Two standards are combined that explain the critical factor of saturated hydraulic conductivity to effectively and accurately measure groundwater flow and transport of contaminants. All saturated hydraulic conductivity measurements are subject to variability—even in the most geologically homogeneous aquifers—caused by local fluctuations in an aquifer's textural characteristics. Averages of these fluctuations constitute a set of values that can be subsumed into a more general probabilistic description of the sample by means of a probability density function. Applying probabilistic procedures to the saturated hydraulic conductivity produces effective hydraulic conductivity, which can be used to estimate average specific discharge, average linear velocity, and other key variables in groundwater flow.

ANSI/ASCE/EWRI Standard 50-08(R2022) provides current guidelines for fitting saturated hydraulic conductivity using probability density functions. Standard ANSI/ASCE/EWRI 51-08(R2022) addresses the calculation of effective saturated hydraulic conductivity (K_e or K_ew)  in local-scale groundwater flow, whether or not it is isotropic. Combined in a single volume, these two standards are the first in a series that addresses the knowledge of probabilistic characterization and behavior of saturated groundwater conductivity.

These standards will be useful to environmental engineers, water resources engineers, and any professional who uses hydraulics in engineering.

An ASCE standard is reaffirmed when it has been reviewed by its technical committee and determined to be current with no need for immediate revision. These standards were reaffirmed in 2016 and 2022.