Integrated approach for identifying the factors controlling groundwater quality of a tropical coastal zone in Kerala, India

The present study examined the factors controlling shallow groundwater quality in two coastal panchayaths (viz., Chennam-Pallippuram and Thykkattussery) of Alappuzha district, Kerala, India, for three sampling seasons: pre-monsoon, monsoon and post-monsoon. The hydrochemical analysis shows significant seasonal fluctuations in groundwater quality, which are principally controlled by the climatic seasonality, contributed by the monsoon phenomenon. The groundwater is highly polluted due to organic load, which is manifested as high total and fecal coliform (TC and FC) contents, especially during MON. Fresh water recharge during MON contributes Ca–Mg–HCO3 type waters, whereas Ca–Mg–Cl and mixed cations-Cl types during PRM imply interaction between groundwater and saline/brackish water of the lake surrounding the study area. Such interaction is also evident by various ionic ratios (e.g., Mg2+/Ca2+, Na+/Cl−) as well as the correlation between Cl− and SO4 2−. The Ca2++ Mg2+ versus TZ+ relationship indicates significance of weathering of carbonate and silicate minerals as well as interaction between groundwater and aquifer matrix, which is also supported by the positive chloro-alkaline indices. Isotopic composition of the groundwater and lake water also suggests the influence of fresh water recharge (mainly during monsoon) as well as interaction of groundwater with lake water in controlling groundwater quality. Factor analysis proposes three dominant processes controlling groundwater quality of the region: (1) interaction of groundwater with brackish water of the Vembanad Lake, (2) geogenic/atmospheric sources, such as weathering, groundwater interaction with aquifer matrix, atmospheric inputs and fresh water recharge and (3) diverse anthropogenic sources of contamination (e.g., domestic waste, septic tanks, and agricultural residues). However, relative influence of these factors on groundwater quality varies temporally to form groundwater with differing chemical composition among the seasons. The present study underscores the exigency to ensure availability of safe drinking water for the coastal zones

Flood monitoring using microwave remote sensing in a part of Nuna river basin, Odisha, India

Floods adversely affect the life of people and property in the coastal districts. It is important to delineate the flood extent and pattern which helps in the vulnerability assessment and also to find out the intensity of damages to facilitate future planning and management. The study area is a part of the Nuna river basin, which suffers from the flood disasters frequently. The present study applies microwave remote sensing (RADARSAT-1 images) to monitor extent, depth and duration of 2003 and 2008 floods in the Kendrapara district of Odisha, India. RADARSAT-1 images of 4, 11, 13 and 20 September of 2003 and 18, 20, 22 and 24 September of 2008 were used to monitor the flood extent, duration and depth. The threshold method was used to delineate flood extent which was used for calculating flood duration and depth. Further, vulnerability assessment of the paddy crop was done to obtain intensity of damage in the area from the 2003 and 2008 floods. Field survey was done to verify and assess the generated results. Areas affected by more than 15 days of flood duration and depth of more than 3 m faced maximum loss. Both the years witnessed major floods in this area with an estimated damage of around INR 174 million ($3.6 million) in 2003 and INR 75 million ($1.6 million) in 2008