The terrain is mostly flat; rivers include the Baro, which is the only navigable river in Ethiopia, the Alworo and the Gilo; major bodies of water include Lakes Alworo and Thatha.
A notable landmark is the Gambela National Park, which covers a large part of the Zone south of the Baro.
Based on the 2007 Census conducted by the Central Statistical Agency of Ethiopia (CSA), this Zone has a total population of 99,556, of whom 50,722 are men and 48,834 women.
The largest ethnic groups of the zone were the Anyuak (66.7%), the Oromo (9.14%), the Amhara (9.1%), Kambaata (4.35%), Mezhenger (2.3%), Tigray (2.19%), Welayta (1.52%), Gurage (1.4%), and Hadiya (1.19%); all other ethnic groups made up 3.44% of the population.
The largest group of the inhabitants said they were Protestant, with 64.81% of the population reporting they embraced that belief, while 29.16% professed Ethiopian Orthodox Christianity, 5.61% were Catholic, 5.3% were Muslim, and 2.2% practiced traditional religions.