Bhutan GIS data—a preview of UW contributions to DRUKDIF

--------------------------------------------------------------------------------------------- This shows the 27 gauging stations used with the VIC model. The updated national border is used.

Thse following maps were created with an old file of political boundaries. They will be recreated with a correct map of boundaries The base image is the Hydrosheds version of the SRTM DEM. Longitudinal profiles of rivers were created by tracing from cell center to cell center.

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More on stream slopes using the new (July 2009) 1" ASTER Global DEM

We are running the VIC hydrological model at a resolution of 2.5' (~ 4×4.6 km). The DEM was first generalized from 3" to 2.5' as follows:

This yields a DEM that tends to respect stream channels better than a DEM derived by other means.

We have implemented the best possible flow direction grid as follows:

The resulting flowdirection grid following the rivers much better than a grid derived from a DEM, even our DEM, as the next figure indicates. --------------------------------------------------------------------------------------------

A small portion of Bhutan drains north into the Tsangpo, reaching the Brahmaputra the hard way. Most of Bhutan drains south across the Indian plain, reaching the Brahmaputra through a number of rivers. In order to avoid modeling most of the Brahmaputra in order to cover Bhutan, we have defined 17 basins: -----------------------------------------------------------------------------------------

An alternative is to clip the basins as they leave Bhutan. This generates 95 watersheds of 1 to 199 cells, covering the 2225 cells of Bhutan (including every grid cells that touches Bhutan), plus 682 cells that are upstream from Bhutan.

This raises the question: what data layers need to extend throughout watersheds that flow into Bhutan. Also, do we want to extend some watersheds into India to reduce the number of watersheds and employ Indian river measurements. -----------------------------------------------------------------------------------------

This is the Wang Chhu Basin, as represented in 2.5' VIC-ready cells. -----------------------------------------------------------------------------------------

We have TRMM rainfall on a quarter-degree grid at daily (actually 3-hour) intervals. -----------------------------------------------------------------------------------------

This is the FAO world soil suborder data: -----------------------------------------------------------------------------------------

This is MODIS satellite land cover. ( (full size maps))

This is Landsat imagery. Two scenes cover nearly all of Bhutan, but two more are required to cover the entire country. -----------------------------------------------------------------------------------------

The stars and pentagons represent river flow stations for which monthly and daily data have been assembled. -----------------------------------------------------------------------------------------

This shows a detail of the 3" (~90m) SRTM DEM from the 2000 Space Shuttle flight. This is the CGIAR conditioned version. -----------------------------------------------------------------------------------------

This shows a detail of a DEM built from a single ASTER satellite scene. The scene contains 14 sprectral bands, along with a backlooking band which we used to create the DEM shown here. Clouds to the right have been mistaken for topography. -----------------------------------------------------------------------------------------

This shows a detail of the new (July 2, 2009) Global DEM mosaicked from 1.2 million ASTER scenes. It is built at 1" (~30m) resolution. ASTER DEM is a product of METI and NASA. -----------------------------------------------------------------------------------------

This shows the number of ASTER scenes combined to obtain a value for each pixel. The maximum number of component scenes in the Bhutan area is 58. -----------------------------------------------------------------------------------------

This is one of the preliminary VIC hydrographs. --------------------------------------------------------------------------------------------------------------------

October, 2009 workshop in Thimphu    (full size)

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