This dataset represents the calculated wetness index value within individual local and accumulated upstream catchments for NHDPlusV2 Waterbodies based on the Composite Topographic Index (See Supplementary Info for Glossary of Terms). Catchment boundaries in LakeCat are defined in one of two ways, on-network or off-network. The on-network catchment boundaries follow the catchments provided in the NHDPlusV2 and the metrics for these lakes mirror metrics from StreamCat, but will substitute the COMID of the NHDWaterbody for that of the NHDFlowline. The off-network catchment framework uses the NHDPlusV2 flow direction rasters to define non-overlapping lake-catchment boundaries and then links them through an off-network flow table. The westness index is calculated using the Composite Topographic Index (CTI) which is based on contributing area, slope, and overland flow and has been developed internally at the EPA for the EnviroAtls (http://edg.epa.gov/data/Public/ORD/EnviroAtlas/National/). As defined for use in EnviroAtlas datasets and as used here, wet areas are typically created by runoff from natural land cover when rain falls on saturated soil. Surface and rill (or small channel) runoff carries excess water to lowland depressions or wet areas. Runoff collects in wet areas until they fill and overflow downstream. In this way, stream networks can be extended into new areas that would not be hydrologically connected during drier times. Wet area expansion and watershed hydrological connectivity differ between humid temperate and semi-arid and arid climates (where drought and soil crusts limit infiltration and produce flashier runoff) (from https://enviroatlas.epa.gov/enviroatlas/datafactsheets/pdf/ESN/PercentForestonWetAreas.pdf). The Mean Composite Topographic Index (CTI)[Wetness Index] were summarized to produce local catchment-level and watershed-level metrics as a continuous data type.