Assessment of the Supply and Demand of Cove Bay Water System on Bowen Island
Basics
Title
Assessment of the Supply and Demand of Cove Bay Water System on Bowen Island
Description
AI-generated: This master's thesis by Timilehin Akinade Oguntuyaki (UBC, August 2020) assesses the water supply and demand of the Cove Bay Water System (CBWS), the largest of seven municipal water systems on Bowen Island, British Columbia. Using a water balance approach applied to the Grafton Lake Watershed, the study analyzes five years of treatment plant and metered water use data (2015-2019), models watershed drainage and lake inflow, and evaluates the Grafton Lake water balance under three groundwater loss scenarios (0%, 10%, 20%). The study finds that summer water use consistently exceeds supply margins, that summer precipitation is a stronger predictor of water demand than temperature, and that the lake balance becomes negative in most summer months. The thesis provides recommendations for demand-side conservation and supply-side management, including rainwater harvesting, lawn restrictions, pricing reform, low-flush toilet mandates, and increased lake storage capacity. Future research directions include applying PCIC climate change projections to 2100 and resuming climate monitoring at the Bowen Island weather station.
Date
January 1, 2020
Creator Organization
University of British Columbia - Faculty of Land and Food Systems
Authors
Timilehin Akinade Oguntuyaki
Document Type
Thesis
Subject Area
Water Resources > Groundwater | Water Resources > Hydrology | Water Resources > Water quality | Water Resources | Water-supply | Water Resources > Watershed management
Metadata
Keywords
Cove Bay Water System
|Grafton Lake
|Grafton Lake Watershed
|water balance
|water supply
|water demand
|water conservation
|groundwater
|surface water
|evapotranspiration
|precipitation
|climate change
|population growth
|Bowen Island
|water treatment plant
|metered water use
|non-revenue water
|lake storage
|summer water use
|Terminal Creek
|saltwater intrusion
Time Period
2015-2019
Relationship - isPartOf
Document ID
2605112019
Document ID
2605112019
Copyright holder
Timilehin Akinade Oguntuyaki / University of British Columbia
Document Filename
oguntuyaki-2020-assessment-of-the-supply-and-demand-cove-bay_2605112019.pdf
Storage Location
analysis/other-sources/
Key Findings
AI-generated: More than 50% of Cove Bay Water System residents used over 300 litres per person per day in summer months (2015-2019), well above conservation targets. Summer precipitation is a statistically significant predictor of summer water demand (R2=0.69), while temperature is not a significant predictor. Watershed drainage into Grafton Lake is negligible during July and August across all five study years. The Grafton Lake water balance is negative in most summer months but positive in winter, when the lake regularly spills at maximum storage capacity (1259 cubic decameters). A 10% loss of watershed drainage to groundwater reduces the annual lake balance by approximately 10.5%; a 20% loss reduces it by approximately 21%. Annual unaccounted water (non-revenue water and leakages) represents 8-16% of total treatment plant output. Average annual residential water use (220 L/P/D) is lower than Metro Vancouver averages, likely reflecting seasonal and part-time residency patterns. The current supply-demand situation is considered adequate but future conditions under climate change and population growth are a concern.
Methodology
Water balance modelling using monthly precipitation and evapotranspiration data derived from the Vancouver Harbour Climate Station (closest proxy to Bowen Island conditions, 2015-2019). Watershed runoff estimated as precipitation minus actual evapotranspiration, with soil water storage capacity (ASWC = 84 mm) based on soil survey data (Luttmerding 1981). Sensitivity analysis applied 0%, 10%, and 20% drainage loss to groundwater. Lake water balance computed as total inflow (direct precipitation plus watershed drainage) minus total outflow (evaporation, treatment plant withdrawals, and controlled release to Terminal Creek at minimum 8.5 L/s). Metered residential and ICI water use data analyzed in three seasonal periods (Jan-Apr, May-Aug, Sep-Dec). Regression analysis conducted for summer precipitation versus water use and summer temperature versus water use. Per capita water use calculated using an assumed occupancy rate of 2.5 persons per connection.
