The Barak valley has a geographical area of 6922.00 Sq. Km excluding 2(two) hill districts. The local rainfall run off of the valley along with that of adjacent hilly areas flows through river Barak and its various tributaries and is drained out to Bangladesh. The Katakhal, Jiri, Chiri, Modhura, Longai, Sonai, Rukni and Singla are the main tributaries of the valley. The tributaries are mainly rain fed and cause flood problems when precipitation occurs.

The Barak sub-basin drains areas in India, Bangladesh and Burma. The drainage area of the sut lying in India is 41723 sq.km which is nearly 1.38% of the total geographical area of the country. It is be on the north by the Barail range separating it from the Brahmaputra sub-basin, on the east by the Na Lushai hills and on the south and west by Bangladesh. The sub-basin lies in the States of Meghalaya. Manipur, Mizoram, Assam, Tripura and Nagaland. The State-wise distribution of drainage area is given below

There are two major physiographic regions in the sub-basin, namely, the hilly region and the plain plains are thickly populated and extensively cultivated. The predominant soil types found in the sub-basin are laterite and red and yellow soils. The culturable area in the sub-basin 0.893 M. ha which is only about 0.5% of the culturable area of the country.