Drainage system of Mizoram

Surface configuration like relief, slope and dissection are important factor which effect the development and pattern of drainage system of the area. The state of Mizoram is drained by a number of rivers, streams and rivulets of various patterns and length. The area receives a considerable amount of rainfall during summer, and most of the stream are ephemeral in nature. Their volumes is very limited in dry season, whereas they swell rapidly during monsoon season. It has been observed that running water is the most decisive agent which has sculpture landforms of the region.

            Most of the drainage line originated in the central part of the state; and flow either towards north or south directed by the north-south trending ridges. The valleys are narrow and have been carved out in softer formations. The rivers at various places formed deep gorges, and cut across the striking ridges forming watergaps. The upper courses of the rivers are often intervened by waterfalls. As the drainage course is controlled by parallel ranges, the drainage of ephemeral and consequent types show trellis, dendretic as well as parallel drainage patterns.

            The northern portion of the region is drained by rivers Tlawng (with its tributaries Teirei, and Tut); Tuivawl, Tuirial, Langkaih and Tuivai; all flowing northward and eventually fall into Barak river in Cachar plain of Assam. The southern hills are drained by rivers Chhimtuipui on the east with its tributaries Mat, Tuichang, Tiau and Tuipui; while Khawthlangtuipui with its tributaries Kawrpui, Tuichawng, Phairuang, kau and De formed the western boundaries with Tripura and Bangladesh; whereas the rivers Tiau and Chhimtuipui (also known as Kolodyne) formed the natural boundary with Myanmar in the east and south.

The major drainage systems in Mizoram can be described as follows:

1. Tlawng Drainage System : River Tlawng is the longest river in Mizoram which measures about 185.5 kilometres inside the region. It originates from Zopui hill, some 8 kilometres east of Lunglei town, at the height of about 1,395 metres. Flowing towards north, it divideds the region into almost two equal parts. After the confluence with tributaries Tut and Teirei from the western bank, it enters Cachar district (where it is known as Dhaleswari), and eventually falls into Barak near Badarpur. The river is navigable as the most important channel of water transport in Mizoram. Rivers Tut and Teirei flow in parallel with river Tlawng for about 100 kilometres and 70 kilometres respectively before they join the main reiver Tlawng.

2. Tuirial Drainage System : Tuirial is also navigable by small boat to a considerable length. Its span inside the state is about 117 kilometres. Originating from north Chawilung hill in Aizawl district, it flows northward to join Barak river in Assam. An important tributary is Tuirini, which joins the main stream from the eastern bank after flowing parallel to it from about 60 kilometres.

3. Tuivawl Drainage System : This system drains the north east portion of the region. The main river, Tuivawl, which rises near Chhawrtui village and spanning about 72 kilometres flows towards north where the tributary Tuivai joins it at Manipur border. It later confluents with Barak river.

4. Tiau Drainage System : The eastern fringe of Mizoram is drained by the Tiau drainage system. River Tiau which spans for about 159 kilometres is a demarcating line between Mizoram and Myanmar. Rising from the north east corner near Khuangphah village it takes a southward direction. After the confluence with main tributary, R.Tuipui, it meets R.Chhimtuipui in an opposite direction. This point gives quite an interesting scene as the two currents encountered with an opposite forces.

5. Chhimtuipui Drainage System : The system drains the north-eastern part of Mizoram. The main river, Chhimtuipui is the biggest river in Mizoram by volume. It originates from the weastern part of Myanmar near Vanum village at an altitude of 2,325 metres, and flows in south direction. It enters Mizoram near Sabawngte village from which it takes the north direction for some 138 kilometres, making the international boundary and meets Tiau river in the opposite direction. From this point, the flow direction is diverted towards north west and meets Tuichang river near Hnahthial village, and eventually flows southern-wards where tributaries Mat (90 kms) and Mengpui confluent it. The rivers Tuichawng and Mat originate from the central part of Aizawl district. Mengpui river rises near Lunglei town and meets the main stream in Saiha district.

6. Khawthlangtuipui Drainage System : The Khawthlangtuipui represents the drainage system of the whole south western part of Mizoram. Originating from Saithah village in Mamit district, the river flows towards south, forming a boundary line between Mizoram and Bangladesh. After taking about 128 kilometres courses, it turns towards south west entering Bangladesh through Tlabung, a sub-divisional headquarters.

            Khawthlangtuipui has numerous important tributaries such Kawrpui, Tuichawng (108 kms) aand Phairuang which associate it from the south. Rivers Kau and De flow parallel to it from the south for a considerable length. This drainage system shows rectangular and parallel drainage pattern. The river is navigable by small boat and serves as an useful transport route, as far as trade with trade with Bangladesh is concerned.

            The whole drainage system of Mizoram on a large scale depicts parallel drainage pattern. This is the outcome of the characteristics parallel mountain ranges. But one should not overlook the presence of trellis drainage pattern produced by numerous consequent and subsequent streams, which flow parallel either to the dip or strike of the ridges. Dendretic drainage system is also observed at Chhimtuipui drainage system where tributaries such as Tiau, Tuichang, Mat and a number of streams united with the main channel.