Drainages are pulses which in turn help us to understand the ongoing process in the hill ecosystem. The Kalrayan hill is known for its dissected terrain condition, rich biological diversity and depletion of natural resources. Therefore, a study on quantitative geomorphometry was carried out in the Kalrayan Hills, Eastern Ghats, Tamil Nadu, using Indian remote sensing 1D LISSIII satellite data. The study area was divided into 36 watersheds and total area is 1158.4 km 2 . It covers the upper part of Vellar basin. The linear, aerial and relief aspects and different morphometric parameters such as stream length, bifurcation ratio, drainage density, stream frequency, drainage texture, relief ratio, basin shape, form factor, circularity ratio, elongation ratio and length of overland flow were computed using standard methods, formulae and geo-spatial technologies. Based on the present drainage morphometric study, it is inferred that the watersheds 3, 4, 6, 9, 11, 12, 15, 17, 18, 19, 20, 22, 24, 27, 32, 33, 34 and 36 are active with reference to geological processes, mean denudational rate, peak discharge, mean annual run off, dominant watershed process and sediment yield per unit area. Multi-criteria analysis is performed to determine the drainage architecture and hydrogeological processes occurring in the present hill area.

The present study attempts to understand the form and geomorphic/hydrologic processes of the 20 watersheds of the Pachamalai hills and its adjoinings located in Tamil Nadu State of southern India from the analysis of its drainage morphometric characteristics. Survey of India's topographic sheets of 1:50,000 is the data source from which stream networks and watersheds of the study area were demarcated followed by the analysis of their morphometric characteristics using ArcGIS software. The results of the analysis formed the basis for deducing the form and processes of the watersheds of the study area. The form of the watersheds inferred from the analysis includes shape, length, slope steepness and length, degree of branching of streams, dissection and elongation of watersheds. The geomorphic/hydrologic processes inferred include denudation rate, potential energy, intensity of erosion, mean annual run off, mean discharge, discharge rate, rock resistivity and infiltration potential, amount of sediment transported, mean annual rainfall, rainfall intensity, lagtime, flash flood potential, flood discharge per unit area, sediment yield and speed of the water flow in the streams. The understanding of variations of form and processes mentioned can be used towards prioritizing the watersheds for development, management and conservation planning.

In the present study an updated tectonic lineament database for Pachamalai hill, a resourcerich hill of central Tamil Nadu state of India has been generated and analysed. Digital Elevation Model generated from CARTOSAT-1 satellite data have been the data source. Lineaments extracted from eight different azimuth angles were compiled together towards the generation of the lineament database, which has been subsequently analysed for their number, length, density and spatial distribution using ArcGIS software. In addition, their orientations were analysed using Rockworks software. Of the 561 lineaments of the study area, about 90% are very short and short lineaments. The total length of the lineaments is 680 sq. km and their density ranges from 0 to 3.4 km/sq. km. The diversely oriented lineaments of the hill reflect the multiple deformation events that have affected the region through geologic time. In about 30% of the hill, the lineament density is high to very high which implies higher degree of deformation, fracturing, shearing and permeability of rocks besides higher soil erodibility and groundwater yield. These high to very high density areas render themselves unsuitable for the construction of dams and reservoirs as the possibility of water leakages into the subsurface, slope and dam failures and rate of sedimentation would be higher. Further, the analysis of the lineaments clearly underlines the need to extract lineaments from different azimuth angles instead of the widely adopted practice of mapping lineaments from single azimuth angle.

In the present study, the chemical characteristics of groundwater with respect to drinking and Irrigation water quality in upper Thirumanimuthar sub-basin, Cauvery River, have been studied. 51 groundwater samples were collected and analysed for pH, conductance, total dissolved solids, total hardness, calcium, magnesium, carbonate, bicarbonate, total alkalinity, chloride, sodium, potassium, sulphate etc. The values analyzed were evaluated in detail and compared with WHO water quality standards. It is observed that, for most of the groundwater quality parameters, the values are not potable for drinking and irrigational use. To understand the spatial distribution of unsuitable zones, ArcGIS was employed. Attributes were linked and spatial interpolation mapping was done. Inverse distance weighted interpolation technique was followed for raster and vector mapping. Finally the overlay analyses were also carried out to locate the worst quality zone.

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