Abstract
Rainfall is a vital component in the rice water demand model for estimating irrigation requirements. Information on how the future patterns are likely to evolve is essential for rice-growing management. This study presents possible changes in the future monthly rainfall patterns by perturbing model parameters of a stochastic rainfall using the change factor method for the Kerian rice irrigation scheme in Malaysia. An ensemble of five Global Climate Models under three Shared Socioeconomic Pathways (SSPs) (SSP1-2.6, SSP2-4.5, and SSP5-8.5) were employed to project rainfall from 2021 to 2080. The results show that the stochastic rainfall generator performed well at preserving the statistical properties between simulated and observed rainfall. Most scenarios predict the increasing trend of the mean monthly rainfall with only a few months decreasing in April and May occurring in off (dry) season. The future patterns 2051–2080 show a significant increasing trend during main (wet) season compared to the near future period (2021–2050). The projected future rainfall under SSP1-2.6 and SSP2-4.5 are higher than SSP5-8.5 from January to July, and December but lower from August to November. The projected annual rainfall will significantly increase toward 2080 during the main-season but uniform during the off-season except under SSP5-8.5, which is significantly decreasing. The output results are essential for rice farmers and water managers to manage and secure future rice irrigation water under the impact of future climate change. The projected changes in rainfall on the river basin demand further study before concluding the impact consequences for the rice sector.Article highlightsThe rainfall generator performs well in simulating future rainfall based on an ensemble of five different GCMs considering three different scenarios emission (low, medium, and high) caused by greenhouse gas and radiative forcing.The future rainfall projection predicted that off (dry) season would become wet, and main (wet) season would become wetter due increase in monthly and annual rainfall.The outcomes of this paper are beneficial for rice farmers and water managers of the study area to manage their rice cultivation and water release from the reservoir schedules to avoid losses due to flood and drought.
Highlights
Malaysia experiences hot and humid weather throughout the year, named equatorial climate
Kurau River Basin, with an area of approximately 322 km2 located in the north of Peninsular Malaysia, is a dominant upstream part of the Bukit Merah Reservoir catchment [5], where it is the primary irrigation source for large scale Kerian rice irrigation scheme
P01 = Probabilities for dry days followed by rain days; P 00 = Probabilities for dry days followed by dry days; P10 = Probabilities for rain days followed by dry days; P 11 = Probabilities for rain days followed by rain days
Summary
Malaysia experiences hot and humid weather throughout the year, named equatorial climate. The Southwest Monsoon features drier weather, while Northeast Monsoon has abundant rainfall [1]. Kurau River Basin, with an area of approximately 322 km located in the north of Peninsular Malaysia, is a dominant upstream part of the Bukit Merah Reservoir catchment [5], where it is the primary irrigation source for large scale Kerian rice irrigation scheme. The Asia region is the leading rice producer with approximately 94% of the world’s production, consuming over 90% of the total irrigation supply from river basins [6, 7]. Malaysia is blessed with rainfall all year round, there is still an unanswered question about water availability coupled with climate change’s impact on rice cultivation in this area
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