Application of Remote Sensing data for Delineation of Ground Water potential zones in the Kalrayan Hills, Tamil Nadu
Sakthivel, R, ManiveL,M and A. Alagappa Moses
Department of Geology, Bharathidasan University, Tiruchirapalli-24. Dept. of Environmental Sciences, Bishop Heber College, Tiruchirapalli - 17.
In the study, an attempt has been made to delineate the ground water potential zones in the Kalrayan Hills, Eastern ghats, Tamil Nadu. In the study, the IRS-1 C FCC data was used and with aid of visual image interpretation keys the following maps were generated like geomorphology, lineament. The following geomorphologic units were also identified viz. Valley fills (VF), Pediment zone (Pz), Residual hills (RH), Bajada zones (Bz), Inselberg (I), Plateau (with moderate, shallow and highly dissected), lineament (L) and etc. In the study area, NE-SW, N-S and NW- SE trending direction lineaments have inferred. It reveals the close relationship between groundwater condition and geology & geomorphology of the study area. It inferred that the areas covered by Bajada zone, Valley fills, Buried pediments (shallow to medium) considered as potential zones for groundwater targeting and the combination of lineaments and fractures may be considered for the same.
Water is an elixir of life and it does play vital role in biotic and a biotic environment. Due to the erratic behavior of monsoons together with unplanned exploitation of groundwater, caused mainly by the development in the living standards of mankind and the growing population which has been further compounded by unpredictable behavior of ground water in hard rock areas causes damage to the extent of depletion of groundwater table. So the assessment of quantity of groundwater is essential for optional utilization especially in hilly terrain. The interpretation of satellite data in conjunction with sufficient ground truth information makes it possible to identify and outline various ground features such as geological structures, geomorphic features and their hydraulic characters, that may serve as direct or indirect indicators of the presence of ground water ( Das et al.1997, Ravindran and Jeyaram(1997). Therefore, a detailed hydrogeomorphological mapping survey can give a clear picture of the groundwater resources and the associated problems. Vaidyanathan(1964; Bhattacharya et al., 1979; Prithvi Raju,1980; Millington et al,1986; Jones,1986; Kunte, 1988; Sinha et al,1990; Steven, 1991 and Thomas et al, 1995) have demonstrated in detail about the application of remote sensing data to demarcate the groundwater prospective zones by means of identifying hydrogeomorphological features. The present study is an attempt to evaluate groundwater conditions in the kalrayan hills, through hydrogeomorphological studies using remote sensing data.
The Kalrayans are a major hill range of Eastern Ghats situated to the north east of Salem district of Tamil Nadu. It lies between 110 20| - 120 05| N latitude and 780 28| - 790 05| E longitude ( Fig.1). It spreads over an area of 1095 Sq.kms. and is endowed with rich natural resources. The vegetation types of kalrayans are scrub jungles of altitude 400m, deciduous forests between 800 to 1300m and sholas at the sheltered pockets on the plateau. The Kalrayan measures 25.76 km (NS) and 37 km (EW) .The chinna kalrayans on the north and the east, pass into the Ariya Goundan and the Kurumba Goundan jaghirs of South Arcot district.( Matthew, 1981).
In the present study, the IRS 1C LISS III data in the form of false colour composites(FCC'S) generated from bands 2,3,&4 on 1:50,000 scale was interpreted using visual interpretation keys such as tone, texture, association and so on. The knowledge of the area was taken into account at the time of interpretation. The interpreted features transferred to the base map on 1:50,000 scale. The geological, lineament maps and other collatoral data were also made use of for the preparation of hydrogeomorphological map.The ground water prospects of the delineated geomorphic units were evaluated using available hydrogeologic characteristics. The hydrogeomorphical map of the area was finalised after field checks at selected locations for verifying the doubtful units.
Results and Discussion
The geological facts reveal that Charnockite and peninsular gneissic complex occupy the major portion of the study area ( G.S.I,1995 maps ).The pyroxinites, syenites, anorthosite,calc-granulite, carbonatites etc., are also occur and belong to Precambrian era(Mathew,1981).
Geomorphological units and associated features
Geomorphological units and associated features identified and mapped in the study area through the visual interpretation of satellite data after integrating the physiographical, geological, structural, hydrogeological and drainage conditions are described in detail. Hydrogeomorphologically, the Kalrayan hills environment is classified into different zones covered by Residual Hills, Inselberg, Bajada zones, Valley fills, Pediment zone, Plateau with moderate, shallow and highly dissected and other geomorphic features have also been identified.
Residual Hills ( RH )
Residual hills (RH) are group of massive hills occupying relatively small area. In the study area the residual hills are identified nearer to Gomukhi reservoir and in and around of Arasampattu village. Forests, agriculture land and plantations cover the study area.
Pediment is a gently sloping area with erosional bed rock, situated in between hills and plains consisting of a veneer of detritus and broad undulating rock floor. This unit is sparsely present in the study areas especially in the northern side of the study area. In the pediment zones, generally the groundwater potentiality is poor to negligible. Groundwater potential in pediment zone depends upon the thickness of the debris( Murthy et al, 1999).
Valley Fills (VF)
Valley fills are linear depressions present in between the hill ranges, filled with pebbles, cobbles, gravel, sand and silt. Valley fills are observed near the villages of Peddanaickanpatty and Mundiyur. The ground water potential ranges from moderate to good. These valleys are developed along the fractures and such places can be exploited for groundwater through deep bores. In general, it is observed that adequate recharge source of ground water is met within valley fillings. Hence, in such places, the groundwater is considered to be moderately better with adequate source of water ( Table-1).
The lineaments are linear or curvilinear feature pattern and play a vital role particularly in geomorphic and structural analysis. These are well expressed on Landsat images (Sabins, Jr, 1987). The Lineaments like joints, fractures etc., developing generally due to tectonic stress and strain, provide important clue on surface features and are responsible for infiltration of surface run off into sub-surface and also for movement and storage of groundwater ( Subba Rao et al,2001). In the study area, numerous lineaments have been identified and most of them show N-S trending direction. The lineament follow the stream courses and intersecting - lineaments are considered as good potentials for groundwater targeting, as they reflect high porosity and hydraulic conductivity of the underlying materials( Sahai et al., 1991; Subba Rao and Prathap Reddy, 1999). In the present study area, the lineament-intersection points and well location has been identified at very close to the following villages Karumanthurai, Innadu, uppur, kattupudur, kidar, vellimalai, maniarkundam Tumbal, and papinaickanpatty.
Bajada Zones (BZ)
Bajadas are the one of the main geomorphic units that are present very close to the foot hills of the study area are identified. The bajada are excellent zones for groundwater targeting especially in the hilly region.
In addition to the aforesaid features, some of the other features have also been identified in the study area like Plateau(PD) with shallow, moderate and highly dissected nature and the features are also used as an important tool for groundwater potential zone demarcation while they are in association with lineaments. In the present study area, the Plateau with lineament has been identified at Maniarkundam, Kidar and Kattupputhur of southernslope portion.
The visual interpretation of IRS 1C data provided information pertaining to hydro-geomorphic features was very useful in understanding the nature and water potentiality of different landforms. The integration of geological and lineament information are important in preparing hydrogeomorphic potential map. The various landform units discussed are the result of different geomorphic processes. The study revealed the capability of remote sensing technology for preparing a hydrogeomorphological map. The study also shows that the interrelationship of hydro geomorphic units and other topographical features and their importance in delineating the groundwater potential zones in the hilly terrain.