The connection between fresh water in wells (aka groundwater, indirectly from rainwater) and surface fresh water bodies (creeks, wetlands , lakes, ponds) in watersheds (directly from rainwater, or precipitation) is a classic story of the "interconnectedness of things". In this case the story is of how the sources of our island's (surface and ground) fresh water systems relate to each other, as far as we know today... 

Our island's surface freshwater story is only a component part of our SSI freshwater resource story... Natural surface freshwater systems (creeks, wetlands and lakes) in our island's watersheds are connected to our subsurface freshwater (groundwater) systems  (in aquifers).  The connection between the visible (surface water) and the invisible (groundwater) is usually via a complex plumbing system operating between the two (aka "hydraulic connectivity").  As a community we impact this with both our surface water off takes (lakes, and creeks; water district supplies and individual household black-pipes) and with abstractions from our subsurface (from shallow or deep groundwater wells).

As our SSI freshwater cataloguing work is revealing for this island, freshwater in any surface freshwater system, may contain a component of groundwater (or base flow) that varies seasonally, by area.  In our island-world all of our precious freshwater originates from seasonal island rainfall and the capture of this surface flow is largely a result of natural processes.  The degree of surface-groundwater interconnectivity (and the amount of surface water run-off vs. infiltration), is influenced by a combination of factors: the surface terrain in (and the area of) a watershed catchment, the ground's characteristics (vegetative cover, soils etc) and the areas subsurface geology (rocks, and/or aquifers or aquicludes).  

Linkages between surface and ground water systems are not unusual.  And, distinctive surface water and ground water chemistries (or "fingerprints") may allow an improved understanding of the degree(s) of this interconnectivity between our island's surface and subsurface systems. 

Our Freshwater Catalogue project largely entails the collection of surface freshwater data, this data collection is oriented towards developing an understanding of surface water flow volumes (what stays on the island and seasonal... variability), and determining what component of surface water flow may actually be groundwater (baseflow)!

To understand where groundwater is coming from in our island's surface freshwater systems we need to gather subsurface information (groundwater data) from the island's various (and complex) aquifers...  Across the island the surface (watershed) drainage systems, as well as subsurface sub-aquifer “regions” capture (focus) freshwater storage in the subsurface.  Aquifer sub-regions are influenced by subsurface  geology, both bedrocks and surficial sediment, and by fault systems.

Within some island watershed areas, and within some aquifer subregions,  we are slowly building a list of wells where we are developing freshwater (groundwater) chemistry profiles.  

There are a lot of island wells... for a comprehensive overview of all our island's registered wells, and more on the (limited) information available on (some) wells, have a look at some of the island data access tools that are available.

Note - if you have additional insights into an area (it's watersheds, creeks, wetlands, wells or dug-outs ...), or are interested in being involved in the FWC project, please contact the SSIFWC Project Lead.

Our FWC wells dataset is growing, from the some 4,000 SSI registered wells, and ignoring those "missing" (potentially around 1300, Golder, 2019).  Our FWC well chemistry sampling set now stands at around 18, for representative subsurface groundwater sampling, we need to grow this well dataset somewhat....   For more information on the FWC wells being sampled (and charts), please have a look at the SSIFWC webmap, drop down menu "Charts- Wells"

The images from our Salt Spring Island FreshWater Catalogue Watershed Stewardship Group facebook group December, 2021 Which Creek Is It (WCIT) competition were of a community well service point, at an island community hall. This location, (like some of the others?) is a favourite freshwater supply venue, for those folks who don't like "Town Water" (not that we really have any of that on SSI...).  Even though freshwater is processed to current heath standards (or should be) the case for all of the island's fresh water supplies. 

Town water is that typically associated with a significant freshwater source (or sources) that are outside of the actual service area (rivers, lakes, large contiguous aquifer areas), perhaps connected by infrastructure  and potentially undergoing heavier processing.  Heavier processing may be a function of the freshwaters "reuse", larger community demands, or other local controls.

The "terroir" of the community well's groundwater that featured in the WCIT competion is granite (grey, greenish or brown).  And yes, there may be a terroir (aquifer layers) affect on a well's freshwater , though not perhaps those delicate hints of peach (or was it water melon...). Igneous and sedimentary rocks where would we be without them...

For more information on a typical well record (this community well), cf. this example well record and well report for further details.

Note: - the well rate here ($/visit) is not to be confused with the actual "well rate" which is a function of many parameters (location, geology, hydraulic head etc...). 

Wells, just like creeks and lakes, can be contaminated, though the timeline for this becoming visible (and remediating for it...) can be very varied indeed.

Shallow wells (often < 10 - 30m deep) dot the island, with some shallow well concentration areas (or sub-aquifer regions), focusing very much on the exploitation of more localised shallow freshwater resources (cf. Golder, 2019). 

Shallow island well groundwater chemistries may be more closely related to "shorter term", a function of freshwater (rainwater) infiltration, and shallow groundwater recharge, at shallower subsurface locations - cf. a future groundwater and aquifers background reading article (in-prep).

Note: - shallow wells are not entirely independent of deep wells - a result of that interconnectedness of things.

Black pipe networks, old, current and new are scattered across Salt Spring Island.  The black pipes are freshwater off-takes of various indgenious forms.  Sometimes these pipes are associated with very shallow in-creek "dam" (or collars), or are simply in (higher maintainance) pipe locations just nestling in a surface creek, or pond, freshwater body.  

Black pipe field sites do always provide clear indications of the degree to which these freshwater abstraction services are still in-use (and not all are, or perhaps need to be, registered?).  If these off-takes operate(d) in the summer they are likely partly, or entirely, "ground water" fed.

