SSI FreshWater Catalogue - Duck Creek/St Marys (DUCK/SMLK)

SSI FreshWater Catalogue

SSI, NORTH Watersheds

Duck Creek (DUCK) Watershed & St Mary Lake (SMLK) Sub-watershed "Notes"

- Tripp Road, North End Road, Epron Road, Channel Ridge highlands, St Mary Lake -

LAST UPDATE 2023/03/22

SSI North Area - overview watersheds (colour coded, CRD, 2018) & watershed note area

North Island, Duck Creek Watershed (DUCK), also known locally as the St. Mary Lake (SMLK) sub-watershed

From our ongoing North Island, Freshwater Cataloguing - notes on the Duck Creek (DUCK) watershed, the St. Mary Lake (SMLK) area is a subwatershed of the larger Duck Creek watershed. Cf. the SSI FWC webmap for field locations and charted information (where available).

The content of these "Notes" entries is dependant on the information that is currently available, from FWC volunteer work, FWC reporting or from other sources. We have no active FWC volunteers in this important watershed area.

Note - if you have additional insights into this area (the watershed, it's creeks or wetlands), can help with site(s) access, or are interested in being involved in data collection for this project area, please contact the SSIFWC Project Lead.

For now these watershed notes draw heavily on Water Preservation Society stewardship observations, and activities associated with the management of WPS watershed lands in the St. Mary Lake sub-watershed area.

Very limited (ad-hoc) FWC data is available from the Duck Creek Watershed area. FWC "field note" addendums to these Duck Creek watershed notes will be added if/as these become available. FWC volunteer field measurements in this watershed will enable us to do more!

General Watershed & FWC Creek(s) Information:

The Duck Creek Watershed is located in the North Salt Spring Island area. The "St. Mary Lake sub-watershed area" lies within Duck Creek watershed area and represents an important sub-watershed region. This sub-region is demarcated by the larger Duck Creek watershed area's freshwater inflows into St. Mary lake itself. Lake surface freshwater inflows are sourced principally by upland freshwater catchment areas to the west (Channel Ridge), a large catchment area to the northwest ("Epron Road valley")* and from a smaller wetland, creek, pond(?) catchment area close to the watershed boundary to the northeast (North End Road). A separate feeder supports additional Duck Creek inflow (to the sea) from southeast corner of the main watershed, the Corness Swamp.

St. Mary Lake is the largest standing body of water (lake) on SSI (Sprague, 2009), and the largest lake within the Southern Gulf Islands. Duck Creek is a significant island riparian area and salmon-bearing stream, discharging to the sea close to Duck Creek park, from the SW corner of St. Mary Lake.

The St. Mary sub-watershed area is THE catchment area for all surface freshwater feed for St. Mary Lake. Any negative anthropogenic changes in the sub-watershed freshwater feed areas (fire, “household” or other spillages etc) may trigger catchment area degradation (contamination, soil erosion, reduced natural ecosystem filtering.... ) on a significant scale. The St. Mary Lake sub-watershed area is vulnerable to freshwater quantity/quality (lake freshwater supply) issues, impacting the local natural ecosystems (and services) and the larger island community. Given the timing for any watershed catchment area recovery, and/or lake flushing to occur, any sort of degradation has the potential to have a significant impact on SSI freshwater supply for some time.

The North Salt Spring  Waterworks District (NSSWD) alone withdraws  around ~85 million imperial gallons (2013) or ~385 million litres of freshwater annually, other users include the Fernwood Highland Water District, local resorts and many lakeside residents.

The definition of a protected, large, forested, St. Mary sub-watershed freshwater catchment area (272 acres) was completed in 2003 and is managed by the SSI Water Preservation Society. This nature reserve was established in an effort to protect the quality of the drinking water from St. Mary's Lake, as a key part of the NSSWD supply network.

Note - walking trails in the WPS nature reserve have different rules than those of the non-watershed Channel Ridge Trails. These nature reserve restrictions are established under a legal covenant and clearly marked on signs as the trails enter WPS lands.

*Epron Creek, located in this North Island, Duck Creek (DUCK) watershed, is a key (year-round?) feeder stream for St Marys Lake in this important subwatershed area. Epron Creek was our May 2021 Which Creek Is It competition entry.

Duck Creek watershed and St. Marys Lake sub-watershed overview (Lidar backdrop), and various area, spring, wetland and creek images

The Duck Creek watershed

The Duck Creek (DUCK) watershed is the fourth largest watershed on the island, some 973.8 hectares (2406.3 acres) in size. The watershed is larger than the Central Island Maxwell Creek and smaller than the Central Island Cusheon Creek watersheds
The watershed receives something like 9,251,100,000 litres (2,443,880,000 gallons) of rainfall (or surface water) per annum ( water volumes are approximate with no consideration of surface/terrain conditions, nor rainfall variability within the catchment area)
The watershed captures close to the volume captured by the Cusheon Creek, the islands second largest watershed.
Duck Creek is the principle creek in the watershed (see posted Duck Creek watershed area map), with this creek system being the single sea-outfall from the watershed
Within the watershed area are approximately 80 groundwater wells. The deepest drilled well located within this region was/is 250 metres (820 feet; Hodge, 1995) and there are several licenced springs
The Duck Creek watershed is a large part of the St. Mary Lake aquifer sub-region
The St. Mary Lake sub-watershed is the site of a principle SSI surface water abstraction, with this lake (serviced by the North Salt Spring Island Water District - NSSWD) contributing to freshwater supplies for some 45% of the island's population.

