Grid with estimated maximum available soil moisture in mm/m with a spatial resolution of 5 * 5 arc minutes. Information with regard to maximum available soil moisture was calculated from the "Derived Soil Properties" of the "Digital Soil Map of the World" which contains raster information on soil moisture in different classes.

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.

Geo-referenced point database on dams in Africa.

This layer represents the spatial distribution of Government Farms, as of 2005, in Namibia, that share geographical overlapping with the Okavango Basin. Source: Ministry of Agriculture, Water and Forestry of Namibia. This dataset is part of the GIS Database for the Environment Protection and Sustainable Management of the Okavango River Basin project (EPSMO). Detailed information on the GIS Database can be found in the “GIS Database for the EPSMO Project” document produced by Luis Veríssimo (FAO consultant) in July 2009, and here available for download.

This map represents the spatial distribution of land under irrigation which is affected by some degree of salinization. It was produced by combining FAO AQUASTAT country statistics regarding irrigated areas affected by salinization with spatial information on irrigated areas where precipitation is not sufficient to leach away salt residues that are built up in the soil due to irrigation. It was assumed that the risk of salinization of irrigated areas can occur only in areas with an Aridity Index lower than 0.65 (where the Aridity Index is defined as Yearly Precipitation divided by Yearly Reference Evapotranspiration).

Grid with estimated reference evapotranspiration per month with a spatial resolution of 10 arc minutes. The dataset contains mean monthly values for global land areas, excluding Antarctica, for the period 1961-1990. The dataset has been prepared according to the FAO Penman - Monteith method with limited climatic data as described in FAO Irrigation and Drainage Paper 56. The dataset consists of 12 ASCII-grids with mean monthly data in mm/day * 10, and one ASCII-grid with yearly data in mm/year.

Delineation of Communal Conservancies in Namibia, that share geographical overlapping with the Okavango Basin. Source: Ministry of Agriculture, Water and Forestry of Namibia. This dataset is part of the GIS Database for the Environment Protection and Sustainable Management of the Okavango River Basin project (EPSMO). Detailed information on the database can be found in the “GIS Database for the EPSMO Project” document produced by Luis Veríssimo (FAO consultant) in July 2009, and here available for download.

Elevation points in meters within the Okavango Basin. Source: Generated under the GIS EPSMO program, by vectorization of existing topographic maps at 1/1 000 000. This dataset is part of the GIS Database for the Environment Protection and Sustainable Management of the Okavango River Basin project (EPSMO). Detailed information on the database can be found in the “GIS Database for the EPSMO Project” document produced by Luis Veríssimo (FAO consultant) in July 2009, and here available for download.

A set of 2 vector layers representing the contour lines at every 100m and 200m within the Okavango Basin. Source: Contour 100m generated under the GIS EPSMO program, by interpolation of the DTM model, and further operations of smoothing tolerance. Contour 200m generated under the GIS EPSMO program, by vectorization of existing topographic maps at 1/1 000 000. This dataset is part of the GIS Database for the Environment Protection and Sustainable Management of the Okavango River Basin project (EPSMO). Detailed information on the database can be found in the “GIS Database for the EPSMO Project” document produced by Luis Veríssimo (FAO consultant) in July 2009, and here available for download.

Grids with monthly values of coefficient of variation of precipitation for the period 1961-1990, at 5 arc min. Based on: New, M., Lister, D., Hulme, M. and Makin, I., 2002: A high-resolution data set of surface climate over global land areas. Climate Research 21:1-25