Modelling optimum sites for locating reservoirs in tropical environments

A team of specialists normally carries out the task of locating reservoir sites based on general guidelines, technical knowledge and experience. Consequently, the procedures used are not based on defined criteria in addition to being time consuming and expensive. Furthermore, the failure of a number of dams and the increase in environmental awareness will require the inclusion of environmental and social factors in the processes besides economy. In this study, criteria were developed and implemented to locate potential sites for reservoirs in the Langkawi Island, Malaysia based on all relevant factors including: topography, geology, hydrology, land use/cover types and settlements. A satellite imagery and digitized geological and elevation maps were utilized to generate the necessary data layers for the developed criteria. Then IDRISI, a raster based geographical information system (GIS) was employed to implement the criteria using the Boolean and the Weighted Linear Combination (WLC) methods. The Boolean method produced five reservoir sites with the 70 Mld water capacity, two of which corresponded well with a field-based study. Whilst the proposed site with the 90 Mld water capacity did not correspond with the field-based study. The WLC method produced five sites with the 70 Mld water capacity, three of which matched those of the field study. Whilst for the 90 Mld water requirement, two potential sites were produced and both have matched those of the field study. The outcomes indicated that the developed criteria were sensitive to physical, environmental and economical settings on the Langkawi Island. Furthermore, GIS and remote sensing can be useful tools for generating, manipulating and handling relevant data layers and ultimately providing management options for decision makers.