Gulf Islands Report


RDN Water Budget Project – Phase One:
Gabriola, DeCourcy & Mudge Islands – Electoral Area B

Phase 1 of the Water Budget project is expected to provide preliminary insight into the sustainability of current water use practices in each water region, and will be used to identify areas of concern for further study.

The main Phase 1 report provides overview of the hydrogeology of the Gabriola, Mudge & DeCourcy Islands (RDN Water Region 7), water budget methods and results.

The report is divided into 5 sections:

  1. islands_report_coverIntroduction
  2. Hydrogeological Conceptual Model
  3. Water Budget
  4. Data Gaps
  5. Recommendations & Conclusions
  6. Appendices

In addition to this report, the Agriculture Water Demand Model helps us better understand the amount of water required for agriculture throughout the region.

Detailed technical graphs and maps are included in the Appendices and links – see PDF downloads marked .

Tips for non-technical readers:

  • Improve your understanding with Water 101
  • Move your mouse over coloured words for definitions and links to more info
  • Consult the Glossary

1. Introduction

1.1 Objectives
1.2 Project Scope and Tasks
1.3 Report Organization

Download Introduction as PDF

2. Hydrogeological Conceptual Model

2.1 Geological Setting
2.2 Hydrogeological Units and Properties

2.2.1 Fractured Rock Aquifers
2.2.2 Hydraulic Properties
2.2.3 Hydrogeological Units
2.2.4 Well Yields and Aquifer Productivity

2.3 Groundwater Flow System

2.3.1 Average Groundwater Levels
2.3.2 Groundwater Flow
2.3.3 Depth of Freshwater Lens

2.4 Seasonal Groundwater Level Variation

2.4.1 Water Level
2.4.2 Seasonal Change in Volume of Stored Groundwater

2.5 Groundwater Recharge and Discharge

2.5.1 Surface Water on Gabriola Island
2.5.2 Estimating Groundwater Recharge from Precipitation

Download Hydrogeological Conceptual Model as PDF

3. Water Budget

3.1 Water Budget Sub-Regions
3.2 Estimation Method for Pumping Water Demand
3.3 Water Demand Results

3.3.1 Residential
3.3.2 Commercial
3.3.3 Agricultural
3.3.4 Total Pumping Demand

3.4 Water Stress

Download Water Budget as PDF

4. Data Gaps

4.1 Properties of Hydrogeological Units
4.2 Water Levels
4.3 Salt Water Intrusion and Depth of Freshwater
4.4 Water Budget

Download Data Gaps & Recommended Data Collection as PDF

5. Recommendations & Conclusions

5.1 Hydrogeological Conceptual Model Assessment
5.2 Water Budget Assessment
5.3 Gaining a Better Understanding for the Future

Download Recommendations & Conclusions as PDF


Download Glossary of Terms for this Report as PDF

See also

List of Tables

  • Table 1: Monthly water stress by water sub-region on Gabriola, Mudge, and DeCourcy Islands for low and high recharge scenarios.
  • Table 2: Recommended data collection.

List of Figures

Most figures presented in the main report are symbolic and designed to visually introduce some sections and to improve understanding of text by non-technical readers. Find detailed technical graphs and maps in the Appendices.

  • Figure 1: Regional District of Nanaimo and Electoral Area B.
  • Figure 2: Nanaimo Group sequence of formations on Gabriola, Mudge, DeCourcy islands.
  • Figure 3: Gabriola syncline and geological units in cross-sections.
  • Figure 4: Fractured sandstone, mudstone, and fault zone.
  • Figure 5: Ocean tides and water level fluctuations in wells.
  • Figure 6: Hydrogeological units on Gabriola Island.
  • Figure 7: Flow through fractures in sandstone and mudstone at exposed cut rock slope.
  • Figure 8: Water table elevation and assumed flow directions: Gabriola Island.
  • Figure 9: Cross-section of the Gabriola Island showing water table, water wells, and geological units.
  • Figure 10: Groundwater flow in conceptual model of Gabriola Island.
  • Figure 11: Freshwater-saltwater boundary and flow directions.
  • Figure 12: Provincial Observation Wells on Gabriola Island.
  • Figure 13: Provincial observation wells on Gabriola Island.
  • Figure 14: Conceptual drawing describing seasonal change in groundwater level observed on Gabriola Island at a well in fractured rock and stepped water table.
  • Figure 15: Water budget sub-regions for Gabriola, Mudge, and DeCourcy islands, showing simplified land use zoning and existing pumping wells (source: RDN, BC MOE).
  • Figure 16: Water use type in sub-regions
  • Figure 17: Monthly summer and winter pumping water demand for sub-regions.
  • Figure 18: Residential pumping water use by use type of fixture and outdoor garden, comparing summer season and rest of year.
  • Figure 19: Average monthly pumping water stress in sub-regions.

6. Appendices

Details on specific components, methodologies and calculations, and technical references are presented in the appendices, with detailed technical graphs and maps.

Appendix A: Geological Review

Appendix B: Hydrogeological Conceptual Model

Appendix C: Tidal Analysis

Appendix D: Water Budget Data and Calculations


islands_report_coverSRK Consulting (Canada) Inc. has prepared the RDN Water Budget Phase 1 – Gabriola, DeCourcy & Mudge Islands Report  for the Regional District of Nanaimo. Any use or decisions by which a third party makes of this document are the responsibility of such third parties. In no circumstance does SRK accept any consequential liability arising from commercial decisions or actions resulting from the use of this report by a third party.
The opinions expressed in this report have been based on the information available to SRK at the time of preparation. SRK has exercised all due care in reviewing information supplied by others for use on this project. Whilst SRK has compared key supplied data with expected values, the accuracy of the results and conclusions from the review are entirely reliant on the accuracy and completeness of the supplied data. SRK does not accept responsibility for any errors or omissions in the supplied information, except to the extent that SRK was hired to verify the data.


This report is protected by copyright vested in SRK Consulting (Canada) Inc. It may not be reproduced or transmitted in any form or by any means whatsoever to any person without the written permission of the copyright holder.