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 Geo-Hydrological study of Gandheshwari Sub-watershed using Remote Sensing and GIS Techniques Subodh Chandra Pal 1, Manisa Shit 2 1- Research Scholar, Visva-Bharati, Santiniketan, W.B., India 2- M.A. in Geography, C.S.J.M. University, Kanpur, India geo.subodh@gmail.com ABSTRACT The present study was conducted on Gandheshwari sub-watershed situated in Bankura district of West Bengal. The remote sensing and GIS techniques have been proved to be very efficient in identification geo-hydrological aspects of the study area. The various thematic maps have been generated like Geology, geomorphology, hydro-geomorphology, geohydrology, structure, soils and land use land cover helped in identification of the potential zones for development planning and forecasting. Lineaments and their intersections appear to be potential sites for groundwater. The study shows that the integration of all attributes provide more accurate results in identification of geo-hydrological characteristics. Key words: Geo-hydrology, hydro-geomorphology, remote sensing, GIS and GPS. 1. Introduction Geo-hydrology and groundwater exploration means to identify and to locate the zone of recharge of groundwater in a particular river basin or a catchment. Geological set up is established for knowing about surface and subsurface nature of terrain. Topographic and surface features are mapped in order to determine from highest to lowest area, where water from different higher places can move and accumulate. These particular zones are present in various terrains. The identification of such places from the entire area, are thus selected for groundwater exploration. Remote sensing and GIS providing some useful information for integrated resources development and environmental management in composition with ground truths on soils, land use, vegetation, surface & groundwater, geology, landforms, topography, settlements, among others, in a regional perspective. Remote Sensing techniques are now being widely used for land resource surveys like this. 1.1 Study area The study area is located in the upper reaches of Dwarkeswar watershed, from latitudes 23 0 13'15", to 23 0 31'25" and from longitudes 86 0 53'11" to 87 0 8'. Gandheshwari is a tributary of Dwarkeswar River which covers an area of 388.6015 km 2. The climate is extreme with maximum temperature up to 42 0 C and minimum temperature down to 6 0 C. The annual rainfall of the study area varies between 1055 and 1070.3 mm. The maximum amount of rainfall received during the monsoon season from June to September about 80.73%. The relative humidity in the month of April is 61(2008) and in the month of September is 99 (2008). The maximum altitude is 435 mt., demarcated in the middle part and the minimum elevation is about 80 mt. observed in the southern part of the sub-watershed. This absolute relief map is generated as shown in figure-6. Submitted on May 2012 published on July 2012 204
1.2 Data used Figure 1: Map showing the study area Survey of India (SOl) topographical sheets (73 M/3, 73 I/14 and 73 I/15) on 1:50,000 scales have been used as a base map for the preparation of geo-hydrological study. Contours available on SOI topographical maps have been used for the preparation of Digital Elevation Model (DEM). SRTM data, Geological map (1:253,440 scale) published by Geological Survey of India was also used. Except these, one satellite data (Table-1) is also used for this work which is in the following. 205
Table 1: Details of the satellite data used in this study Satellite Sensor Path/Row Bands Date of acquisition Spatial Resolution LANDSAT ETM+ 108/56 1,2,3,4 Nov. 18 th 2006 30*30mts. 2. Objectives The main objective of the present paper is to identify the geo-hydrological condition of the entire study area. 2.1 Methodology The methodology includes the generation of thematic layers on geomorphology, lithology, slope and land use/ land cover of the area (described earlier). Geographic Information System (ArcGIS 9.1) was used for the preparation of thematic layers. The weightages of individual themes and feature score were fixed and added to each layers depending on their suitability to hold groundwater. This process includes overlay analysis of several no of layers. A probability weighted approach has been adopted that allows a linear combination of probability weights of each thematic map and different categories of derived thematic maps have been assigned scores, by assessing the importance of it in groundwater occurrence. The maximum value is given to the feature with highest groundwater potentiality and the minimum being to the lowest potential feature. The procedure of weighted linear combination dominates in raster based GIS software systems. After assigning the weightages and scores to the themes and features, all the themes were converted to raster format using Spatial analyst, extension of ArcGIS software. The hydrogeomorphological map of the area was finalized after field checks at selected locations for verifying the doubtful units. A detailed ground water quality survey was also conducted to understand the groundwater flow of the entire study area. 3. Results and discussion 3.1 Drainage Network Drainage network analysis is important for geo-hydrological studies. Drainage pattern reflects the characteristic of surface as well as subsurface formation. Drainage density (in terms of km/km 2 ) indicates closeness of spacing of channels as well as the nature of surface material. More the drainage density, higher would be runoff. Thus, the drainage density characterizes the runoff in the area or in other words, the quantum of relative rainwater that could have infiltrated. Hence lesser the drainage density (Figure-3), higher is the probability of recharge or potential groundwater zone. Hence, drainage density is an important index in geo-hydrological studies, and can be evaluated from the satellite images or others. Drainage map (Figure-2) of the study area reveals only two types of drainage patterns viz. dendritic and radial. 206
