Girish Gopinath

Application of remote sensing and GIS for the demarcation of groundwater potential zones of a river basin in Kerala, southwest coast of India

An integrated hydrogeological investigation has been made to delineate the groundwater‐potential zones of the Muvattupuzha river basin, Kerala, along the southwest coast of India. The basin is characterized by charnockites and gneisses of Archean age covering more than 80% of the area and the remaining by Pleistocene laterites and Miocene formation. The basin receives high rainfall, measuring 3100 mm/year. However, acute water shortage occurs during the premonsoon season and hence, a number of dug wells are made to tap the groundwater. Seasonal rainfall during NE and SW monsoons is the major source of groundwater recharge. Further, hydrogeomorphology, geology, fracture systems and the slope of the terrain also play a significant role on the movement and behaviour of the groundwater of this basin. The integration of conventional and remote sensing data has been made through geographic information system (GIS) and it is found that about 50% of the area can be identified as very good or good potential zones, whereas the remaining area falls under moderate and poor categories. Most of the Muvattupuzha sub‐basin and the western part of the Kothamangalam and Kaliyar sub‐basins are classified as good groundwater‐potential zones, although the eastern upstream part of the basin has poor groundwater potential.

Change Detection Studies of Sagar Island, India, using Indian Remote Sensing Satellite 1C Linear Imaging Self-Scan Sensor III Data

Abstract The coastal zone of Sagar Island, India, is subjected to various cyclic and random processes that continuously modify the region. The shoreline and land-use/land cover changes have been studied using Indian Remote Sensing Satellite 1C (IRS IC) linear imaging self-scan sensor (LISS) III satellite data from 1998 and 1999. A comparison between a topomap of 1967 and satellite data of 1999 established that during these years about 29.8 km of coastline was eroded, whereas the accretion is only 6.03 km2. A comparison of satellite data from 1998 and 1999 showed that the island had undergone severe erosion of about 3.26 km2, while the accretion was just about 0.08 km2. Change detection studies based on land-use patterns of the region revealed that the areal extent of mangrove vegetation of the island during 1998 and 1999 was 2.1 km2 and 1.3 km2, respectively. The areal extent of agricultural fields during these periods was 130.4 km2 and 118.6 km2, respectively. These results can be used to develop an index for temporal land-use changes in the region as an aid to quantify the extent and nature of the development change and to understand the surrounding environment, which in turn may help the planning agencies to develop sound and sustainable land-use practices.

Critical coastal issues of Sagar Island, east coast of India

Sagar Island, situated in the east coast of India and one of the biggest deltas in Sundarban group, faces coastal erosion and degradation of coastal vegetation and various natural hazards. Erosion is mainly due to clay mining, wave activities, and the impact of river and tidal currents of Muri Ganga and Hugly Rivers. Further, the coastal zone of Sagar Island faces increasingly severe problems of rapidly growing human population, deteriorating environmental quality, and loss of critical habitats. Sagar Island has been victimized several times by tropical cyclones and influenced daily by tidal fluctuations. The island needs immediate attention on the coastal zone in order to protect the shoreline and ecosystem. The capability of satellite remote sensing to provide synoptic, repetitive, and multispectral data has proved to be very useful in the inventory and monitoring of critical coastal issues. Sagar Island and its environs are subjected to both natural and anthropogenic activities that continuously modify the region.

Identification of groundwater prospective zones using irs-id liss iii and pump test methods

The role of hydrogeomorphological units and lineaments in the storage of groundwater from the Muvattupuzha river basin has been investigated using IRS ID LISS III data. Other than the usual water bodies such as river course, reservoirs and ponds, the major hydrogeomorphological units identified in this basin in the descending order of their groundwater potential are: valley fills, moderately dissected plateau, pediments, residual mounts, residual mount complex, linear ridges, residual hills and structural hills. Majority of the lineaments trends in NW-SE and WNW-ESE directions. Even though the eastern part of the basin is characterised by moderate to high lineament density, the above area is found to be poor to moderate groundwater prospect zone because of high gradient and structural hills. The pump test analyses of dug wells from different hydrogeomorphic units also confirm that valley fills are the most promising unit for groundwater prospecting than the rest.

