Index-based groundwater vulnerability mapping models using hydrogeological settings: A critical evaluation

•Various index-based groundwater vulnerability assessment models have been discussed.•A comparative analysis of the models and its applicability in different hydrogeological settings has been discussed.•Research problems of underlying vulnerability assessment models are also reported in this review paper.

Groundwater vulnerability maps are useful for decision making in land use planning and water resource management. This paper reviews the various groundwater vulnerability assessment models developed across the world. Each model has been evaluated in terms of its pros and cons and the environmental conditions of its application. The paper further discusses the validation techniques used for the generated vulnerability maps by various models. Implicit challenges associated with the development of the groundwater vulnerability assessment models have also been identified with scientific considerations to the parameter relations and their selections.