Figure 2: Map showing the Stream Orders Figure 3: Map showing the Drainage Density 207
3.2 Slope Analysis Slope is one of the factors controlling the infiltration of groundwater into subsurface; hence an indicator for the suitability for groundwater prospect. In the gentle slope area the surface runoff is slow allowing more time for rainwater to percolate, whereas high slope area facilitate high runoff allowing less residence time for rainwater hence comparatively less infiltration. For the generation of slope, the digital elevation model (DEM) has done (Figure- 5) by the interpolation of contours, which in turn digitized from SOI Toposheets using ArcGIS. DEM is a digital representation of continuous variation of topographic surface with the elevation or ground height above any geodetic datum. The generated DEM is used for generation of slope using 3D analyst an extension tool of ArcGIS. This helps for appreciating, the terrain and a supporting factor for the slope analysis. The slope analysis has been carried out in the sub-watershed level (Figure-4) and is divided into several classes according to groundwater holding capacity. Figure 4: Map showing the Average Slope 208
Figure 5: Map showing the Digital Elevation Model Figure 6: Map showing the Absolute Relief 209
3.3 Lithology In order to understand the groundwater conditions of the study area, a general lithological map has been prepared with the help of LANDSAT ETM+ satellite imagery, geological map (GSI) and ground truth. This may provide some information about the movement and storage of ground water. As it is the extended part of the Chotonagpur plateau region therefore the area is mainly covered with gneiss, granitic gneiss, pyroxene granulite, felspathic schist etc (Figure-7). At places these are out cropped while at other places there are underlain by weathered formation as evinced from the lithology of wells in the area. It is this weathered and fractured zone, which forms potential groundwater zones. There are thin strips of alluvium deposits seen along the stream course, which could be potential groundwater zones. 3.4 Structure Figure 7: Map showing the Geological Structure Lineament study (Figure-8) of the area from remotely sensed data provides important information on sub-surface fractures that may control the movement and storage of ground water (Pradeep Raj et al., 1996). Sub-surface permeability is a function of fracture density of rocks (Sharma, 1979). In all 22 lineaments have been identified and marked in the area. They are having varying dimensions and areal extents as well. Lineaments are nothing but the manifestation of linear features that are identified from remote sensing data. These linear features usually represent faults, fractures or shear zones and are identified on satellite images on the basis of tonal contrast, stream / river alignment, and differences in vegetation and knick-points in topography. The concentrations of lineaments are more in southern region of the study area than the northern region. Therefore the density of lineaments increases to words the lower reach of Gandheshwari river basin than the upper reach as well. 210
Figure 8: Map showing the Lineament Density Figure 9: Map showing the Hydrogeomorphological Units 211
3.5 Hydro-Geomorphology The drainage basin is a fundamental geomorphic unit and the watershed acts as a source area for precipitation that eventually provide to the stream channels by various path. The drainage basin morphology being an important aspect of geomorphic analysis has been undertaken in the present context to determine the various properties of form elements, their distributional variation, interrelationship, determination of correlation coefficients etc. Remote sensing studies provide an opportunity for better observation and more systematic analysis of various hydro-geomorphological units coupled with geological parameters in this study area which is considered very useful technique in preparing integrated hydro-geomorphological maps for targeting groundwater. The study area was broadly divided into several hydrogeomorphic units (Figure-9), which are based on the visual interpretation of satellite imagery, topographical map and field check. The delineation of the hydrogeomorphic unit aimed at demarcating areas of ground water potential zones for development. These hydrogeomorphic units (Table-2) were identified and verified during field checks and then a hydrogeomorphological map was prepared. Table 2: Details of hydro-geomorphological units and their characteristics Hydrogeomorphological units Alluvial plain/flood plain Colluvial Valley fills Buried pediment (shallow) Buried pediment (moderate) Buried pediment (deep) Washed plains Denudational upland with Inselberg Description Flat surface adjacent to stream/river, composed by Clay, Silt and Sand. Accumulation zone of colluvial materials derived from surrounding uplands; shallow to deep; fine loamy to clayey soils. Nearly flat to gently sloping topography, shallow to moderately deep, loamy soils followed by regolith zone. Gently sloping topography; very deep, clayey to fine loamy soils. Gently sloping zone of colluvial and alluvial sediments at the foot of the hill. Nearly flat surface along the rivers formed of recent sediments. Broad uplands of considerable elevation, steeply sloping on all Soil characteristics and existing land use /land cover Moderately deep to deep, fine textured moderately well drained soils. Moderate