Watershed prioritization based on morphometric analysis coupled with multi criteria decision making

Kuttiyadi river basin in the South Indian state of Kerala has been analyzed for planning watershed management activities. Geohydrological behavior of the watershed was analyzed by calculating the morphometric parameters. Linear, relief, and areal parameters were determined using standard equations. Kuttiyadi is a sixth order basin, characterized by maximum relief and gradients in the eastern part, exhibiting highest runoff and susceptibility to flooding and inundation. Relative drainage density data suggest that subwatersheds II and III are mature basins in steady state equilibrium with components like climate, lithology, tectonism, and landscape components. Multi criteria decision making approach was followed for watershed prioritization. Given the interrelationship that exists among the different morphometric parameters as well as the complexity due to the integrated effect of these parameters on soil erosion, analytic network process was employed. Length of overland flow was found to be the most influential morphological parameter in watershed prioritization. High priority subwatershed identified in this study must be taken up for immediate action with respect to soil conservation activities. Suitable locations for construction of check-dams as water conservation structures were identified. This study has shown that morphometric analysis along with multi criteria decision making would serve as a powerful tool in watershed planning where complex interrelationship exists among different morphological parameters.

Geospatial Analysis of Long-Term Morphological Changes in Cochin Estuary, SW Coast of India

ABSTRACT Kumar, P.K.D.; Gopinath, G.; Murali, R.M., and Muraleedharan, K.R., 2014. Geospatial analysis of long-term morphological changes in Cochin estuary, SW coast of India. The Cochin estuary along the SW coast of India has undergone tremendous environmental changes due to continuous alterations. Geospatial information available since 1967 has been compiled to evaluate the long-term morphological changes. Quantification of geomorphological changes that occurred over the decades was made to have an integrated profile to ascertain the changes in the extent. Toposheet maps (1967) and satellite imageries for 2004 and 2011 have been interpreted. Quantitative comparison of inner island segments showed significant changes in island widths through time. It was found that the areas covered by the islands within the estuary during 1967, 2004, and 2011 were 81.62, 89.26, and 89.52 km2, respectively, and those covered by the water body were 130.68, 121.3, and 118.01 km2, respectively. The shrinking rate of the estuarine system was estimated to be 0.288 km2/y. About 11 km2 of island area was found to be prograded, and 3 km2 was eroded. In effect, the reduction in the aerial extent of the estuarine system was estimated to be 12.67 km2. The evolution of the western estuary margin has been characterized by a strong progradation during the past 4 decades. The results obtained conclusively show that the estuary is being inflicted with major geomorphic changes at several segments, resulting in reduction in the extent. Geomorphic differences may lead to factors in modifying estuarine flows, which ultimately affect the dynamic processes within the estuary. Observed trends of morphological changes generate concern in the background that the region may continue to remain vulnerable in the coming decades due to development pressures in the adjoining hinterlands.

Hydrodynamic and Geomorphic Controls on the Morphology of an Island Ecosystem in the Vembanad Lake, West Coast of India

Abstract Textural characteristics of the surficial sediments around Perumbalam Island located within the Vembanad Lake, southwest coast of India, were studied on a seasonal basis to understand the geomorphic response of the region. Sediment grain size increased from the northern to southern end of the island, indicating a progressive sorting by tidal currents. In contrast, an increase in the clay and organic carbon content in the sediments of the northern part of region suggests that their distribution is controlled by the productivity of the overlying water column. The evolution of this island is believed to be due to fluvial inputs from Muvattupuzha River. The braid shape of the island is attributed to the high-energy flow along the wedge of the estuary facing the river mouth, which has resulted in a build up of land along the southern boundary. The intense accretion on the southeastern and western sides of the island observed through satellite imagery reveals the fluvial influence on the evolution and morphology of this coastal lagoon.

