Rainfall Analysis of Bhadra Command Area (Karnataka)

Analysis of monthly and annual rainfall data of 17 stations located in 3 districts of Karnataka falling under the Bhadra Command Area (BCA) for a period 1975–2005 has been used in this study. Statistical parameters like mean, standard deviation, co-efficient of variation and co-efficient of skewness for monthly and yearly rainfall sets of data have been determined. The average depth of rainfall over the command area has been computed by arithmetic mean, Thiessen Polygon and Isohyetal methods. The co-efficient of variation (C_v) of annual rainfall varies from 14% to 83%. The co-efficient of variation (C_v) and coefficient of skewness (Cs) of annual rainfall are shown to be non-symmetrically distributed at all stations. The average depths of annual rainfall over the study field calculated from different methods were found to be 769.5mm, 612.20mm and 686.54mm respectively. The study shows that the monsoon (June–September) rainfall contributes about 55% of the mean annual rainfall. But the results of 3 yearly and 5 yearly moving average curves also showed increase in rainfall trend over the study area.