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Various Drought Indices For Monitoring Drought Condition In Aravalli Terrain Of India 
C. Bhuiyan 
Department of Civil Engineering, Indian Institute of Technology Kanpur 
Kanpur-208016, India, bhuiyan@iitk.ac.in 
Working Group VII/5 
KEYWORDS: GIS, Precipitation, Vegetation, Hazards, Spatial, Temporal, Analysis 
ABSTRACT: 
Drought is a natural hazard that has significant impact on economic, agricultural, environmental, and social aspects. The western 
regions of India (Rajasthan and Gujarat provinces) have suffered with severe droughts at many times in the past. The frequent 
occurrence of drought in these regions is due to poor and untimely monsoon, abnormally high temperature especially in the summer 
and various other unfavourable meteorological conditions. Further, due to growing use of water with growing population, the ground 
water level is found to be continuously declining. The Aravalli region of southern Rajasthan is covered by hard rock and irregular 
topography with average elevation of 550 m. In the present work, multi-sensors data have been used to deduce surface and 
meteorological parameters (vegetation index, temperature, evapotranspiration) of Aravalli region for the years 1984 - 2000 together 
with actual ground data (rainfall, temperature, ground water level) for detailed drought analysis. Using various surface and 
meteorological parameters, numerous drought indices have been computed and maps of various drought indices have been generated 
through GIS based interpolation. The Standardised Precipitation Index (SPI) has been used to quantify the precipitation deficit. A 
Standardised Water-level Index (SWI) has been developed to assess ground water recharge deficit. Vegetative drought index has 
been calculated using NDVI values obtained from Global Vegetation Index (GVI) of NOAA AVHRR data. Spatial and temporal 
variations in meteorological, hydrological, and vegetative droughts in the Aravalli terrain have been analysed and correlated for 
monsoon and non-monsoon seasons during the years 1984 -2000. The results show that none of the drought indices follows any 
particular spatial and temporal patterns in this hilly terrain of western Indian region. The detailed analysis reveals that 
meteorological, hydrological and vegetative droughts are not linearly inter related. These indices have been further compared with 
the vegetation and temperature condition indices approach followed by NOAA. The study shows that combination of various indices 
offer better understanding and better monitoring of drought conditions for hilly, semi-arid terrain like Aravalli of western India. 
1. INTRODUCTION 
Drought is a disastrous natural phenomenon that has significant 
impact on socio-economic, agricultural, and environmental 
spheres. It differs from other natural hazards by its slow 
accumulating process and its indefinite commencement and 
termination. Being a slow process although drought often fails 
to draw the attention of the world community, its impact 
persists even after ending of the event. A single definition of 
drought applicable to all spheres is difficult to formulate since 
concept, observational parameters and measurement procedures 
are different for experts of different fields. Beside, the concept 
of drought varies among regions of differing climates (Dracup 
et al., 1980). In general, drought gives an impression of water 
scarcity resulted due to insufficient precipitation, high 
evapotranspiration, and over-exploitation of water resources or 
combination of these parameters. There are various methods 
and indices for drought analysis and they measure different 
drought-causative and drought-responsive parameters, and 
identify and classify drought accordingly. However, since these 
parameters are not linearly correlated with each other, 
correlation among various kinds of drought is also difficult. 
Rainfall has a direct impact on water resources, particularly in 
iard-rock hilly terrains like the Aravalli of semi-arid western 
India where monsoon-rainfall is the only possible mean for 
ground water recharge. A continuous spell of poor rainfall in 
successive years in combination with high temperature affects 
ground water recharge and imparts stress on ground water 
resources leading to severe drought in many parts of this terrain. 
The present study aims to analyse the effects of precipitation on 
aquifer recharge and vegetation of the Aravalli terrain. In the 
present study, regional aspect of drought has been addressed. 
Spatiotemporal variation of seasonal drought patterns and 
drought severity in the Aravalli Terrain has been analysed using 
Geographic Information Systems (GIS) through various popular 
and widely used drought indices. Since aquifer-recharge, 
agricultural activities, and ecological changes in the Aravalli 
terrain are controlled by the monsoon rain, the present study of 
drought analysis has been carried out season wise — the 
monsoon and the non-monsoon or pre-monsoon. Standardised 
Precipitation Index (SPI) has been used to monitor 
meteorological drought. SPI offers a quick, handy, simple 
approach with minimal data requirements (Komuscu, 1999). 
Standardised Water-level Index (SWI) has been developed for 
efficient analysis of hydrological drought. Normalised 
Difference Vegetation Index (NDVI), Vegetation Condition 
Index (VCI), Temperature Condition Index (TCI), and 
Vegetation Health Index (VHI) have been employed to assess 
vegetative drought in the terrain. 
The pictorial results generated through various drought 
indices have been studied, analysed, compared, and correlated. 
Beside drought intensity, drought duration in different parts of 
the terrain has been monitored and interpreted through visual 
observation of the resultant maps. Drought frequency and speed 
of drought development in hydrosphere and biosphere has also 
been monitored and analysed. An attempt has been made in this 
paper to provide a comprehensive idea of drought through 
interpretation and correlation of various drought parameters. 
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