Extreme Rainfall Analysis for Development of Rainfall Intensity Duration Frequency Curves for Semiarid Region of Andhra Pradesh in India

In semiarid regions, water being the main constraint, the rainfall intensity-duration-frequency (IDF) curves play a significant role in water resources engineering and management. The IDF curves are used to assess the heavy rainfall events, climatic regimes classification, to derive design storms, etc. The objective of the present study is to develop IDF curves for the Ananthapuramu district in semiarid region of southern India. Annual peak rainfall data of 56 years (1966-2021) at Agricultural Research Station, Ananthapuramu, were analyzed for extraction of peak rain-storm intensity value, their corresponding durations and the frequency using Gumbel distribution method. The short-duration rainfall intensity was estimated using empirical reduction method described by the India Meteorological Department. The parameters of the IDF equation and correlation coefficient for different periods were calculated (2, 5, 10, 25, 50 and 100 years). The results of the data analysis indicated that rainfall intensity decreased with increase in rainfall duration. Further, a rainfall of any given duration will have larger intensity if its return period is large. The most frequent rainfall durations in the study area are 15, 30, and 45 min, and they were found to account for 22.4%, 28.2%, and 32.4%, respectively, of the total daily rainfall, whereas the percentage of the daily rainfall during 1-, 2-, and 3-h storm events was 34.9%, 44.5%, and 50.9%, respectively. By using these relations, short-duration rainfall can be quickly estimated, saving time, money, and other resources. The IDF curves can be recommended for the prediction of rainfall intensity and frequency of return period for Ananthapuramu district in semiarid region of Andhra Pradesh.