The construction of a dam helps address water scarcity in both residential and irrigation. This study uses GIS and AHP Multi-Criteria Decision Analysis to determine suitable dam sites in terms of topographical, hydrological, and environmental factors. In general, from the analysis southern, southwest and central part of the Abay basin werefound to be the densest area with high suitability for constructing dam while northeast and eastern parts were found as low or extremely low suitable area for constructing dam. Accordingly, 26.36% of the Abay basin is in the highly suitable and very high suitability in which only 0.03% was very highly suitable; 72.01% of the Abay basin area was found in the moderate suitability; 1.59% on low or extremely low suitability. Based on the suitability map, 39 dam sites were proposed with 17 being large, 9 intermediate, and 3 small based on height. The height of dams varies from 12 m to 174 m, width from 165 to 1025 m, storage from 3.16Mm 3 to 8532.4Mm 3, and surface area from 0.24 Mm 2 to 148.49 Mm 2 . Equations were developed to support future design, such as inundation area, volume, and annual sediment trapped with an accuracy of 50%, 80%, and 90% respectively. These reservoirs improve livelihoods and reduce drought, act as a flood buffer, and recharge groundwater aquifers. They also trap sediment to benefit future generations and reduce flash floods in the high rainy season in Sudan. Some senior researchers in the Blue Nile like Whittington believe that it is economical if dams are built upstream rat her than downstream, and more water will be available for downstream users to use, reducing evaporation and seepage losses(Whittington et al., 2004). These planned reservoirs apart from their use for irrigation, they can trap a lot of sediment (353.7 M. tons/year) that could have been deposited in GERD which reduces the life time of our great dam that will benefit our children and grandchildren economically. These dams help not only in trapping sediment but also harness the flood that inundates Sudan in the high rainy season. Keywords: GERD, GIS, MCDA, AHP, and Dam Site,