Effect of climate change on probable maximum precipitation of Neyyar river basin

Unexpected climate changes have hampered the stability of hydraulic structures. Therefore, accurate design criteria are essential for making the structures long-lasting. Probable Maximum Flood (PMF) is a crucial parameter for designing high-risk hydraulic structures like large dams, spillways, aqueducts, etc. PMF is significantly influenced by Probable Maximum Precipitation (PMP). The value of PMP is expected to change in future due to the intensification of hydrological cycle. Underestimation of PMP will lead to a risky design and over-estimation makes the design uneconomical. This study is to recalculate the PMP of Neyyar River Basin incorporating the effects of climate change in future. The historical PMP map (1961-2000) and future PMP map (2001-2099) was developed for the study area. The GCM data from HadCM3 which ranks first for Indian condition is used for this study and the two scenarios A2 and B2 scenarios are considered which are suitable for Neyyar region. For the downscaling of rainfall, the Statistical DownScaling Model (SDSM), a combination of multiple regression models and stochastic weather generator, is used. The bias correction was also done to eliminate the systematic biases. The rainfall trend of the study region is decreasing in nature which is evaluated using a nonparametric test called Mann Kendall Trend Test. The difference in historical PMP and standard PMP is only 6.75% therefore the procedure to estimate PMP is correct. The A2 PMP and B2 PMP decreased 6.48% and 19.81% respectively when compared to historical PMP. In future, this decreased PMP can be utilized for future design thereby an economical design is possible