What does an observation well primarily measure?

An observation well is primarily designed to measure water levels in an aquifer. These wells are constructed specifically to monitor the static water level, which provides crucial data about the groundwater table. By measuring the water level, hydrogeologists can assess changes over time, understand aquifer recharge rates, monitor the impacts of groundwater extraction, and evaluate the overall health of the aquifer system.

While other options, such as measuring groundwater extraction rates and water quality, are important aspects of groundwater studies, they are not the primary function of observation wells. Groundwater extraction rates are typically assessed through different monitoring methods or specific extraction wells. Water quality is normally tested using dedicated water sampling wells or through routine testing at regular intervals, rather than being a primary measurement from observation wells. Surface water flow is monitored through different hydrological instruments and is distinct from the function of observation wells, which focus on groundwater levels specifically.