World number six Disi clocked 60:43 (one hour and 43 seconds) while Alemu, ranked 10th in the world, took 1 hour 10 minutes and 30 seconds to travel the distance of 21 km.
Disi took home the winner's purse of USD 20,000 while Alemu will be richer by USD 18,500.
Kenya's Isaac Macharia (60:47) and Tanzania's Dixon Marwah (62:02) followed Disi on second and third spots.
The Kenyan duo of Patrick Mbuvi and Wilson Kiprotich, who is the world number three and was one of the pre-race favourites, finished fourth and fifth respectively in a photo finish after both clocked 62:03.
Alemu, meanwhile, was succeeded by compatriot Atsede Habtambu, who clocked 1:10:36. Kenya's Kenya's Alice Timbill came third with a timing of 1:10:40.
The Indians in the fray also improved their performance with last year's top finisher Ram Singh Yadav once again being the local champion ending 16th this time.
Yadav clocked 1:06:09 to finish a rung ahead of Deep Chand, who missed out on becoming the Indian champion by just a second to end 17th. Mukesh Kumar was the Indian third with a timing of 1:06:12. Mukesh finished 18th overall.
Kavita Raut was the new Indian women's champion as last year's champion Pampa Chanda failed to even make the top-20.
Kavita finished 15th overall with a timing of 1:18:34.
Photograph: Getty Images | Text: PTI