Note: - contamination of these local "black pipe" water supply systems and aquatic ecosystems(!) by anthropogenic activities in and around our island's creeks , has happened.  Please look after our creeks! 

Well sampling for our FWC project and for characterising groundwater freshwater chemistry is straightforward, from a suitable faucet will do!  Well chemistry data:

• improves our understanding of potential seasonal changes in our groundwater wells (illustrating the degree of connectivity between the surface rainwater driven systems, and the timing of infiltration into the subsurface)

• how our wells groundwater (aquifer) chemistry ties back into our surface freshwater catalogue sampling (the proportions of groundwater that feeds our creeks and lakes - baseflow).

Our FWC field chemistry data (measured with the Oakton devices that we use in the field) gives valuable insights into the components of our surface, creek freshwater and can, in some circumstances, be used to back-out the groundwater component of our streams.  This surface freshwater information , along with considerations of the subsurface geology (aquifers) that influence the groundwater component(s), available from well chemistry sampling, is important stuff, for any determination of how groundwater contributions (so-called baseflow) influence our island’s surface creeks “health” and the short, or longer term, recharge of our islands aquifers (- our island’s groundwater systems…).  More on this subject in the "background reading" on chemistry ("What is Conductivity") and an impending "Groundwater & Aquifers" article on this website.

Our “FWC Oakton chemistry reveals groundwater contributions” working model (Millson, 2020) was confirmed in a recent FWC summer project study by Simon Fraser University (Howe and Allen, 2020).  A key recommendation of this SFU study, to get a better handle on the relationships between creek and groundwater base flow, was to undertake Oakton chemistry sampling from more island wells (both shallow and deep).  The acquired FWC well data helps investigate (quantify) how surface freshwater is impacted by in-creek groundwater inflows and how these may relate to deeper, subsurface groundwater discharge levels (and also to deeper groundwater recharge timing).  

As you can see from the Howe & Allen 2020 report maps there are a small number of wells with "public" chemistry data available across the island, and almost none of these shallow. We need more well chemistry data!

If you are interested in providing access to your well, for some simple freshwater chemistry to support our FWC project, please contact the SSIFWC Project Lead for further information.

It is early days for working models for our small collection of FWC sampled wells where we have chemistry sampling, but some of our well chemistry data is already proving interesting, providing insights into surface to groundwater connectivity variations:

Central island variability, from a close-proximity well dataset (WSCK watershed):
very localised (< 250m separation) differences in individual well chemistry (conductivity) responses, are suggestive of variations in surface freshwater attributed to rainfall dilution.  Variability in the chemistry signatures of the two regularly FWC sampled Weston Creek watershed wells may indicate local elements of "instantaneous” recharge, with seasonal surface precipitation(?) directly influencing well groundwater at one site (112 Deep), with groundwater signatures at the other site (104 Deep)  showing no impact of seasonal rainfall l, and no indictations of direct shallow to deep connectivity.

These chemistry differences between wells may highlight the influence of "local" fracture networks (with increased and instantaneous(?) near-surface (shallow -deep aquifer connectivity) at 104 Deep?  The absence of these seasonal changes in the 112 Deep may suggest that this well bore is potentially more isolated from near-surface freshwater interactions (and related shallow - deep rock connectivity and fracture networks?).  The significant differences between wells suggest variations in the degrees of interconnectedness of things (surface freshwater, shallow and deep aquifers), and locally(?), significant natural plumbing (hydrological connectivity) variability!

Central island variability, from a close-proximity well dataset (FLCK watershed):

Variations in conductivity patterns between wells within the Central Island Fulford Creek watershed show similar (dissimilar) well-to-well variations - also function of varying shallow-deep hydraulic connectivity?

Variability in the chemistry signatures of the two regularly FWC sampled Fulford Creek watershed wells may indicate local elements of "instantaneous” recharge, with seasonal surface precipitation(?) directly influencing well groundwater at one site (mid Kitchen Rd Deep), with groundwater signatures at the other site (117 Dukes Rd Deep)  showing no impact of seasonal rainfall, and no indictations of direct shallow to deep freshwater (hydraulic) connectivity.

South island variability, from shallow and deep wells:
Early data indicates possibly variable well freshwater conductivities between deep and shallow (by surface freshwater chemistry comparisons) suggests well conductivity rises in the winter and falls in the summer…   

A possible model, assuming conductivities in deep aquifers are a function of longer residence times (and isolation from surface water).  We maybe seeing something on “soak-times” and more access to a larger surface area/rock (fracture network in this well… (cf our FWC, 2020 Howe and Allen SFU reporting), though why higher conductivities would be more visible in the winter is not clear... (perhaps more deep water cycling, with increased deep circulation during associated winter hydraulic head increases) a working model TBC? 

And.... more to follow.

The story of the island's subsurface rocks, their varying ability to act as aquifers, and storing and facilitating the movement of freshwater in our wells and creeks: fractures (with freshwater storage varying with rock mechanical strength, +) vs. freshwater in rock porosity (varying with rock type), is yet to play out!   For both "aquifer" types there is some good news, and some bad news... 

• In the ground fractures in our islands rocks play a very significant role in controlling our  island's in-the-ground freshwater storage and access to groundwater (some would say that's all folks...)

• Fracture distribution on our island (and there water storage) varies dramatically from place to place, this is as a result of the striking range of rock types and structure (folding, faults)

• Areal fracture distribution in our island's rocks is dependant upon variations in "rock strength" (amongst other things relating to structure).

• Fracture density (and the degree of fracture connectivity) vary significantly with rock type(s) and by area (amongst other things relating to structure).

It is challenging to drill a well solely targetting fracture networks... something for an upcoming  "SSI Fractured Reservoirs" storyline.