IDENTIFICATION AND MAPPING OF GROUNDWATER POTENTIAL AND RECHARGE ZONES USING GIS AND REMOTE SENSING: THE CASE STUDY ON MOJO CATCHMENT, ETHIOPIA

Abstract

Groundwater is the primary source of drinking water for both developed and developing countries, including Ethiopia. The issue of unsustainable groundwater utilization is becoming increasingly visible and it is the main concern of this study. The main objective of this research work was to assess the groundwater potential and recharge zones of the Mojo watershed by integrating remote sensing data using GIS and Erdas imagine tools. To address this concern, seven thematic layers were considered as critical factors for evaluating groundwater potential based on watershed characteristics such as geology, rainfall, lineament, slope, Land cover, drainage density and soil. The weight of each thematic layer was assigned and normalized according to their significance importance and relationship with groundwater recharge using analytical hierarchy process approach on basis of satty’s 1-9 scales out of GIS platform. Based on weight analysis geology, lineament and rainfall are the three dominant groundwater controlling parameters. finally ground water potential zones are obtained by overlaying all integrated thematic maps using a weighted sum overlay analysis tool in Arc GIS 10.3.The result depicts five categories of groundwater potential zones; very low, low ,moderate, high and very high. Greater portion of the study area about (31.8%) fall within low potentiality zone. 21.7% and 8.98% of the total watershed fall under high and very high potential zones respectively. Only (11.3%) total area has very low potential rate. Small part of west and east areas and major part of downstream regions covered with low and very low potential rate. Most part of northern regions lay under moderate groundwater potential rate. In similar way groundwater recharge zones produced using the same thematic layer with additional parameter (runoff map). As per result perceived five category of recharge zones were produced such as; 13.1% very poor, 20.4 %poor, 29.8% moderate, 25.8 % good, and 10.8 % very good. The resulted map was validated using existing spring data, hand dug well and borehole yields. The validation analysis showed 74% and 70% of agreement between the groundwater inventory data and prepared maps respectively. From this study it can be conclude that remote sensing and GIS tools are important and efficient in assessing groundwater potentiality and recharge zones for effective management of groundwater resources