Computation of monthly rainfall probabilities at various probability levels for different agroclimatic regions of Punjab

Rainfall data was taken for Ludhiana for 51 years (1951–2001), Amritsar for 30 years (1972–2001) and Patiala for 32 years (1970–2001) representing central plain region; Ballowal Saunkhari for 17 years (1984–2000) in the sub-mountainous undulating region and for Bathinda for 25 years (1977–2001) in the western region of Punjab. Monthly rainfall probabilities for these selected locations were worked out using gamma distribution. The probability of rainfall occurrence was higher from June to September but very low during other months of the year. The probability of rainfall was highest for July followed by August and it was lowest for November at all the stations. During July, rainfall of 240 mm at Ballowal Saunkhari, 148 mm at Amritsar, 137 mm at Patiala, 115 mm at Ludhiana and 70 mm at Bathinda at 75% probability was observed while rainfall of 470 mm at Ballowal Saunkhari, 307 mm at Patiala, 300 mm each at Ludhiana & Amritsar and 218 mm at Bathinda was observed at 25% probability level. During November rainfall of only 1 mm at Ballowal Saunkhari, Patiala, Ludhiana, Amritsar and Bathinda occurred at 75% probability level whereas it was 15 mm at Ballowal Saunkhari, 13 mm at Patiala, 11 mm rainfall at Ludhiana, 10 mm at Amritsar and 8 mm at Bathinda at 25% probability level. The probabilities of rainfall can be used for a number of agricultural purposes such as land use planning, choice of crops, cropping system and resource allocation problems.