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Item 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 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 Simulation of varada aquifer system for sustainable groundwater development(2008) Ramesh, H.; Mahesha, A.Groundwater flow modeling has been used extensively worldwide with varying degrees of success. The ability to predict the groundwater flow is critical in planning and implementing groundwater development projects under increasing demand for fresh water resources. This paper presents the simulation of the aquifer system for planning the groundwater development of Varada basin, Karnataka, India using the Galerkin finite-element method. The government of Karnataka State, India is implementing the World Bank assisted project, "Jal Nirmal" for a sustainable development of the region, thereby ensuring a safe supply of drinking water to the northern districts of the state. Varada basin is one of the beneficiaries of the project in Haveri district. Field tests carried out in the study area indicate that the region is predominantly a confined aquifer with transmissivity and storage coefficients ranging from 5.787×10-6m2/s (0.500 m2/day) to 4.213×10-3m2/s (3.640×102m2/day) and 0.011-0.001× 10-2, respectively. This study mainly emphasizes the spatial and temporal variability of groundwater potential under different developmental scenarios. The model predictions were reasonably good with correlation coefficients ranging from 0.78 to 0.91 with the root mean square error of about 0.46-0.78 during calibration and validation. The stated accuracies are based on comparisons between measured and calculated heads. The outcome of the study would be a useful input for the conjunctive use of surface water and groundwater planning for the sustainable development of the region. © 2008 ASCE.Item Conceptual model for the safe withdrawal of freshwater from coastal aquifers(2009) Mahesha, A.The effect of subsurface barrier on the motion of the saltwater-freshwater interface in coastal aquifers is analyzed for wide ranging freshwater pumping scenarios. A Galerkin finite-element model considering sharp interface approach is used for this purpose. A semi-pervious subsurface barrier extending up to impervious bottom of the aquifer is considered at certain distance inland, parallel to the seacoast. The effect of barrier is analyzed in checking the advancement of the saltwater-freshwater interface under different scenarios of freshwater withdrawals at seaward and landward locations of the barrier and compared with nonbarrier conditions. The results indicated that barrier is able to check the advancement of the intrusion significantly and in certain cases, the progress is completely stalled for withdrawals on the landward side. Also, marked variations in the interface profile are observed as compared to no barrier condition, especially, for the seaward freshwater developments. From the model, nearest possible locations from the seacoast have been worked out for the safe withdrawal of freshwater where their effects are negligible on the saltwater advancement. © 2009 ASCE.Item Tropical, Seasonal River Basin Development through a Series of Vented Dams(2011) Shetkar, R.V.; Mahesha, A.Tropical rivers are predominantly seasonal in nature, and managing water resources during the deficit period is becoming more difficult because of the rapidly increasing demand for water. The present investigation focuses on harvesting Netravathi River water in the southern Indian peninsula through a series of vented dams with an estimated storage capacity of 102 Mm3 for use during the deficit period. A brief hydraulic design of a vented dam at a specific location is presented. The spacing and capacity of these reservoirs were worked out on the basis of the dam height and the river characteristics. The proposed vented dams are seasonal dams, and the closure of the vents will be decided on the flow available (i.e., 95% dependable flow), the storage capacity, and the minimum water release required for the downstream ecosystem. The appropriate time to start storing water in the vented dams was estimated to be in the month of November, and the entire process of storing water in the vented dams may last for about 41 days. An operational protocol for the storing process is presented. The investigations of aquifer parameters were performed by using electrical resistivity, pumping, and soil tests. The results indicated that the aquifer is shallow, unconfined in nature, and had a depth ranging from 18 to 30 m and hydraulic conductivity ranging from 62.6 to 406 m/day. A multiple regression model developed to assess the groundwater recharge in the adjoining well fields indicated that water table fluctuations may be 30% of reservoir level fluctuations. Because the river is also tidal in nature, a saltwater exclusion dam is proposed at the lower reaches of the river to prevent the entry of saltwater along the river during the summer period. © 2011 American Society of Civil Engineers.Item Terrain analysis and hydrogeochemical environment of aquifers of the southern west coast of Karnataka, India(2012) Honnanagoudar, S.S.; Venkat Reddy, D.; Mahesha, A.Dakshina kannada district is situated in peninsular region. The peninsula is composed of geologically ancient rocks of diverse original and most of them have undergone metamorphism. The early Precambrian tonalitic gneisses invaded by granites, granulites and dolerite dykes. Granulites are mostly restricted to areas south of Mangalore. High grade alumina rich (corundum bearing) metamorphic schists have been encountered and younger alkaline intrusive rocks like Aegerine syenites have been reported. There are five rivers and estuaries. Number of lineaments cut across each other and some lineaments are