Intensity Duration Frequency Curve Generation using Historical and Future Downscaled Rainfall Data Indian Journal of Ecology (2021) 48(1): 275-280 Manuscript Number: 3206 NAAS Rating: 4.96 Abstract: Intensity–duration–frequency curves are used extensively in engineering to assess the return periods of rainfall events. The estimation and use of IDF curves rely on the hypothesis of rainfall series stationarity, namely that intensities and frequencies of extreme hydrological events remain unchanged over time. However, changes in the hydrologic cycle due to the increase in greenhouse gases are projected to cause variations in intensity, duration, and frequency of precipitation events. Quantifying the potential effects of climate change and adapting to them is one way to reduce vulnerability. Since rainfall characteristics are often used to design water management structures, reviewing and updating rainfall characteristics for future climate scenarios is necessary. In this study, IDF curves relationship is determined to utilize statistical analysis of rainfall data for a record of 38 years. The methods used are Log-Normal, Normal, and Gumbel (EV-I). The distributions were carried out with return periods of 2, 5, 10,25, 50, and 100 years with durations of 1, 2, 3, 6, 12, and 24 hours. Highest intensity values were observed for the Gumbel method and the values obtained from other methods were close to each other. Keywords: IDF, Hydrologic, Statistical, Empirical, Hypothesis, Vulnerability Sunny Agarwal, Sanjeet Kumar and Umesh K. Singh Department of Civil Engineering, Koneru Lakshmaiah Education Foundation Deemed to be University, Guntur-522 502, India E-mail: sunnycujiwem@gmail.com Precipitation is a crucial component of Hydrological cycle through which ground water recharges and surface water rejuvenates in the form of rivers, ponds, wells, stream networks etc (Agarwal and Kumar 2019). Due to inadequacy and severity of precipitation, numerous risks and hazard prevailing in the society (Bezak et al 2017, Asadi et al 2017a). Thus, knowledge of extreme precipitation events of different intensities is required for designing various Hydraulic structures which regulates storm runoff viz. flood detention reservoirs, sewer systems etc (Kumar et al 2018, Agarwal 2019). Such information is of enormous importance to hydrology, which is expressed as an association with intensity, duration and return period of rainfall (inverse of probability of exceedance). Quantification of rainfall is of utmost importance in designing and risk analysis pertaining to various hydrologic and hydraulic studies (Asadi et al 2017b, Sujatha et al 2019). Precipitation data is generally used for numerous assessment and exploration related to climate, environment, drainage etc (Kesanapalli 2018). Using these data Intensity-duration-frequency curves can be prepared for a region, which proclaim the alliance between rainfall intensity, duration and return period for a specified duration. In this IDF plot duration of rainfall is taken along abscissa, intensity of rainfall along ordinate while return period as third component. Application of this plot or curve can be observed in LULC planning, soil protection schemes, sewer and storm water management (Ahamed and Agarwal 2019). To determine flow carrying capacity of channels and pumping stations for managing, planning and designing of water resources projects, this IDF curve is helpful in many aspects. Statistical methods pertaining to water resource assessment can be more prominent to manage intense or severe rainfall events. These methods play a crucial role by analyzing the extreme weather scenario like floods; thus, suitable measures can be adopted to mitigate the risk of loss of life and property. Hence, utmost precipitation events evaluation gives direction in various civil engineering works like reservoir management, flood forecasting, hydraulic structure designs etc. Numerous studies (Mailhot et al 2007, Paola et al 2014, Kumar et al 2019) have been carried to establish interrelation between different places across the globe to incorporate IDF curve applications in various domains. For developing countries like India, Pakistan, Afghanistan, Myanmar, Bhutan, Nepal etc. these relationships are not done accurately for many regions. Some research studies are conducted using design IDF curves where water resources projects are existing while the area is ungauged. Three methods for probability distribution analysis is used by (AlHassoun 2011) to approximate the intensity of rainfall in Riyadh, Saudi Arabia. These methods are namely Log Pearson Type III, Gumbel and Log Normal which were used for IDF curve generation alternatively of Mechanics, Energy and Environment. Similarly, IDF relations and its governing