Table 1. Dataframe for the VIC model application to the Mekong river basin. Time step = daily, spatial scale = 1 km, 8 km, and 25 km. 

Attribute Class

Derived Parameter

Data Source & Processing/Derivation

Physical Template

Topographic data were taken from 30-arcsecond GTOPO30 Digital Elevation Model (DEM), obtained from the U.S. Geological Survey, from their web site http://edcdaac.usgs.gov/gtopo30/gtopo30.html

Basin mask (watershed boundary delineation), basin network (gridded integrated elevation file that contains elevation of watershed boundary line, stream network and contour),  id (grid identification coverages  (used to locate the hydrological stations for calibration/ verification)

DEM was used to derive a basin delineation map and  to extract flow accumulation matrix, from which the river routing network at the several scales was computed and manually corrected as necessary. Elevation bands, which are used to represent sub-grid variability in topography, were derived from the 30-arcsecond DEM.

Soils

Two sources of soil type data are used, to obtain the dominant soil type in each grid cell:

Soils#1: 5-minute FAO/UNESCO digital soil map of the world (FAO, 1995).

Soils#2: 1:50k high resolution data from the MRC.

Soil file  The soil file provides, for each grid cell, data on the soil texture (sand and clay content) of each soil layer.

It is from this soil texture information that the various other soil parameters, listed below, are obtained.

From the dominant soil type data (above), two soil characteristics – soil texture and bulk density – are estimated by consulting the World Inventory of Soil Emission Potentials (WISE) pedon database (Batjes, 1995), which contains attributes for a large number of soil profiles from around the globe. Consultation of the WISE database is performed using the SOILPROGRAM by Carter and Scholes (1999). This is the procedure used and described in Nijssen et al. (2001a) to obtain soil texture and bulk density.

The following assumptions were made for running the SOILPROGRAM: The depth of the VIC upper soil layer was initially taken as .1m and that of the second layer as 1.0m. The depth of the third layer was equivalent to 100mm of water storage, which corresponds to a depth of about .25 m, depending upon the porosity. The depth of the second soil layer was subsequently changed during the process of calibration. Once the processing was completed at 5-minute resolution, soil attributes were aggregated to the 8 km and 25 km resolution.

Soil parameter file . This file specifies, for each grid cell, the value of each of the following soil parameters:

b_infilt: Parameter of the variable infiltration curve

Ds_max: Maximum velocity of baseflow [mm/day]

Ds: Fraction of Ds_max for which non-linear baseflow begins

Ws: Fraction of maximum soil moisture for which non-linear baseflow begins

c: Exponent in the infiltration curve (normally set to 2)

Ksat: Saturated hydraulic conductivity (mm/day)

Expt: Parameter describing the dependence of unsaturated hydraulic conductivity on soil moisture

Phi_s: Soil moisture diffusion parameter

Init_moist: Initial moisture content of the soil layer (mm)

elev: Average elevation of the grid cell (m)

depth: Soil layer depth (m)

avg_T: Average soil temperature, used as the bottom boundary for soil heat flux solutions.

d_p: Soil thermal damping depth (depth at which the soil temperature remains fairly constant throughout the year; ~ 4m) (m)

bubble: Bubbling pressure of the soil (cm)

quartz: Fraction of the soil mass composed of quartz

bulk_density: Bulk density of the soil layer (kg m^-3)

soil_density: Soil particle density (normally set to 2685kg m^-3)

Wcr_fract: Fractional soil moisture content at the critical point (~70% of field capacity)

Wpwp_fract: Fraction soil moisture content at the wilting point

soil_rough: Surface roughness of bare soil (m)

annual_prec: Average annual precipitation (mm)

resid_moist: Residual moisture in the soil moisture layer

Most of these parameters are derived from the above soil file data on texture, using the methods described in Nijssen et al (2001a), which are based on the methods of Cosby et al. (1984). The program TRIANGLE by Gerakis (1999) was used to convert the texture information given in the soil file to the textural classes used by Cosby et al. (1984), which are those of the United States Department of Agriculture (USDA).

