56 ISEIS Journal of Environmental Informatics Journal of Environmental Informatics 35(1) 56-80 (2020) www.iseis.org/jei Water Quality Management of a Cold Climate Region Watershed in Changing Climate N. K. Shrestha and J. Wang * Athabasca River Basin Research Institute (ARBRI), Athabasca University, 1 University Drive, Athabasca, Alberta, Canada T9S 3A3 Received 21 June 2017; revised 07 March 2018; accepted 19 April 2018; published online 15 Feburary 2018 ABSTRACT. Cold climate regions provide a multitude of ecosystem services. However, cold regions under a changing climate could be more vulnerable than others because their glaciers, freezing soils and peatlands are sensitive to the slightest of changes in climate. This has posed serious threats to the water resources, sustainable goods production and ecosystem services that depend on regional water quality. Therefore, proper watershed management is imperative. In this paper, we investigate this issue in a cold climate water- shed in central Alberta, Canada with the main objective of quantifying the impacts of climate change on water quality status. We modified specific water quality related processes of a process-based model – Soil and Water Assessment Tool (SWAT) with a view of better representing the reality of cold climate regions. A SWAT model is then built-up, followed up by a multi-site and multi-objective (streamflow, sediment and water quality) calibration, validation and uncertainty analysis in a baseline period (1983 - 2013). The cali- brated and validated model is then fed with a high spatial resolution (25 km) daily future climate data – the CanRCM4. Improvements on stream water temperature (Ts) and dissolved oxygen (DO) simulations justified the modifications. This model is able to simulate the dynamics of other water quality variables (carbonaceous biochemical oxygen demand – cBOD, total nitrogen – TN and phosphorus – TP) with a wide range of accuracy (very good to satisfactory) in the base period. Agriculture areas account for the highest amount of annual TN (11.16 kgN/ha) and TP (2.88 kgP/ha) yield rate in the base period leading to poor water quality status in the immediate downstream reaches. The situation would be further exacerbated (16.52 kgN/ha and 4.89 kgP/ha) in future. Finally, we tested different alternative management options to compare the water quality status of the Athabasca River Basin (ARB) under a changing climate. Significant reduction in future nutrient concentrations (~ 20% on TN and 60% on TP) can be achieved using a certain combination of management practices and the ecological status of the basin can be improved. This demonstrates that the modified SWAT model can be applied to other cold climate regions, and that the results can be translated to help in managing the ARB in a more holistic way. Keywords: cold climate region, Athabasca river basin, water quality, climate change, SWAT, CanRCM4 1. Introduction Recent observations show ample evidence of climate change impacts on the environment and ecosystems (IPCC, 2007; IPCC, 2014) of cold climate regions. For example, in Canada, increases in annual air temperature, annual preci- pitation and permafrost temperature, shifts in precipitation types (decreasing snowfall and increasing rainfall), a decrease in snow cover, and shrinking glaciers (ECCC, 2016) are testi- monials to this, and the trend is likely to further exacerbate in the future. As a result, economic, natural ecosystems, and hu- man health could be impacted (GoC, 2014). There is growing realization that adaptation is necessary and focus is being drawn on improving the resilience of individuals and societies to climate extremes, and on enhancing their ability to thrive in such adverse conditions (Eyzaguirre and Warren, 2014). Specific to the Athabasca River Basin (ARB) in Alberta, * Corresponding author. Tel.: +1-780-394-4883; fax: +1-780-497-3411. E-mail address: junyew@athabascau.ca (J. Wang). ISSN: 1726-2135 print/1684-8799 online © 2020 ISEIS All rights reserved. doi:10.3808/jei.201900407 Canada, climate change may cause serious issues for eco- system services and sustainability such as terrestrial carbon storage, climate regulation, water retention and infiltration, and biodiversity (ETCW, 2010; GoC, 2014; Lemmen et al., 2014; Eum et al., 2017; Shrestha et al., 2017a). Studies have indeed shown that rising annual air temperatures in the basin have led to several undesirable changes such as earlier spring freshet (Eum et al., 2017), glacier retreat and reduced snow cover (ETCW, 2010; Warren and Lemmen, 2014), increased permafrost temperatures (Bush et al., 2014), and increased green water flow and decreased green water storage (Shrestha et al., 2017a). Similarly, increased precipitation and changes in patterns (from snowfall to rainfall) have brought higher incidence of flooding in the basin (Toth et al., 2006; Eum et al., 2017; Shrestha et al., 2017a;). Consequently, higher rates of erosion and increased sediment transport through the basin’s river reaches are expected (Walling, 2009). These alterations would cause substantial changes to physical and chemical properties of river water, which could be detrimental to the aquatic ecosystems’ biodiversity (ETCW, 2010). For example, increasing air temperature would lead to decreased oxygen level concentrations in rivers (Pietroniro et al., 1998). Sim-