parallel to each other. The Arabian sea class is the largest among other land cover features in the study area. The river/tidal creek land cover appear as long irregular and sinous in outline. Mulki river, Netravati river, Gurupur river at southern terrain. The qualities of groundwater at sandy aquifer are good, lateritic/weathered gneissic rocks it is sweet. © 2012 CAFET-INNOVA TECHNICAL SOCIETY.Item 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.Item Saltwater intrusion in coastal aquifers subjected to freshwater pumping(2014) Mahesha, A.; Lakshmikant, P.Investigations are carried out to analyze the effect of freshwater pumping on saltwater intrusion in coastal aquifers in the presence of a semipervious subsurface barrier along the coast. A conceptual, unconfined aquifer with a subsurface barrier subjected to simultaneous freshwater pumping at single/multiple locations perpendicular to the coast is considered for the analysis. The location, width, and the conductivity of the subsurface barrier being held constant, the effect of freshwater pumping at seaward and landward locations from the barrier is investigated on the interface motion. The performance of the barrier is compared with a nonbarrier condition. The numerical model developed predicts the behavior of the saltwater-freshwater interface and the piezometric surface due to simultaneous pumping at single/multiple wells across the sea cost. The barrier is effective in checking the progress of saltwater for freshwater pumping on the landward side of the barrier compared to no barrier condition. The freshwater pumping on the seaward side of the barrier should be limited to smaller rates. Additionally, safer zones for simultaneous freshwater withdrawal are identified for single, two, three, and four wells without the advancement of saltwater intrusion. The results obtained are of general nature and would be useful in determining the ideal location and rate of freshwater withdrawal minimizing the saltwater intrusion in coastal aquifers. © 2014 American Society of Civil Engineers.Item Predictive Simulation of Seawater Intrusion in a Tropical Coastal Aquifer(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2016) Lathashri, U.A.; Mahesha, A.The solute transport in a tropical, coastal aquifer of southern India is numerically simulated considering the possible cases of aquifer recharge, freshwater draft, and seawater intrusion using numerical modeling software. The aquifer considered for the study is a shallow, unconfined aquifer with lateritic formations having good monsoon rains up to about 3,000 mm during June to September and the rest of the months almost dry. The model is calibrated for a two-year period and validated against the available dataset, which gave satisfactory results. The groundwater flow pattern during the calibration period shows that for the month of May a depleted water table and during the monsoon month of August a saturated water table was predicted. The sensitivity analysis of model parameters reveals that the hydraulic conductivity and recharge rate are the most sensitive parameters. Based on seasonal investigation, the seawater intrusion is found to be more sensitive to pumping and recharge rates compared to the aquifer properties. The water balance study confirms that river seepage and rainfall recharge are the major input to the aquifer. The model is used to forecast the landward movement of seawater intrusion because of the anticipated increase in freshwater draft scenarios in combination with the decreased recharge rate over a longer period. The results of the predictive simulations indicate that seawater intrusion may still confine up to a distance of approximately 450-940 m landward for the scenarios considered and thus are sustainable. © 2015 American Society of Civil Engineers.Item Groundwater level modeling using Augmented Artificial Ecosystem Optimization(Elsevier B.V., 2023) Nguyen, N.; Deb Barma, S.D.; van Lam, T.; Kisi, O.; Mahesha, A.Nature-inspired optimization is an active area of research in the artificial intelligence (AI) field and has recently been adopted in hydrology for the calibration (training) of both process-based and statistical models. This study proposes an improved AI model, Augmented Artificial Ecosystem Optimization-based Multi-Layer Perceptron (AAEO-MLP), to build a monthly groundwater level (GWL) forecasting model. AAEO-MLP model is built on the novel Augmented version of Artificial Ecosystem Optimization and traditional MLP network. In AAEO, Levy-flight trajectory and Gaussian random are utilized in exploration and exploitation to improve the optimizing ability. The AAEO-MLP model is tested on two time-series (1989–2012) datasets collected at two wells in India. Various explanatory variables such as monthly cumulative precipitation, mean temperature, tidal height, and previous measurements of GWL were considered for predicting 1-month ahead of GWL. The performance of AAEO-MLP was benchmarked against 17 different models (original AEO, 3 different variants of AEO, and 13 well-known models) in terms of forecasting accuracy based on six metrics (e.g., mean absolute error, root mean square error, Kling–Gupta efficiency, normalized Nash–Sutcliffe efficiency, Pearson's correlation index, a20 index). Furthermore, convergence analysis and model stability are employed to indicate the effectiveness of AAEO-MLP. The compared results express that the AAEO-MLP is superior to other models in terms of prediction accuracy, convergence, and stability. Overall, the results depict that the AAEO is a promising approach for optimizing machine learning models (e.g., MLP) and should be explored for other hydrological forecasting applications (e.g., streamflow, rainfall) to further assess its strengths over existing methods. © 2022 Elsevier B.V.