A case study on the changing pattern of monsoon rainfall duration and its amount during the recent five decades in different agroclimatic zones of Punjab state of India

Rainfall is an important part of hydrological cycle and any alteration in its pattern influence water resources. In Punjab, the monsoon season of 77 days extending during three months July, August and September, receives rainfall at an average rate of 6 mm/day. In the present study, monsoon rainfall data for three parts of the state, viz., the north eastern region (1984-2020), Central plain region (1970-2020) and the south western region (1977-2020) of the state have been analyzed using non-parametric tests, i.e., descriptive statistics, trend analysis, Mann Kendall test and Sen's slope. Though, the duration of the monsoon season has increased over the last two decades at 0.8 day/year, the rate of rainfall has decreased as rainfall has been less than normal during 17 of the past 20 years. The monsoon rainfall analysis for the five decades indicates a significant decrease in rainfall at 0.7 mm/year which has mainly been due to a decline in rainfall in the north eastern region. The Sen's slope value of-4.77 (Ballowal) and-0.60 (Bathinda) indicate a decreasing trend of rainfall in the region. The decreasing trend in rainfall received during the July-August months with Sen's slope values ranging between-0.04 to-2.50 and-0.24 to-3.14, indicates that the months which contribute similar to 70 percent to total rainfall are not a good signal for the agriculture sector in the state.