INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES Volume 3, No 1, 2012

INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES Volume 3, No 1, 2012 Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0 Research article ISSN 0976 4380 Evaluation of hydrogeomorphological landforms and lineaments using GIS and Remote Sensing techniques in Bargur Mathur subwatersheds, Ponnaiyar River basin, India Sethupathi A.S 1, Lakshmi Narasimhan C 2, Vasanthamohan.V 3 1- Infosys Technologies Ltd., Bangalore 560100, India 2- Department of Geology, Anna University, Chennai-600025, India 3- Department of Geology, National College, Tiruchirapalli 620001, India lakshmina_c@yahoo.com ABSTRACT The Landsat ETM satellite data is used to demarcate hydrogeomorphological landforms and lineaments to evaluate groundwater potential of the study area. The Bargur - Mathur subwatersheds of Ponnaiyar river basin is occupied mostly by hard rocks and half of the portion in the study area is covered mainly by both wet and dry cultivation. The major hydrogeomorphic units identified in the area are, Structural Hills, Denudational Hills, Residual Hills, Inselberg, Pediments, Buried Pediment Inselberg Complex, Pediplains, Valley Fills, Linear Ridges, Boulders and Rocky Knobs. Most part of the study area is occupied by pediplains with various thicknesses and the ground water potential is directly related to thickness of pediplain. Field observations showed that ground water occurs under unconfined conditions with water table at shallow to deep depth. From the lineament map, the lineament density and lineament intersection maps prepared to understand the impacts on groundwater percolation. Finally, the hydrogeomorphology and Lineament maps are overlaid following the weighted index overlay method, which delineates groundwater potential zones. An integrated remote sensing and geographic Information System (GIS) based approach has been used for demarcating groundwater potential zones in the study area. Keywords: Hydrogeomorphology, Lineament, Remote Sensing, GIS, Bargur Mathur subwatersheds 1. Introduction Generally, hard rock areas are always prone to frequent water crisis, it is important to understand hydrogeomorphological nature of landforms and lineament distribution with respect to the permeable nature of subsurface, percolation, runoff status of the region. Lineament study of the area from remotely sensed data provides important information on sub-surface fractures that may control the movement and storage of groundwater. In recent years extensive use of satellite remote sensing has made it easier to define the spatial distribution of different groundwater potential zones based on the geomorphology and it's associated features (Sankar, 2002). Satellite Remote Sensing techniques are also extremely useful techniques for groundwater exploration, especially for delineating hydrogeomorphological units (Baldev et al, 1991; Krishnamurthy, 1993; Krishnamurthy and Srinivas, 1995). Satellite image from Landsat 7 ETM has been analyzed for lineaments (Lattman, 1958; O'Leary et al, 1976), hydrogeomorphological studies (Tiwari and Rai, 1996), land use and land cover mapping (Anderson et al, 1976) and for groundwater development works. Lineaments can play a major role in identifying suitable sites for artificial recharge of Submitted on Feb 2012 published on July 2012 178

groundwater because they reflect rock structures through which water can percolate and travel up to several kilometers (Krishnamurthy et al, 2000). The selected study area for this study are draught prone Bargur Mathur subwatersheds, which are located in the northern part of Tamil Nadu State in India and is situated between northeastern part of Krishnagiri district and southwestern part of Vellore district (Fig.1). The study area is drained by Bargur and Mathur rivers. These two rivers merge at the southeast corner, where the Pambar river originates and finally joins the river Ponnaiyar. The study area covers an area of 781 sq.km in the Survey of India toposheet numbers 57L/6, 57L/7 and 57L/11 on a scale of 1:50,000. The study area lies between latitudes 12 17 40 and 12 41 53 and longitudes 78 14 56 and 78 31 38. The area has a sub-tropical climate without any sharp variations. Temperatures vary from 40 C in summer to around 20 C in the winter season. The average rainfall is 857mm/yr. Based on the Public Work Department report (2004), these subwatersheds fall under the critical zone, where groundwater discharge is greater than groundwater recharge. 2. Scope and objectives Figure 1: Base map of the study area The scope of the study is to analyze hydrogeomorphological landforms and lineament distributions to evaluate potential groundwater zones within the study area. The objective includes delineation and evaluation of hydrogeomorphological landforms and lineaments distributions based on their hydrogeological characteristics, classify and assigning weightage to each classes of hydrogeomorphology and lineament distribution and integrate them under GIS environment. 179

