In this technical commentary, we discuss some of the most common sources of uncertainty in recording groundwater levels, which is an important factor in regional or site-specific assessments of geoenvironmental, geotechnical, and hydrogeologic conditions. Uncertainties associated with groundwater levels are usually pervasive because of: (1) measurement error (monitoring system), (2) term vagueness, and (3) natural variability over time and space in exploratory wells and/or geotechnical borings. These uncertainties can easily lead to erroneous evaluations of environmental and geohazards, such as water contamination, landslides, and ground failure (subsidence and liquefaction).