GIS Based Solutions for Waste Disposals
The zones of doubly plunging synclinal geological structures extending to deeper levels are suitable because these structures can hold the wastes. Similarly, the zones of least lineament density will not allow the pollutant transport and contaminate the groundwater systems. The zones of deeper weathering is preferred so that such wastes discharged could percolate down and get stored.
While the regions of null or nil slope prevent the flowage of pollutants/wastes, the regions of drainage density minima facilitate percolation rather than runoff. The regions of water level deep, least natural recharge and centripetal groundwater flow are the further additional positive parameters which give credentials to the sites as these give least possibilities for the mixing up of the pollutants derived from the wastes into the groundwater systems and in case the pollutants reach the water table also such zones of centripetal groundwater flow will not allow them to get into the aquifer because of the eddying due to centripetal flow. GIS Approach Keeping this concept in mind, a model study was conducted in plains adjoining the Western Ghats in southwestern part of Tamil Nadu to demonstrate the concept of selecting suitable sites for the disposal industrial and domestic wastes. In the said study, the basinal / doubly plunging synclinal structures were interpreted using satellite data and GIS image was generated buffering out such structures using GRAM GIS. The fracture density was worked out from the lineaments/fractures interpreted again from satellite data and the zones of least fracture density (total length of fractures per unit area) were buffered out in GIS environment (Fig. 1). In the same way, maps were prepared on the thickness of regolith cover by analysing the geophysical resistivity data and the zones of deeper weathering were buffered out in GIS (Fig. 2). The slope morphometry worked out from topographic sheets were converted into GIS image and the zones of null slope were identified. Similar buffered GIS raster images were generated showing the zones of poor drainage density (total length of drainages per unit area), deeper groundwater level, areas of natural recharge minima and the zones of centripetal groundwater flow.  Fig. 1: GIS Image - Lineament Density Minima (Green & Blue),Western Ghats, Tamil Nadu |