This tabular data set represents the percent of United States Environmental protection Agency's (U.S. EPA) Level 3 Regions compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data is the "Level III and IV Ecoregions of the Continental United States" produced by the U.S. EPA (2013). Units are percent. The level 3 ecoregions are an 85-class classification scheme of areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources (EPA, 2013). Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).