Spatial distribution of radon in groundwater in the coastal tracts of southern Kerala, India was studied to understand its linkage with the monazite bearing beach sand deposits in the area. The mean radon concentrations were below the guideline value recommended by United States Environmental Protection Agency in about 94 % samples analyzed. Annual effective ingestion and inhalation doses of water-borne radon were found to be well below the average doses reported from all natural sources. The study indicated that radionuclides in the monazite-rich beach sands do not contribute significantly to the radon concentration in groundwater in the area.

Parts of the coastal tracts of southern Kerala, India are among the well-known High Background Radiation Areas (HBRA) of the world, attributed to the presence of radionuclides in the monaziterich beach sand deposits. A comparative study of the radon concentrations in groundwater in the high and normal background radiation areas in the coastal tract has been taken up using analytical data of 24 ground water samples collected from tube wells of ranging in depth from 6.0 to 300.0 m. The radon concentration in the samples ranged from 0.88 to 25.80 Bq.L-1. The mean radon concentration in the study area, including those from the HBRA are within the maximum contamination levels of 300 pCi.L-1 (11.10 Bq.L-1) recommended by the United States Environmental Protection Agency except for a sample collected from Chavara. Groundwater from the high background radiation areas has significantly higher concentrations of radon ranging from 2.84 - 25.80 Bq.L-1 when compared to the normal background areas where the concentrations range from 0.86 - 7.46 Bq.L-1. Radon concentration does not show significant correlation with depth of sampled wells. The mean annual effective doses of ingestion and inhalation from water-borne radon, though comparatively higher in HBRA, are well below the average doses reported from all natural sources.

Hydrogeochemical characteristics of groundwater in phreatic aquifers of Alleppey district were studied. Factor analysis has been applied to the chemical analysis data of 32 water samples collected from dug wells to extract the principal factors corresponding to the sources of variation in the hydrochemistry. 12 hydrochemical parameters were correlated and statistically examined. Varimax rotation was used to define the factor scores and percentage of variance in the hydrogeochemistry. A four-factor model is extracted and explains over 80.394% of the total groundwater quality variation. Factor-1 has high loading values of Electrical Conductivity (EC), Ca ++ , and Cl -, and reflects the signature of saline water. Similarly strong correlation exists between F3 score and pH. The correlation coefficient matrix between EC and Na + , Cl -, SO 4 --is significant. The mineralogy of coastal aquifers and the marine aerosol are playing significant role in the hydrogeochemistry of groundwater in the phreatic aquifer system.

Kuttanad near the western coast of Kerala is a low lying area below mean sea level. The hydrogeological scenario in this wet land dominated tract, known as kole lands, was investigated by using the lithological and geophysical data generated under the R&D exploration programme of Central Ground Water Board (CGWB) during the year 2000, as also other related data generated till the year 2009. The hydrogeology of the tract is complex, and the presence of carbonaceous and organic matter in the soil and sub-soil influences the geochemical and geo-electric characteristics of the sub-surface geological formations as reflected by SP and resistivity logs. The lithologs and geophysical logs of bore wells were used to define the aquifer geometry. While the lateral and vertical variations of the aquifer systems identified were high, the bottom aquifer was relatively brackish over a large area. The gamma log behavior in these granular zones is anomalous and misguiding in nature. The radioactivities recorded against clay horizons were in the range of 130 to 200cps and in the granular zones 150 to 350 cps. The presence of monazite bearing sands at certain depths was responsible for anomalously high gamma counts against granular zones. The water quality in the granular zones was inferred from the electrical logs. The depth of occurrence of high radiation sand beds was also demarcated.

There are 36 islands in Lakshadweep archipelago, of which 10 are inhabited. The study focuses on the hydrogeological conditions prevailing in nine of these inhabited islands. Groundwater is the major source of fresh water and the well density is high in the range of 296 to 620 per km 2 . The aspect ratios of these islands indicate that the shape of the islands have significant role on the stability of fresh water lens. The changes in water level do not reflect the real changes in the water resources as it is greatly influenced by tides. Moreover, the Ghyben-Herzberg relation in its ideal form does not hold good in these tiny oceanic islands. Hence, the rainfall recharge in the islands was assessed based on daily water budgeting. A relation between water surplus and annual rainfall could be established. This approach of recharge estimation could be applied for similar oceanic islands.