The sampling program for the Wasi watershed focused on sampling streamflow from a range of headwater systems during baseflow conditions. Samples were collected between May 7th and August 28th, 2012, following the spring freshet and through the summer months.
Sampling locations across the Wasi watershed (Figure 2-1) were distributed with the purpose of capturing isotopic variability in stream water and source water with 22 surface water, 18 groundwater, and 3 precipitation sampling locations. Of the 22 surface water sampling locations, 18 sites were co-located with existing long-term sample sites used by the NBMCA to characterize total phosphorous contributions along the Wasi’s mainstems downstream of tributary confluences. Four additional surface water sampling locations were added to the NBMCA’s long-term monitoring program. Two of these additional sites were Wasi Lake (WaLk) and Graham Lake (GrLk), and the other two were wetlands based on the Wistiwasing River management study (TEAG & AJRA, 1989). Wetlands 3 (WL3) and 13 (WL13) (Figure 2-1) (amongst others) were identified as important habitat and surface water attenuation locations (TEAG & AJRA, 1989). Thus, these two headwater wetlands were included in surface water sampling locations as possible sites influencing isotopic concentrations in streamflow; WL3 was added to the sampling regime after May 7th start-up.
A total of 15 nested stream sampling sites were along the mainstems (including lakes) and 7 minor tributary sites (some of which were ephemeral) with upstream wetlands and/or small water bodies, agriculture and golf course (personal communication, Kristen Green, Sept., 3, 2013).All stream water samples were collected from flowing parts of the stream using an instantaneous grab sample following standard protocols (USGS, 2006). Similarly, stream grab sample protocols were used to collect samples from both GrLk and WaLk, ~10 m offshore.
Continuous discharge records from the Water Survey of Canada (WSC) hydrometric station (02DD024) on the Wasi River near the outlet to Callander Bay was used as a proxy for the hydrological conditions in the Wasi watershed (W10, top, right in Figure 2-1).
Groundwater divides in small watersheds, particularly in glacial till deposits, can be complex where surface waterbodies can serve as discharge and/or recharge areas. In the complex systems where groundwater flow paths can differ from those of surface water’s, the interaction
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of groundwater with various rates of movement, amount, and types of sediment can have a substantial effect on streams and shallow groundwater chemistry (Winter, 2003). To account for potential spatial and/or temporal variability in groundwater chemistry, groundwater was sampled primarily from private residential well systems (volunteered by Wasi watershed residents) scattered throughout the Wasi Watershed (Figure 2-1). Groundwater wells were sampled between 1 and 7 times, depending on availability. Sites included 12 drilled wells and 6 dug wells (Appendix B).
Ten of the drilled wells, varying in depth from 25 to 164 m, were either matched to the Ministry of Environment (OMOE) (Ontario) well records or had owner reported depths. Only two drilled wells (1250 & 1969) had no available depth data. Of the dug wells, five were reported by owners to be between 6.1 and 31 m (Appendix B). One dug well (capped with one visible tile showing (~4’ in depth) continuously flowed from a side spout, and was considered a flowing artesian well (Arti) (Latitude 46˚6’46.902”, Longitude -79˚9’14.996”) (Figure 2-1). This well was located within 10’ of a municipal roadway and had no available depth data. For groundwater sampling, residential water holding tanks were purged, from both dug and drilled wells, with the outflow monitored by a YSI™ Professional Plus handheld multiparameter instrument. Groundwater samples were collected once the water temperature and other field parameters stabilized (Hamilton, 2011).
Precipitation samples were collected to support this study using Ambient Weather® rain gauges with a 10.2 cm opening for sites P1 and P2. Site P3 collected precipitation in a glass container with a 10 cm diameter opening. All three precipitation sites were located ~1 m above the ground surface near three surface water sample sites; P3 near Wasi River outlet, P1 and P2 near Graham Creek and Wasi River headwaters (Figure 2-1). Mineral oil was used in the gauges to minimize evaporation between sampling periods (IAEA, 2000). Installation of P1 was on May 7th, P2 on May 24th, and P3 on June 25th. Precipitation was collected biweekly from May 7th to July 4th, then event based collection from July 4th to August 28th.
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Figure 2-1: The Wasi watershed, located in Northeastern Ontario, drains into Lake Nipissing with an elevation ranging from outlet to ridge of 193 to 467 masl, respectively.
Subwatershed delineations defined by the North Bay-Mattawa Conservation Authority (NBMCA) (2011). Provincial data layer of Ontario for streams, waterbodies, and wetlands were provided by Digital Moving Target Indicator (DMTI) CanMap® datasets (2005).
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Figure 2-2: Quaternary geology in the Wasi watershed (NBMCA, 2011). See Figure 2-1 legend for more detail. Quaternary geology and overburden (not shown) data layer (1:50,000) created by Schlumberger Water Services derived for the Provincial Groundwater studies in 2005 was received from NBMCA (2011). Provincial data layer of Ontario for streams, waterbodies, and wetlands were provided by Digital Moving Target Indicator (DMTI) CanMap® datasets (2005).
A total of 312 samples (187 surface water, 79 groundwater, and 23 precipitation) were collected for stable water isotope analysis. All water samples were filtered through a 0.45µm Millipore® syringe filter into 20 ml glass scintillation bottles (Garbarino et al., 2006), and stored in opaque coolers immediately after collection to reduce photo-degradation and growth of biological matter (Eglington, 2001). In addition, bottles had short necks and cone-shaped caps displacing headspace wrapped in Paraffilm® tape for positive seals (U.S. Geological Survey, 2006). Approximately 15% (n = 47) of paired field duplicates were taken to assess the combined storage, transport and analytical uncertainty/repeatability. For all water samples, simultaneous measurements of δ2H and δ18O were quantified with a Picarro L2120-i Liquid Water Isotope
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Analyzer in the Department of Geography at Nipissing University. Results are reported in per mil (‰) units relative to Vienna Standard Mean Ocean Water 2 (VSMOW2) (Ying et al., 2010) following a 2-point calibration based on Isomass© certified waters in addition to an internal laboratory standard (Appendix C). The internal laboratory standard was assessed using an international ring test in 2012 (unpublished data). To control for memory effect, the mean of the last three of six injections was used (Picarro, 2010). ChemCorrect™ software was run on all δ18O and δ2H measurements confirming no influence of organic contaminants (i.e.
methanol). Precision of δ18O and δ2H was better than 0.14 and 0.35‰ (n = 371), respectively.
Accuracy was better than 0.18 and 0.38‰ (n = 93), respectively. Field duplicates taken to assess sampling and laboratory handling (USGS, 2006) had an average difference of 0.11 and 0.28‰
for δ18O and δ2H, respectively (Appendix C).
Isoscapes were generated for each sampling day and for averages of early (May 7th to June 29th) and late (June 30th to August 28th) sampling periods. Surface water δ18O and δ2H were interpolated using ArcMap Geographic Information System processing software (ERSI, 2010) using Inverse Distance Weighted (IDW) method. This method weights the value of data points in close proximity to interpolate unknown cells. Thus, the further the distant cell is from a data point, the less influence that data point will have in estimating the cell value. All interpolations used the default weight factor of two and a fixed radius of 22 (the minimum number of data points required to estimate unknown cells) (ESRI, 2010). Interpolation of surface water longitudinal data were used to show downstream changes in isotopic concentration after mixing with upstream tributaries and/or groundwater discharge areas (Kendall et al., 2010). Using surface water isoscapes and Quaternary geology maps, each tributary and its underlying material were assessed to aid in the determination of the geographic source of contributing water to streamflow (Kendall et al., 2010).