Nature's bounty

Summer is already upon us and the specter of severe power and water shortage has already started haunting us. Politicians, as usual, are handing out assurances left, right and centre and none seem to be really bothered about the real problem plaguing the State.

The water table across the State has gone down alarmingly and almost all the districts of  north Karnataka, including, Gulbarga, Bijapur, Bagalkot, Bidar, Raichur, Hubli-Dharwad, Haveri and Gadag have reported depleting water levels.

The rivers are drying up and the levels in the reservoirs are also fast receding. What bodes ill for the people and the state is the failure f the authorities in coming up with a comprehensive and long term water policy.

Harnessing rain water, recharging ground water, desilting tanks and lakes, recreating the storm water drainage, introducing better water management techniques and first of all immediately halting deforestation of forests and green patches and taking up sustained and productive afforestation seems to be the only way.

Let us see the hydrological features of the State and its potential. Since this is a vast topic, this post is restricted to reservoirs and this is the first part of the auricles on waters of Karnataka  .

Karnataka has the potential to show to the rest of the country the way to go forward in water management techniques. The eighth largest State in India, Karnataka has four main physiographical regions that distinguish it. They are the coastal region which comprise a 240 kms land mass between the Arabian Sea and the Western Ghats: the Malnad region which is to the east of the Western Ghats and which has several peaks: the north and south plains which form part of the Deccan Plateau.

The State has two types of drainages or watersheds: the east-flowing rivers Krishna and Cauvery with their many tributaries and the west-flowing rivers. The Western Ghats are the wedge between the watersheds and they feed both the east-flowing and west-flowing rivers with a large quantity of water.

The surface flow, in many rivers and their tributaries, like the Cauvery, Krishna, Tungha, Bhadra, Kapila, Shimsha has been interrupted by dams, bunds, reservoirs for irrigation and power generation.

The main river of the State is Krishna and its flows from Maharashtra to Andhra Pradesh and it carries an annual discharge of 37 000 million m3. Krishna is fed by five main tributaries of which Tungabhadra and Bhima are the largest. A majority of the tributaries and their subtributaries have been regulated by construction of dams and reservoirs.  The Cauvery, which originates in Talacauvery in Kodagu, flows into Tamil Nadu, and being an upper riparian State, Karnataka taps a substantial quantity of the river water. The main river is harnessed by the dam at Krishnarajasagar and all the tributaries upstream and below Krishnarajasagar are also regulated to create reservoirs.

The east-flowing rivers are harnessed mainly for irrigation, while the west flowing streams are regulated to tap their potential to generate hydro-electric power.

Karnataka, like Tamil Nadu has a traditional irrigation system of impounding surface flow of water by constructing small earthen dams across streams, creeks and rivulets and they are generally called as tanks.

Tanks are present in all the districts of Karnataka, except Kodagu and Government estimates say there are 4 605 large irrigation tanks, covering 213 404 hectares, with an average area of 50 hectares, as opposed to 19 673 small tanks, with an average area of less than 7 hectares.

Karnataka has 74 reservoirs and they cover an area of 223 887 hectares, nearly four times that of Tamil Nadu. Among the 74 reservoirs, 46 are classified as small, viz., < 1 000 ha with a waterspread of 15 253 ha. If irrigation tanks are also included, the total surface water area of small reservoirs is 228 657 ha.

The 16 medium reservoirs have an area of 29 078 ha and the large reservoirs (> 5 000 ha), over 179 556 ha. Among the small reservoirs, those less than 500 ha outnumber the rest. Thus, Karnataka has 437 292 ha of water area under different categories of man-made impoundments.

The largest reservoir in Karnaataka is Linganamakki in Shimoga district. Incidentally, Shimoga district has the maximum number of reservoirs in the State. The districts of Bellary, Belgaum, Mandya, Bijapur, Uttar Kannada, Chitradurga, Hassan and Mysore also have large reservoirs.

Small reservoirs are mostly irrigation structures, distributed in all the districts. Kolar has the maximum of such structures with  625 tanks and 2 reservoirs. Shimoga (662 units; 13 762 ha) and Bellary (193 and 46 022 ha).

Riverine resources of Karnataka
Name of the river/tributary	Annual mean discharge (million m3)	Main river	Flowing to (Neighbouring State)	Ultimate destination
East flowing
Main river Krishna	37 000	-	Andhra Pradesh	Bay of Bengal
Bhima	12 690	Krishna	Do	do
Ghataprabha	5 380	do	Do	do
Malaprabha	1 980	do	Do	do
Tungabhadra	14 700	do	Do	do
Vedavati	1 410	do	Do	do
Main river Cauvery	6 200	-	Do	do
Herangi	1 130	Cauvery	Tamil Nadu	do
Hemavati	2 520	do	Do	do
Shimsha	1 700	do	Do	do
Arkavati	850	do	Do	do
Lakshmanathirtha	425	do	Do	do
Kabini	2 600	do	Do	do
Suwarnavati	820	do	Do	do
West flowing
Sharavati	4 545	Sharavati	-	Arabian Sea
Kalinadi	6 537	Kalinadi	-	do
Netravati	4 615	Netravati	-	do
Gangavati	4 925	Gangavati	-	do