Streamflow input to Lake Athabasca, Canada

Hydrology and Earth System Sciences Open Access Ocean Science Open Access Solid Earth Open Access Hydrol. Earth Syst. Sci., 17, 1681–1691, 2013 www.hydrol-earth-syst-sci.net/17/1681/2013/ doi:10.5194/hess-17-1681-2013 © Author(s) 2013. CC Attribution 3.0 License. cess Model Development Streamflow input to Lake Athabasca, Canada K. Rasouli1 , M. A. Hernández-Henrı́quez2 , and S. J. Déry2 1 Department of Civil and Environmental Engineering, University of Waterloo, 200 University Ave W., Waterloo, Correspondence to: S. J. Déry () The Cryosphere Received: 4 July 2012 – Published in Hydrol. Earth Syst. Sci. Discuss.: 2 August 2012 Revised: 24 March 2013 – Accepted: 7 April 2013 – Published: 2 May 2013 Abstract. The Lake Athabasca drainage area in northern Canada encompasses ecologically rich and sensitive ecosystems, vast forests, glacier-clad mountains, and abundant oil reserves in the form of oil sands. The basin includes the Peace–Athabasca Delta, recognized internationally by UNESCO and the Ramsar Convention as a biologically rich inland delta and wetland that are now under increasing pressure from multiple stressors. In this study, streamflow variability and trends for rivers feeding Lake Athabasca are investigated over the last half century. Hydrological regimes and trends are established using a robust regime shift detection method and the Mann–Kendall (MK) test, respectively. Results show that the Athabasca River, which is the main contributor to the total lake inflow, experienced marked declines in recent decades impacting lake levels and its ecosystem. From 1960 to 2010 there was a significant reduction in lake inflow and a significant recession in the Lake Athabasca level. Our trend analysis corroborates a previous study using proxy data obtained from nearby sediment cores suggesting that the lake level may drop 2 to 3 m by 2100. The lake recession may threaten the flora and fauna of the Athabasca Lake basin and negatively impact the ecological cycle of an inland freshwater delta and wetland of global importance. 1 Introduction Lake Athabasca, straddling the provinces of Alberta and Saskatchewan, forms the third largest lake (by area) in northern Canada. It receives direct runoff from a large catchment area spanning 271 000 km2 including the Athabasca, Fond du Lac, and other small river catchments. Lake Athabasca Open Access ON, N2L 3G1, Canada 2 Environmental Science and Engineering Program, University of Northern British Columbia, 3333 University Way, Prince George, BC, V2N 4Z9, Canada forms a large, natural reservoir of freshwater in the upper reaches of the 1.8 × 106 km2 Mackenzie River basin, thus influencing the timing and amount of pan-Arctic river discharge (e.g., McClelland et al., 2006). It is the site of the ecologically sensitive Peace–Athabasca Delta (PAD) that depends on spring flood events for freshwater recharge (Peters et al., 2006; Smith and Pavelsky, 2009; Wolfe et al., 2008a,b). The Athabasca River, the longest river entirely within Alberta, is especially important for societal needs and economic development such as for domestic water consumption and for irrigation of agricultural lands. This waterway is also important for the oil sands industry near Fort McMurray, Alberta, as bitumen extraction requires significant amounts of water that are currently being sourced from the river itself. Thus the cumulative impacts of industrial and other anthropogenic activities, in addition to climate change, are affecting the lake’s water balance and surrounding ecosystem (Schindler and Donahue, 2006). Previous studies on streamflow variability and trends in the Lake Athabasca watershed have focused on the Athabasca River itself. Summer streamflow in the headwaters of the Athabasca River declined by about 0.2 % per year over the 20th century, reducing riparian groundwater recharge and imposing water deficit stress on floodplain forests (Rood et al., 2008). Further downstream, May to August streamflow declined by 33.3 % from 1970 to 2003 on the Athabasca River near Fort McMurray in response to receding Rocky Mountain glaciers and lower snowpack levels (Schindler and Donahue, 2006). Abdul Aziz and Burn (2006) found strong increasing trends in the December to April flows, as well as in the annual minimum flow, in the Athabasca River system. They also reported weak decreasing trends in the early Published by Copernicus Publications on behalf of the European Geosciences Union. 1682 K. Rasouli et al.: Streamflow input to Lake Athabasca, Canada summer and late fall flows as well as in the annual mean flow for the Athabasca River. Woo and Thorne (2003) reported increasing variability in annual streamflow of the Athabasca River near Fort McMurray in the late 20th century. Recent sediment cores extracted from a pond adjacent to Lake Athabasca place the recent hydrological variability of the Athabasca River into a 5200 yr context (Wolfe et al., 2011). Their proxy record of water levels of Lake Athabasca shows drops between 2–4 m below the 20th century mean in the mid-Holocene that may reoccur by 2100 with continued climate change. Despite some of these recent advances in our knowledge of the hydrology of the Lake Athabasca basin, little information exists on total streamflow input to Lake Athabasca. Previous studies have focused on the Athabasca River itself but have not investigated lake inflows from other main contributors such as the Fond du Lac River and other small rivers that collectively contribute ∼ 43 % of its total input. In the current research, we investigate quantitative changes through analysis of hydrological regime variability and trends across the Lake Athabasca basin using an observational data set of streamflow. The total streamflow input to Lake Athabasca and the gauge contribution of different tributaries from 1960 to 2010 are also examined. Furthermore, the reasons and periods of decline in lake level, as well as the prospects for the future, are investigated and compared with the results found from the nearby sediment core studies. Thus the main objective of this study is to assess the changes in streamflow input to Lake Athabasca and to compare these results with recent sediment core studies in the area. In the next sections, the study area and data are introduced. Next, the methodology and hydrological regime variability and trend detection tools are explained. The results follow and the paper ends with a discussion of the implications of our work. 2 Study site The Lake Athabasca basin is located between 52◦ 100 N and 60◦ 100 N and 100◦ W and 120◦ W, covering an area of 271 000 km2 in the Canadian provinces of Saskatchewan and Alberta as well as the Northwest Territories (Fig. 1). The catchment elevation varies between 3747 m at Mount Columbia and 205 m near the lake shore. The Athabasca River drains from the Rocky Mountains in Jasper National Park. Elsewhere, the landscape in the lower Lake Athabasca basin is m (...truncated)