| Abstract/Description or Keywords |
The Slocan Lake Water Quality Monitoring Program was undertaken from 2010 to 2013 with funding from the Columbia Basin Trust. The research was conducted by Galena Environmental, with the assistance of volunteers from the Slocan Lake Stewardship Society, as well as other members of the community. This report presents the methodology and research results of the program. The goal of the project was to obtain baseline information about Slocan Lakeęs present conditions and potential trends to aid the development of a future lake management plan. The program consisted of two components: a nearshore component conducted annually over a five-week period, and an offshore component carried out monthly from spring to fall each year. For the nearshore component water samples from seven nearshore sites were collected at 5 to 10 cm below the surface and analyzed for identification and counts of total coliforms, fecal coliforms and Escherichia coli (E. coli). For the offshore component measurements were taken of water temperature, dissolved oxygen, specific conductivity, total dissolved solids and pH, on the water column at five meter intervals, between 5 to 60 m depth, from four offshore sites. Water samples were taken at 5 and 50 m depths and analyzed for nitrate as N, nitrite as N, Kjeldahl nitrogen, total nitrogen, total phosphorus and chlorophyll-a. In three of the four sites, samples were taken for zooplankton identification and counts. In addition, water samples were taken at the four sites for analyses of heavy metals on a one time basis during the sampling season. Comparisons were made when appropriate with previous studies which had used the same sampling sites (Andrusak et al,. 2002; Galena Environmental, 2009). General parameters readings as well as nutrient concentrations demonstrate the oligotrophic status of Slocan Lake. Thermal stratification takes place in the summer with a metalimnion forming at 15 to 25 m depth. Oxygen concentration profiles show an orthograde curve characteristic of oligotrophic lakes. Nutrient concentrations were low and did not show a trend, except in 2010 when total nitrogen was significantly lower and phosphorus was significantly higher than in the other years. However, this result has been attributed to laboratory error. Chlorophyll-a concentration generally ranged between <0.5 to 1.8 _g/L, exhibiting low productivity levels typical of oligotrophic conditions. No significant differences between sites were found. Water hardness was below 50 mg/L, classifying Slocan Lake water as soft, and according to the alkalinity guidelines with low sensitivity to acidic inputs (>20 mg/L). Analyses of metals from 2008 Slocan Lake Water Quality Monitoring Program were compared to those from the present study and used for interpretation of metal results. Total metals concentrations tested were below the BC Water Quality Guidelines, with the exception of cadmium and zinc. Cadmium levels in all 20 samples taken between 2008 and 2011 exceeded the maximum concentration for the protection of freshwater life by approximately a magnitude of 10X. Mean concentrations of zinc were 15.6 _g/L in 2010 and 19.8 _g/L in 2011, with all twelve samples above 10 _g/L, indicating that the 30-day average maximum guideline for freshwater life of 7.5 _g/L is likely being exceeded. Copper and nickel concentrations tested above the maximum guideline criteria for aquatic life in Site 4 in 2008, with values of 11.4 _g/L and 25 _g/L, respectively. In nearby Carpenter Creek water samples showed high concentrations close to or above the maximum guideline levels for the protection of aquatic life for aluminum, chromium, lead and nickel. Coliform counts in the seven nearshore samples were below the maximum level for drinking water and primary contact recreational use (swimming or bathing). The two highest fecal coliform counts were in the samples taken from the Silverton Hotel site (9 and 8 cfu), while the third highest came from the site near Silverton Creek (7 cfu). These three counts occurred in the last two years, raising concerns about water quality deterioration at the Silverton Hotel site. It is recommended that microbial source tracking (MST) be incorporated into future analyses to discern bacteria leaching from septic tanks and those of animal origin. The diversity of zooplankton species found at the three offshore sites saw a decrease from 2001 from eight species (three copepods and five cladocerans) to five (two copepods and three cladocerans). Also there has been a drastic reduction in zooplankton density (89%) and biomass (86%) in comparison to data from 2001, although the main decline took place in 2010 and 2012. Due to the high cadmium and zinc concentrations in Slocanęs Lakeęs water, as well as the decline in zooplankton, and the increase of E.coli counts at some of the nearshore sites, it is recommended that monitoring of Slocan Lake be continued. The high metal concentrations found in Carpenter creek are also of concern. According to a study by the Water Investigation Branch (1977), there are one hundred abandoned mines within Silverton and Carpenter Creek basins, and "at least thirteen are known to have abnormal mine drainage". It is recommended that in addition to continue monitoring of Slocan Lake, water and sediments from these creeks be tested. A study on the potential impact on fish and macroinvertebrate populations in these drainages is also recommended. |
