An approach for assessing cumulative effects in a model river, the Athabasca River basin

Abstract

Novel approaches addressing aquatic cumulative effects over broad temporal and spatial scales are required to track changes and assist with sustainable watershed management. Cumulative effects assessment (CEA) requires the assessment of changes due to multiple stressors both spatially and temporally. The province of Alberta, Canada, is currently experiencing significant economic growth as well as increasing awareness of water dependencies. There has been an increasing level of industrial, urban, and other land-use related development (pulp and paper mills, oil sands developments, agriculture, and urban development) within the Athabasca River basin. Much of the historical water quantity and quality data for this basin have not been integrated or analyzed from headwaters to mouth, which affects development of a holistic, watershed-scale CEA. The main objectives of this study were 1) to quantify spatial and temporal changes in water quantity and quality over the entire Athabasca River mainstem across historical (1966–1976) and current day (1996–2006) time periods and 2) to evaluate the significance of any changes relative to existing benchmarks (e.g., water quality guidelines). Data were collected from several federal, provincial, and nongovernment sources. A 14% to 30% decrease in discharge was observed during the low flow period in the second time period in the lower 3 river reaches with the greatest decrease occurring at the mouth of the river. Dissolved Na, sulfate, chloride, and total P concentrations in the second time period were greater than, and in some cases double, the 90th percentiles calculated from the first time period in the lower part of the river. Our results show that significant changes have occurred in both water quantity and quality between the historical and current day Athabasca River basin. It is known that, in addition to climatic changes, rivers which undergo increased agricultural, urban, and industrial development can experience significant changes in water quantity and quality due to increased water use, discharge of effluents, and surface run-off. Using the results from this study, we can begin to quantify dominant natural and man-made stressors affecting the Athabasca River basin as well as place the magnitude of any local changes into an appropriate context relative to trends in temporal and spatial variability.

Assessing the sublethal effects of in‐river concentrations of parameters contributing to cumulative effects in the athabasca river basin using a fathead minnow bioassay

“…The concentrations of dissolved sodium and dissolved chloride in the 100% sodium chloride treatment (25.43 and 38.90 mg/L, respectively) and the concentration of sulphate in the 100% treatment of the sulphate experiment (101.37 mg/L) were chosen to imitate these levels ( Table 1). Although the concentrations of dissolved sodium and chloride used in the present study were slightly higher than was seen in the Athabasca River by Squires et al [8], they are still representative of the average concentrations of these parameters in the Athabasca River. The concentration of sulphate in the 100%, however, was approximately twice the amount of average sulphate measured in the Athabasca River.…”

“…The 100% concentrations chosen for the sodium chloride and dissolved sulphate experiments were based on the average levels of these parameters found along the river continuum of the Athabasca River as published in previous research [8]; therefore, they were ecologically relevant to the Athabasca River Basin. The dilutions series used were 0% (control), 6.25, 12.5, 25, 50, and 100% (25 ppm Na/38 ppm Cl).…”

“…Data obtained from various government and industry sources has been graphed, and significant trends in average concentrations of dissolved chloride, dissolved sodium, and sulphate both across the Athabasca River and over time were computed [8]. Using this data, we know that the highest average concentrations (across the years 1996-2006) of these parameters in the Athabasca River are 21.09 mg/L dissolved sodium, 22.71 mg/L dissolved chloride, and 45.27 mg/L sulphate.…”

“…There is the potential for some of these components to make their way into the Athabasca River through seepage and air deposition [7]. Previous research has shown that the highest concentrations of sodium and chloride along the Athabasca River mainstem occurred in the mouth reach of the river basin [8]. Assessing water directly from the mouth of the Athabasca River, downstream of all major inputs, would help determine the current and potential future impact these developments can have on aquatic biota.…”

“…As a result, salinity is becoming an increasing concern to the oil sands industry and its regulators in northern Alberta [12]. Recently, it has been noted that dissolved sodium, chloride, and sulphate concentrations have increased significantly in the lower reaches of the Athabasca River over 40 years [8].…”