sentences:  At Lelwa it empties the Mbalamu River, which comes from the extreme north of the Usambara Mountains, and the Mglumi River into the Umba.Just before the Umba flows into the Indian Ocean, it crosses the border to Kenya.The mouth itself marks the most eastern point on the border between Tanzania and Kenya, which was largely made in a straight line to the northwest towards Lake Victoria in the 19th Century.