The groundwater and aquifer parameters of most importance are:

• Gradient, the change in elevation of water over distance;
• (K), the hydraulic conductivity;
• n, the porosity;
• ne, the effective porosity;
• S, the aquifer storetivity;
• Aquifer thickness;
• Aquifer lithology;
• Aquifer carbon content.

Of these parameters, aquifer thickness and lithology can be determined while drilling the well, or from "through the casing" radiation/electric logging of completed or installed wells. Reasonably, accurate estimations of n, ne and the carbon content can be determined from laboratory analysis of samples collected during drilling. The gradient can be calculated from the groundwater elevations in a minimum of three wells. In order to determine the remaining parameters some type of aquifer testing must be done. The type and duration of the aquifer test used is dependent on the data needed.

Two types of aquifer tests are routinely performed at contaminated sites: slug/bail tests and pump tests: