Okanagan Large Lakes Water Quality Monitoring Program
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Environmental Protection Division Okanagan Large Lakes Water Quality Monitoring Program Ellison Lake Wood Lake Kalamalka Lake Okanagan Lake Skaha Lake Osoyoos Lake 1 Environmental Protection Division Table of Contents • Goals & Objectives…………………..................................................… 3 • Trophic Status………………………………………………………………............. 4 • Data Collection………………………………………………………………………... 5 • Key Water Quality Parameters………………………………………………… 6 • Trophic Status & Water Quality……………………………………………..... 7 • Okanagan River Basin……………………………………………………………… 8 • Physical Characteristics of Okanagan Basin Lakes...................... 9 • Ellison, Wood and Kalamalka Lakes………………………………………… 10 • Ellison Lake………………………………………………………………….............. 11 • Wood Lake………………………………………………………………………………. 16 • Kalamalka Lake……………………………………………………………………….. 21 • Okanagan, Skaha and Osoyoos Lakes……………………………………… 26 • Okanagan Lake………………………………………………………………………… 27 • Skaha lake………………………………………………………………………………… 32 • Osoyoos Lake…………………………………………………………………………… 36 • Determining Lake Trophic Status................................................. 43 • Example: Skaha Lake Trophic Status 1970-2008……………………….. 44 • Trophic Status of Okanagan Basin Lakes…………………………………. 45 • Summary......................................................................................... 46 • Future Monitoring……………………………………………………………………. 47 • Partners, More Information and Contacts.………………………………. 48 2 Environmental Protection Division Goals & Objectives Goals of Lake Sampling Program • Provide water quality data for the large Okanagan Basin lakes to inform decision makers within government, industry, and the public. • Assess the status and trends in lake water quality in response to watershed and climate change, pollution control and other management actions such as Liquid Waste Management Planning. • Compare water quality status to established Water Quality Objectives for key parameters and determine Trophic Status Water Quality Objectives • Water quality objectives are site-specific management targets based on an evaluation of historical data and reasonable expectations for a particular water body, as well as consideration of the generic BC and national water quality guidelines, which are safe limits of the physical, chemical, or biological characteristics of water for various uses. 3 Environmental Protection Division Trophic Status • Trophic status refers to the degree of biological productivity within a lake and is generally characterized by nutrient concentration (total phosphorus and nitrogen), algal growth (chlorophyll-a) and water clarity (Secchi depth). • Trophic categories : Oligotrophic - lakes that are clean and clear with very low levels of nutrients and biological production. Mesotrophic - lakes with moderate productivity and nutrient concentrations. Eutrophic – lakes that are productive with generally high levels of nutrients. Hypereutrophic – very productive lakes that have significant algal blooms throughout much of the summer and fall. • The trophic status of a lake is a key component of water quality. It is associated with lake basin geology, local climate, natural chemical make-up and can be altered through human activities such as wastewater discharge (point-sources), agriculture , erosion, septic tank seepage, and recreational activities (non-point sources). 4 Environmental Protection Division Data Collection • Lake water quality data is generated by Ministry of Environment staff, sampling the lakes twice a year. • First in the early spring before nutrient uptake by plankton and before heating and stratification of the water column occurs. • Second in the fall when much of the nutrients in the surface waters have been used by plankton and decomposition of sinking organic matter begins to reduce dissolved oxygen in the bottom waters of the lakes. • Many of these monitoring sites have been sampled for over 30 years, offering a unique data set for assessing the impact of watershed processes, climate Water samples are collected using a Van change, fisheries or waste management actions. Dorn water sampler at a variety of depths. 