Wabamun Lake Water Quality 1982 to 2001
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WABAMUN LAKE WATER QUALITY 1982 TO 2001 WABAMUN LAKE WATER QUALITY 1982 TO 2001 Prepared by: Richard Casey, M.Sc. Limnologist Science and Standards Alberta Environment September 2003 W0309 Pub. No: T/695 ISBN: 0-7785-2503-1 (Printed Edition) ISBN: 0-7785-2504-X (On-Line Edition) Web Site: http://www3.gov.ab.ca/env/info/infocentre/publist.cfm Any comments, questions, or suggestions regarding the content of this document may be directed to: Environmental Monitoring and Evaluation Branch Alberta Environment 10th Floor, Oxbridge Place 9820 – 106th Street Edmonton, Alberta T5K 2J6 Phone: (780) 427-6278 Fax: (780) 422-6712 Additional copies of this document may be obtained by contacting: Information Centre Alberta Environment Main Floor, Great West Life Building 9920 – 108th Street Edmonton, Alberta T5K 2M4 Phone: (780) 944-0313 Fax: (780) 427-4407 Email: [email protected] SUMMARY Wabamun Lake, approximately 60 km west of Edmonton, is large, shallow, and generally well mixed. Sport fish in the lake include northern pike, yellow perch, and lake whitefish. There are a unique mix of land uses in the lake watershed, which include undisturbed bush and forest, agriculture, two coal mines with active and reclaimed areas, three coal-fired power plants, major transportation (road and rail) corridors, residences, and recreation. The mines supply fuel for the power plants, operated by the TransAlta Utilities Corporation (TAU). Industrial wastewaters, runoff and cooling water from the Whitewood mine and Wabamun power plant are discharged to the lake. Over time, TAU operations associated with the mines and power plants in the watershed have caused cumulative and ongoing impacts on the lake level. In order to eliminate these effects on the lake water balance, TAU built the Wabamun Lake Water Treatment Plant (WL-WTP) to treat water from the Sundance cooling pond and pump it to the lake. The cooling pond contains water pumped from the North Saskatchewan River (NSR), local runoff, and various wastewaters from the Highvale mine and Sundance power plant. The WL-WTP uses chlorination and ozonation treatments to eliminate the potential transfer of fish parasites (including zooplankton hosts) and larval fish from the NSR to the lake. The WL-WTP began pumping treated water to the lake in late 1997, but relatively large volumes were not pumped until after 1998. In 2001, TAU submitted an application to Alberta Environment to build a second WTP that would pump more treated water to the lake (total capacity = 23 x 106 m3 of treated water per year). In the early 1980s, Alberta Environment established a formal water quality monitoring program at Wabamun Lake. The program was designed to determine long-term patterns in the overall water quality of the lake. It was not designed to evaluate the effects of specific activities (e.g., point and non-point source inputs) in the watershed. The objectives of this report are: 1. To summarise patterns in the water quality of Wabamun Lake using data collected by Alberta Environment from 1982 to 2001 2. To evaluate the main changes of lake water quality as they relate to aquatic biota, lake level, lake water balance, and effects of the WL-WTP inflow to the lake. The water quality of Wabamun Lake from 1982 to 2001 was similar to other freshwater lakes of central Alberta. However, various temporal trends in the water quality of the lake were found over the 20-year period. The main change in the overall water quality of the lake was an increase of total dissolved solids (TDS) by about 30%. Some major ions (i.e., components of TDS) showed greater annual concentration increases in the lake after 1992. This trend was probably due to the absence of flushing of major ions from the lake by more dilute surface inflows (e.g., precipitation and runoff) after 1992, when lake outflow (via Wabamun Creek) ceased. The overall pattern of increasing TDS in Wabamun Lake was also found in regional lakes with similar basin characteristics (small basin area : lake area) and limited or no hydraulic flushing of the lakes over the same 20-year period. The overriding cause of the TDS increases in these lakes was likely due to the prevailing climate conditions. The trophic state (or fertility) of Wabamun Lake was moderately to highly productive (i.e., meso-eutrophic) from 1982 to 2001, which was similar to previous assessments using 1970s data. Wabamun Lake Water Quality 1982 To 2001 i Metal samples in Wabamun Lake were mostly restricted to the 1999 to 2001 period, except for one sample taken in 1996. Overall the data showed no pronounced spatial differences in metal concentrations among the three sites sampled from 1996 to 2001. Temporal patterns were evident for some metals in the