Spring water provides a unique opportunity to study a range subsurface processes in regions with few boreholes or wells. Because springs integrate the signal of geological and hydrological processes over large spatial areas and long periods of time they are an indirect source of information, however. This review illustrates a variety of techniques and approaches that are used to interpret measurements of isotopic tracers, water chemistry, discharge, and temperature. As an example, a set of springs in the Oregon Cascades is considered. By using tracers, temperature and discharge measurements, it is possible to determine the mean-residence time of water, infer the spatial pattern and extent of groundwater flow, estimate basin-scale hydraulic properties, calculate the regional heat flow, and quantify the rate of magmatic intrusion beneath the volcanic arc.