ASCE/EWRI Standard 50-08 provides current guidelines for fitting saturated hydraulic conductivity using probability density functions. Standard ASCE/EWRI 51-08 addresses the calculation of effective saturated hydraulic conductivity (Ke or Kew) in local-scale groundwater flow, whether or not it is isotropic. Both Standards are bound in the same volume. These are the first in an anticipated series of standards that will address the knowledge of probabilistic characterization and behavior of saturated groundwater conductivity. These Standards will be useful to environmental engineers, water resources engineers, and anyone who uses hydraulics in engineering.