lake. Concentrations of four metals declined in the lake, while one showed a small increase from 1999 to 2001. Some metal concentrations also showed consistent increases or decreases in the lake in each of the three years. These patterns may be due to temporal influences of metal loads in natural streams, which generally occur in the open-water period, compared to more atypical inflows (i.e., WL-WTP treated water and ash lagoon discharge) occur throughout the year. All metal concentrations in the lake were less than water quality guidelines for the protection of freshwater aquatic life and livestock watering. All boron and some manganese concentrations in the lake were greater than guidelines for irrigation uses. Two commonly used herbicides (2,4-D and MCPA) were found at low concentrations in the lake in 1995 (the only year when pesticides were sampled). The concentrations were below water quality guidelines for the protection of freshwater aquatic life. Preliminary analysis of plankton sampled in Wabamun Lake from 1990 to 2001 showed no overall changes in the phytoplankton and zooplankton communities during this period. Changes in the lake water quality that were likely associated with effects of the WL-WTP inflow to the lake, from 1999 to 2001, were: (1) step increases of TDS and some major ion (notably sulphate) concentrations in the lake; (2) a step decrease or declining concentrations of calcium and carbonate in the lake; and (3) small decreases of phosphorus and chlorophyll-a (equivalent to algal biomass) concentrations in the lake, which generally remained at lower levels in the three- year period. Lower phosphorus concentrations (often a limiting nutrient in Alberta lakes) probably caused the concurrent reductions of chlorophyll-a in the lake. Sulphate and TDS increases in the lake were likely related to the influences of higher concentrations of these variables in the treated water (compared to the lake). Sulphate and calcium made up the highest annual loads of major ions in the treated water, compared to the individual masses of these ions in the lake. The water quality of the WL-WTP treated water could be affected by: the quality of the raw water (Sundance cooling pond); treatment chemicals used and efficacy of the WL-WTP; and seasonal conditions in the cooling pond. The small declines of phosphorus in the lake were probably related to phosphorus co- precipitating with calcium carbonate (calcite) onto the lake bottom. This process occurs naturally in hardwater lakes, such as Wabamun Lake. Various water quality data indicate that calcite precipitation in the lake was likely enhanced from 1999 to 2001, due to the new WL-WTP inflow to the lake. Other potential inputs from the WL-WTP to the lake include disinfection by-products (DBPs), which were present at low levels in the final treated water. Alberta Environment initiated a sampling program in 2002 to determine the spatial and temporal variability of DBPs in the vicinity of the treated water discharge and in the lake. Wabamun Lake Water Quality 1982 To 2001 ii TABLE OF CONTENTS SUMMARY....................................................................................................................... i LIST OF TABLES .......................................................................................................... iv LIST OF FIGURES.......................................................................................................... v LIST OF APPENDICES ................................................................................................. vi ACKNOWLEDGEMENTS............................................................................................. vii 1.0 INTRODUCTION .................................................................................................. 1 2.0 METHODS............................................................................................................ 5 2.1 Monitoring Program Design, 1982 to 2001......................................................... 5 2.2 Field and Laboratory Measurements.................................................................. 5 2.2.1 General Characteristics, Major Ions, Nutrients, and Trophic State ............ 5 2.2.2 Metals.......................................................................................................... 7 2.2.3 Pesticides..................................................................................................... 8 2.2.4 Quality Assurance ....................................................................................... 8 2.2.5 Plankton ...................................................................................................... 8 2.3 Data Analysis ......................................................................................................... 8 3.0 RESULTS