II.

Physical Geography

The terrain rises through a series of foothills in the south to the Lesser Himalaya mountains and, on the Tibetan border, to the ranges of the Great Himalaya. The state’s main rivers are the Brahmaputra, known in Arunachal Pradesh as the Siang, and its tributaries—the Tirap, the Lohit, the Subansiri, and the Kameng. The climate of the foothills is subtropical; in the mountains, temperatures decrease rapidly with altitude. Rainfall averages between 2,000 and 4,000 mm (80 to 160 in) a year. The state’s diverse terrain and climate is reflected in its plant and animal life. There are over 500 species of orchid, and the abundant forests range from alpine to subtropical. Animals inhabiting Arunachal Pradesh include tigers, leopards, elephants, red pandas, and deer.