Karnataka accounts for about six percent of the country's surface water resources of 17 lakh million cubic meters.About 40 % of this is available in the east flowing rivers and the remaining from west flowing rivers. 

There are seven river basins: 

1) Krishna   2) Cauvery    3) Godavari       4) West flowing rivers  
5) North Pennar 6) South Pennar    7) Palar   Drainage area in the state : 191.79 Sq.Kms.  Estimated average yield   : 97,352. 
 

Krishna basin :                    About 43.74 per cent of the Krishna basin lies in the the State. The rivers course for 483 km lies in the State. The Tungabhadra which has a drainage area of 66,237 sq km is the largest and the important of the Krishna's tributaries. Its major tributaries are the Bhima, Koyna, Panchaganga, Dudhaganga, Tungabhadra, Hiranyakeshi, Ghataprabha and the Malaprabha. This basin covers 13 districts and about 60 per cent of the geographical area of the State.       Krishna : The river Krishna rises in the Western Ghats, at an altitude of 1,336 metres near Mahabaleshwar in Maharashtra, flows from west to east for a length of about 1,400 km, through Maharashtra, Karnataka and Andhra Pradesh. The Krishna has a drainage area of about 2.59 lakh sq km. Together with its trihutaries, it flows for about 704 km length in the State.      Ghataprabha : The Ghataprabha river rises in the Western Ghats, at an altitude of S84 metres and tlows eastwards for a length of 283 km before joining the Krishna. The river debouches by 53 metres at Gokak Falls in Belgaum Dt. The total catchment area of the river and its tributaries accounts for 8,829 sq.km in Maharashtra and Karna,taka States.      Malaprabha: We river Malaprabha also rises in Western Ghats at an altitude of 792 metres in Belgaum Dt. The river flows first in easterly and then in north-easterly directions and joins the Krishna at Kudalasangama, about 304 km from its source. The principal tributaries are the Bennihalla, Hirehalla and the Tas Nadi. The total catchment area of the Malaprabha and its tributaries is 11,549 sq km., wholly in Karnataka.      Bhima: The Bhima river also rises in Western Ghats, at an altitude of about 945 metres and flows south-east wards through Maharashtra and Karnataka. It flows for 861 km before joining the Krishna near Kudlu in Raichur taluk. The latter 298 km of the Bhima's course is in the State. It has a drainage area of 70,614 sq km out of which 18,315 sq km lies in Karnataka.      Tungabhadra: The Tungabhadra is formed north of Shimoga at an elevatibn of about 610metres by the union of twin rivers, the Tunga and the Bhadra, mhich rise together in the Western Ghats at an elevation of about 1,198 metres. The Varada and the Hagari are its important tributaries. It has a drainage area of 71,417 sq.km out of which 57,671 sq.km lies in the State. It flows for a distance of 293 km. in the State.  Cauvery basin : About 42.2 per cent of the area of the Cauvery basin (81,155 sq km) lies in Karnataka. This basin covers 18 per cent of the State area comprising seven districts. Its major tributaries in Karnataka are the Hemavati, Lakshmanatirtha, Harangi, Kabini, Suvarnavati, Lokapavani, Shimsha and the Arkavati.      Cauvery: The river Cauvery has its origin in the Western Ghats in Kodagu Dt. It flows for a length of 320 km in the State. The river flows generally in a south-east direction. The Chunchanakatte Falls (about 20 m) and the Shivasumdra Falls (about 100 m) exist in the State.      Hemavati: The river Hemavati rises in the Western Ghats at an elevation of about 1,219 metres and joins the river Cauvery near Krishnarajasagar. The drainage area is about 5,410 sq.km and the approximate length of the river is 245 km.      Kabini: The river Kabini has a total course of about 230 km and a catchment area of about 7,040 sq.km. It joins the Cauvery river at Tirumakudal Narasipur.      Godavari basin : Godavari basin has a drainage area of 4,405 sq.km. Only a small part of Godavari basin lies in the State. The river Manjra is the major tributary of the Godavari and it flows for about 155 km in the State.  Pennar and Palar basins : The North Pennar, South Pennar and the Palar rivers drain about 13,610 sq.km in the State.  West Flowing Rivers : There are numerous west flowing rivers, chief among which are the Sharavati, Kali, Gangavati(Bedti), Aghanashini and the Netravati. The catchment area of all west flowing rivers is 26,214 Sq.Kms. They are mostly harnessed for power generation.  Ground Water Resources : About 4.4 % of india's ground water resources (2.7 lakh mcum)lies in Karnataka.The total annual recharge of ground water estimated in the state is about 17,99,591 hectare meters(ham).Net annual utilisation is estimated at 5,76,921 ham as as on 1991.