Seasonal Variations in Groundwater Chemistry of a Phreatic Coastal and Crystalline Terrain of Central Kerala, India

This article investigates the seasonal variation in geochemical characteristics of groundwater in phreatic aquifers of the coastal plain and crystalline terrain of central Kerala, India. Within the coastal plain, the western barrier island area shows values of electrical conductivity (EC, > 3 times), Na+, K+, Cl− (four times), Mg2+ (10 times), Ca2+ (two times), and HCO3 −+ CO3 2− (approximately two times) higher than those of the eastern coastal plain during both seasons. In contrast, pH and SO4 2− concentrations showed little variation. The alkaline nature and high EC of groundwater in the western barrier island–coastal plain is found to result from the intrusion of saltwater from the adjacent Vembanad estuary. In contrast, groundwater of the crystalline terrain is found to be slightly acidic with low EC. Within the crystalline terrain, the area east of Muvattupuzha River showed high EC values during both seasons while other parameters showed marginal variation. The trilinear diagram reveals that most of the groundwater samples from the crystalline terrain, which is of type IV (Ca2+–Mg2+–Cl−–SO4 2−) during the premonsoon period, changed character to type II (Na+–K+–Ca2+–HCO3 −) during the postmonsoon period. This shift is possibly caused by the addition of Na+ and HCO3 through the leaching of the country rock. Results for the western barrier island reveals that most of the samples are affected by the saline water incursion. Fecal contamination is found to be comparatively high in the groundwater of the coastal plain versus that of the crystalline terrain. This study indicates that the groundwater from the crystalline terrain is of higher quality than that of the coastal plain. The study further reveals the need for seasonal or multi-seasonal sampling when a geochemical characterization is performed and the recognition of physical events, such as heavy precipitation or droughts, when interpreting the geochemical characteristics of an aquifer.

Spatial Characters of a Tropical River Basin, South-West Coast of India

An evaluation of drainage network of Mahe river basin (394 km2), Kerala, India, with a humid tropical setting is carried out using geospatial techniques. The streams of the basin generally conform to Horton’s laws. However, the correlation between mean stream length and stream order is low (r = +0.55), probably due to an abrupt increase in mean stream length in the highest orders of the subwatersheds. The Subwatersheds in the extreme eastern part of the basin are characterized by maximum relief, and gradients exhibit highest runoff and susceptibility to flooding and inundation. The lineament zones and associated tectonic activity control the drainage patterns and disposition of subwatersheds. The various linear and spatial morphometric parameters of each subwatershed are ranked based on their susceptibility to flooding. Subwatersheds III–VI are environmental hot spots, where implementation of flood control and mitigation measures should be urgently focused. The other subwatersheds steady are found to be in steady state equilibrium with components like climate, lithology, tectonics and topography that determine origin and development of a drainage basin. Major flooding rarely occurs in Mahe, in spite of favourable morphometric characters in other parts of the basin, and is attributed to permeable lateritic nature and dominant areal extent of SW IX in the western most extreme.

VERTICAL ELECTRICAL SOUNDINGS FOR DELINEATION OF GROUNDWATER PROSPECT ZONE IN A CRYSTALLINE TERRAINS OF THE MUVATTUPUZHA RIVER BASIN, KERALA, INDIA

ABSTRACT The Muvattupuzha basin is characterised by lateritic capping followed by weathered/fractured rock and hard bedrock consisting of Pre-Cambrian and Archean gneisses. Groundwater in the Muvattupuzha river basin occurs under water table conditions in latentes and semi-confined to confined conditions in fractured crystalline. Vertical Electrical Soundings (VES) were conducted in the four sub basins of the Muvattupuzha (Muvattupuzha, Kothamangalam, Kaliyar and Thodupuzha) and the results were analysed qualitatively and quantitatively using both geological and hydrogeological information so as to demarcate potential groundwater zone in the phreatic aquifer and a few promising zone for putting medium to deep bore wells. It is found that among four sub basins, a large area of the Muvattupuzha sub basin is characterised by good to moderate phreatic groundwater potential zone while the rest of the basin fall under the category of poor to moderate. Certain promising sounding stations are identified in the basin for tapping groundwater from the third and fourth layers by putting medium to deep bore wells.