Estimating Groundwater Storage in Weathered Crystalline Rock Aquifers of Aroca Catchment, Northern Uganda using Geophysical Methods and Aquifer Tests

Table of Contents

1. INTRODUCTION

1.1 Background

1.2 PROBLEM STATEMENT

1.3 OBJECTIVES

1.3.1 Main Objectives

1.3.2 Specific Objectives

1.4 Justification and Significance of the study

1.5 Scope of work

1.6 Study Area

1.6.1 Location and Demography

1.6.2 Climate

1.6.3 Drainage and hydrology

1.6.4 Geology of the Aroca catchment

1.6.5 Hydrogeology

2. LITERATURE REVIEW

2.1 Geology and geological setting

2.1.1 Regional Geology

2.1.2 Evolution of weathered crystalline rock aquifers

2.2 Groundwater occurrance

2.2.1 Geometry of weathered crystalline rock aquifers

2.2.1.1 Lithological Logs

2.2.2 Geoelectrical resistivity

2.2.2.1 Principle of electrical resistivity method

2.2.2.2 Electrical profiling

2.2.2.3 Vertical Electrical Sounding (VES)

2.2.3 Magnetic Resonance Sounding (MRS)

2.2.3.1 Principle of MRS method

2.2.3.2 MRS measurements

2.2.3.3 MRS parameters and aquifer geometry

2.2.3.4 MRS flow related parameters

2.2.3.5 MRS storage related parameters

2.3. Hydraulic properties of crystalline rock aquifers

2.3.1 Lithological logs

2.3.2 Aquifer tests

2.3.2.1 Theoretical estimation of storage

2.3.2.2 Determination of aquifer hydraulic parameters

2.3.2.3 Derivative analysis

2.3.2.4 Hydrogeological conceptual models

3. MATERIALS AND METHODS

3.1 Materials

3.2. Methods

3.2.1 Archived/historical data collection

3.2.2 Field activities

3.2.2.1 Monitoring well construction

3.2.2.2 Aquifer tests

3.2.2.3 MRS measurements

3.2.3 Laboratory analyses

3.2.4 Data analyses

3.2.4.1 Litho-stratigraphic analysis

3.2.4.2 Use of geoelectrical resistivity (VES) and borehole lithological logs

3.2.4.3 Hydraulic parameters analysis

(a) Laboratory data analysis

(b) Aquifer test analysis

(c) MRS data analysis

3.2.5 Generation of a hydrogeological conceptual model

4. PRESENTATION AND DISCUSSION OF RESULTS

4.1 Aquifer characteristics

4.1.1 Borehole log analysis

4.1.2 Physio-chemical analysis

4.1.3 Spatial lithological distribution and basement spatial variation analysis

4.1.4 Delination of hydrogeologic units using geophysical technique

4.1.4.1 Geoelectrical resistivity (VES)

4.1.4.2 MRS aquifer geometry

4.1.4.3 Comparison of MRS, VES layer model and lithological logs

4.1.5 Hydraulic properties of aquifers

4.1.5.1 Estimates of hydraulic parameters from pedotransfer functions

4.1.5.2 Static water level and hydraulic head distribution

4.1.5.3 Aquifer tests analysis

4.1.5.4 Parameterization of MRS hydraulic parameters

(a) MRS flow hydraulic parameters

(b) MRS drainable groundwater storage

4.2 Conceptual hydrogeological model

4.3 DISCUSSION OF RESULTS

4.3.1 Aquifer Geometry

4.3.2 Hydraulic properties of aquifers in the region

4.3.3 Comparison of MRS hydraulic flow parameters

4.3.4 Conceptual cross-sectional model model

5. CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusions

5.1.1 Aquifer architecture

5.1.2 Aquifer hydraulic properties

5.1.3 Hydrogeological conceptual model

5.2 Recommendations

Objectives and Research Themes

The primary objective of this dissertation is to quantify groundwater storage and assess aquifer geometry within the deeply weathered crystalline rock aquifers of the Aroca catchment in Northern Uganda, utilizing a combination of geophysical methods and hydraulic testing to support sustainable groundwater development.

• Characterization of aquifer geometry using magnetic resonance sounding (MRS), electrical resistivity (VES), and lithological logs.
• Determination of hydraulic properties (transmissivity and hydraulic conductivity) through aquifer tests and MRS parameterization.
• Estimation of drainable groundwater storage and water content using MRS techniques.
• Development of a hydrogeological conceptual model to understand the subsurface architecture and groundwater occurrence.

Excerpts from the Book

Summary of Chapters

1. INTRODUCTION: Outlines the significance of groundwater in Uganda, stating the problem of limited reliable data regarding aquifer geometry and storage in the Aroca catchment.

2. LITERATURE REVIEW: Explores the regional geological setting and existing methodologies for characterizing weathered crystalline rock aquifers using geophysical and hydraulic tests.

3. MATERIALS AND METHODS: Describes the field activities, including the construction of a monitoring well, aquifer testing, and MRS/VES geophysical measurement protocols.

4. PRESENTATION AND DISCUSSION OF RESULTS: Analyzes the gathered borehole logs, geophysical parameters, and hydraulic test data to define aquifer characteristics and build a hydrogeological model.

5. CONCLUSIONS AND RECOMMENDATIONS: Summarizes the findings on aquifer architecture, hydraulic properties, and provides guidance for future groundwater abstraction and management strategies.

Keywords

Groundwater, Magnetic Resonance Sounding (MRS), Transmissivity, Storage, Geometry, Aroca catchment, crystalline rock aquifers, hydraulic conductivity, hydrogeological model, regolith, saprolite, vertical electrical sounding (VES), borehole logs, aquifer tests, Northern Uganda

Frequently Asked Questions

What is the core focus of this research?

The research focuses on characterizing the geometry, hydraulic properties, and groundwater storage capacity of deeply weathered crystalline rock aquifers in the Aroca catchment, Northern Uganda.

Which primary methodologies are employed in this study?

The study integrates non-invasive Magnetic Resonance Sounding (MRS) with Electrical Resistivity (VES), analysis of borehole lithological logs, and long-duration aquifer pumping tests.

What is the main objective of the dissertation?

The main objective is to provide a reliable quantification of groundwater storage and a comprehensive assessment of aquifer geometry to aid sustainable safe water provision.

What are the critical thematic areas covered?

The topics include geology and geological settings, groundwater occurrence, aquifer hydraulic properties, and the generation of a conceptual hydrogeological model for the region.

What does the main body address?

The main body presents field data collection techniques, analysis of subsurface hydrogeological materials, and the comparative evaluation of various aquifer models.

What defining keywords characterize this work?

Key terms include Magnetic Resonance Sounding (MRS), Transmissivity, Groundwater storage, crystalline rock aquifers, and hydrogeological conceptual models.

Does the MRS method provide accurate aquifer details at greater depths?

The study notes that MRS, like most geophysical methods, suffers from resolution loss with increasing depth, making the fissured zone beneath the regolith more challenging to resolve clearly.

How does the aquifer system in the Aroca catchment behave?

The aquifer system is characterized as mostly unconfined to leaky, utilizing water from weathered clasts to the base of the regolith and fissures within the underlying saprock.