Research

TECHNICAL REPORTS

WPS gathers and distributes locally-focused scientific studies related to our mission of water conservation. Some — but not all — of the reports below were written by WPS members. The views expressed in each report are those of the authors, not of WPS. Click on the blue headlines to access the full text of each article.

Reports relevant to all SSI watersheds
Reports about north SSI watersheds
Reports about mid SSI watersheds
Reports about south SSI watersheds

CITIZEN SCIENCE

Freshwater Catalogue volunteers collect data and local knowledge to improve our understanding of the island’s surface and groundwater over time.

All SSI watersheds

Salt Spring Island Water System Survey
Shannon Cowan, 2020

In brief
The average Salt Spring surface-source system user consumes only 67% of the provincial municipal average (2016). The average Salt Spring groundwater system user consumes 30% of the provincial municipal average.

Salt Spring Island groundwater recharge potential mapping
K. Antonio Barroso, Matt Vardal & Gilles Wendling, 2019

The [map of the] aquifer recharge potential […] clearly shows a high contrast between areas on Salt Spring with low recharge potential (northern and eastern island, including the peninsulas), and areas with moderate to high recharge potential (west central and southern part of the highland).

Aquifer recharge systems are complex and vary greatly across the Island. […] A detailed water budget study is recommended to properly manage the water resource on Salt Spring.

Aquifer mapping and monthly groundwater budget analysis for aquifers on Salt Spring Island
Nick G. Gorski & Jillian P. Sacré, 2019

In brief
There is not a lack or shortage of available groundwater associated with the Salt Spring Island bedrock aquifers on a regional basis. However, on a local basis, the low transmissivity/hydraulic conductivity of the rock on Salt Spring Island means that groundwater use from individual wells can commonly exceed the capacity of the local rock to bring water to the well when the well is installed in lightly fractured and non-fractured rock or the fracture network intersected by the groundwater well is poorly connected to a larger source. […] Seasonal groundwater shortages in the dry season are also observed across the island due to local exhaustion of groundwater storage. […]

Salt water intrusion represents a real concern to groundwater availability in certain areas of Salt Spring Island (particularly in the north part of the Island along the northeast coast and in the Ganges Harbour/Long Harbour area).

Water Conservation on Salt Spring Island:
Report 1 — Technologies and Methods
Sandra Ungerson and Rob Kline, 2019

In brief
[This report] presents evidence for a broad range of applicable technologies, methods, and resources that can be implemented to increase water supply, and efficient water use across system and consumer types, on Salt Spring Island. These technologies are all being used globally, successfully. Some are even being utilized in British Columbia and the Gulf Islands.

Water Conservation on Salt Spring Island:
Report 2 — Literature Review
Ian Peace, 2019

In brief
[This literature review describes] some global examples of wastewater reclamation that predicts some of the economic and social feasibility conditions that would be required for such wastewater reclamation models to be applied for use in Ganges, Salt Spring Island.

Agriculture water demand model — report for Salt Spring Island, BC
Ted van der Gulik & Stephanie Tam, 2017

Rainwater Harvesting: An Investigation of the Current Use on Salt Spring Island
Kendra Anderson, Angela LeBlanc, Charlene Lloyd & Derek Wilcox, 2017

In brief
SSI is an ideal location to encourage [rainwater harvesting] at a broad scale because of the supportive an environmentally conscious community. Overall, residents expressed concern surrounding the costs associated with [rainwater harvesting] systems. Additionally, existing regulations are affecting public perceptions regarding the accessibility and ease of installing these systems. Education on water conservation and the benefits of [rainwater harvesting] is clearly lacking for those that are not experiencing water shortages.

Risk of saltwater intrusion in coastal bedrock aquifers: Gulf Islands, BC
Jeanette Klassen & Diana M. Allen, 2016

In brief
Several hazards were identified for this coastal area that have the potential to lead to salinization of aquifers, including storm surge, sea level rise, and pumping. […] The final coastal hazard map suggests that coastal hazards are limited to a few areas on Salt Spring Island, particularly in narrow bays and inlets (e.g. around Ganges Harbour); these areas could experience inundation (up to ~400 m inland) related to sea level rise and storm surge. Overall, however, coastal hazards are relatively limited across most of Salt Spring Island.

