Rivers and drainage system of Meghalaya
One of the world’s wettest regions is found in Meghalaya. Mawsynram and Cherrapunji (Sohra) in the East Khasi Hills district are geographically considered as the rainiest places in the World. — Cherrapunji, which has an average annual precipitation of about 11,430 mm (450 inches) during monsoon season (from May to September) and Mawsynram, a village directly west of Cherrapunji, where rainfall of around 17,800 mm (700 inches) per year has been recorded. The area receives rainfall on an average for 160 days in a year, spread over 6 to 8 months from March to October.
Physiographically, Meghalaya represents a remanant of an ancient plateau of Pre-Cambrian Peninsular shield, block lifted to its present height and is referred as Meghalaya Plateau or as Shillong-Mikir massif. It is the detached northeastern extension of Indian Peninsular shield, part of which lies beneath the alluvium deposited by Ganga Brahmaputra system of rivers. The rivers of the State are rainfed and therefore their discharge dwindles during summer. Important rivers in Garo Hills region are Daring, Sanda, Bugi, Dareng and Simsang. In the central and eastern part of the plateau are Umkhri, Digaru, Umngot and Myntdu rivers.
The surface water resource is tapped in a number of places by constructing dams across the rivers. The reservoirs, like the Umium and Kopili, so developed are not only used for irrigation and drinking water but also for generating electricity. Inspite of this, the area experiences shortage of water during the summer resulting in crisis for drinking water. This is mainly due to topographical and geomorphological conditions apart from alterations of the natural land surface by way of development, mining and urbanization.
Moreover, the characteristic hilly and steep sloping terrain condition in the area with localized small valleys results in very high surface run-off during the monsoon.
Some of the important rivers of Meghalaya are as follows:
Digaru
Digaru is a river originating in the Garo-Khasi hills of Meghalaya state in India, flowing towards the northeast and then meeting the Kolong river and then merging with the Brahmaputra river. The name Digaru originated from a Kachari/Mech word ‘Di’ which means water and ‘Garo’ means the people living in the Garo hills. Hence Digaru literally means “water of the Garo”.
Kopili River
The Kopili originates in the Meghalaya plateau and flows through southern Assam before its confluence with the Brahmaputra. In Assam it drains the districts of Karbi Anglong, Dima Hasao, Kamrup and 
Nagaon. The river flows for a total length of 290 kilometres (180 mi) and has a catchment area of 16,420 square kilometres (6,340 sq mi). It is noted for several spectacular waterfalls along its course which has several deep gorges and rapids in the 120 kilometres (75 mi) of its flow before debouching into the plains at Nagaon district.
Myntdu River
Myntdu River is one of the major water bodies in Jaintia Hills District, Meghalaya, locally known as ‘ka Tawiar ka Takan’ (Our Guardian Angel) in the Pnar dialect. It is a blessing to the residents of the town of Jowai and adjacent places. Its abundant water is used to irrigate the Myntdu Valley, located on the outskirts of Jowai town. The river, originating at 1,420 metres (4,660 ft) above sea level, is fit for hydro-power development.
The river flows across Jowai, and then through Leshka (where a Hydro Project Dam is being constructed) to reach a village Borghat, within Jaintia Hills, before finally entering Bangladesh, where it is locally called ‘Shari’.
Piyain River
Piyain River a trans-boundary river of India and Bangladesh. It is a tributary of the Surma river, which is originates from the Umgat river of Assam. The river enters Bangladesh through Sylhet district. The length of the river is 145 km. Piyain river has emerged from the river om or Umagat river or Assam.
Someshwari River
Someshwari River, known as Simsang River in the Indian state of Meghalaya, is a major river in the Garo Hills of Meghalaya and Netrakona District of Bangladesh. It divides the Garo Hills into two parts.