The St. Mary Lake sub-watershed

St. Mary Lake sub-watershed covers 7 square kilometres with the lake covering nearly 2 square kilometres
The lake contains nearly 16 million cubic metres of water with a maximum depth of approximatley 17 metres
Estimates of flushing, to replace the entire volume of freshwater in St. Mary Lake, are estimated at some 5-15 years... ( Sprague, 2009; Squires & Bodaly, 2020).

Historical & Other Watershed Insights:

A short history of the St. Mary Lake (subwatershed) area and it's use as an island freshwater resource is available on the NSSWD website. Work on the chemistry have been undertaken by Squires & Bodaly (2020 and references there-in) and Safe Yield Analysis for St. Mary Lake has been done by the NSSWD and by Hodges (2018, 2017).

Anecdotally, there are indications from oral history that St. Mary Lake has a history of seasonal changes/shifts in colour, it is possible that these changes may be attributed to historic cyanobacterial blooms in the lake water body.

Note - any local insights, or interested in contributing to the historical/other notes on our islands' watersheds, please contact the SSIFWC Project Lead.

FWC "Citizen Science" & Other Watershed Notes - Reporting:

A part of the St. Mary Lake geological fault system (a fault plane or fault zone) expresses itself as a spring on the north of Booth Inlet (Golder, 2019). The exact nature of the through-going N. to S. geological faults within the St. Mary Lake area is unknown, though these lineaments have the potential to contribute to groundwater inflow into the lake, via lake-bed inflow, as is speculated for several other SSI lake systems (eg Weston Lake, in the central island Weston Creek watershed).

To the south and south east of St Mary Lake, in north of the Duck Creek watershed area and in the adjacent McFadden watershed to the north, the N. to S. St. Mary Lake through-going faults may also act as conduits for more saline water incursions (Hodge, 1995; Greenwood, 2011; Laroque et al., 2015), and/or play a role in controlling/maintaining flow in McFadden Creek (over geological time... faults are known to leak!).

To-date there is no FWC reporting for this watershed. Further local data collection in this area would provide improved insights into how this watershed (and it's related freshwater ecosystems) work, are impacted by seasonal (or climatic…) changes, and will help with an improved understanding of how surface water catchments (eg Epron Creek) in the watersheds contribute to aquifer recharge and local island water resource availability...

Interested in being involved in this watershed area - please contact the SSIFWC Project Lead.

FWC Images and Videos:

Duck Creek Watershed FWC field images. Note - all FreshWater Catalogue images & videos copywrite belongs with the WPS and the FWC. We are grateful for due acknowledgement of copywrite in any use or publication of these educational resources.

Other Local Area Resources:

Barnett et al., 1993., Salt Spring Island Water Allocation Plan.
Hodge, W. S., 1995., Ground Water Conditions on Salt Spring Island.
SSI Salmon Enhancement Society, 1998., Habitat Restoration and Salmon Enhancement Program.
Sprague, J. B., 2009., Nine Lakes on Salt Spring Island, B.C.; Size, Inflow, Precipitation, Runoff and Evaporation.
Greenwood, H. J., & Mihalynuk, M. G., 2009., BC Geological Survey, Open File 2009-11 Salt Spring Island Geology.
Greenwood, H.J. 2011., Saltspring groundwater in bedrock. A preliminary study for Saltspring Water Council.
McCullough M., 2011., Anadromous Coastal Cutthroat Trout Habitat Reconnaissance. FLNRO.
Larocque, I. Allen, D. M. & Kirste, D., 2015., The Hydrogeology of Salt Spring Island, SFU.
Hodges, D. O., 2018., Technical Note Water Diversion Licence Limits for St. Mary's Lake, Salt Spring Island.
Ecofish Research Ltd., 2018., Duck Creek Instream Flow Study. Prepared for NSSWD.
Hodges, D. O., 2017., Safe Yield Analysis for Surface Water Resources.
GW Consultants., 2019., Salt Spring Island Groundwater Recharge Potential Mapping for IT, circulated with 2019/10 meeting reporting.
Squires, M., Bodaly, D., 2020., Phosphorous Loading to St. Mary Lake via Stream Inflows, 2019-20.
Squires, M., Bodaly, D., 2020., Summary of Six Reports, Gulf Island Lakes (New Work 2014-2020), B.C., Canada.
North Salt Spring Water District (NSSWD), cf. website History of North Salt Spring Waterworks, Hydrology Reports, and St Mary Lake
Water Preservation Society, cf. website St Mary Lake Brochure.

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