An official website of the United States government.

We've made some changes to EPA.gov. If the information you are looking for is not here, you may be able to find it on the EPA Web Archive or the January 19, 2017 Web Snapshot.

Watershed Index Online

WSIO Indicator Data Library

Data Tables, Services and Downloads

Regional Indicator Data

One route for users to obtain watershed indicator data from WSIO is through creating and downloading a custom WSIO tool with user-selected data for their area of interest. WSIO indicator data tables containing all active WSIO indicators are also available for download below.  The lower 48 states' currently available data are split into ten data tables that correspond with EPA Regions 1 through 10.  Note that HUC12s that straddle the borders between two regions appear in both regional tables. Each regional data table is an Excel .xlsx file containing approximately 460 watershed indicators compiled at the HUC12 scale. Metadata are included in each file.

Free EXCEL Viewer

Top of Page

Indicator Metadata

This Excel .xlsx file contains indicator names, definitions and data source information for all WSIO indicators.  It is the same metadata file that appears in each of the downloadable WSIO data tables. Some of the most commonly used datasets are available as map services from this site, as described below. A map service makes maps, features, and attribute data available online and can be used in a variety of applications.

Top of Page

Key Datasets Available as Map Services and Data Downloads

Some of the most frequently used WSIO geospatial datasets are available as map services and data downloads below.  These are national-scale GIS datasets, not tabular indicator data as above. 

Conterminous US Watershed Hydrologic Unit Code (HUC12 and HUC8) Boundary Layers

HUC12This is the exact version of the HUC12 boundaries used in WSIO indicator compilation, offered here because HUC12 boundaries available through other sites sometimes undergo minor revisions without notice. This dataset is consistent with the "WBD Snapshot" version of HUC12 boundaries that was integrated with the National Hydrography Dataset (NHD) Plus version 2 nationally, and is a common source used by most EPA water projects involving geospatial watershed data. The HUC8 layer is fully consistent with the HUC12 snapshot because it was derived directly from it by dissolving interior HUC12 boundary lines.

Top of Page

Water Mask

Water MaskThis dataset was developed using grid analysis to combine surface water features (rivers, lakes, reservoirs, estuaries, wetlands, oceans) of the National Land Cover Dataset (NLCD) and the 1:100,000 scale National Hydrography Dataset (NHD) Plus version 2 (which includes mapped point, linear and areal surface water features). The combination of these two datasets represents surface waters of all kinds and is referred to as the Water Mask.

Top of Page

Hydrologically-Connected Zone

Hydrologically Connected ZoneThe Hydrologically Connected Zone (HCZ) is determined using grid analysis to combine surface water features of the National Land Cover Dataset (NLCD) and the 1:100,000 scale National Hydrography Dataset (NHD) Plus version 2 with areas contiguous to surface water that also have a wetness index value of 550 or greater. The combination of these three datasets represent the Hydrologically Connected Zone (HCZ).

Top of Page

Riparian Zone

Riparian ZoneThe Riparian Zone (RZ) is determined using grid analysis of an approximate 100 meter buffer placed around the combined surface water features of the National Land Cover Dataset (NLCD) and the 1:100,000 scale National Hydrography Dataset (NHD) Plus version 2. The combination of these two datasets and all cells with a distance of 108 meters or less from surface water are included in the RZ.

Top of Page

Wetness Index

Wetness IndexThe Wetness Index is a Computed Topographic Index (CTI) derived from the National Hydrography Dataset Plus flow accumulation and slope of the Digital Elevation Model using the equation: grid wet_ndx = 100*(ln  (flow accumulation/tan(slope)) + 3x3 mean of ln  (flow accumulation/tan(slope))/2. This information was used to identify areas in the landscape likely to be wet. Values greater than 800 have been determined to represent areas which are usually wet.  Due to exceptionally large size this dataset cannot be offered for download on this site.

Top of Page