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Unexpected mistreatment of groundwater from coastal aquifers may possibly cause salt water intrusion in coastal aquifers. Coastal areas are mostly overpopulated with productive agricultural lands and expanded irrigated farming actions. Field and modeling studies were started to consider the special effects of possible seawater intrusion into the coastal aquifers. Groundwater levels were measured at 61 locations in Nagapattinam and Karaikal coastal region, identified flow direction pointing toward the coast with no major change in groundwater table. Groundwater samples were collected and analyzed for major ionic parameters, represented higher concentration of conductivity, total dissolved solids, sodium and chloride along the coastal parts of the study area. A computer package for the simulation of dimensional variable density groundwater flow, SEAWAT, has been used to model the seawater intrusion in the coastal aquifers of the study area. The model was stimulated to predict the amount of seawater incursion in the study area for a period of 50 years. The simulation results signify saline water intrusion mainly due to up coning of saline water owing to over drafting of groundwater.

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ABSTACTThe absence of perennial river, semi arid climatic condition and growing neediness of water increased the usage of groundwater. In the area proposed for the study, all the water necessities are fulfilled with groundwater. Hydrochemistry of groundwater is influenced by geogenic and anthropogenic sources. Hence to assess the chemical characteristics of groundwater in the study area, a total of 74 groundwater samples were collected and analyzed for physical parameters such as pH, conductivity and Total Dissolved Solids along with major cations and anions using standard procedures. The dominant cations and anions were, Na ˃ Ca ˃ Mg ˃ K and HCO ˃Cl> NO3 ˃ F ˃ PO4 ˃SO4 respectively. Hydro chemical facies demarcated were NaCl , CaNaHCO3 , CaHCO3 and CaMgCl. The facies suggests ionic exchange, dissolution, silicate weathering and anthropogenic sources are responsible for the variation in groundwater chemistry of the study area. The silicate group minerals show over equilibrium conditions sulphate and halide group minerals indicate under saturation condition. The saturation values trend increases along the flow path. Identified hydro geochemical process were verified and quantified using hydro geochemical inverse mass-balance modeling (net geochemical reactions along a flow path,PHREEQC,WATQ4F).

Modeling hydrogeologic processes facilitates in accurate prediction/forecasting of groundwater level variations. Still, the uncertainty in model prediction is a major concern that requires detailed investigation. There could be several factors which introduce uncertainty such as inherent assumption, various levels of model complexity and simplicity. In general, model inputs, parameters and structure are the major sources of uncertainty while quantifying model prediction uncertainty. In this study, a genetic programming (GP) based models have been employed for forecasting groundwater level variation along with prediction uncertainty quantification. Though various sources induce uncertainty in the model prediction, the input uncertainty quantification has received little attention. Hence, the input uncertainty has been considered for the analysis in this study. The proposed method is demonstrated using measured monthly values of rainfall and corresponding groundwater level data of Amarawathi basin, India. It is observed that the prediction along with uncertainty quantification improves the confidence level of models while making decisions, in particular for effective planning and management of groundwater resources.

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White spot syndrome virus (WSSV) is one of the most prevalent, widespread and devastating pathogen associated with shrimp population. The present study was aimed at screening the wild caught shrimps from Andaman and Nicobar Islands (ANI) for WSSV infection. Shrimp samples of different penaeid species including and collected from nine different landing centers across the coast of ANI were screened for WSSV infection. Presence of white spots, a typical clinical sign of white spot disease was observed on the exoskeleton of WSSV infected shrimp samples. Out of 241 shrimp samples, 39 samples of were found positive for WSSV by nested PCR. Histopathological examination revealed eosinophilic to basophilic intranuclear inclusion bodies in gill tissue which are typical characteristics of WSSV infection. Nucleotide sequence of WSSV isolated from ANI showed 100% identity to the sequences of WSSV reported from Thailand, Taiwan, China, Egypt, Mexico, Korea, France and 99% identity to WSSV reported from India. The detection of WSSV in wild of ANI further confirms the virus spread and biogeography.