The Stream Probabilistic Monitoring Program was established in 2005 and began collecting data in 2006. This program assesses water chemistry using methodology of the Stream Chemistry Monitoring Program and evaluates the aquatic macroinvertebrate assemblage using the approach of the Stream Biological Monitoring Program. Physical habitat data (for example stream channel substrate, bank condition) also are collected and used to augment the chemical and biological data.
The unique aspect of this program is the method in which sample locations are selected. The SPMP does not rely on repeated sampling of a fixed set of hand-selected monitoring sites. Instead, sampling points are selected randomly from the network of all classified streams in the state, and a new set of sites is sampled each year. The site selection methodology, which was developed by the EPA Research Division and has been adopted nationwide, is a method that can be used to generate a statistically unbiased estimate of the conditions of any resource.