Application of geographical information system and analytical hierarchy process for groundwater potential zone mapping,Case study: Eastern Province, Rwanda

Abstract

Groundwater is considered as earth’s the best and largest fresh water resource, and it is the main water source for human’s daily water consumption like bathing, drinking, cleaning, washing, etc. Identification of groundwater potential areas is very important for future planning for different water use opportunities that can need abstraction mainly in dray areas with low annual rainfall. The groundwater recharge is influenced by different mainly the rainfall, lithology, land use land cover, lineament density, drainage density and slope. During our study for groundwater potential zone mapping as a case study in Eastern Province of Rwanda, Geographical information System (GIS) and Analytical Hierarchy Process (AHP) were used. GIS Was used for analyzing and organizing special and attribute data and finally it was used for weighted overlay analysis of thematic layers (rainfall, lithology, land use land cover, lineament density, drainage density and slope). AHP was used during the pairwise comparison of thematic layers and determines influence and scale of each layer to Groundwater recharge. The weighted percentage for each layer was determined and then used in GIS for overlay analysis. In order to make sure that the pairwise comparison is consistent, the consistent ratio for our matrix of 6x6 was 4.6% which is lower than 10% as a recommended as high limit for large matrix. The main goal of our research was to assess the groundwater potential zones using GIS and AHP model and the Eastern Province of Rwanda was taken as case study. The eastern province was chosen because of its water scarcity due low precipitation and long dry period. The groundwater should be looked after as an alternative source of water that can complement the existing surface water sources. The groundwater should be used for small scale irrigation, domestic use and cattle watering which are dominant in Eastern province. The generated final map of groundwater recharge zone is showing that Bugesera and Rwamagana District are well recharged, Kayonza and Kirehe have a low groundwater stock. In general, the East part of Eastern province including the Akagera National Park has a very low groundwater storage comparing to the remaining parts of this Province