  reflects  whether the  subsurface  characteristics  can  prevent  or  favour the transport of  contamination of  contaminant  into the  aquifer repositories and  vulnerability is  greatly  enhanced  by the   groundwater  flow  velocity,  a factor  that is  dependent on hydraulic  conductivity of the  protective  layers and  depth of the  water  table.  The  protective  layers  have  very high  thickness and  low  hydraulic  conductivity  for  effective  groundwater   protection and  also  a  percolation  time of  more  than ten years (Hinsby et al., 2006;  Weatherington-Rice et al., 2006). Groundwater   quality  once  contaminated  can  lead to  water-borne  diseases, and  its  inaccessibility  due  to  drawdown  can  affect  human health.  This  may  jeopardize the  economic  activities   in a  society.  Several  researches  have  been  carried  out  on aquifer  vulnerability in various  parts of  Nigeria. Aweto, (2011) employed   the  use of  geoelectric  parameters on near  surface  materials  to  assess  the  vulnerability  at  Oke-lla, southwestern Nigeria  and  discovered  that the  aquifer  within the  weathered  basement  rock   occurs  at  a  relatively  shallow  depth  (3.9m -   15.7m)   and  therefore  prone to  near surface  contamination.  Akana (2016) investigated  some  towns in Yenagoa using  fifteen  VES  stations   under  the  schlumberger  configuration and  quantitatively  modeled  the VES  data  to produce   Dar-Zarrouk parameters. The  southern  part  exhibited  good to moderate  protective  capacity  rating  while  the  northern part of the  study area showed poor to weak aquifer  protective  capacity