A case study has been done to study the rainfall distribution pattern and its variability for the selection of crops and cropping pattern of Bidar region, Karnataka with a predominant pigeon pea and sugarcane cropping systems. The study revealed that the overall mean annual rainfall of Aurad was 846 mm, which was distributed as 673.7 mm, 101.6 mm, 60.2 mm and 10.7 mm in monsoon, post monsoon, summer and winter respectively. The average annual rainfall of Bhalki was 874.7 mm with average rainy days of 51 days. The mean annual rainfall of Humnabad is 797 mm with 27 per cent variability spread over 50 mean rainy days. The analysis of rainfall data indicate that the average annual rainfall for the Basavakalyan was 759 mm spread over with a mean rainy days of 49.9 days. The mean annual rainfall for Bidar is 937.3 mm with coefficient of variation of 22.2 per cent indicated that the annual rainfall was more or less stable over the years. Within the rainy season, August was the highest rainfall contributing month (21.3 per cent) followed by July (19.9 per cent). Rainfall during monsoon season and its variability govern the cropping system of Bidar. There is an ample scope for rain water harvesting from July to September which can be utilized as crop saving irrigation as well as per sowing irrigation for succeeding rabi crops which are generally sown on residual soil moisture.

An attempt was made to study the five year wise rainfall trends of Kalayan Karnataka. The study period spans for a period of 50 years from 1971-2020 which was divided into ten periods comprising each 5-year moving average to detect long term trends and further a linear tend was added as parametric test. Long term changes in rainfall characteristics were determined by both parametric and non-parametric tests. The analysis revealed that the period from 1991-1995 was found to be highest mean rainfall receiving period for the Bidar (1078.9 mm), Kalaburgi (976.7 mm) districts whereas for the Yadgir (1171.1mm) district it was from 1986-1990. However for Raichur (875.5 mm) and Koppal (670.7 mm) districts the period from 2001- 2005 was found to be highest mean rainfall receiving period whereas 1971-1975 was found to be for Ballari (705.7 mm) district. The highest CV was recorded during the period from 1981-1985, 1976-1980, 1976-1980, 2016-2020, 1976-1980 and 2006-2010 from Bidar (34.5%), Kalaburgi (36.8%), Yadgir (43.3%), Raichur (39.7%), Koppal (30.9%) and Ballari (30.8%) respectively indicating higher variability and lesser dependability. Sen’s slope estimator showed that there is a positive trend for the Bidar, Raichur and Koppal rainfall pattern. However, Kalaburagi, Yadgir and Ballari exhibited a decreasing trend.