Hydraulic responses to pumping depend on aquifer characteristics, fluid properties, well construction, and pumping rate. A well function is used here to represent the hydraulic responses (drawdown) to pumping or to describe the flow toward a pumping well under a set of idealized conditions. In application, we wish to determine the hydrogeological properties from observed responses such as hydraulic head variations. Once the properties are determined, one can predict the responses due to pumping or use the properties to formulate models of groundwater flow.