2.1 Methodology In order to delineate hydrogeomorphological and lineament maps, the geo-coded 1:5000 scale Landsat ETM (Enhanced Thematic Mapper, dated March 18, 2000) satellite imagery was used. Basic image characteristics like tone, texture, shape, color, associations, etc were used, along with field parameters such as topography, relief, slope factor, surface cover, soil and vegetation cover were considered while delineating hydrogeomorphic and lineament maps. From lineament map, other maps such as lineament density and lineament intersection maps are prepared. Then suitable logical weights are assigned to each unit of thematic maps and integrated in GIS using the spatial overlap method to delineate groundwater potential zones. 3. Geology of the study area Figure 2: Geology map of study area Fig.2 shows a wide array of litho units ranging from alkali syenites, ultramafic complexes (such as pyroxenites, gabbros, dunites, carbonatites, syenites, epidote hornblende gneiss, hornblende biotite gneiss and migmatites, high grade metamorohites like charnockite), granitoid gneisses and younger dolerite like intrusives exposed in the study area. These rock types represent different time segments within Archean era. The gneissic rocks are characteristically less compact rocks with more weathered and fractured overburden material. Groundwater occurs under the water table conditions in weathered, jointed and fractured formations. 180

3.1 Hydrogeomorphology The figure 3 illustrates various hydrogeomorphic units interpreted from the satellite imagery and each unit is described elaborately in the following sections. 3.2 Structural Hills Figure 3: Hydrogeomorphology Map In the study area, the structural hills are in the linear as well as in the arc shapes and exhibited by many definite trend lines (Figure 3). This unit is mostly found on the top portion in the north, northeastern and western parts of the study area. Mainly, the Maharajagadai Reserve Forest (RF), Maharajagadai Extension RF, Kurumanipalli Nadimuru RF, Paipalatyam RF and Nerrlakotta RF are covered by structural hills. This unit is structurally controlled by numerous joints, fractures and lineaments which facilitate some infiltration and mostly act as runoff zones. From the satellite imagery, the structural hills are interpreted by dark green tonal variation and by thick vegetation. There are few lineaments running more than 10 Km in the structural hills. These have been identified in the imagery by the streams flow along them. The structural hills have total coverage area of 81.75 sq.km and occupy 10.4 % of the study area. Since this unit is mainly acting as runoff zone, the groundwater prospects are very poor. 3.3 Denudational Hills Denudational hills (Figure 3), with an average height of 700 m above mean sea level occupy the western part of the study area and are marked by sharp to blunt crest lines with rugged 181

tops. They are exposed as a group of massive hills with resistant rock bodies and rounded summits and are formed due to differential erosion and weathering. Denudational hills are identified in the satellite imagery by their massive size and domal to elliptical shape. They appear as dark green in color in the satellite imagery. These hills are covered with big boulders and sparse vegetation in contrast to structural hills. This landform, in general, act as high runoff zone, due to its moderate to steep slope (5 o to 25 o ). Denudational hills due to their relief acts as watershed boundary also. The total coverage of this unit is 20.23 sq.km and it occupies 2.6 % of the study area. The groundwater potential of this landform in general is very poor. 3.4 Residual Hills The residual hills are the end product of the process of pediplanation, which reduces the original mountain masses into a series of scattered knolls standing on the pediplains (Thornbury, 1990). In the study area, the residual hills (Fig.3) are composed of massive rock with a height average of 600m mean sea level. The residual hills are more resistant formation from differential erosion and weathering. This unit occurs as isolated patches and found at lower altitudes. In spite of their isolated occurrence, their continuity in a linear or curvilinear fashion gives indication that they are structurally controlled. The residual hills have geomorphic expression in the form of inselbergs, tors, linear and curvilinear ridges, exfoliated domes with partially debris cover at the foot slope (Tripathy et al. 1996). In the satellite imagery they appear as isolated patches and with dark green color tone with radial drainage pattern. This unit is scattered all over the study area and its total coverage is 31 km 2 and it occupies 3.9% of the study area. Due to steep slope most of the rain water is washed off immediately without much infiltration and hence the groundwater prospect in this unit is poor. 3.5 Inselberg Inselberg (Figure 3) are isolated hillocks being formed as remnants of weathering and denudation processes and this unit is present in a scattered manner in the central part of the study area and along east of Jagadevipalayam. They are mostly barren, rocky, usually smooth, rounded small hills abruptly rising above the surrounding plains. Inselberg in the study area are made up of granites and gneisses rocks. Slope ranges are moderate to very steep slope and the elevation of this landform is nearly 500 m. Its coverage is 3.7 sq.km area and it occupies 0.5% of the study area. This unit is acting as surface runoff zone due to steep slope and groundwater prospects are very poor. 3.6 Pediments Pediment as the term suggests, is a feature usually formed at the foot of a mountain. Pediments (Figure 3) occur as gently undulating plains with moderate slope dotted with outcrops of gneisses with thin layers of soil. The pediment is a terrestrial erosional foot slope surface inclined at a low angle and lacking significant relief in all three dimensions. It usually meets the hill slope at an angular neck line, and may be covered by transported material. The low moisture content of this unit gives a bright signature in the satellite imagery, especially around the hills. This unit is scattered around the study area and its coverage is 98.6 km 2 and it occupies 12.5% of the study area. Pediment follows steep slopes in the study area and is considered as the most suitable hydrogeomorphic class because it checks the velocity of 182

