<P> India experiences an average precipitation of 1,170 millimetres (46 in) per year, or about 4,000 cubic kilometres (960 cu mi) of rains annually . Some 80 percent of its area experiences rains of 750 millimetres (30 in) or more a year . However, this rain is not uniform in time or geography . Most of the rains occur during its monsoon seasons (June to September), with the northeast and north receiving far more rains than India's west and south . Other than rains, the melting of snow year round over the Himalayas feeds the northern rivers to varying degrees . The southern rivers, however experience more flow variability over the year . For the Himalayan basin, this leads to flooding in some months and water scarcity in others . Despite extensive river system, safe clean drinking water as well as irrigation water supplies for sustainable agriculture are in shortage across India, in part because it has, as yet, harnessed a small fraction of its available and recoverable surface water resource . India harnessed 761 cubic kilometres (183 cu mi) (20 percent) of its water resources in 2010, part of which came from unsustainable use of groundwater . Of the water it withdrew from its rivers and groundwater wells, India dedicated about 688 cubic kilometres (165 cu mi) to irrigation, 56 cubic kilometres (13 cu mi) to municipal and drinking water applications and 17 cubic kilometres (4.1 cu mi) to industry . </P> <P> According to 2011 report of the Food and Agriculture Organization of the United Nations, India's basin wise distribution of catchment area and utilizable surface water resources is presented in the following table: </P> <Table> <Tr> <Th> (hide) Basin number </Th> <Th> River basin unit </Th> <Th> Region </Th> <Th> Draining into </Th> <Th> Catchment area (% of river irrigated India) </Th> <Th> Average runoff (km) </Th> <Th> Additional available surface water (km) </Th> </Tr> <Tr> <Td> 1.1 </Td> <Td> Ganges (GBM) </Td> <Td> North </Td> <Td> Bangladesh </Td> <Td> 26.5 </Td> <Td> 525.02 </Td> <Td> 250 </Td> </Tr> <Tr> <Td> </Td> <Td> Brahmaputra (GBM) </Td> <Td> Northeast </Td> <Td> Bangladesh </Td> <Td> 6 </Td> <Td> 537.24 </Td> <Td> 24 </Td> </Tr> <Tr> <Td> 1.3 </Td> <Td> Meghna / Barak (GBM) </Td> <Td> East </Td> <Td> Bangladesh </Td> <Td> 1.5 </Td> <Td> 48.36 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> Other Northeast rivers </Td> <Td> Northeast </Td> <Td> Myanmar, Bangladesh </Td> <Td> 1.1 </Td> <Td> 31 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> Subernarekha </Td> <Td> East - southeast </Td> <Td> Bay of Bengal </Td> <Td> 0.9 </Td> <Td> 12.37 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td> Brahmani - Baitarani </Td> <Td> East - southeast </Td> <Td> Bay of Bengal </Td> <Td> 1.6 </Td> <Td> 28.48 </Td> <Td> 6.8 </Td> </Tr> <Tr> <Td> 5 </Td> <Td> Mahanadi </Td> <Td> Central - east </Td> <Td> Bay of Bengal </Td> <Td> 4.4 </Td> <Td> 66.88 </Td> <Td> 18.3 </Td> </Tr> <Tr> <Td> 6 </Td> <Td> Godavari </Td> <Td> Central </Td> <Td> Bay of Bengal </Td> <Td> 9.7 </Td> <Td> 110.54 </Td> <Td> 50 </Td> </Tr> <Tr> <Td> 7 </Td> <Td> Krishna </Td> <Td> Central </Td> <Td> Bay of Bengal </Td> <Td> 8 </Td> <Td> 78.12 </Td> <Td> 76.3 </Td> </Tr> <Tr> <Td> 8 </Td> <Td> Pennar </Td> <Td> Southeast </Td> <Td> Bay of Bengal </Td> <Td> 1.7 </Td> <Td> 6.32 </Td> <Td> 58 </Td> </Tr> <Tr> <Td> 9 </Td> <Td> Kaveri </Td> <Td> South </Td> <Td> Bay of Bengal </Td> <Td> 2.5 </Td> <Td> 21.36 </Td> <Td> 6.9 </Td> </Tr> <Tr> <Td> 10 </Td> <Td> East flowing rivers between Mahanadi and Pennar </Td> <Td> Central - east </Td> <Td> Bay of Bengal </Td> <Td> 2.7 </Td> <Td> 22.52 </Td> <Td> 19 </Td> </Tr> <Tr> <Td> 11 </Td> <Td> East flowing rivers between Kanyakumari and Pennar </Td> <Td> Southeast </Td> <Td> Bay of Bengal </Td> <Td> 3.1 </Td> <Td> 16.46 </Td> <Td> 13.1 </Td> </Tr> <Tr> <Td> 12 </Td> <Td> West flowing rivers between Tadri and Kanyakumari </Td> <Td> Southwest </Td> <Td> Arabian Sea </Td> <Td> 1.7 </Td> <Td> 113.53 </Td> <Td> 16.7 </Td> </Tr> <Tr> <Td> 13 </Td> <Td> West flowing rivers between Tapi and Tadri </Td> <Td> Southwest </Td> <Td> Arabian Sea </Td> <Td> 1.7 </Td> <Td> 87.41 </Td> <Td> 24.3 </Td> </Tr> <Tr> <Td> 14 </Td> <Td> Tapi </Td> <Td> Central - west </Td> <Td> Arabian Sea </Td> <Td> </Td> <Td> 14.88 </Td> <Td> 11.9 </Td> </Tr> <Tr> <Td> 15 </Td> <Td> Narmada </Td> <Td> Central - west </Td> <Td> Arabian Sea </Td> <Td> 3.1 </Td> <Td> 45.64 </Td> <Td> 14.5 </Td> </Tr> <Tr> <Td> 16 </Td> <Td> Mahi </Td> <Td> Northwest </Td> <Td> Arabian Sea </Td> <Td> 1.1 </Td> <Td> 11.02 </Td> <Td> 34.5 </Td> </Tr> <Tr> <Td> 17 </Td> <Td> Sabarmati </Td> <Td> Northwest </Td> <Td> Arabian Sea </Td> <Td> 0.7 </Td> <Td> 3.81 </Td> <Td> 3.1 </Td> </Tr> <Tr> <Td> 18 </Td> <Td> West flowing rivers between Kutch and Saurashtra </Td> <Td> Northwest </Td> <Td> Arabian Sea </Td> <Td> 10 </Td> <Td> 15.1 </Td> <Td> 1.9 </Td> </Tr> <Tr> <Td> 19 </Td> <Td> Rajasthan inland basin </Td> <Td> Northwest </Td> <Td> India </Td> <Td> 0 </Td> <Td> Negligible </Td> <Td> 15 </Td> </Tr> <Tr> <Td> 20 </Td> <Td> Indus tributaries </Td> <Td> Northwest </Td> <Td> Pakistan </Td> <Td> 10 </Td> <Td> 73.31 </Td> <Td> 46 </Td> </Tr> <Tr> <Td> </Td> <Td> Total (per International Treaty) </Td> <Td> </Td> <Td> </Td> <Td> 100 </Td> <Td> 1869.37 </Td> <Td> </Td> </Tr> </Table> <Tr> <Th> (hide) Basin number </Th> <Th> River basin unit </Th> <Th> Region </Th> <Th> Draining into </Th> <Th> Catchment area (% of river irrigated India) </Th> <Th> Average runoff (km) </Th> <Th> Additional available surface water (km) </Th> </Tr>

Which river has the largest catchment area in india