ASSESSMENT OF DROUGHT FOR MITIGATION

Abstract

This study was carried out for the Arkavathy basin of the Cauvery River system, Karnataka, India. The main aim of the study was to identify the drought characteristics in the basin and to derive a drought susceptibility map using GIS and Remote Sensing technique. Annual and seasonal rainfall departures, annual and seasonal probability distribution from the corresponding mean and the Standardized Precipitation Index analysis have been applied for identification of drought characteristics and severity assessment of drought events. Annual and seasonal rainfall data for the period 1901 to 2014 have been analysed. From the results of annual rainfall departure it is revealed that the average drought return period in the basin is 4-5 years. In the year 1983 the maximum annual and seasonal rainfall deficits were -87.31% and -94.54% respectively. The probability distributions of annual and seasonal rainfall have been analysed. The maximum annual mean rainfall recorded at Ramanagara with a magnitude of 880 mm and the probability occurrence of the annual mean and seasonal mean rainfall were 53.50% and 50.10% respectively. The Standardized Precipitation Index analysis was carried out to identify the severity of the drought event in the basin. The most recent drought conditions prevailed at Doddaballapura and Anekal stations in the study basin were with annual rainfall deficiency of -45.92% and -43.66%, Standardized Precipitation Index values as -1.57 and -1.14 in the years 2012 and 2014 respectively. The spatial representations of topographic feature, land use pattern, soil type, runoff potential, surface water availability, drought return period and annual rainfall deficit layers were prepared in spatial domain using Geographical Information System (GIS) and integrated values of weights for various indicators have been computed in 250 m x 250 m grid. The factors weights and the different layers i.e. river reach, land use pattern, soil type, runoff potential, surface water availability, drought return period and annual rainfall deficit were integrated using the overlay technique of the ARC-GIS to obtain the final drought susceptibility map for the year 2012. Methodology adopted for this study provides satisfactory estimation of drought susceptibility scenarios of the study basin - using different indicators and factors. The map of susceptibility to drought may be helpful to the administrative departments for introducing the drought mitigation plans and decision making.