surface runoff and thus provides more chance of water accumulation. Overall groundwater prospect is good in this unit. 3.7 Buried Pediment Inselberg Complex Pediments dotted with a number of inselberg in gneisses which cannot be separated and mapped as individual units are referred to as Pediment Inselberg Complex (Figure 3). A number of small isolated island-like hills that stands out in prominence in a dome form because of their resistance to weathering within the extensive pediment zone. This unit present in a scattered manner in the central part as well as in the northern part of the study area and this unit has covered over 2.29 km 2 area in the study area and it occupies 0.3 % of the study area. Only a pediment zone within this entire unit is suitable for artificial recharge, hence it is categorized lower than pediment alone. 3.8 Pediplain The pediplains are formed as a result of weathering under arid and semi-arid conditions, representing the end stage of cyclic erosion (King, 1950; Sparks, 1960). A Pediment is developed by a combination of process including stream erosion, weathering, sheet wash and lateral plantation. When the sediment developed over a large area as a result of continuous process of pedimentation, it is normally termed as a pediplain (Agarwal and Garg, 2000). Pediplains are the result of coalescence of pediments, predominantly occupying large area. There are three pediplains observed in the study area, which are shallow buried pediplain, moderate buried pediplain and deep buried pediplain. The pediplains are characterized by the presence of relatively thicker weathered material. The extent and thickness of weathering depends on the slope, resistance of the underlying rock to weathering, presence of joints and fractures and precipitation and climatic conditions of the area. Depending upon the thickness of weathered materials, the tonal nature on the satellite imagery and degree of slope they are broadly classified as shallow (up to 5 m), moderate (5 20 m) and deep (>20 m). In the continuous process of pedimentation, when pediment gets buried by detritus and regolithic cover, it is termed as a buried pediment in which the sub-surface rock subsequently undergoes weathering. Most of the agricultural lands in the study area are constituted by buried pediplains. Depending upon the thickness of the weathered zone, the groundwater potential is moderate to good and eligible for construction of a well. 3.9 Shallow Buried Pediplains The shallow buried pediplains (Figure 3) unit is characterized by low weathering thickness of the materials up to 5m. The low moisture content of this unit makes a medium grey tone on the imagery. This unit has a thick soil zone and sparse vegetation. Groundwater availability is believed to be poor to moderate in view of their elevated ground compared to moderate and deep buried pediments. However, the gentle slope adjacent to the stream courses and tanks has moderate potential zones. This unit found mostly in the 0 to 3 degree slope region and it is distributed in the central, western, southwestern and southern portions of the study area. Since, weathered thickness is less in this unit the groundwater prospects are moderate to poor range. This unit has a total coverage of 132.4 sq.km area and it occupies 16.8% of the study area. The area covered by this hydrogeomorphological unit can be used for development of groundwater resource in terms of shallow wells (Subba Rao et al, 2001). 183

