Browsing by Author "Vyshali"

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Characterization of a coastal aquifer a case study
(2009) Saldanha, J.P.; Vyshali; Mahesha, A.
The present study deals with the characterization of the coastal aquifer in the Pavanje river sub-basin through the pumping tests and the electrical resistivity tests. The electrical resistivity tests are also used to study the geology of the aquifer and possible saltwater intrusion. The transmissivity of the region varies from 50 m2/d 160 m2/d and the specific yield up to 8%. The results of the electrical resistivity tests indicate that the top surface is having a resistivity of 400 1000 ohm-m with an average thickness of 5 m and the bottom layer is having the resistivity of 80 300 ohm-m with an average depth of 20 m. Additionally, an attempt was made to model the groundwater flow in the region using FEFLOW software for the period between June, 2006 and April, 2007. The model is run for different pumping scenarios considering the probable developments in the region. Saltwater intrusion is predicted at some specific locations due to low water table condition during the summer. The water budget estimation indicates that there is significant groundwater outflow from the area during June to November. Hence, it is necessary to carry out investigations to arrest this outflow which may be utilized during the lean season. 2009 Taylor & Francis Group, LLC.
Characterization of a coastal aquifer—a case study
(2009) Saldanha, J.P.; Vyshali; Mahesha, A.
The present study deals with the characterization of the coastal aquifer in the Pavanje river sub-basin through the pumping tests and the electrical resistivity tests. The electrical resistivity tests are also used to study the geology of the aquifer and possible saltwater intrusion. The transmissivity of the region varies from 50 m2/d—160 m2/d and the specific yield up to 8%. The results of the electrical resistivity tests indicate that the top surface is having a resistivity of 400—1000 ohm-m with an average thickness of 5 m and the bottom layer is having the resistivity of 80—300 ohm-m with an average depth of 20 m. Additionally, an attempt was made to model the groundwater flow in the region using FEFLOW software for the period between June, 2006 and April, 2007. The model is run for different pumping scenarios considering the probable developments in the region. Saltwater intrusion is predicted at some specific locations due to low water table condition during the summer. The water budget estimation indicates that there is significant groundwater outflow from the area during June to November. Hence, it is necessary to carry out investigations to arrest this outflow which may be utilized during the lean season. © 2009 Taylor & Francis Group, LLC.
Parameter estimation and vulnerability assessment of coastal unconfined aquifer to saltwater intrusion
(2012) Mahesha, A.; Vyshali; Lathashri, U.A.; Ramesh, H.
The focus of the present work is to characterize a tropical, coastal aquifer and to carry out its vulnerability to saltwater intrusion using hydrogeological parameters. The characterization of the aquifer involves pumping tests, vertical electrical sounding, and water quality analysis carried out at 41 monitoring wells. The area under investigation lies between two tropical, seasonal, tidal rivers, i.e., Pavanje and Gurpur rivers, joining the Arabian on the west coast of India. The aquifer is predominantly shallow and unconfined, having moderate to good groundwater potential with transimissivity and specific yield ranging from 49.2 to 461:4 m2/day and 0.00058 to 0.2805, respectively. The electrical resistivity tests indicated that the thickness of the aquifer ranges from 18 to 30 m. The study also investigates the saltwater affected areas in the region the vertical electrical sounding and water quality analysis. The resistivity results revealed several probable isolated saltwater intruded pockets in the region with resistivity less than 70 Om. From the salinity analysis of water, the locations that are affected during February to May (summer) and throughout the year are identified. The wells that are located close to the coast (< 350 m) and at lower elevations (well bottom < +1 m) were found to be saline throughout the year. Also, wells along the banks of the river show considerable salinity (> 200 ppm) during the summer period from tidal inflow along the rivers. The water samples were also analyzed for chloride to bicarbonate ratios during December to May at all the monitoring wells and were found to be exceeding the allowable limit at several locations. The saltwater vulnerability maps are derived for the area by the index-based method using the hydrogeological parameters. The method was found to be effective while compared to the field observations. The results from the analysis indicate that the aquifer is medium to highly vulnerable to saltwater intrusion at majority of the locations. The impact of projected sea level rise by 0.25 and 0.50 m from the climate change is also assessed on the vulnerability of the region to saltwater intrusion. 2012 American Society of Civil Engineers.
Parameter estimation and vulnerability assessment of coastal unconfined aquifer to saltwater intrusion
(2012) Mahesha, A.; Vyshali; Lathashri, U.A.; Ramesh, H.
