BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//pretalx//talks.geoinfo-lab.org//YQSBBP
BEGIN:VTIMEZONE
TZID:+07
BEGIN:STANDARD
DTSTART:20000101T000000
RRULE:FREQ=YEARLY;BYMONTH=1
TZNAME:+07
TZOFFSETFROM:+0700
TZOFFSETTO:+0700
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
UID:pretalx-foss4g-asia-2024-YQSBBP@talks.geoinfo-lab.org
DTSTART;TZID=+07:20241216T153000
DTEND;TZID=+07:20241216T155000
DESCRIPTION:According to the United Nations World Water Development Report\
 , groundwater accounts for 26% of the world's renewable freshwater\, with 
 around 2.5 billion people relying primarily on it for basic water needs. T
 he most realistic and cost-effective strategy to increase universal access
  to clean water\, meet the 2030 sustainable development goals (SDG)\, and 
 minimize climate change impacts is broad exploitation and management of gr
 oundwater. The study area is Nigeria's capital Abuja\, generally character
 ized by moderate precipitation and few surface water sources. The water tr
 eatment plant\, designed with a capacity of 10\,000 cubic meters per hour 
 of treated water\, was aimed at supporting a population of 500\,000 people
  34 years ago. However\, due to population growth and urbanization\, the w
 ater supply is no longer meeting demand. Groundwater demand and consumptio
 n in Abuja have increased significantly over the last decade due to fast p
 opulation expansion\, urbanization\, and industrialization. Understanding 
 groundwater potential and aquifer vulnerability is critical for sustainabl
 e resource management. \n\nGeologically\, Abuja is underlain by Precambria
 n rocks of the Nigerian Basement Complex\, which cover approximately 85% o
 f the land surface\, and sedimentary rocks\, which cover approximately 15%
 . In the study area\, four significant lithologic units are visible\; thes
 e include the Older Granites\, the Metasediments/Metavolcanics\, the Migma
 tite-Gneiss Complex\, and the Nupe sandstones of the Bida Basin\, which oc
 cupies the southwestern region of the territory.\n \nThis study aims to ma
 p groundwater potential and aquifer vulnerability zones using Hydrogeophys
 ical method\, which incorporates geoelectrical resistivity through vertica
 l electrical sounding (VES) and geographic information system (GIS) approa
 ches. With a maximum current electrode separation (AB/2) of 100m\, the Sch
 lumberger electrode configuration was used to acquire the field resistivit
 y data in 823 locations across the study area using a DC resistivity meter
  (Campus Ohmega Ω). \n\nThe resistivity method works by passing an elect
 ric current into the ground through two electrodes and measuring the conse
 quent potential difference across two other electrodes. The electrode spac
 ing gradually increases while the electrode array's center point remains f
 ixed. However\, as the current electrode spacing grows\, the current penet
 rates deeper into the ground\, and the apparent resistivity reflects the r
 esistivity of the deeper layers as well. The resistance is estimated as th
 e ratio of potential difference to current in ohms(Ω). Using a global po
 sitioning system (GPS)\, the absolute coordinates of the survey points (VE
 S) were determined. \n\nThree to five subsurface geoelectrical layers were
  identified in the research area with the aid of IPI2Win software. Vertica
 l electrical sounding (VES) data are often interpreted using the IPI2Win s
 oftware\, which is a user-friendly geophysical software designed to proces
 s resistivity data and generate one-dimensional models of subsurface layer
 s Layer resistivity and thickness were estimated using the software by ite
 rating the model with the observed field data acquired using the Schlumber
 ger array. The H-type sounding curve is the most dominant among the identi
 fied curve types. \n\nThe interpreted data were used to determine paramete
 rs including Depth to Bedrock\, Transverse Resistance\, Longitudinal Condu
 ctance\, Reflection Coefficient\, and Layer resistivity. Using scaling cri
 teria\, the longitudinal conductance was used to determine the aquifer pro
 tective Capacity (Vulnerability)\, and the result revealed the dominance o
 f moderate vulnerability across the study area.\n \nThe groundwater potent
 ial zones in the research area were characterized based on the following c
 riteria as established by previous authors in this field: Areas with overb
 urden thickness ≥ 30m and reflection coefficient < 0.8 were classified a
 s very high groundwater potential\; Areas with overburden thickness ≥13m
  and reflection coefficient < 0.8 were classified as High groundwater pote
 ntial\; Areas with overburden thickness ≥ 13m and reflection coefficient
  ≥ 0.8 were classified as moderate potential while areas with overburden
  thickness <13m and reflection coefficient ≥ 0.8 were classified as low 
 potential\, and finally\, areas with overburden thickness >13m and reflect
 ion coefficient < 0.8. were classified as very low potential. These criter
 ia were written as Python codes that classify the area into five groundwat
 er potential zones. The area covered by each zone was calculated after the
  geospatial analysis: the very high GPZ occupies about 19.70% of the study
  area\, high 20.30%\, moderate 20.0%\, low 19.74%\, and very low 20.31%.\n
  \nOrdinary Kriging (OK) interpolation algorithm was used to generate the 
 layer resistivity map\, layer thickness map\, depth to bedrock map\, aquif
 er vulnerability map\, and groundwater potential zone maps using the smart
 -map QGIS plugin. Smart-Map is a QGIS plugin that allows the generation of
  interpolated maps in the QGIS environment. Kriging is an unbiased linear 
 interpolation technique that uses a weighted average of nearby samples to 
 estimate unknown values in specific areas. It is deemed the best interpola
 tion method for spatially varying data. For this study\, the resistivity (
 VES) data was randomly distributed over a large area\, and the sampling di
 stance between one VES data and the other ranged from 0.5km to 10km.\n\nTh
 is study evaluated groundwater parameters in the study area based on the g
 eo-electric properties of the earth material. The results reveal that weat
 hered/fractured basement and sandstone formations in the study area are su
 bstantial aquifer systems that host potable water. Data from some drilled 
 boreholes across the study area were used to cross-validate the VES result
 s against borehole log records.  This knowledge aided in a better understa
 nding of aquifer disposition\, vulnerability\, and potential consequences.
  The study's findings will provide a geo-database for groundwater potentia
 l zones in the Federal Capital Territory (Abuja)\, with significant implic
 ations for sustainable groundwater resource design and management.
DTSTAMP:20260416T204827Z
LOCATION:Room34-1104
SUMMARY:Hydrogeophysical Analysis of Vertical Electrical Soundings for Grou
 ndwater Potential and Aquifer Vulnerability Evaluation in the Federal Capi
 tal Territory\, Abuja\, Nigeria - DANLAMI IBRAHIM
URL:https://talks.geoinfo-lab.org/foss4g-asia-2024/talk/YQSBBP/
END:VEVENT
END:VCALENDAR