Groundwater is an important environmental resource. If icecaps and snow are excluded, it represents 96- 97% of the available freshwater on Earth. Due to growing global demands for groundwater, accurate estimates of its stocks, recharge rates, and their regional distribution are essential. Despite a significant number of existing global groundwater balance studies, estimated numbers of available stocks and recharge differ with a variance of up to 585%. The aim of this study is to identify and analyze the factors that contribute towards uncertainties and limitations of existent groundwater assessment studies and methods. It discusses possibilities for reducing their magnitude and explores the potential for generating more accurate estimates of available global groundwater resources.