INTRINSIC GROUND WATER VULNERABILITY ASSESSMENT TO CONTAMINANTS USING GIS BASED DRASTIC MODEL IN HAWASSA CITY, ETHIOPIA

ABSTRACT Groundwater is a vital and valuable renewable resource for human life and economic development all over the world. Due to its dynamic nature (flow system), interaction with potential pollutants, anthropogenic activities, geochemical system and its intrinsic characteristics, ground water introduces to contaminants. In this paper, the assessment of ground water vulnerability to contamination is investigated for Hawassa city by using of geospatial techniques (GIS based) through modeling (DRASTIC) which involves seven different intrinsic ground water characteristics. To achieve this, seven thematic were produced and overlyed to get the vulnerable areas from their index. Finally, the study found that the ground water of Hawassa city is luckily moderately vulnerable though it has low protective layer. The result shows that very low vulnerable (26%), low (35%), moderately (37%) and 2% high vulnerable area. the west central part of the city has high vulnerable areas. whereas, the southern and eastern part of the city shows low vulnerability to contaminates. The study also revealed that estimated net ground water recharge of the study calculated from annual rainfall of 993 mm was found 171.92 mm. The study recommends that a comprehensive study should be taken which involves both the source and the intrinsic vulnerability studies to fully understand the ground water vulnerability to contaminates of the study area, which helps decision makers of the city to formulate regulations concerning ground water management practices, to select solid waste disposal sites, landfill sites and land use management in our beautiful city Hawassa.