Table 2. Status of VIC/Mekong  dataframe development (for the purposes of clarity, the status of each category of attributes in Table 1 is summarized, not each parameter)

Remaining work (if any)

Target Date

Physical Template

Network (1, 25 km)

                -

Done

Network  (8 km)

Aggregate 1 km to 8 km

8/22

Soils

 FAO (8 km, 25 km)

Done

 FAO (1 km)

Disaggregate 8 km to 1 km

8/22

MRC (1 km, 8 km)

(1) Complete transference to  VIC scheme

(2) Aggregate to 1 km, 8 km

~ 9/5 (hopefully earlier)

Vegetation Attributes

Reference IGBP (1km, 25 km)

Done

Reference IGBP (8 km)

Aggregate 1 km to 8 km

8/22

MODIS (1 km, 8 km)

(1) Complete transference to  VIC scheme

(2) Aggregate 1 km to 8 km

~ 9/5 (hopefully earlier)

AVHRR  1980-200 Time Series (8 km, only)

(1) Complete download & pre-processing  

(2) Extract LAI, derive other parameters

~9/15-9/30

Scenarios

Resolve process: transition matrices on MODIS, Activity 1 Scenarios

9/15

Gridded Surface Climatology

Network (1, 25 km)

                -

Done

Network  (8 km)

Aggregate 1 km to 8 km

8/22

Streamflow (gauging stations)

Done

Table 3. Dataframe for DHSVM parameters for application to the Mae Chaem river basin. Time step = 1 hour, spatial scale = 150 m. (snow-related parameters eliminated)

Attribute Class

Derived Parameter

Data Source & Processing/Derivation

Physical Template

Area

Coordinate system  =  UTM

Center latitude  =  2059308 (18 ^o15’)

Center longitude  =  433969 (98^o22’)

Extreme north  =  2128608.0 (19 ^o15’)

Extreme west  =  394144.0 (98^o00’)

# rows  =  924

# colums  =  531

Grid spacing = 150 meter

ICRAF DEM (topo-map derived) 30 meter, UTM. Originally 30 m and aggregated to final 150 m

Basin mask

ICRAF. Boundary-modified to be consistent with the DEM, 150 m

Stream network map

Derived from DEM

Stream routing system

Processed through complex script into stream segments with identified stream class and stream computational orders

 Stream class attributes

 Channel hydraulic properties associated with stream class ID. Default values are hardwired in the program.  

Soils

Soil data very sparse, and restricted to lowlands.  Soil mapping unit Land Development Division (LDD), Ministry of Agriculture (LDD), with 62-group soil description, slope, moisture, permeability)

2). Map of soil site location from individual projects (ICRAF).

Soil map, soil depth, # soil types, # soil layers, soil description,

Interim soil map derived from SoilData program and resampled to 150 meter, UTM

Soil depth generated from the same script that generates stream routing.

Soil parameters

Parameters computed (PC) from: SoilData program, Soil texture calculator program from Washington State University, Tindall et al,  1999

Lateral saturated hydraulic conductivity (meter/s)

(PC)

Exponent for change in lateral conductivity with depth

Assume constant 3 across the area

Maximum infiltration rate (meter/s)

Assume constant 1e-5 

Surface albedo of soil (meter/s)

Assume 0.2 , based on the typical value for loam.

Number of soil layers

Soil porosity (0-1) for each soil layer

Get saturated water content from A, and calculate porosity = saturated water content / 0.9

Pore size distribution index for each soil layer

Assume constant 0.12 for both layers across the area

Bubbling pressure for each soil layer

(PC)

Field capacity (0-1) for each soil layer

(PC)

Wilting point (0-1) for each soil layer

(PC)

Bulk density of each soil layer (kg/m³)

(PC)

Vertical conductivity of each soil layer (meter/s)

(PC)

Thermal conductivity of dry soil for each soil layer (W/m/^oC)

(PC)

Thermal capacity for each soil layer (J/kg/K)

(PC)

Vegetation

Base land cover map from the Land Development Division (LDD), Ministry of Agriculture, Thailand Landuse 1:50000; 1989; Originally 30 m and aggregated to final 150 m

LDD categories to UMD classes

Inspection and assignment

Vegetation parameters

Assigned on basis of class (ABC)

Overstory Present

(true or false)

Understory Present