5 Environmental Protection Division Key Water Quality Parameters • Sites are sampled in the epilimnion (depth <10m) and hypolimnion (depth >20m) during the spring and fall for the following parameters: 1. Physical – Secchi Depth (water clarity) – Temperature 2. Nutrients – Total Phosphorus, Dissolved Phosphorus & Ortho-phosphorus – Total nitrogen, Total Kjeldahl Nitrogen & Nitrate+Nitrite 3. Ions – Silica 4. Chlorophyll-a (algal productivity) • Extra parameters for spring sampling: Hardness (CaCO3), Bromide, Chloride, Sulphate, Calcium & Magnesium 6 Environmental Protection Division Trophic Status and Water Quality Total Phosphorus • Phosphorus levels in lakes increase due to inputs of sewage, sediments eroded from soils in the watershed, seepage from septic tanks, fertilizers from agricultural activities and internal loading. • Phosphorus is a key nutrient used by phytoplankton (floating algae). Increased phosphorus leads to increased algal production, reduced water clarity, increased taste and odour concerns for drinking water purveyors, and undesirable conditions for fish production. Total Nitrogen • Nitrogen is another important nutrient for lakes, and can have an effect on the biological productivity and ecology of waters since the balance between phosphorus and nitrogen plays an important role. • Nitrogen sources include: atmospheric deposition, nitrogen fixation in the water and sediments, and watershed inputs from surface and groundwater (e.g. sewage, agriculture, runoff, etc). Chlorophyll-a • Chlorophyll-a (Chl-a) is the primary pigment used by phytoplankton in photosynthesis. Generally, high levels of Chl-a indicate high algal production and low levels of Chl-a indicates low algal production in a water body. The Chl-a level present in a lake increases with increasing nutrient loading and decreases water clarity (measured by Secchi Depth). Secchi Disc Depth • Measures the transparency of water and is influenced by the light absorption characteristics of the water and its dissolved and particulate matter such as phytoplankton. Secchi disc sampling • The Secchi Disc Depth is the mean depth at the point where a black and white disc 20 cm in diameter disappears when viewed from the shaded side of the vessel. 7 Environmental Protection Division The Okanagan River Basin N Kalamalka • The Okanagan River Basin drains through a chain of lakes in Wood the Southern Interior of BC before crossing the US/Canada border and flowing into the Columbia River (Ellison, Wood, Ellison Kalamalka, Okanagan, Skaha, and Osoyoos lakes). • These lakes provide important habitat for aquatic life, Okanagan community drinking water, irrigation water to orchards and vineyards, and provide a variety of tourism and recreational opportunities. • Water quality sampling has been ongoing for the past 20-40 years on each lake by Ministry of Environment staff and partners. Skaha • Key water quality parameters will be presented in the following pages for the six lakes noted above. Trends will be discussed and the data graphs will be updated on an bi-annual basis. Osoyoos 8 Environmental Protection Division Physical Characteristics of Okanagan Basin Lakes Mean Theoretical Okanagan Basin Surface Volume Maximum Watershed Depth Flushing Lake Area (HA) (DAM3) Depth (m) Area (km2) (m) Time (yrs) Ellison Lake 210 5400 2.5 5 138 1.2 Wood Lake 930 199,500 22 34 151 22 Kalamalka Lake 2,590 1,520,000 59 142 572 51 Okanagan Lake 35,100 24,644,000 76 230 6,061 52.8 Skaha Lake 2,000 588,000 26 55 6,890 1.2 Osoyoos Lake 2,300 397,000 14 63 8,280 0.7 9 Environmental Protection Division Ellison, Wood and Kalamalka Lakes N • Ellison, Wood and Kalamalka lakes are the first three valley bottom lakes in the Okanagan River system. Kalamalka • All three valley bottom lakes receive water from Lake headwater lakes and streams. • All are hydrologically linked by surface and groundwater flow. • Differences in water quality are due to land use Wood Lake and distinct physical characteristics of each lake. • None of these lakes currently receive point source nutrient inputs. Ellison Lake 10 Environmental Protection Division Ellison Lake • Receives water from Vernon Creek and drains via Middle Vernon Creek into Wood Lake. • Small, shallow, productive lake with reduced water clarity. • Limited public recreation and beach sites, as well as some commercial and residential developments. • Popular lake with wakeboarding and water- skiing enthusiasts. Photo Credit: www.buygold.net/tripusa2002/kelowna02.html 11 Environmental Protection Division Ellison Lake: Spring Total Phosphorus • Ellison Lake is relatively shallow (5 m maximum depth) and as a result, nutrient rich sediments are easily re-suspended by wind and wave action leading to high levels of total phosphorus. • Spring total phosphorus has been quite variable over the past three decades and although there appears to be a decreasing long-term trend, it is quite variable. 12 Environmental Protection Division Ellison Lake: Spring Total Nitrogen Ellison Lake Central (site 0500265) 1.0 • Total nitrogen concentrations Epilimnion (<5m) have been quite variable over time, and have remained 0.8 relatively high during the monitoring period. 0.6 • As with phosphorus, the shallow nature of Ellison Lake likely 0.4 leads to elevated levels of nitrogen from the re-suspension Total (mg/L) Nitrogen of bottom materials. 0.2 0.0 1975 1980 1985 1990 1995 2000 2005 2010