limitation of wetness. Single crop cultivation. Moderately deep to deep, fine textured moderately well drained soils. Moderate limitation of wetness. Single crop mainly terrace cultivation. Very shallow to shallow coarse textured soil with occasional weathered outcrops of country rocks. Wastelands with or without scrub. Shallow to moderately deep, loamy skeletal soil. Single crop area low productive potential Moderately deep to deep, fine textured loamy skeletal to coarse loamy soil. Single crop area with marginal rabi crops. Medium productive potential. Moderately deep to deep, fine textured loamy soil. Single crop cultivation with low productive potential. Moderately deep to deep, fine textured loamy soil. Single crop cultivation with moderate productive potential. Very shallow, coarse loamy soil on moderately steep to very steep hill slopes and escarpments Groundwater prospects Good Moderate to good Poor Moderate Moderate Good Poor 212
Lineaments/faults directions. having different degrees of hardness. Open to dense forest and plantation. Not suitable for agriculture / pasture /orchards. Linear fractures of joints, ----------------------- fractures, faults. Good to moderate 3.6 Land Use and Land Cover Land use/land cover is one of the important parameter for the geo-hydrological study because the land use pattern of any terrain is a reflection of the complex physical processes acting upon the surface of the earth. These processes include impact of climate, geologic and topographic conditions on the distribution of soils, vegetation and occurrence of water. So it is necessary for future development and management to have timely and reliable information on environmental status through land use studies. The land use /land cover data sets are generated from the digital image classification of LANDSAT, ETM+ satellite images. This classification is performed taking nine classes within the entire study area, namely water body, dense forest, mixed forest, agriculture, agriculture fallow land, lateritic up land, built up land, dry fallow land and sand (Figure-10). Overall accuracy achieved is 89%, after carrying out an accuracy assessment using ground truth (reference sample points) data sets. Figure 10: Land use/ Land cover Map 213
3.7 Groundwater Potential Zones After the integration of all thematic maps, resulted map has been classified into several groundwater potential zones (Figure-11). Groundwater potential map clearly indicate that alluvial plain which is composed of sand, silt and clay with nearly level slope and very low drainage density has very good potentiality and development and valley fills associated with lineaments is highly promising area for groundwater extraction. The structural hills, denudational hills and residual hills are considered as poor to very poor groundwater potential zone. However, these land landforms act as run-off zones because of their steep slope. Lineaments particularly joints, fractures and their intersection enhances the potential of hydrogeomorphic units. Thus the generated groundwater potential map serves as a base line for future exploration. 3.8 Ground Water Scenario Figure 11: Map of the Groundwater Potential Zones The occurrence and movement of groundwater depend upon the rock formations present in the area. It also depends upon the topography, structure, and geomorphology, as well as hydro-geological properties of the water-bearing materials. The movement of groundwater concentrating towards the north-north-west direction to south-south-east direction where the seasonal groundwater fluctuation are also take in to account which is fully based on the field data of open dug-well (Figure-12 and 13). Alluvium comprises of silt, sand, and clay 214
particles; it is an excellent aquifer; while rests of the others are showing moderate or poor aquifer. 3.9 Groundwater favourable Zone The hydro-geomorphological units (Figure-9) such as Alluvial Plain, Valley Fills, are most favourable zones for groundwater exploration & development in the study. Hence, these areas are marked as good to very good favourable zones. In case of Buried Pediment with lateritic upland (deep, moderate, shallow) region have been identified as a moderate favourable zone and the region of denudational upland with inselberg with low lineament density has been identified as the least favourable zone for groundwater exploration & development in the study. A glance at Figure-11 reveals that the southern part of the study area have excellent groundwater potential as compared to the upper middle basin and north-north-eastern part of the basin. These are also verified from field. This information is very useful for the further groundwater development in the study area. Figure 12: Map showing the Groundwater condition at Pre-monsoon season 215
4. Conclusion Figure 13: Map showing the Groundwater condition at Post-monsoon season Remote sensing and GIS techniques have been used to integrate various geoinformative thematic maps, which play major role for the geo-hydrological study. The integrated groundwater potential map has been categorized on the basis of cumulative weightage assigned to different features of thematic maps. Further, comparison of groundwater yield data collected from the field also supports that there are more number of high-yield wells in the favourable zones derived from GIS. The integrated map thus deciphered could be useful for various purposes such as development of sustainable scheme for groundwater in the area. From the results it is suggested that, proper rainwater harvesting and artificial recharge methods and measures should be implemented in the moderate to nil potential zones to overcome the water scarcity problem. 216
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