Rainfall in Karnataka

The economy of Karnataka is mainly agrarian and most of it is dependent on the rainfall; mainly the southwest monsoon. The extent of arid land in the state is second only to Rajasthan.^[15] Only 26.5% of sown area (30,900 km²) is subjected to irrigation and hence the rest of the cultivated land is entirely dependent on rainfall.^[16] Rainfall also influences the quantity of water available in the rivers which in turn influences the amount of drinking water available to the population and the amount of electricity that can be generated in the hydroelectric power stations in the state. The importance of rainfall is such that Karnataka sometimes had to resort to costly artificial methods like cloud seeding in order to induce rain artificially.^[17] Rainfall is also crucial to recharge the depleting ground water and Karnataka has come up with innovative methods like rainwater harvesting in order to solve the drinking water scarcity in the state.

Karnataka is a pioneer in the concept of rainwater harvesting with The Karnataka State Council for Science and Technology (KSCST) implementing one of the largest rainwater harvesting projects in the world. 23683 schools in rural Karnataka were selected for this project with the main goal of providing drinking water by using the method of rooftop harvesting.^[1] In this project, rainwater collected on the rooftop is channeled through a system of PVC pipes and stored in an enclosed surface tank. The pipeline consists of a first-flush filter which flushes out the first rainfall along with other contaminants that may exist on the roof and then subsequent cleaner rainwater is allowed to pass on to the tank. A sand bed filter is used to further eliminate impurities in the water before it gets collected in the tank.^[1] Further precautions are taken to prevent dust and insects from entering the tank.

A year of deficient rainfall leads to the following consequences:

• Agricultural output will be impacted: While this has a direct impact on the economy of the state, it also leads to other social issues like the suicide of farmers. Due to the crop failure, the farmers would not be in a position to repay the loans they had taken for agriculture and few of them take an extreme step of suicide.^[18]
• Drinking water scarcity: A lot of towns and cities in Karnataka are dependent on rivers for the supply of drinking water and any deficiency in rainfall leads to the lesser amount of drinking water being supplied to the homes.
• Shortage of electricity: Deficient rainfall leads to a drop in the amount of electricity produced by hydroelectric projects and hence drastic measures like compulsory power cuts have to be employed to counter this shortage.^[19]

Heavy rains can lead to a significant loss of life and property and also cause damage to the crops.^[20] Excess rains also cause an impact in major cities with inundated roads causing traffic jams. An example of this was in the year 2005 when the Madivala lake overflowed on to the Hosur Road in Bangalore forcing many schools and offices to close.^[21]

The average annual rainfall in Karnataka is 1248  mm.^[22] The state is divided into three meteorological zones. North Interior Karnataka, South Interior Karnataka, and Coastal Karnataka. Coastal Karnataka with an average annual rainfall of 3456  mm is one of the most rainy regions in the country. Contrasting this, South Interior Karnataka and North Interior Karnataka receive only 1126 and 731  mm of average annual rainfall.^[23]

The average annual rainfall in the districts of Karnataka varies from 562 mm (22.1 in) in the Bagalkot district to 4,119 mm (162.2 in) in the Udupi District. Bagalkot, Chitradurga and Koppal are the districts which receive the least rainfall whereas Udupi, Dakshina Kannada, Uttara Kannada, Hassan, Kodagu, Chickmagalur and Shivamogga districts receive the heaviest rainfall.