3.10 Moderate buried Pediplains The moderate buried pediplains (Figure 3) is a major hydrogeomorphic unit in the study area. This unit is moderately weathered with a thickness various from 5 20 m, 0 to 1 degree slope and is well distributed throughout the region of the study area except the top north portion. This unit is interpreted by light red color to moderate red color in the satellite imagery. Mostly, this unit is found to have a well distributed drainage pattern in the study area. This unit occupies the topographically low-lying area and associated mostly with lineaments. Groundwater prospects in this unit are considered as moderate to good. However, higher yields may be expected from this hydrogeomorphological unit as it is associated with lineaments. This unit covered about 372 sq.km area and it occupies 47.3% of the study area. Groundwater can be withdrawn from this unit through development of shallow and deep wells, because of weathered material ranging from 10 to 20 m (Subba Rao et al, 2001). 3.11 Deeply buried Pediplains Deeply buried pediplains (Figure 3) exhibit a deep red color in the satellite imagery covered by thick vegetation. This unit has a few lineaments. The groundwater prospects in this unit appear to be good, because of the occurrence of high thickness of weathered material. The thickness of weathered zone varies from 20 to 25 m and favors a good amount of groundwater to circulate within this zone before reaching the deeper fracture zone. Hence, infiltration would be good. Total coverage of this unit is 6.7 sq.km area and it occupies 0.8% of the study area. Groundwater potential is very good and may be utilized for development and exploration of groundwater through deep wells (Subba Rao et al, 2001). 3.12 Valley Fills Valley fills (Figure 3) are low linear areas occurring between hills. These units occupy the lowest reaches in topography with nearly level slope. The valley fill deposits are colluviofluvial in origin derived from weathering and deposited by the action of streams at the floor of valleys. Depending upon the parent rock, the valley fills deposits vary in composition and texture (Agarwal and Garg, 2000). Normally, they are covered with red, brown and black coarse gravel to sandy and clayey soils. In the study area, the valley fills are identified between the structural hills on the northern part of the study area. The drainage pattern over the valley fills is parallel to sub-parallel indicating that the drainage is by and large controlled by the lineaments. They exhibit dark reddish tone and medium texture in the satellite imagery, which indicates high moisture content due to intensive cultivation. This unit occupies in upper northern part of the study area and it covers 2.9 sq.km area and occupies 0.4 % of the study area. Groundwater prospects in valley fills are good to excellent because of the topographical location at the bottom of the hill and geological composition consisting of highly porous materials. Subsurface water potential is also good to excellent in the valley fills (Murthy and Rao, 1999). This unit acts as both depths. 3.13 Linear Ridges Linear ridges or dykes (Figure. 3.) are discordant or cross-cutting, tabular intrusion into the country rock. Most dykes are vertical or near vertical, having pushed their way through the overlying country rock. In the present study area the dykes are orienting NWW- SEE direction and crosscutting the country rocks. This unit appears as dark tone in the satellite imagery. They occur in linear, narrow, low-lying relief and are barren. Theses dykes act both 184

