Identification of Flood and Drought Years over the Northeast Indian Region Using Normalized Index

Abstract

The hydro-climatic condition over Indian region is governed by the southwest monsoon season (June to September), as a majority of annual rainfall occur in this season. The presence of flood and drought years influences the cultivation system and thus, the economy of the country as the Indian agricultural system is highly dependent on the natural rainfall. This study aims to identify the flood and drought years for the north-east Indian region from 1916 to 2015 by using sub-divisional rainfall data collected from Open Government Data (OGD) Platform of India. For this investigation, the normalized index (NI) of annual rainfall is utilized to recognize a particular year as drought or flood year. The century-long monthly rainfall data collected for four sub-divisions of the north-east Indian region spanning across 9 states (Arunachal Pradesh, Assam, Meghalaya, Nagaland, Manipur, Mizoram, Tripura, Sikkim, and Sub-Himalayan West Bengal) is utilized to compute the annual rainfall, average, standard deviation, and the normalized index. The results for each sub-division have been plotted to identify the normal, drought, or flood years. The results reveal that there is a significant inter-Annual variation of rainfall over all the sub-divisions, leading to frequent drought and flood years. This study recommends the application of the normalized index over north-east Indian region due to its ease of computation and uniformity.