UMRR LTRM Sampling Strata

The LTRMP samples probabilistically using a stratified random sampling design within five reaches of the Upper Mississippi River (UMR) and one reach of the Illinois River. These six reaches represent a judgment sample of reaches within the Upper Mississippi River System (UMRS), and, as a result, inferences about either the UMR or the UMRS from LTRMP data must rely on models rather than on the design.