as conduits and barriers for groundwater flow. It covers 2.05 sq.km area and it occupies 0.3 % of the study area. The groundwater prospects in this hydrogeomorphic unit are poor; but in the study area these dykes act as subsurface barriers for groundwater movement within the weathered mantle making the prospect of groundwater good. 3.14 Boulders and Rocky Knobs Boulders (Figure 3) are spread in the south eastern and central portion of the study area. These are basically massive boulders with eroded material. This unit is interpreted by light green color in Landsat ETM satellite imagery. Sparse vegetation is found in this unit. It covers 15.8 sq.km area and it occupies 2 % of the study area. Groundwater prospects are very poor in this unit as it acts as runoff zone. The rocky knob is totally a barren rock and exposed as a rock exposure and found at the south eastern portion of the study area. It covers 2.3 sq.km area and it occupies 0.3 % of the study area. Due to the lack of moisture content, groundwater prospects are very poor. 3.14.1 Water bodies There are totally, 214 tanks (Figure 3) present in the study area, out of which Penkondapuram Eri and Odikuppam Eri are larger ones. 3.15 Lineament Analysis In the study area, 194 lineaments have been mapped through visual interpretation of satellite imagery and all are cross checked during the field investigation. They are having varying dimension and the smallest of them is 0.2 Km long and the longest of them is 28.6 km. In the present study, lineaments were classified based on their length into three categories as Major (>15km); Medium (5-15km) and Minor (<5km). Lineament map shows that there are three predominant sets of lineaments, one set trending NW-SE and second set trending NE SW and last set trending N45E S45W (Fig. 4.). Details on lineament interpretation as follows 1. Three long prominent lineaments were interpreted in the satellite imagery, which starts from Maharajagadai reserved forest in the northwestern side of the study area and ends with the Pambar river in the south eastern side of the study area. The Bargur and Mathur rivers are flowing exactly along these major lineaments and this infers that these two rivers are structurally controlled. These major lineaments lengths are 28.5 Km, 21.3 Km and 17.3 Km respectively. 2. There are lot of criss-cross lineaments follow along the Mathur river in the down south and southwestern part of the study area. 3. Central part of the study area, from east to west, there are many parallel running discontinuous lineaments run along with dykes. 4. Disoriented criss-cross lineaments occupy the top northern portion, northwestern portion, and central western portion of the study area. 5. From the lineament map, the lineament density and lineament intersection maps are prepared. 3.16 Lineament Density Lineament density is one of the important thematic maps prepared from the lineaments, which are critically used in groundwater studies related to hard rock terrain (Subba Rao, 185

1992; Krishnamurthy et al. 1996; Subba Rao et al. 2001;). Based on the concentration and length of lineaments, a lineament density map was prepared. The lineament density map was generated in Surfer 8.0 software using Kriging method (ESRI, 2001), which was later imported into ArcGIS software for GIS integration purpose. The lineaments present in the study area have varying dimensions. The lineament map was superimposed on a grid map of 1km * 1Km and the total length of lineaments passing from each grid was measured and plotted in the respective grids centers. The values obtained for each grid were interconnected by isolines and based on the concentrated and length of lineaments, a lineament density map was prepared. The lineament density zone was classified into three classes which are high density lineament zone (2 to 4 km with in a grid), medium density lineament zone (1 to 2 km with in a grid) and low density lineament zone( < 1km with in a grid) (Fig. 5.). The high density lineament occupied 225.4 sq.km area, the medium density lineament occupied 280.9 sq.km and the low density lineament occupied 399.5 sq.km area. The high density lineament occupied as patches throughout the study area, the other two lineament density types are well distributed throughout the study area. 3.17 Lineament Intersection Figure 4: Lineament Map of Study area The total numbers of lineaments intersected in square kilometer area is plotted in the respective grid center for generating contour map (Figure 6). The lineament intersection in 186

the study area varied from 5 to nil. Lineament intersections classified in to four classes as; high, medium and low lineament intersection zone using the Kriging method in Surfer 8.0 software and were brought into ArcGIS platform for further analysis. The high and medium lineament intersection zones are distributed as patches in the study area. Figure 5: Lineament density 187

Figure 6: Lineament Intersection Map Incorporating the results from the evaluation of hydrogeomorphic conditions and lineament distribution of the study area, and adopting weighted indexing method, applied on each class of thematic maps such as geology, geomorphology, physiography, hydro-geomorphology, structure, geo-hydrology, lineaments, land use/land cover, it is possible to delineate groundwater prospective areas in the study area. 4. Conclusion The Hydrogeomorpholy analysis of a watershed is a very simple tool, which covers the modern techniques of remote sensing and GIS. This technique coupled with geological data can certainly be used in in evaluating the parameter pertaining to groundwater and accurate zoning of ground water potential of a region. Lineaments, particularly joints/fractures and their intersection appear to be potential sites for groundwater exploitation. In the present study area, the valley fills, pediplains and buried pediments are appearing to have good groundwater potential. Remote sensing techniques with an emphasis on geology, geomorphology, physiography, hydro-eomorphology, structure, geo-hydrology, land use/land cover help in identification of the potential zones for developmental planning and predicting limitations to their implementation with reasonable accuracy.the present information, if depicted in the form of a prospect map along with thematic layers and the use of GIS for the ultimate data integration based on the user defined criteria with weighted approach, would provide firsthand information to local authorities and planners to identify possible potential sites for groundwater exploration. 188

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