Brief report and feasibility study on desalinization for Salt Spring Island BC
Devesh Bharadwaj, 2016

In brief
Separating salt from seawater is an energy intensive process and in some cases, a last resort. […] [However, water] availability and quality is a rising issue on some parts of Salt Spring Island. […] Using a desalination plant not only accommodates for the increase in water demand but can also make the island independent of the rainfall rate and groundwater levels as the main source of water. […] With the low [greenhouse gas] emissions associated with electricity use for the potential plant and multiple options of sea water intake and brine disposal, a [desalinization] plant can be a reliable option with minimal environmental effects.

Determining the hydraulic properties of fractured bedrock aquifers of the Gulf Islands, BC
D.M. Allen, E. Liteanu, T.W. Bishop and D.C. Mackie, 2015

In brief
[T]he fact that we do observe linear flow in many wells is a strong indication that our conceptual model consisting of a hierarchy of fracturing is reasonable, and that vertical fracture zones probably do play a major role in controlling flow on the Gulf Islands.

Hydraulic conductivity values […] gave fairly consistent results between formations. This result was somewhat unexpected, but may perhaps be explained by the fact that joint spacing, and thus, permeability is expected to be higher where bedding thickness is smallest, such as in the transition zones between the mudstone- and sandstone-dominant formations.

Drought analysis and implications for Salt Spring Island, BC
Donald O. Hodgins, 2015

In brief
The 2015 spring drought (April through June) was by far the most severe in the 100-yr record, with a return period well in excess of 100 years. Droughty springs occur throughout the record, but show no indication of becoming more frequent or more severe, on average. The likelihood that a droughty spring will be following by a droughty fall and winter, leading to a shortfall in the lake refilling (for St. Mary Lake), is low, of the order of one in 1000 years. There is no doubt that the [St. Mary Lake] climate is becoming wetter. The data suggest an increase of about 200 mm in the past century, or about 20% of the current annual total of 965 mm. The data also indicate that the year-to-year variations in total and fall-winter rainfall (the change from one year to the next) are increasing compared with 100 years ago.

The hydrogeology of Salt Spring Island
Isabelle Larocque, Diana M. Allen & Dirk Kirste, 2015

In brief
Overall, the hydrogeology of Salt Spring Island is consistent with that of the other Gulf Islands. The main difference is the presence of igneous fractured rock in the south-central part of the island […] The igneous rock units, which are of Carboniferous to Permian age, are broadly composed of granite, rhyolite and pyroxene. Despite the difference in rock type, the general hydrogeology of the igneous rocks is consistent with that of the sedimentary rocks.

The amount of recharge to aquifers remains uncertain on Salt Spring Island and on the Gulf Islands more broadly, despite the wide variety of methods used in previous studies and study to estimate recharge (e.g., water level fluctuation method, water balance modeling, etc.).

The groundwater chemistry of Salt Spring Island is generally consistent with that of the other Gulf Islands. In the sedimentary rocks, cation exchange is a dominant process that influences the chemistry. Groundwater evolves from rainwater to a Ca-HCO₃ composition as a result of calcite dissolution, through to a Na-HCO₃ composition due to cation exchange, and finally to a Na-Cl composition due to mixing with seawater. […] However, there are unique characteristics of the Salt Spring Island water chemistry given the presence of the igneous rocks. Contrary to the sedimentary rocks, igneous rocks do not have ion exchange sites due to the absence of clay minerals. As a result, no cation exchange takes place as the groundwater flows through the system.

Water for life on Salt Spring Island
Phaedra Henley, 2009

In brief
Salt Spring has the potential for turning around its increasingly critical water situation. To accomplish that requires a science-based framework for understanding the pressures that have led to and continue to promote the current situation. Actions based on this understanding should not only be directed toward alleviating symptoms in our surface water — lakes and streams — (and also in ground water) such as high levels of phosphorus, heavy metal or microbial contamination, but as well toward reducing the pressures that have led to these undesirable conditions. This will involve setting guidelines that limit human activities within watersheds such that the aggregate stress from these activities does not compromise the health of the watershed.

Nine lakes on Salt Spring Island, BC: size, watershed, inflow, precipitation, runoff and evaporation
John Sprague, 2009

In brief
SIZE: St. Mary Lake dwarfs all the other lakes of Salt Spring, in size and amount of standing water. St Mary contains about 16 million cubic metres of water, while the other lakes range from a little over 2 million down to only about 0.1 million cubic metres.

