Trends in Rainfall, Length of Growing Period and Drought Occurrence in Karnataka, India

Abstract

Climate has a vital role on biosphere of the earth. Of the major climatic parameters, rainfall is one of the most important parameters that influence the agriculture of the region and food production. A study was undertaken to analyze the trend of the rainfall pattern of Karnataka by using the daily rainfall data from 1980 to 2013 of 392 stations and its length of growing period (LGP) along with drought extent. Annual rainfall normals and rainy days normals over different stations was tested Mann-Kendall test was used for significance of trends in annual rainfall and annual rainy days. Also the frequencies of moderate and severe meteorological droughts were computed. Weekly values of precipitation and potential evapotranspiration were considered for computing length of the growing period. The mean annual rainfall of Karnataka in the last thirty three years was 1122±133 mm with a coefficient of variation (CV) of 12 %. Eighty two percent of the stations in the state shown no significant trend in annual rainfall while seventy one percent of the stations shown no significant trend in annual rainy days. Around 97% of the stations in the state show a probability of <10% of occurrence of severe droughts. Drought prone areas have been defined for Karnataka based on LGP concept. LGP varied between 168 days in Aland Taluk of Kalburagi district to 259 days in Beltangadi taluk of Dakshina Kannada district. According to LGP, agro-climatic zones of Karnataka have been re-delineated into new sub zones.