Identifying groundwater prospect zones through earth observation techniques in Bilate Watershed, Rift Valley Lakes Basin, Ethiopia

Abstract

AbstractGroundwater is one of the most valuable natural resources gifted to mankind, especially in surface water scarce locations. Most parts of the Ethiopia is dependent on the aminity for common needs, irrigation, etc. Lack of scientific approach in its exploitation and management makes the resource underutilized. Therefore, Remote sensing (RS) and Geographic information system (GIS) were utilized to decipher potential groundwater zones (PGWZ) existing in Bilate watershed of the nation so as to economize, speed up and technicalize the system. Ground truth of the results so obtained was verified to confirm the reliability of the techniques used. Through RS, optical and microwave data were obtained, while GIS was helpful to collect information on water points mapping and 2D resistivity survey in locating the aquifers. Especially, resistivity studies revealed the existence of both pyroclastic and rhyolite intrusions that act as water barriers and the basaltic and ignimbrite rocks that favor aquifer affluence. During the process of identification and quantification of PGWZ in the watershed, analytical hierarchy process (AHP), weighted linear combination (WLC), and digital elevation model (DEM) were employed in thematic layer formation, reclassification, overlay analysis and map production. As a result, five PGWZ having very high (19.8%), high (35.3%), moderate (22.6%), low (19.3%), and very low (2.9%) prospects were identified. Similarly, over 75% of the area was found to be moderate to high category in PGWZ. Accuracy of the qualitative groundwater inventory was proved to be 92.64 percent. Thus, combining high-resolution optical/microwave data and GPS information with AHP model has ascertained the accuracy of PGWZ identified. So ultimately, the present work lays foundation for the use of advanced spatial techniques in finding out natural resources useful for the welfare of the nation and its populace.Keywords: AHP; Bilate watershed; GPSGroundwater potentialSentinel data2D resistivityDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also. AcknowledgmentsThe authors would like to express special gratitude to Arba Minch University, Water Resources Research Center for financially supporting the study. We are also grateful to the Ethiopian National Meteorological Agency, South Water Works construction enterprise, Ethiopian Geological survey, Ethiopian Mapping Agency, and Ministry of Water, Irrigation, and Electricity for providing the relevant data. The authors also express special thanks to the European Space Agency for enabling the free use of sentinel data from the ESA Sentinel Scientific Data Hub. Finally, we thank Mr. Tigabu Baye, a geologist, who helped during the geophysical survey and interpretation of the 2D resistivity survey. We also wish to thank the two anonymous reviewers, Michael Nones, Editor-in-Chief and Associate Editor, whose suggestions were helpful in significantly improving this manuscript.Availability of data and materialsThe data are available upon request to the authors.Disclosure statementThe authors declare that they have no competing interests.