Rainfall variability for crop water management under changing climate in Himachal Pradesh

Abstract Spatial and temporal rainfall variability under rain-fed scenarios has a greater influence on the sustainability of a cropping system and food security. A rainfall analysis was conducted on a monthly, annual, and seasonal basis across selected agro-climatic zones (I, II, and III) of Himachal Pradesh. The results indicated that South–West (SW) monsoon (July–October) rainfall contributed to 84% of zone-I, 76% for zone-II, and 47% for zone-III of the total annual rainfall. The mean annual precipitation concentration index (PCI) value reflected irregular monthly precipitation distribution (PCI > 20) for zone-II and zone-III, whereas moderate precipitation distribution value of PCI = 11–15 was for zone-I indicated less variability in rainfall. The Sen’s slope estimator revealed that the rainfall decreased at a rate of − 8.021 mm/year, − 6.830 mm/year, and − 5.050 mm/year in zone-I, zone-II, and zone-III, respectively. The water balance study showed that peak surplus water availability observed a shift from July to August month corresponding with peak rainfall during the SW monsoon in recent decades for all agro-climatic zones. During 1986–2020, low-hill regions (zone-I) experienced water surplus during monsoon season and deficit during winter season, while the mid-hill regions (zone-II) experienced water deficits during monsoon season and surplus during winter season. Therefore, the erratic rainfall pattern and shift of available water balance have an impact on agricultural productivity by shortening the cropping calendar and time duration between the two crops. Thus, findings can be used to develop agronomic management strategies for sustainable crop management.