INFLOW: [T]he greatest yearly inflows of water occur in Cusheon and Ford Lakes, each with almost 4 million cubic metres per year (m³/yr). […] St. Mary and Blackburn have somewhat smaller yearly inflows of about 3 million m³/yr, followed by Stowell Lake with almost 2 million m³/yr. Inflows to Bullocks, Maxwell, Weston and Roberts Lakes range from 1 million down to less than 0.6 million m³/yr. Diversions into Maxwell Lake have boosted its yearly inflow from last place to sixth place among the nine lakes.

REPLACEMENT TIMES: The fastest are Blackburn and Ford Lakes, which average just over a month [to replace 95% of their water molecules]. Stowell Lake, Cusheon Lake, Roberts Lake, and Bullocks Lakes take about 4 months. Maxwell Lake, after diversion of streams into it, takes almost eight years. St. Mary Lake is the slowest to flush, with a replacement time of almost fifteen years. […]

PRECIPITATION: Yearly rain and snowfall has historically averaged 0.98 metres in the Cusheon drainage basin. The average for all of Salt Spring Island is 0.959 metres in a year.

RUNOFF: The annual surface runoff, directly from the land into creeks, is estimated as 48% [based on a] robust average of eleven estimates by earlier workers at various locations on Salt Spring Island.

[…] Salt Spring lakes are unusual in two respects, compared to “typical” lakes elsewhere in Canada and the world. First, the major inflow of water comes as heavy winter runoff, followed by dry creeks in summer. Second, most of the lakes are of unusual size compared to their drainage basins. Blackburn, Ford and Stowell are small lakes set in relatively large basins. Weston, Maxwell and St. Mary are large lakes in small basins. Roberts, Cusheon, and Bullocks Lakes are more typical in size, relative to their drainage areas.

North SSI watersheds

Arrested development: The saga of a ‘sustainable’ planned village on Salt Spring Island, 1985-2016 (BC Studies, 2020)
J.I. Little, 2020

In brief
As a newcomer to Salt Spring and a regular walker on Channel Ridge, I began to wonder how the abandoned development site could come into being on an island that has long been experiencing pressure for more population growth. […] The first questions this research note addresses, then, are: What happened and why? On a broader scale, it asks what this environmental scar reveals about recent attitudes towards the natural environment and about the relationship between property developers and the wants and needs of the broader community.

Water diversion license limits for St. Mary Lake
Donald Hodgins, 2018

In brief
The Province issues licenses for surface water withdrawal [that specify] the maximum amount that can be withdrawn over a defined period of time, usually one day or one year. For St. Mary Lake, all licenses total 573 dam³ [1 dam³ = 1,000,000 L] for the critical June-October summer season. However, for an extreme drought the available safe yield during summer is about 350 to 380 dam³, substantially less than allowed by license. […]

[T]he basic design principle is to allocate water licenses up to a limit that is available for climate average hydrological conditions, taking critical environmental flow thresholds into account. The Province recognizes that the full allocation will not be met during droughts, and has implemented a complex procedure for restricting or denying withdrawals. […] The weaknesses [of this principle] are obvious: there are dry winters when the runoff is inadequate to replenish the fully allocated storage, and there are summer droughts that result in significant shortages of water to meet the licensed withdrawal total. Periods when restrictions come into force are inevitable.

Current demand appears to be well below the licensed total for St. Mary Lake. […] However, summer demand (June-October) is roughly 340 dam³ without water restrictions, leaving a reserve of about 12% of the safe yield [figure adjusted for environmental flows and evaporation].

Drought-limited water supply and demand for St. Mary Lake and Lake Maxwell
Donald Hodgins, 2018

In brief
The maximum amount of water available from St. Mary Lake and Lake Maxwell for potable supply is about 1,000 to 1,100 dam³/year [1 dam³ = 1,000,000 L]. This is the limit for the worst drought on record for the past 100 years. It is sufficient to supply about 4,000 single-family dwellings each year. Current demand (2017) is approximately 880 to 900 dam³/yr, leaving a reserve of 15% to 20% of supply (about 170 dam³ or 660 single-family dwellings). Climate change over the next 100 years could potentially reduce this reserve by about one-half. The safe supply reserve would then be less than 100 dam³, or approximately 300 to 350 single-family dwellings. […]

Water diversion licenses issued by the Province for both lakes total 2257 dam³/yr, more than twice the supply available in a severe drought. [This does not] seem appropriate for future planning, and for allocation of the water resource.

