Regional groundwater flows generally provide a constant source of water because they are commonly less affected by seasonal recharge variation. Such a regional groundwater system in the Abbay BasinAbbay Basin’s aquifer can be an important source of water. The focus of this study is, thus, to describe the state of the regional groundwater flow components of the Abbay BasinAbbay Basin. Two conceptual models, larger northwestern groundwater basinNorthwestern groundwater basin and Abbay basinAbbay Basin, were evaluated to test the conceptualization of inter- and intra- boundary regional groundwater flow for the basin. The northwestern groundwater basinNorthwestern groundwater basin that merges Abbay, Tekeze, Mereb and Baro Akobo surface water basins was found to better describe Abbay BasinAbbay Basin’s regional groundwater system. A regional groundwater flow direction, access depths and potentiometric surface maps were estimated by use of output from this model. The model was calibrated using 11,474 water points inventoried within this larger basin. The model has shown that there is effective recharge of 15.385 BCM per year in the Abbay BasinAbbay Basin. The study reveals, three quarter (by area) of the basin’s regional groundwater can be accessed by drilling up to 500 m depth. Shallower regional groundwater is observed closer to the main water bodies (main river course and Lakes) and in the lowlands of Abbay basinAbbay Basin. The recharge and potentiometric maps together reveal that at high recharge locations, regional groundwater flow paths extend from high to low regional potentiometric areas over distances of greater than tens of kilometres.