water Article Runoff Projection from an Alpine Watershed in Western Canada: Application of a Snowmelt Runoff Model Kyle Siemens 1, *, Yonas Dibike 1,2 , Rajesh R Shrestha 1,2 and Terry Prowse 1,2   Citation: Siemens, K.; Dibike, Y.; Shrestha, R.R; Prowse, T. Runoff Projection from an Alpine Watershed in Western Canada: Application of a Snowmelt Runoff Model. Water 2021, 13, 1199. https://doi.org/10.3390/ w13091199 Academic Editor: Renato Morbidelli Received: 24 February 2021 Accepted: 21 April 2021 Published: 26 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Geography, Water and Climate Impacts Research Centre, University of Victoria, P.O. Box 1700 STN CSC, Victoria, BC V8W 2Y2, Canada; yonas.dibike@canada.ca (Y.D.); rajesh.shrestha@canada.ca (R.R.S.); prowset@uvic.ca (T.P.) 2 Environment and Climate Change Canada, Watershed Hydrology and Ecology Research Division, University of Victoria, 2472 Arbutus Rd., Victoria, BC V8N 1V8, Canada * Correspondence: siemensk@uvic.ca Abstract: The rising global temperature is shifting the runoff patterns of snowmelt-dominated alpine watersheds, resulting in increased cold season flows, earlier spring peak flows, and reduced summer runoff. Projections of future runoff are beneficial in preparing for the anticipated changes in streamflow regimes. This study applied the degree–day Snowmelt Runoff Model (SRM) in combination with the MODIS to remotely sense snow cover observations for modeling the snowmelt runoff response of the Upper Athabasca River Basin in western Canada. After assessing its ability to simulate the observed historical flows, the SRM was applied for projecting future runoff in the basin. The inclusion of a spatial and temporal variation in the degree–day factor (DDF) and separation of the DDF for glaciated and non-glaciated areas were found to be important for improved simulation of varying snow conditions over multiple years. The SRM simulations, driven by an ensemble of six statistically downscaled GCM runs under the RCP8.5 scenario for the future period (2070–2080), show a consistent pattern in projected runoff change, with substantial increases in May runoff, smaller increases over the winter months, and decreased runoff in the summer months (June–August). Despite the SRM’s relative simplicity and requirement of only a few input variables, the model performed well in simulating historical flows, and provides runoff projections consistent with historical trends and previous modeling studies. Keywords: Snowmelt Runoff Model (SRM); climate change; degree–day; Upper Athabasca River Basin; hydrology; MODIS 1. Introduction Streamflow forecasts are a valuable source of information for water resource man- agement, e.g., to assess water availability for irrigation, hydroelectricity generation, and municipal or industrial use [1]. For most regions north of 45 ◦ N and mountainous regions, runoff is primarily derived from snowmelt [2]. In snowmelt-dominated northern regions, changing temperatures may be of greater interest in forecasting flow than precipitation, as it is temperature that controls the timing and magnitude of meltwater [3]. With warming temperatures, changes in seasonal runoff patterns have been observed in numerous rivers originating in the Rocky Mountains over the last century. As an example, an analysis of historical streamflow trends for 14 free-flowing rivers located throughout the Canadian and Northern USA Rocky Mountains found slightly increased winter flows and considerably reduced summer flows in most rivers over the previous century [4]. The reduction of the winter snowpack in a warmer climate and a potential reduction in summer runoff are of great significance to regions such as western Canada, where water usage peaks in the summer due to demand for irrigation and municipal water withdrawals [5]. Moreover, climate change is expected to intensify the hydrological cycle, increasing the global average temperature and precipitation, although there could be reductions in precipitation in some Water 2021, 13, 1199. https://doi.org/10.3390/w13091199 https://www.mdpi.com/journal/water