Landsat Dynamic Surface Water Extent: Mapping Water Pixel by Pixel

The confluence of the Wabash and Ohio Rivers on April 12, 2021: left, a Landsat surface reflectance image; right, the Dynamic Surface Water Extent (Interpreted Layer). USGS images.

What it is

The Landsat Collection 2 Level-3 Dynamic Surface Water Extent (DSWE) science product gives raster data showing surface water inundation in each pixel of Landsat 4–9 imagery.

Why it matters: surface water extent is shaped by weather and climate, stream network hydrology, and geological processes such as isostatic rebound — and changes in it affect land use, the management of ecosystems and their services, and water management overall.

How it's made

• Inputs: generated from Collection 2 U.S. Analysis Ready Data surface reflectance, using the cloud, cloud shadow and snow information in the Level-2 "QA_PIXEL" quality band.
• Sensors: Landsat 4–5 Thematic Mapper, Landsat 7 Enhanced Thematic Mapper Plus and Landsat 8–9 Operational Land Imager.
• Grid: 30-meter pixels in the Albers Equal-Area Conic projection on the WGS 84 datum, on fixed, non-overlapping tiles.

Coverage

The conterminous United States, Alaska and Hawaii:

What changed in Collection 2

Agreement between Collection 1 and Collection 2 in the High Confidence Water class is excellent. The changes:

• it uses the Collection 2 Digital Elevation Model;
• a Land Cover Mask was added to the Interpreted Layer masking;
• the Interpreted Layer with Mask Applied was split in two: with Some Masks Applied and with All Masks Applied;
• the static Hillshade threshold was replaced with a dynamic threshold for commission masking;
• the Percent Slope thresholds were removed from the masking, so the Percent Slope band is no longer included.

The layers

Six rasters and a metadata file:

The interpreted layers sort pixels into classes such as not water, high confidence and moderate confidence water, and conservative and aggressive partial surface water.

Getting and citing it

• Download: from EarthExplorer, under Landsat › Landsat Collection 2 Level-3 Science Products or Landsat C2 U.S. Analysis Ready Data (ARD), listed as "Landsat 4-9 C2 Dynamic Surface Water Extent" — or through the commercial cloud; see Landsat Data Access for cloud and bulk options.
• Documentation: the product page has the product guide and the algorithm description.
• Citing: use of Landsat Collection 2 Level-3 science products is not restricted. The suggested credit is "Landsat Collection 2 Level-3 Dynamic Surface Water Extent science product courtesy of the U.S. Geological Survey," with Jones (2019), "Improved automated detection of subpixel-scale inundation—Revised Dynamic Surface Water Extent (DSWE) partial surface water tests," Remote Sensing 11(4): 374.

Sources

Based on U.S. Geological Survey, "Landsat Collection 2 Level-3 Dynamic Surface Water Extent Science Product," Fact Sheet 2022–3084, USGS; a work of the United States government in the public domain. The figure is restored from the fact sheet's PDF. The source gives the tile size as 5,000 square meters, which cannot be right for 30-meter pixels; this page leaves it out.