GlobWat uses spatially distributed input layers consisting of monthly precipitation, number of wet days per month, coefficient of variation of precipitation, monthly reference evapotranspiration, maximum soil moisture storage capacity, maximum percolation flux, irrigated areas, land use, and areas of open water and wetlands. All these input layers are based on freely available spatial dataset with a resolution of 10 arc minutes for the climate dataset and 5 arc minutes for all the terrain and land dataset (data sources are provided in the downloadable files).
The water balance is calculated in two steps. First a vertical water balance is calculated that includes rainfall dependent evapotranspiration and evapotranspiration from crops under irrigated circumstances (for which it is assumed that it can be provided by surface water or groundwater). In a second stage, a horizontal water balance is calculated to correct for incremental evapotranspiration from open water and wetlands and to calculate discharges from river (sub-) basins taking into consideration the water needed for irrigation.
Un example of GlobWat input (reference ET) is available as WMS link in the Data and Resources section of this metadata.
Data publication: 2021-12-22
Supplemental Information:
All input and output files are provided below: grid are ASCII-grid, 5 arc min resolution, GCS-WGS84. The excel file "filename-keys" provides further description of files.
Source code and executable files are available upon request.
Contact points:
Metadata contact: AQUASTAT FAO-UN Land and Water Division
Contact: Jippe Hoogeveen FAO-UN Land and Water Division
Online resources:
GlobWat input files, part 1: monthly precipitation (10.6 MB)
GlobWat input files, part 2: monthly reference evapotranspiration (8.6 MB)
GlobWat input files, part 3: rain days per month (3.7 MB)
GlobWat input files, part 4: monthly coefficient of variation of precipitation (11.4 MB)
GlobWat input files, part 5: soil related parameters (soil moisture, percolation flux, rooting depth and calibration factors, 2 MB).
GlobWat input files, part 6: land use, irrigation areas, administrative areas and basins codes (5 MB)
List of input and output files (36 KB)
GlobWat v 1.0 executable and Fortran codes (1.3 MB). [Error in .bat corrected on October 3 2018]
Output grid with yearly actual evaporation corrected for incremental evapotranspiration of irrigation, water and wetlands (3.8 MB)