The focus of the present work is to characterize a tropical, coastal aquifer and to carry out its vulnerability to saltwater intrusion using hydrogeological parameters. The characterization of the aquifer involves pumping tests, vertical electrical sounding, and water quality analysis carried out at 41 monitoring wells. The area under investigation lies between two tropical, seasonal, tidal rivers, i.e., Pavanje and Gurpur rivers, joining the Arabian on the west coast of India. The aquifer is predominantly shallow and unconfined, having moderate to good groundwater potential with transimissivity and specific yield ranging from 49.2 to 461:4 m2/day and 0.00058 to 0.2805, respectively. The electrical resistivity tests indicated that the thickness of the aquifer ranges from 18 to 30 m. The study also investigates the saltwater affected areas in the region the vertical electrical sounding and water quality analysis. The resistivity results revealed several probable isolated saltwater intruded pockets in the region with resistivity less than 70 Om. From the salinity analysis of water, the locations that are affected during February to May (summer) and throughout the year are identified. The wells that are located close to the coast (< 350 m) and at lower elevations (well bottom < +1 m) were found to be saline throughout the year. Also, wells along the banks of the river show considerable salinity (> 200 ppm) during the summer period from tidal inflow along the rivers. The water samples were also analyzed for chloride to bicarbonate ratios during December to May at all the monitoring wells and were found to be exceeding the allowable limit at several locations. The saltwater vulnerability maps are derived for the area by the index-based method using the hydrogeological parameters. The method was found to be effective while compared to the field observations. The results from the analysis indicate that the aquifer is medium to highly vulnerable to saltwater intrusion at majority of the locations. The impact of projected sea level rise by 0.25 and 0.50 m from the climate change is also assessed on the vulnerability of the region to saltwater intrusion. © 2012 American Society of Civil Engineers.
Simulation of saltwater intrusion in the pavanje-gurpur basins of karnataka
(2008) Vyshali; Palchaudhury, M.; Mahesha, A.
The development and management of fresh groundwater resources in coastal aquifers are seriously constrained by the saltwater intrusion. The Dakshina Kannada district is one of the rapidly developing districts of Karnataka. Due to the increase in population, urbanization and industrialization, the district is facing severe shortage of freshwater resources during the summer period. Also, the rivers of the district are being seasonal and tidal in nature, saltwater intrusion into the adjoining aquifers during the non-monsoon period is greatly felt up to several kilometers inland along and around the river courses. Hence the present work is aimed at simulation of saltwater intrusion in the Gurpur and Pavanje river basin aquifers using Saturated-Unsaturated Transport (SUTRA) model and comparing it with the field observations. The model is also used to predict the impact of increasing stress on freshwater aquifers due to the developmental activities. The results from the investigation indicate that the model prediction agrees well with the observed salinity levels in the study area. As such, the saltwater intrusion is not a severe problem in the region except a few pockets. The study also includes the evaluation of the basin characteristics through field tests and water quality/level observations through a network of wells. The coastal aquifers are predominantly shallow unconfined aquifers with transmissivity and specific yield values ranging from 49.2 461.4 m2/day and 0.00058 0.2805 respectively. The aquifers along the river courses are getting contaminated during the summer months only and region in the proximity of the sea is affected throughout the year. The optimal pumping rates have also been worked out for the region with potential groundwater development to avoid the problem of saltwater intrusion. The results from the study would be useful in the sustainable groundwater development in the region. 2008 Taylor & Francis Group, LLC.
Simulation of saltwater intrusion in the pavanje-gurpur basins of karnataka
(2008) Vyshali; Palchaudhury, M.; Mahesha, A.
The development and management of fresh groundwater resources in coastal aquifers are seriously constrained by the saltwater intrusion. The Dakshina Kannada district is one of the rapidly developing districts of Karnataka. Due to the increase in population, urbanization and industrialization, the district is facing severe shortage of freshwater resources during the summer period. Also, the rivers of the district are being seasonal and tidal in nature, saltwater intrusion into the adjoining aquifers during the non-monsoon period is greatly felt up to several kilometers inland along and around the river courses. Hence the present work is aimed at simulation of saltwater intrusion in the Gurpur and Pavanje river basin aquifers using Saturated-Unsaturated Transport (SUTRA) model and comparing it with the field observations. The model is also used to predict the impact of increasing stress on freshwater aquifers due to the developmental activities. The results from the investigation indicate that the model prediction agrees well with the observed salinity levels in the study area. As such, the saltwater intrusion is not a severe problem in the region except a few pockets. The study also includes the evaluation of the basin characteristics through field tests and water quality/level observations through a network of wells. The coastal aquifers are predominantly shallow unconfined aquifers with transmissivity and specific yield values ranging from 49.2–461.4 m2/day and 0.00058–0.2805 respectively. The aquifers along the river courses are getting contaminated during the summer months only and region in the proximity of the sea is affected throughout the year. The optimal pumping rates have also been worked out for the region with potential groundwater development to avoid the problem of saltwater intrusion. The results from the study would be useful in the sustainable groundwater development in the region. © 2008 Taylor & Francis Group, LLC.