Several important waterways lead into this region. The Cartius is a subequatorial river that gnerally flows west by northwest, entering the jungle region and emptying into Lake Ushindi. It was once thought that the Cartius was a tributary of the Vosk River but it is not. The subequatorial Cartius is a different waterway from the Thassa Cartius. The explorer, Ramus, discovered this difference. The earlier Gor novels, most specifically Nomads of Gor, fails to differentiate between these two rivers. They state that the Cartius does flow into the Vosk, which is not true. In these novels, you should substitute the Thassa Cartius for the Cartius. The Thassa Cartius is the actual tributary of the Vosk. This is important when you are discussing Ar as that city claims the land between the Vosk and the Cartius. In actuality, they claim the land down to the Thassa Cartius and not the actual Cartius.

Falls of Bila Haruma: 100 pasangs east of Lake Ngao, the Ua river is blocked by this waterfall.
Ua River: Ua is an inland word, not Gorean, and means “flower.” An extremely large river (as wide as the Vosk) in the Equatorial Rain Forests, it connects Lake Ngao and Lake Shaba with Lake Shaba as it's source. It is a major river, at least as big as the Vosk. There are many cataracts on the Ua which make it very difficult to cross.
Swamp Land: The lands south and central between lake Ushindi and Lake Ngao, thousands of pasangs in area.
Canals of Bila Haruma: Man-made canal from Lake Ushindi to Lake Ngao.
Nyuki: It is located on the northeast shore of Lake Ushindi between the Kamba and Thassa Cartius Rivers.
Kamba River: Kamba is an inland word, not Gorean, and means “rope.” A wide leisurely river that flows directly into Thassa west of Lake Ngao and Ushindi in the jungles near Schendi.
Flood Plains: Plains located between the Kamba River and the Nyoka, northwest of Lake Ushindi.
Nyoka River: Nyoka is an inland word, not Gorean, and means “serpent.” A wide leisurely river that flows into Schendi harbor and then enters Thassa west of Lakes Nagao and Ushindi.
Cartius River: An important subequatorial waterway it is actually three rivers, Cartius Proper, Subequatorial Cartius, and Thassa Cartius. The Thassa (or Northern) Cartius is located far south of Ar and feeds into the Vosk. It was formerly the southern border of the Empire of Ar. It flows west by northwest, enters the rain forests and empties into Lake Ushindi. The Cartius Proper is as wide as the Vosk, and is surrounded by rain forests for much of its length. The Subequatorial Cartius flows southeast splitting into the Upper and Lower Fayeen Rivers.
Lake Ushindi: Ushindi is an inland word, not Gorean, and means ”victory.” A large equatorial lake, located in the jungles near Schendi, it is drained by the Kamba and Nyoka Rivers. Six Village Ubarates occupy the southern shore of Ushindi; and floodlands, marshes and bogs lie west of the lake. The inland village of Nyuki is located on its northern shore.
Lake Shaba: This lake was unknown until discovered in "Explorers of Gor". A large lake and the source of the Ua, it is named after the geographer who discovered it. There are the ruins of an ancient civilization on its shore.

"I never trust a man until I know what he eats."

(Explorers of Gor, p.383)