The Surface Water Record

Ganges-Brahmaputra Regional Display

Observing the Earth's changing surface water in near real time

Standard Description:

This map provides, with daily updating: current surface water based on NASA MODIS data, satellite-based discharge measurements (at the numbered and clickable sites), and the observed recent history of flooding or surface water contraction (2000 to present).

Mapped water expansions (bright blue) may be short-term, from inland flooding or coastal storm surges. Or expansions may be long-term, from post-2000 construction of new reservoirs or increases in rice agriculture or aquaculture. Reductions in surface water may be from temporary drought conditions, or persist over longer periods (for example, some progressively shrinking wetlands). Note: in mountainous areas, local shadows are commonly mis-classified as water. See also the Record Guide

Map Legend

At the time of map date:

Large areas of purple are dry land (formerly water in February, 2000, when the reference SWBD water database was obtained). At higher latitudes, such areas may be ice-covered water. In cloudy regions, even the 14 day compositing period may not provide complete geographic coverage (e.g., expressed as purple areas within lakes or along shorelines). Small areas of purple are water mapped by SWBD, but are too small to be mappable by MODIS. Dark blue is current water, imaged by MODIS and by SWBD in 2000 ("permanent" water). Bright blue is flooding: expanded water areas mapped by MODIS compared to SWBD. Any post-2000 reservoir or new water body is also depicted in bright blue.Light blue-gray is all previous flooding imaged and mapped by the Flood Observatory (now dry land).

River measurement sites: Yellow dots: low flow (<50 % mean daily runoff for this date). Blue dots: normal flow. Purple dots: moderate flooding (>1.33 yr recurrence). Red dots, major flooding (> 5 yr recurrence).

Brief interpretation of this display:

On July 10, 2014, major flooding was underway along the Yamuna River (at site #211), but, as in prior years, flooding is confined to a narrow floodplain and has not yet been imaged and mapped by the MODIS processor. To the east, monsoon season flooding has intiated along the Ganges and tributaries, but has not yet reached the moderate flooding threshold. In the center of the bottom portion of the map, site 2031 indicates unusually low flow conditions, and MODIS water mapping of two reservoirs to the east also show a much-contracted water extents. MODIS data also indicate initiation of flooding along the Brahmaputra, but the microwave measurement sites show that flooding has not yet reached the moderate flooding threshold.

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