The Central Asia Equal Area Projection and Model Grid

The Central Asia Equal Area Projection and Model Grid (CAEAP-MG) dataset includes raster and vector representations of 1-km cells defining a uniform equal-area grid encompassing the Republics of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The grid is extended south into Afghanistan for purposes of encompassing the northward drainages into Central Asia including the Amu Darya, Tejan, and Morghab River. Projection information is provided in the projection.wkt file. The CAEAP-MG 1-km grid (file CAEAPMG01km.tif) consists of 3,200 columns and 2,500 rows where the value of each cell of the datasets corresponds to the cell number. The columns and rows are numbered as attributes from the top left corner of the grid, to correspond to the traditional row and column numbering system of the MODFLOW groundwater-flow simulation code (Hughes and others, 2017; Langevin and others, 2017). The 1-km grid is analogous to Clark and others (2018) for the United States. A vector representation of this grid is in the CAEAPMG01km.shp file. Mean altitude and standard deviation of altitude data is provided in CAEAPMG01km_mu.tif, CAEAPMG01km_sd.tif, CAEAPMG10km_mu.tif, CAEAPMG10km_sd.tif, CAEAPMG100m_mu.tif, CAEAPMG100m_sd.tif, CAEAPMG500m_mu.tif and CAEAPMG500m_sd.tif. Altitude data was computed from the 30 m FABDEM V1-2 dataset (Neal and Hawker, 2023). The Albers projection was chosen for the CAEAP-MG because of the capability to best preserve area, which is crucial for (1) volumetric calculations for water-resources or other related Earth-science investigations (Kuniansky, 2016), (2) physical process and statistical studies requiring area-weighted computations, and (3) studies combining groundwater and surface-water interactions.

The Albers projection parameters were defined with the false origin latitude and longitude at 39.65 degrees North and 67 degrees East, respectively. The location corresponds to the city of Samarkand, Uzbekistan. These decimal latitude and longitudes convert without loss of precision to integers for degrees, minutes, seconds. The coordinate system is centered on the city of Samarkand, Uzbekistan, and as a result, the false latitude and longitude are at 0 m north and 0 m east, respectively. The Albers projection standard parallels at 38.5 degrees and 44.5 degrees were informed by Kuniansky (2016) and Snyder (1982, p. 94), and are suitable by inherent shape preservation for in the southern part of Central Asia. The upper left coordinate (easting, northing) of the upper left cell of CAEAP-MG in the Albers projection is -1600000, 1800000, in units of meters, with a rotation of zero degrees.