The textbook "Sources of Chloride and its Impact on Groundwater" offers a comprehensive analysis of the effects of de-icing salt on groundwater quality. It highlights the increasing contamination of groundwater due to the use of de-icing salt and the associated challenges. The author, Amen Alyaari, examines the interactions between road de-icing and the environment, particularly the sources of chloride and their impacts on soil, vegetation, and shallow groundwater. A central element of the study is the analysis of the transport processes of chloride from de-icing salt to adjacent groundwater resources. Additionally, a conceptual, mathematical, and numerical model of groundwater flow and substance transport is developed, utilizing modern software packages such as the Groundwater Modelling System (GMS). This book is aimed at professionals and students in the fields of mathematics and natural sciences who are engaged in environmental issues and groundwater research.