Citation: Ahmed, S.I.; Rudra, R.; Goel, P.; Amili, A.; Dickinson, T.; Singh, K.; Khan, A. Change in Winter Precipitation Regime across Ontario, Canada. Hydrology 2022, 9, 81. https://doi.org/10.3390/ hydrology9050081 Academic Editor: Kwok-Wing Chau Received: 15 March 2022 Accepted: 6 May 2022 Published: 10 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 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/). hydrology Article Change in Winter Precipitation Regime across Ontario, Canada Syed Imran Ahmed 1,2, *, Ramesh Rudra 1 , Pradeep Goel 3 , Arezoo Amili 1 , Trevor Dickinson 1 , Kamal Singh 1 and Alamgir Khan 4 1 Water Resources Engineering, School of Engineering, University of Guelph, Guelph, ON N1G 2W1, Canada; rrudra@uoguelph.ca (R.R.); arezoo.amy.amili@gmail.com (A.A.); wdickins@uoguelph.ca (T.D.); kamalgurmit@pau.edu (K.S.) 2 Department of Civil Engineering and Technology, NED University of Science and Technology, Karachi 75270, Pakistan 3 Ministry of the Environment, Conservation and Parks, Etobicoke, ON M9P 3V6, Canada; pradeep.goel@ontario.ca 4 MNS Department of Agriculture, University of Agriculture, Multan 60000, Pakistan; alamgir.khan@mnsuam.edu.pk * Correspondence: sahmed@uoguelph.ca or imranahmed@neduet.edu.pk; Tel.: +1-519-824-4120 (ext. 54321) Abstract: The focus of this study is to investigate the effects of climate change on the hydrologic regimes in Ontario, Canada. The variables include total precipitation, the form of precipitation (snowfall and rainfall), and the temperature during winter. The winter season is hydrologically significant for Canadian conditions. The historical data for 70 years, from 1939 to 2008, on total precipitation, snowfall, rainfall, and temperature over the winter period were analyzed using least- squares regressions, Alexandersson’s Standard Normal Homogeneity Test, and the Mann–Kendall test for 13 stations across Ontario to identify positive and negative trends and their significance. The analysis of the precipitation indices reveals no significant trend in the winter total precipitation, decreasing trends in winter snowfall, and increasing trends in winter rainfall. The snowy day analysis depicts a large scatter across the province, with the number ranging from 40 days to 80 days, which shows that the number of snowy days varies considerably over the years at all stations. The analysis showed that the change in snowy-rainy days is attributed to the significant upward trend of the daily mean winter minimum temperature for almost all the stations. Therefore, the changes in the form of precipitation during winter may affect water management including streamflow, tile drainage flow, soil erosion, sediment and nutrient transport to surface water bodies, and the effectiveness of best management practices being used for managing non-point source pollution. Keywords: climate change; trend; rainfall; snow; winter minimum temperature; snowy day; rainy day 1. Introduction Global warming, due to an increase in greenhouse gases, is one of the most funda- mental aspects of the climate system and it can be implicated as one of the basic factors contributing to rising of environmental temperatures. An increase in temperature can affect human lifestyles, economics, and ecosystems, as well as human health and social well- being [1]. Also, the United States Global Change Research Program (USGCRP) reported that the global average surface temperature has increased at an average rate of 0.17 ◦ F per decade since 1901. It was also found that this rate of warming is similar to the rate in the US, which has become faster than the global rate since the late 1970s [2]. Nerantzaki et al. [3] recently discussed the effects of global warming by providing an insight into the fluctuation of future water requirements and a quantification of future water deficits. By using the Water Exploitation Index for the spatial variability of future water stresses, a decrease in both surface and karstic spring flows is foreseen, especially after 2060. Canada has also experienced a warming trend at a higher rate due to its high latitude [4]. In southern Canada, the annual mean temperature increased by between 0.5 and 1.5 ◦ C from Hydrology 2022, 9, 81. https://doi.org/10.3390/hydrology9050081 https://www.mdpi.com/journal/hydrology