Maxwell Lake, Rippon Creek and Larmour Creek Watersheds water availability — climate change assessment
Craig Sutherland & Wendy Yao, 2017

In brief
Although there is sufficient storage to support withdrawal to NSWWD water system up to the licensed withdrawal limit there would not be sufficient inflow under 10-year drought conditions to refill Maxwell Lake prior to following summer draw down period. [We recommend that withdrawals] from Maxwell Lake be capped at 72% of the licenced withdrawal limit (477,900 m³) such that inflow from Larmour Creek, Rippon Creek and Maxwell Lake watersheds can refill Maxwell Lake after 10-year drought conditions

Safe yield analysis for surface water resources [in the St. Mary Lake watershed]
Donald Hodgins, 2017

In brief
[…] There were nine drought years in the total 35-yr record [1981-2005] providing yield estimates that were used for an extreme value analysis. Some key findings are:

  • June-October yield values of ~ 415 dam³ [1 dam³ = 1,000,000 L] in 2015 have a return period of about 25 years, with an equivalent annual yield of 705 dam³. 1987, the worst drought year on record, has a return period of 80 years, with a yield of ~ 360 dam³ (annual 612 dam³).

  • For return periods of 50 to 100 years, the dry-season yield would be about 380 to 350 dam³ respectively. The annual equivalent is 650 to 595 dam³. Current withdrawals (2014) are about 580 dam³, leaving little additional capacity in St. Mary Lake.

  • Increasing the storage until refilling limits withdrawals would provide about 930 dam³ annually, assuming that winter outflows equivalent to what currently is discharged through the fish ladder would be acceptable to the BC Ministry of Environment. If higher environmental flows are required, the benefit of raising the weir is reduced. […]

  • The yield calculations for 2009, 2014 and 2015 are considered reliable because of the weir control of outflows and relatively good information on withdrawals. The long-term yield estimates for 1981-2006 are less certain because of possible errors in the discharge estimates to Duck Creek, in withdrawals, and the difficulties is calculating changes in storage from the adjusted water level series. Application of a hydrological model, including a rigorous uncertainty analysis for the yield estimates, should be considered to further support the safe yield assessment.

Phosphorus to St. Mary Lake from wintering waterbirds
John Sprague, 2017

In brief
Wintering waterbirds probably contribute about 13 kg of phosphorus to St. Mary Lake in their excrement. This is a relatively small amount, somewhat more than the 10 kg which is thought to come from groundwater entering at the bottom of the lake. […] Almost all of the food intake by the birds is vegetation, invertebrates and fish that were available in the lake. Accordingly, the phosphorus in the birds’ food was already in the lake, and the excreted phosphorus was simply cycling through the birds and returning to the lake. From one point of view, there has been no new phosphorus added to the lake. From another point of view, the phosphorus was previously locked up in vegetation, fish, or invertebrates, but after passing through the waterbirds, it was released into the water, presumably in a soluble form. Thus it would be available to stimulate algal growth.

Analysis of phosphorus inputs to St. Mary Lake from septic systems
Donald O. Hodgins, 2016

In brief
On-site sewage treatment systems are working efficiently, with phosphorus retention factors immediately under the drain fields exceeding 95% for the slightly acidic soils around St. Mary Lake. The evidence also shows that no phosphorus attributable to septic systems is reaching the shoreline waters of the lake, indicating that even if phosphorus plumes form in the groundwater below drain fields, all of it is adsorbed to soil particles before reaching the lake. […] Because a load of about 5 kg, or less, is negligible in terms of the phosphorus content of the lake and other external sources, wastewater collection and treatment facilities are not necessary, and would provide no benefit for water quality in St. Mary Lake.

Three perceptions of St. Mary Lake challenged by SSIWPA studies
Maggie Squires, 2015

In brief
The results of the 2014-15 study challenges [the following] common perceptions about St. Mary Lake:

  1. The lake is eutrophic and getting worse

  2. Cyanobacteria are bad because they produce toxins, and aquatic plants are nuisance weeds

  3. Internal loading is more than external loading.

Although St. Mary has occasionally experienced increases in [phosphorus] levels, the long‐term record does not suggest overall increase over time.

While it is true that some cyanobacteria […] produce toxins, the cyanobacteria in St. Mary Lake also fix atmospheric [nitrogen] when [nitrogen] availability is low relative to [phosphorus] availability.

Due to strong control by iron of net [phosphorus] release from sediments, external [phosphorus] inputs from the watershed & direct rainfall may be greater than internal [phosphorus] inputs. This result raises questions related to the use of artificial aeration as a remediation strategy to improve water quality.

