Hydrological information for Dam site selection by Integrating Geographic Information System (GIS) and Analytical Hierarchical Process (AHP)

Abstract

Over time, dams have provided substantial amount of benefits to mankind for they constitute an effective and sensible method if constructed on a suitable site, for sustainable growthand managingof groundwater resources.It’s a tradition that dam selection in Kenya is done manually whereby engineers only use contour and topographic maps, without taking into consideration some watershed properties and characteristics which are mostly discovered through automated techniques and procedures of GIS analysis ona Digital Terrain Model (DTM).This study aims to investigate and demonstrate Hydrological information for dam site selectionby integratingGeographic Information System (GIS) withMulti-Criteria Decision Analysis (MCDA). Hydrological layers of water accumulation through catchments and basins were generated from the DEMusing Arc Hydro tools. These toolsare fully dependent on ArcGIS and areusedto calculate, delineate and derive hydrologic thematic layers to describe various characteristics of the catchment area.The main software used forthis study was ArcGIS. Global Mapper was also used for manipulating the Digital Elevation Model (DEM).Seven criteriawere considered for this study which included topographic factors (slope), geological factors, soil type, catchment size, land cover, proximity to river and proximity to roads.By usingAnalytic Hierarchy Process(AHP) Pair-wise comparisons, each criterionwas assigned a weightwithslope being considered as the most important factor. Weighted overlay analysis was performed in ArcGIS and determination ofsuitable dam site was done from the summation of weight of each contributing factor. A final suitability map was generated which indicated that 10% of the total study area showed thatthe area was highly suitable, 14% was suitable, 45% was moderately suitable, 23% was low suitable, while 8% was not suitable for dam construction. The highly suitable classification had four possible sites of 2.8, 3.5, 8.0and 37.8km2. The larger site was the most recommended. The formation of contours within this site is not very wide and therefore allows for various dam options with considerable weir length.From the results, it is evident that integratingGIS with AHPMulti-Criteria Decision Analysishas been successful in arriving at a suitable locations for a dam site selection. Therefore both are proficientand supportivedecision-making tools.