Map Descriptions
Page 9: Map A - Bowen Island showing the Grafton Lake Watershed outlined in red, with watershed boundaries and topographic contours (Whitehead Consultants Ltd, 2003). Page 9: Map B - Detailed map of the Grafton Lake Watershed showing Grafton Lake in the northwest portion of the watershed, with terrain contours and watershed boundary in blue (Bowen Island Municipality). Page 29: Soil map of the Grafton Lake watershed area cropped from the BC Soil Survey map (Luttmerding, 1980), showing soil type designations including RO-CE-EU, CE-BW, MY-BO, CE, MY-BO-CE, BO-CE-RO, and Rock Outcrops, with Grafton Lake visible in the upper right.
Graph Descriptions
Page 2: Bar graph showing the Bowen Island population trend 1981-2016, with population rising from approximately 1500 to 3680. Page 13: Line graph showing corrected monthly treatment plant water use 2015-2019, with anomalous Nov-Jan 2016-2017 values corrected to average. Page 15: Grouped bar chart of mean seasonal metered water use (m3/connection) for all users, 2015-2019, showing summer values 2-3 times higher than other seasons. Page 16: Grouped bar chart of mean seasonal residential water use (m3/connection), 2015-2019. Page 17: Grouped bar chart of mean seasonal ICI water use (m3/connection), 2015-2019. Page 20: Histogram of frequency distribution of average annual residential water use in L/P/D, 2015-2019. Page 20: Histogram of frequency distribution of average summer residential water use in L/P/D, 2015-2019. Page 21: Line graph comparing summer precipitation (May-Aug) at four stations (Bowen Island, West Vancouver, Gibsons, Vancouver Harbour), 1994-2012. Page 21: Scatter plot of mean maximum summer temperature versus precipitation at Vancouver Harbour, 1976-2019, with 2015-2019 years labelled. Page 22: Five paired line graphs showing monthly water use versus monthly precipitation for each year 2015-2019. Page 23: Scatter plot of monthly summer precipitation versus water use (treatment plant data) with regression line (R2=0.69). Page 23: Scatter plot of summer mean maximum temperature versus water use with regression line (R2=0.29, not significant). Page 26: Line graph showing annual precipitation trend at Vancouver Harbour, 1971-2019. Page 27: Line graph showing summer (Apr-Aug) and winter (Nov-Mar) precipitation trends at Vancouver Harbour, 1971-2019. Page 28: Five line graphs (one per year) showing monthly potential ET versus actual ET for 2015-2019. Page 30: Grouped bar chart of monthly drainage (mm) by year, 2015-2019, showing zero drainage in July-August. Page 30: Bar chart of monthly average drainage 2015-2019, showing November as highest (approximately 229 mm). Page 32: Bar chart of Grafton Lake monthly evaporation by year (m3), 2015-2019, peaking in July. Page 33: Bar chart of monthly average lake evaporation 2015-2019. Page 34: Two-panel graph showing annual Grafton Lake balance (m3/year) and percentage decrease from 10% and 20% drainage loss scenarios, 2015-2019. Page 35: Two-panel graph showing annual watershed drainage under 0%, 10%, and 20% groundwater loss scenarios, 2015-2019.
Image Descriptions
Page 9: Satellite and aerial composite image showing Bowen Island and Howe Sound with location inset map of the broader Metro Vancouver region. Bowen Island is highlighted in red in the regional map.
Page Count
41
Publisher Location
Vancouver, British Columbia
File Size
1.6 MB
File Format
application/pdf
Geographic Locations
Bowen Island | Grafton Lake Watershed | Grafton Lake | Howe Sound | British Columbia | Metro Vancouver | Cove Bay | Millers Landing | Snug Cove | Queen Charlotte Heights | Cates Hill | Terminal Creek