Journal Articles
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Item The effect of subsurface barrier on the motion of the sea water - fresh water interface in coastal equifers is analysed for sudden drawdown conditions. A Galerkin finite element model is used for this purpose to carry out the parametric studies on the effect of location, width and hydraulic conductivity of the barrier. The results indicated marked variations in the interface profile as compared to no barrier condition. The width and hydraulic conductivity play a decisive role in delaying the interface response for any drawdown situations. Among the various barrier locations considered, the barrier at Lo was found to be most effective in checking the intrusion.(Effect of subsurface barrier on salt water intrusion) Mahesha, A.; Babu, M.2001Item Parametric studies were carried out to analyse the effect on sea water intrusion of freshwater recharge through a finite width strip parallel to the coast. A vertically integrated one-dimensional finite element model was used for this purpose. The studies included the analysis of the effect of location, width, intensity and the period of recharge on sea water-freshwater interface motion. Relationships were established between the interface motion and the recharge parameters applicable to wide ranging practical cases. From the studies, the ideal location for recharge was identified to achieve the maximum repulsion of intrusion. The width of recharge also affects the interface motion and the widths greater than 2% of the initial intrusion length were effective in controlling the intrusion. The results indicated that the reduction of intrusion up to 30% could be achieved through strip recharge. © 2001 Taylor & Francis Group, LLC.(Effect of strip recharge on sea water intrusion into aquifers; Effet d’une bande de recharge sur l’intrusion d’eau de mer dans les aquifères) Mahesha, A.2001Item The effect of subsurface barrier on the motion of the sea water—fresh water interface in coastal aquifers is analysed for sudden freshwater drawdown conditions. A Galerkin finite element model is used for this purpose to carry out the parametric studies of the effect of location, width and hydraulic conductivity of the barrier. The results indicated marked variations in the interface profile as compared to no barrier condition. The width and hydraulic conductivity play a decisive role in delaying the interface response for any drawdown situations. Among the various barrier locations considered, the barrier at initial length of intrusion L0 was found to be most effective in checking the salt water intrusion. © 2002 Taylor & Francis Group, LLC.(Effectiveness of subsurface barrier on salt water intrusion) Mahesha, A.; Babu, M.2002Item The motion of seawater-freshwater interface was studied for the linearly varying hydraulic conductivity in coastal confined aquifers. The problem under consideration included a series of freshwater injection wells located at a certain distance parallel to the coast. The hydraulic conductivity was assumed to be decreasing linearly from the coast towards inland. The motion of the interface was monitored for different gradients of the hydraulic conductivity and compared with the homogeneous case. The results indicated up to 12% lag in the repulsion of the interface depending on the injection rate as compared to the homogeneous case. Log-normal distribution was also considered for the hydraulic conductivity and a specific example is presented for illustrative purposes. © 2004 Taylor & Francis Group, LLC.(Effect of hydraulic conductivity on seawater—fresh water interface motion in coastal aquifers) Mahesha, A.; Satish, M.G.2004Item Transient motion of seawater-freshwater interface in coastal confined aquifers due to a series of injection-extraction well system is studied using an areal finite element model. The seawater near the coast and the freshwater is injected by a series of wells inland. The combined action of freshwater ridge formed by the injection wells and the extraction trough formed by the extraction wells resulted in the reduction of intrusion up to 80%. The well spacing affects the performance of the wells significantly and the spacing of less than 10% of the initial intrusion length was found to be effective in controlling the intrusion. Performance of the combined system of wells proved to be significantly better than the series of seawater extraction wells alone. The results from the present study would be useful in designing the system of injection-extraction wells in coastal aquifers to combat seawater intrusion.(Motion of seawater interface due to freshwater injection seawater extraction barrier) Mahesha, A.; Satish, M.G.2004Item Effect of permeability of subsurface barrier on salt water intrusion in coastal aquifers(2006) Mahesha, A.; Lakshmikant, K.Semi-pervious, subsurface barriers are considered to be one of the viable solution for the control of saltwater intrusion in coastal aquifers. Investigations are carried out in this work to assess the performance of the barrier with different permeabilities using a finite element model. The advancement of saltwater - freshwater interface and the water table profiles are monitored for fresh water withdrawals at inland locations under the scenarios of wide ranging hydraulic conductivities of the barrier. The results indicated that barrier is able to check the advancement of the intrusion significantly with the hydraulic conductivity being less than certain limit. The performance of the barrier is also compared with no barrier conditions. Marked variations in the interface and water table profiles are observed as compared to no barrier condition. The performance of the barrier was not found to be satisfactory beyond certain limit of permeability.Item Tropical river basin development- a case study in selection of sites for vented dams(2008) Shetkar, V.S.; Mahesha, A.Scarcity of water in various parts of the country is of major concern in the recent years. Even places with very high annual rainfall face the water shortage during the non-monsoon months. This indicates scope for the improvement in planning, development and management of water resources. Dakshina Kannada, a coastal district of Karnataka, on an average receives more than 3000 mm of annual rainfall and still faces acute shortage of drinking water during the summer months. The river Netravathi which is a tropical, seasonal river of the district is the major source of water for the region including rapidly progressing Mangalore city with a population of more than 5 lakhs. Due to the hydro-geological characteristics of the area, construction of major dams across the rivers is not feasible. Under these circumstances, construction of small structures such as vented dams may be appropriate in conserving the river water. To achieve the required storage and to conserve the river water, a series of such dams is proposed. The average annual yield of the river is about 11,502 Mm3. At present, the amount of utilized is less than 1% and there is large scope for conserving river water. This paper highlights the site selection criterion for the construction of such vented dams across the river Netravathi. These dams when constructed will allow optimal river basin development without causing inundation. The total capacity of the dams is about 101.91 Mm3 with further scope to increase the height of the dams by providing proper bank protection works. The vented dam at the downstream end of the river nearest to the sea also serves the purpose of salt water exclusion, protecting the adjoining aquifers from salt water intrusion during the summer months. © 2008 Taylor & Francis Group, LLC.Item 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.