GIS-based model of groundwater occurrence using geological and hydrogeological data in Precambrian Oban Massif southeastern Nigeria

Gregory Udie Sikakwe

doi:10.1007/s13201-018-0700-3

Abstract

This research modeled geological and hydrogeological controls on groundwater occurrence in Oban Massif and environs southeastern Nigeria. Topographical, hydrogeological, and structural maps, including lithology samples from drilled bores, well completion, and pumping test data in the study area were procured. Collection of coordinates of rock sample locations and structural data on strike and dip of rock exposures was collected. Geological and structural information collected was overlaid on the topographical, hydrogeological and structural map and digitized to produce the geological map of the study area. Thematic map on geological groundwater prospect map of the study was prepared using multicriteria evaluation. Relative weights were assigned to various rock types based on their relative contribution to groundwater occurrence and the map was reclassified using geographic information system (ArcGIS10.1) analysis. Depth ranges of the various lithologic units from drilled boreholes were used to construct lithologic correlation section of the boreholes across the study area using RockWorks16 Program software. Hydrogeological parameters such as storativity, specific capacity, transmissivity, drawdown, pumping rate, static water level, total depth, and well yield were computed from well completion reports and aquifer test. Results shows that the geologic groundwater prospect map was categorized into very good (28.73 m2), good (9.66 m2), moderate (35.08 m2), fair (49.38 m2), and poor (77.63 m2) zones. Aquifer parameters showed ranges such as (specific capacity (1.81–31.16 m2/day/m), transmissivity (0.0033–12 m2/day), storativity (9.4 × 10−3–2.3), drawdown (2.2–17.65 m), pumping rate (0.75–3.57 l/s), static water level (0–20.5 m), and total depth (3.3–61 m). Borehole depths obtained in the basement are shallower than those in the sedimentary area. Aquifer test parameters obtained from boreholes across the study indicate better correspondence with zones identified as good water prospect in the study. It was evident that well yield is not a very reliable aquifer performance indicator, because it depends largely on the efficiency of the pump installed. Therefore, other aquifer parameters must be employed in aquifer performance assessment. The geologic formation is paramount in determining aquifer performance. The result of this groundwater occurrence is useful as a guide for groundwater developers, which engineers in water resource management and land-use planners to select suitable areas to implement development schemes and also government agencies.

Highlights

Groundwater is noted to be one of the most valuable natural resources used as a major source of water in villages and communities for agricultural, industrial, and domestic purposes (Rahmati et al 2016)
The task of groundwater potential mapping becomes relatively more complex task involving complex decision owing to lack of reliable data and the highly variable nature of the geologic environment (Kellgren 2002; Anabazaghan et al 2011) in hard rocks which has low or absence of primary porosity; the intersection of secondary structural features is crucial for productive groundwater (Baramurugan et al 2010)
Intensive hydrogeological investigations are precondition to thoroughly appreciate groundwater condition in hard rock region (Baramurugan et al 2010; Solomon and Quiel 2006; Anbazhagan et al 2015) to delineate groundwater potential zones through GIS and remote sensing which act as powerful tools, and several studies have been carried out in different parts of the world (Saraf and Chowdhury 1998; Ganapuram et al 2009; Ndatuwong and Yadev 2014; Pandian and Kumanan 2013; El-Naqa et al 2009)

Summary

Introduction

Groundwater is noted to be one of the most valuable natural resources used as a major source of water in villages and communities for agricultural, industrial, and domestic purposes (Rahmati et al 2016). Groundwater exploitation in hard rocks is difficult, because, in hard rocks, water is restricted to secondary porosity and to the fractures and the weathered zones. Such areas experience water shortage, because drilling on hard rocks has low success ratio. Intensive hydrogeological investigations are precondition to thoroughly appreciate groundwater condition in hard rock region (Baramurugan et al 2010; Solomon and Quiel 2006; Anbazhagan et al 2015) to delineate groundwater potential zones through GIS and remote sensing which act as powerful tools, and several studies have been carried out in different parts of the world (Saraf and Chowdhury 1998; Ganapuram et al 2009; Ndatuwong and Yadev 2014; Pandian and Kumanan 2013; El-Naqa et al 2009)

Methods

Results

Conclusion