The study methodology is outlined in Figure 2. To start with, the Wereda
boundary map and all other maps were re-projected from the Geographic Coordinate
System (GCS) to Adindan_UTM_Zone_37N projection coordinate system
(PCS) so they could match when overlayed. The DEM Map produced by NASA
(no date available) was transformed from the Geographic to the Goode Homolosine
projection to facilitate the calculation of slope. Slope is defined as “the
change in elevation (a rise) with a change in horizontal position (a run)” (Bolstad
2008: 417). Portions of Weredas were then reclassified into two slope categories:
less or equal to 3 degrees, and greater than 3 degrees. This is a very important
step because slope values are used as the principal weighting factor in the calculation
of Wereda suitability indices (see formula in the Results section). A slope
of 3 degrees is used as a reasonable cutoff point, and as an upper limit of gravityassisted
irrigation with no need for mechanical pumping