What are test holes primarily used for in the context of water well site determination?

Test holes are primarily utilized to verify and augment information obtained from other sources during the water well site determination process. This practice is essential because it enables hydrogeologists and engineers to gather on-site data regarding the geological and hydrological conditions of an area.

By drilling test holes, professionals can assess factors such as soil composition, groundwater levels, and the presence of any contaminants. This direct assessment can often reveal conditions that existing data may not fully describe, thereby leading to more informed decisions regarding well placement and development.

The other options, while related to the broader context of water well operations, do not accurately capture the primary function of test holes. For instance, installing pumps pertains to the next phase of well development rather than initial site assessment. Measuring water temperature and testing water quality would typically occur after a well has been established, rather than during the exploratory phase that test holes represent.

Overall, the role of test holes in verifying and adding critical geological and hydrological data is what makes this answer the most appropriate choice.