Analysis of phosphorus and algal abundance data for St. Mary Lake, British Columbia
Donald O. Hodgins, 2015

In brief
There has been no significant change in seasonally-averaged amounts of phosphorus in St. Mary Lake over the past 40 years, and by inference from the sediment core data, over the last 150 years. There are, however, large changes of the amount of P seasonally, and from year to year.

Water balance analysis of St. Mary Lake, British Columbia
Donald O. Hodgins, 2015

In brief
If we consider the balance between storm water runoff, and water removed from the lake, the calculations show that it is positive for only one or two months each year (storm water in exceeds flows out). These usually occur between November and January. In five of the eight years examined, the greatest amounts of runoff were found in November and December, when nutrient loading through internal processes is highest. In other months, outflows and withdrawals typically exceed runoff.

Estimates for external phosphorus loads to St. Mary Lake, British Columbia
Donald O. Hodgins, 2015

In brief
Net external total phosphorus loads to St. Mary Lake are highly variable from year to year, ranging from about 70 kg/yr to 300 kg/yr. The net loading averages approximately 140 kg/yr based on a little over 9 years of data.[…] Since no significant change in phosphorus content has been detected over the past 150 years, or so, the net positive external load must be cycled to bottom sediments through internal lake processes. […] [Phosphorus] removal from storm water runoff would have little impact on the phosphorus dynamics of the lake. Moreover, it would be difficult with so many points of entry, and removal efficiencies are not yet established. Any benefit would need to be carefully quantified to ensure that it is worth the effort and expenditure.

Review of St. Mary Lake restoration options
Ken Ashley, 2008

In brief
St. Mary Lake has experienced accelerated eutrophication due to human activities in the watershed. As a result, the water quality of St. Mary Lake has deteriorated considerably since the 1970s. […] The core element of a St. Mary Lake water quality improvement and protection plan must include a comprehensive watershed nutrient management program to reduce point and non-point source nutrient loading. Without this approach, no lake restoration technique will be effective in the long term.

Hypolimnetic aeration is well suited to St. Mary Lake as internal phosphorus loading has been identified as the single largest [phosphorus] source to St. Mary Lake, and the phosphorus in the lake is sensitive to changes in the oxidation-reduction potential, and will sequester phosphorus when the overlying water is aerobic. […] Food web biomanipulation should also be considered if large bodied zooplankton are being excessively grazed by planktivorous fish. […] Iron addition, in combination with hypolimnetic aeration, may be effective if sediment core samples indicate the sediment iron-phosphorus ratio is less than 15:1 due to pyrite formation.

Mid SSI Watersheds

Linking watershed exports & the ecology of Blackburn & Cusheon Lake, 2014-16
Maggie Squires & Drew Bodaly, 2016

In brief
Major new findings include the following:

  • groundwater appears to be an underappreciated flow component

  • septic field failures at the Cedar View Trailer Park may episodically contribute nutrients to Cusheon Lake

  • net dissolved inorganic [phosophorus] load was substantially lower than the previously modeled estimate of [phosphorus] load (CWMP 2007) yet provided realistic predictions of lake water phosphorus concentration

  • lake waters undergo strong seasonal cycles including NO₃ depletion-replenishment, and low-high water clarity.

[…] Both lakes were relatively turbid during the winter when flushing with inflow water was frequent, and relatively clear during the spring-summer when inflow and outflow ceased; and, in both lakes, a late summer/early fall algal bloom was triggered by internal mixing (deepening of the epilimnion) and bloom collapse coincided with lake turnover (mixing to the lake bottom). […] Based on summer chlorophyll and [total phosphorus] levels in lake water […] Blackburn Lake is between mesotrophy (intermediate productivity) and eutrophy (high productivity) while Cusheon is between oligotrophy (low productivity) and mesotrophy. […]

Recommendations for improving lake water quality include

  • monitoring outflow from the garbage transfer station (once a garbage dump):

  • regular inspection of lakeshore and streamside septic fields (by residents) to detect and repair field failures as soon as they occur

  • a halt in activities that discourage beaver dams and log jams at the Cusheon Lake outflow; rewatering of the Blackburn wetlands

  • removal of the abandoned pump house and pipes on the Blackburn lakeshore and of the pumps, pipes, and rock dam in the vicinity of the Blackburn Lake outflow

  • seeking of public support for the installation of holding tanks where septic fields are within 100 feet of the Cusheon lakeshore.

