Dr. Abdullah Mah
Training Services Manager, Earth Resources Mapping Ltd.
Building a hydro-power station or stations in a rugged terrain such as in the Himalayas requires thorough studies of geological lithologies, water drainage patterns, surface and subsurface structures. If hydro-power is to be generated from Dam water then selecting suitable dam sites requires careful consideration of environmental impacts. Image processing technology can play a vital role in the studies of the categories mentioned. Detailed field studies can be followed, once Image Processing accomplishes the initial stage of the studies. In the studies of the above mentioned areas using Image Processing technology, ER Mapper can be effectively used to achieve the objectives. This paper will look at some of the various techniques that can be applied to mapping suitable sites for hydro power generation in rugged terrain. The areas that will be covered are as follows:
Geological Mapping: In geological mapping, reflectance information of rocks in the SWIR and emissitivity of the rocks in the TIR are very important. From the many types of data available, at present, ASTER data is the most appropriate one. It has 3 bands of VISNIR, 6 bands of SWIR and 5 bands of TIR. Moreover, data can be requested almost free. Geoscientists have used ASTER data for geological mapping. A wizard dedicated to process ASTER data is also developed in ER Mapper.
Water Drainage Patterns: From (DEM’s) drainage patterns can easily be identified. Once mapped drainage patterns can be saved as vector files and used them as layers in forward modelling or simply overlaid them on raster images for comprehensive interpretation and decision-making.
Structural Mapping: Geoscientists can easily extract surface structure from DEMs and sub-surface structure from Magnetics and Gravity data. Major fault zones and fractures are weak zones where Dams should not be built. Regional and local structures can be identified from Airborne, Spaceborne data, DEM, Magnetics and Gravity by GIS & RS softwares. For verification detailed field geological mapping and structural mapping are required to be carried out.
Dam sites selection: If hydro power is to be acquired from DAM water, then using the Watershed algorithm developed by us can easily process DEM and highlight the best suitable dam-sites. Certainly, selecting the most suitable Dam-site will require detail studies of both surface and sub-surface structures of the Dam-site area and its surroundings. Detail field geological mapping and structural mapping are necessary. Those field information can be easily integrated with remotely sensed data in GIS platform for the best dam-site selection.
Environmental Impact: Two issues, one is the impact of Dam at the downstream areas. Once a Dam is built, the downstream areas will have very little water. Hence the distribution of water from the Dam to maintain the natural environment will be quite challenging. The second issue is, if in case, due to any reason, the Dam is destroyed, the impact of flood at downstream areas will be enormous. Modelling of these environmental impacts can be carried out using various GIS techniques.