ISLSCP II River Routing Data (STN-30p) 
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File Description
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The STN data set for ISLSCP II is made up of two data files at spatial 
resolutions of 0.5 and 1.0 degree in both latitude and longitude, denoted as 
hd and 1d, respectively, in each filename: river_routing_stn_1deg.zip and 
river_routing_stn_hdeg.zip.

When expanded, each data set contains a number of global, gridded data layers 
and two associated attribute tables as follows:

stn_basin_id_XX.asc: Basin grid, which assigns unique identifiers to groups
                     of grid-cells forming individual river basins. 
                     XX can be hd or 1d, depending on the spatial resolution 
                     of the data set.

stn_flow_accum_XX.asc: Flow accumulation grid or upstream area grid (km2),
                       which provides the catchment area estimate for each 
                       grid cell according to the STN-30p network.

stn_flow_direction_XX.asc: Flow direction grid, which represents the
                           horizontal connectivity of the continental 
                           land mass.

stn_dist2mouth_XX.asc: Distance in km to the outlet of river basins.

stn_mainstem_length_XX.asc: Mainstem length [km] grid.

stn_stream_order_XX.asc: Strahler stream order grid.

stn_elevation_hd.asc: Adjusted elevation (m) grid, which combines HYDRO1k
                      aggregated elevation at 30-minute resolution with 
                      STN-30p, where the inconsistencies between the
                      elevation and the flow direction data sets (i.e.
                      increasing elevation along downstream flow path) 
                      were eliminated. Note: this data layer is only  
                      available at 0.5  degree resolution.
 
stn_slope_hd.asc: Slope (degree) along the STN-30p grid, provides slope
                  information for each grid cell along the cell's flow 
                  direction. Note: this data layer is only availabe at
                  0.5 degree resolution.

stn_basin_attribute_XX.dat (table): Basin attribute table contains 
                                    attribute information such as basin
                                    name, catchment area, mainstem length, 
                                    etc. for each individual basin. See
                                    below for table descriptions.

stn_cell_attribute_XX.dat (table): Cell attribute table contains 
                                   attribute information for each land 
                                   cell. See below for table descriptions.

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ASCII File Format
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All of the files in the ISLSCP Initiative II data collection are in the ASCII 
grid format. The file format consists of numerical fields of varying length,
which are delimited by a single space and arranged in columns and rows:

 0.5 degree files: contain 720 columns by 360 rows.
 1.0 degree files: contain 360 columns by 180 rows. 

Values in the files for flow accumulation, distance to river mouth, mainstem 
length, slope and elevation are written as real numbers while files for basin 
ids, flow direction, and stream order are written as integers. Missing values
over water are assigned the value of -99. Missing values over land are assigned 
the value of -88.

The flow direction grid is given as the standard ARC/INFO representation
of the 8 flow direction grid using the following encoding scheme:
+---+-----+-----+
|32 | 64 | 128 |
+---+----+-----+
|16 |    |  1  |
+---+----+-----+
|8  | 4  |  2  |
+---+----+-----+

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Attribute File Contents
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The two attribute tables are tab-delimited, with strings in quotes and
the first line contains field names as follows.

stn30p_basin_attribute_XX.asc files:
BASINID         - Basin ID number (1-6152).
BASINNAME       - Basin Name (GHAASBasin#### or real basin name from 
                  GEMS/GLORI).
BASINORDER      - Strahler stream order at mouth (1-6).
COLOR           - Optimized color (7 - 11) to display basins.
BASINLENGTH     - Mainstem length [km].
BASINAREA       - Basin area [km^2].
CONTINENTNAME   - Continent name.
SEANAME         - Name of the recipient sea.
OCEANNAME       - Name of the recipient ocean.

stn30p_cell_attribute_XX.asc files:
CELLID          - Cell ID number (1-59132).
BASINNAME       - Basin name.
ORDER           - Strahler stream order.
BASINID         - Integer basin identifier.
BASINCELLS      - Number of 30-minute cells upstream.
TRAVEL          - Number of cells downstream.
CELLAREA        - Cell area [km^2].
SUBBASINLENGTH  - Mainstem length [km] upstream.
SUBBASINAREA    - Upstream area [km^2].
DISTTOMOUTH     - Distance [km] to river mouth defined as
                  confluence with equal or higher order stream.
DISTTOOCEAN     - Distance [km] to the outlet of river basins.
CELLLENGTH      - Length [km] of 30 minute river segment.