Hydrogeology is the study of how water moves through and interacts with the Earth's subsurface materials. It focuses on groundwater, which is water found beneath the Earth's surface in soil and rock formations. Hydrogeologists examine the distribution, flow, and quality of this water, as well as how it is affected by natural processes and human activities. This field is essential for managing water resources, understanding aquifers, and addressing issues like contamination and water supply. Hydrogeologists use various tools and techniques, including geological mapping and hydraulic testing, to assess groundwater systems and ensure sustainable water use.