Phosphorus carried by small culverts into Cusheon Lake
John Sprague, 2007

In brief
This study assessed seven culverts [under Horel and Cusheon Lake Roads] as a source of phosphorus for Cusheon Lake, and [compared phosphorus concentrations and loads] to those in Blackburn Creek (upstream of Blackburn Lake). […]

The concentration of phosphorus in the culvert water was usually similar to the concentration in Blackburn Creek. However, the first two flushes of runoff had very high concentrations in the culverts — two to three times higher than the creek. Phosphorus apparently accumulated on the land around Cusheon Lake during the dry season, and washed off with the first big rains. Presumably the higher phosphorus is related to human activity in this built-up area. […]

Phosphorus content of certain creeks and lakes in Cusheon Lake basin
John Sprague, 2007

In brief
During the winter and early spring, creeks feeding Roberts Lake had surprisingly high concentrations and loads of phosphorus. […] Along the most downstream section of Blackburn Creek that bordered a modular-home park, a small number of measurements of dissolved phosphorus indicated an average increase of 24 grams of phosphorus per day. That gave some confirmation of an earlier theoretical estimate of a 21-gram increase as the result of normal seepage from septic fields at the modular-home park.

Apparant sources of phosphorus affecting Cusheon Lake
John Sprague, 2007

In brief
The amount of phosphorus [in Cushion Lake] is the overall factor that controls the strength of algal blooms. […] Average phosphorus concentration has been 16.6 μg/L [mesotrophic, = somewhat enriched] in the most recent decade (1996 to 2006). […] If the total loading of phosphorus to Cusheon L. were reduced by 18 kg per year (15%), the lake would probably attain an acceptable status in the lower mesotrophic zone [with only] minor algal blooms, and few problems with toxic cyanobacteria. This reduction is recommended. […] ([Meeting] the provincial goal for a “drinking-water lake,” would require [an unrealistic reduction of] 38 kg).

Near-elimination of the direct human input from septic fields (25.5 kg) could be done by complete collection of sewage from all residences (or connecting to a specially-built sewer) with central waste treatment. […] [The] conventional cure of aerating bottom water is not feasible in this shallow lake, and use of a chemical precipitant might not be favoured. […]

Phosphorus runoff from the upper Cusheon basin
John Sprague, 2007

In brief
During most of the year, particulate phosphorus [in upper Blackburn Creek] was the dominant form in the water. Dissolved phosphorus, the most readily available form for algae and other biota, was a small fraction of the total. It appeared to have a base concentration of 8 to 24 [parts per billion], probably derived from groundwater emerging as springs. However, during the very first small freshet after the summer dry period, there was a peak of phosphorus which was almost entirely dissolved, not particulate. That peak might largely represent soluble phosphorus from the ashes of “burn piles” and from decay of vegetable matter during the previous dry season. […]

South SSI Watersheds

Pilot water quality report for streams discharging into W̱E¸NÁ¸NEĆ/Hwune’nuts (Fulford Harbour)
P.S. Ross, J.A. Millson, A. Parkinson, and S. Scott, 2023

In brief
[…] We conducted a small-scale study of water quality in seven creeks entering Fulford Harbour at three points in time in 2022 and 2023. Measurements were made of basic water properties in situ, including temperature, conductivity, pH, dissolved oxygen (DO), and flow. […]

Basic freshwater properties data fell within the range measured previously both in Fulford Harbour streams and at other freshwater sampling sites on Salt Spring Island. […] There were no exceedances of BC Environmental Quality Guidelines for the protection of aquatic life for any of the water properties or metals. Fecal coliforms were detected in 93% of water samples, and E. coli was detected in 91% of samples, indicative of land-based biological contamination of creeks from wildlife, livestock, pets and/or humans. Fecal coliform [and E. coli counts] were highest in summer […]. Variations in E. coli in some creeks highlight the potential for sporadic releases of pathogens into Fulford Harbour. […] [This is concerning given the] anticipated future re-opening of shellfish harvesting […]

The water quality of Weston Lake, Salt Spring Island
Richard Nordin, 1986

In brief
The root cause of the deteriorating water quality in Weston Lake is an increasing supply of nutrients [mainly from humans and cows]. […] The obvious solution […] is to reduce the amount of phosphorus which enters the lake. However, this is neither easy nor inexpensive since both the sewage disposal and agriculture practices are established and difficult to modify. […] [Filtration or in-lake restoration approaches] would be less desirable since no change is made to the cause (nutrients) of the unacceptable algal growth. […] In summary there appears to be no easy solution to the problem of heavy algal growth in Weston Lake.