Nexus of climate change, irrigation requirement and water balance for paddy production in Chandra Canal Irrigation System, Nepal

The major focus of this study was to evaluate the impact of changing climate on irrigation requirements and agricultural water balance for cereal crops including paddy in the command area of Chandra Canal Irrigation System, Nepal. It examined the historical temperature and rainfall patterns (1992 to 2022) and their implications for agriculture to propose adaptive cultivation strategies. A mixed-method case study approach was undertaken to conduct trend analysis based on climatic meteorological data using linear regression, Mann–Kendall test and Sen’s slope estimator. The selected GCMs for precipitation were ACCESS-ESM1-5, BCC-CSM2-MR, EC-Earth3, MPI-ESM1-2-LR, and NorESM2-MM. Similarly, for maximum and minimum temperature selected GCMs were INM-CM4-8, INM-CM5-0, MPI-ESM1-2-HR, and NorESM2-MM. This research also projected future precipitation and temperature using the statistical downscaling model under two climate scenarios, SSP245 and SSP585 for three future periods including near (P1, 2024–2050), mid (P2, 2051–2075), and far (P3, 2076–2100). Findings of this study indicated that the average annual rainfall was increased by 16.1 mm, while non-monsoon precipitation was found to be decreased by 0.69 mm/year. Also, the water requirements of monsoon paddy varied annually, with the highest value 573 mm in 2009 which was, however, within the range suggested by FAO for rice production. Looking to 2100 AD scenario, a projected water surplus was expected from June to December, while January to May anticipated a water deficit for paddy. This study recommends smart water management in monsoon season to ensure year-round irrigation and water saving irrigation strategies like alternate wetting and drying and drought tolerant climate-smart paddy variety if spring rice would be cultivated.