Delineation of groundwater recharge zones and identification of artificial recharge sites in West Medinipur district,West Bengal,using RS,GIS and MCDM techniques

Artificial recharge plays a pivotal role in the sustainable management of groundwater resources. This study proposes a methodology to delineate artificial recharge zones as well as to identify favorable artificial recharge sites using integrated remote sensing (RS), geographical information system (GIS) and multi-criteria decision making (MCDM) techniques for augmenting groundwater resources in the West Medinipur district of West Bengal, India, which has been facing water shortage problems for the past few years. The thematic layers considered in this study are: geomorphology, geology, drainage density, slope and aquifer transmissivity, which were prepared using IRS-1D imagery and conventional data. Different themes and their corresponding features were assigned proper weights based on their relative contribution to groundwater recharge in the area, and normalized weights were computed using the Saaty’s analytic hierarchy process (AHP). These thematic layers were then integrated in the GIS environment to delineate artificial recharge zones in the study area. The artificial recharge map thus obtained divided the study area into three zones, viz., ‘suitable,’ ‘moderately suitable’ and ‘unsuitable’ according to their suitability for artificial groundwater recharge. It was found that about 46% of the study area falls under ‘suitable’ zone, whereas 43% falls under the ‘moderately suitable’ zone. The western portion of the study area was found to be unsuitable for artificial recharge. The artificial recharge zone map of the study area was found to be in agreement with the map of mean groundwater depths over the area. Furthermore, forty possible sites for artificial recharge were also identified using RS and GIS techniques. Based on the available field information, check dams are suggested as promising artificial recharge structures. The results of this study could be used to formulate an efficient groundwater management plan for the study area so as to ensure sustainable utilization of scarce groundwater resources.     

Sea level rise and tigers: predicted impacts to Bangladesh’s Sundarbans mangroves

The Sundarbans mangrove ecosystem, shared by India and Bangladesh, is recognized as a global priority for biodiversity conservation. Sea level rise, due to climate change, threatens the long term persistence of the Sundarbans forests and its biodiversity. Among the forests’ biota is the only tiger (Panthera tigris) population in the world adapted for life in mangrove forests. Prior predictions on the impacts of sea level rise on the Sundarbans have been hampered by coarse elevation data in this low-lying region, where every centimeter counts. Using high resolution elevation data, we estimate that with a 28 cm rise above 2000 sea levels, remaining tiger habitat in Bangladesh’s Sundarbans would decline by 96% and the number of breeding individuals would be reduced to less than 20. Assuming current sea level rise predictions and local conditions do not change, a 28 cm sea level rise is likely to occur in the next 50–90 years. If actions to both limit green house gas emissions and increase resilience of the Sundarbans are not initiated soon, the tigers of the Sundarbans may join the Arctic’s polar bears (Ursus maritimus) as early victims of climate change-induced habitat loss.     

Correlation between nitrate contamination and ground water pollution potential

AQUIPRO, a PC-based method, was used to assess aquifer vulnerability using digital water well logs. The AQUIPRO model is a parameter/factor weighting system for rating the pollution potential of an aquifer. This method uses the well depth, as well as the clay and partial clay thickness in a well, to generate pollution potential scores. In this model, aquifer protection increases as the AQUIPRO vulnerability scores increase and ground water pollution potential decreases. Computerized water well records of 2435 domestic wells with partial chemistry data were used to determine the ground water pollution potential of Kalamazoo County, Michigan. Theoretically, low AQUIPRO pollution potential scores should have more frequent occurrences of ground water contamination events than areas with high AQUIPRO scores with similar land-use, well construction, and well densities. The relative AQUIPRO scores were compared with the frequency of occurrences of nitrate-N in ground water wells. The average nitrate-N concentrations within each relative AQUIPRO vulnerability scores category were also compared. The results indicate that domestic wells containing 5 mg/L or more nitrate-N showed a positive correlation between the frequency of occurrences of nitrate-N and relative decrease of AQUIPRO (r2 = 0.99) vulnerability scores. In other words, as the ground water pollution potential increases, the occurrence frequency of nitrate-N also increases. Furthermore, the results show that as the relative AQUIPRO (r2 = 0.96) vulnerability scores decrease, the mean nitrate-N concentrations also increase.     

An index to assess agricultural drought in India

Summary Crop drought or moisture stress is a function of the difference between actual evapotranspiration and evapotranspiration requirements of the crop under given atmospheric conditions.In the present work the climatic water balance approach is utilized to develop a crop moisture index for the kharif crop season over India.The difference between actual and climatologically derived evapotranspiration have been accumulated for different consecutive weeks of the crop season and made comparable in time and space through suitable weights. The lowest weighted deficit values have then been used for successive weeks to evolve the Crop Moisture Index. This index enables detection of degree of moisture stress experienced by the crop and can be used in drought monitoring.

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Zusammenfassung Dürre oder Feuchtestreß ist eine Funktion der Differenz zwischen tatsächlicher Verdunstung und dem Verdunstungsbedarf für bestimmte Kulturpflanzen unter gegebenen atmosphärischen Bedingungen. In vorliegender Studie wird die klimatische Wasserbilanz verwendet, um einen Feuchtigkeitsindex für die Kharif-Anbauzeit in Indien zu erstellen.Die Differenz zwischen aktueller und klimatologisch errechneter Verdunstung wurde für einige aufeinanderfolgende Wochen der Erntezeit aufsummiert und durch geeignete Gewichtungen in Zeit und Raum vergleichbar gemacht. Die am wenigsten veränderten Defizitwerte wurden dann für aufeinanderfolgende Wochen zur Errechnung eines Feuchtigkeitsindex herangezogen. Dieser Index ermöglicht die Quantifizierung des für die Pflanzen relevanten Feuchtestresses und kann für die Aufzeichnung von Dürren verwendet werden.

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With 2 Figures     

Change detection study of islands in Hooghly estuary using multidate satellite images

River estuarine environment constitutes a highly dynamic fluvio-morphological setting where processes of accretion and deposition are active. Hooghly estuary, being one of the largest of estuaries in the east coast of India, needs constant monitoring. Multidate satellite images of IRS-1A L1SS-I and Landsat MSS for 1975–1991 period are studied to detect long term morphological changes in this estuary. The study reveals that the estuarine islands like Sagar, Ghorarmara and Suparbhanga are eroding whereas Lohachara islands has completely eroded off Nayachara island near Haldia due to its shape and size bifurcates the river into two channels. The island as revealed from Satellite images is in accretional phase where the total surface area has increased. The study, therefore, indicates that constant monitoring of spatial and temporal changes in this type of environment would help to understand physical processes.     

Adsorption Kinetic Modeling of Safranin onto Rice Husk Biomatrix Using Pseudo‐first‐ and Pseudo‐second‐order Kinetic Models: Comparison of Linear and Non‐linear Methods

Batch kinetic studies were carried out for the removal of safranin from aqueous solution using a biomatrix prepared from rice husk. The adsorption kinetic data were modeled using the pseudo‐first‐order and pseudo‐second‐order kinetic equations. The linear and non‐linear forms of these two widely used kinetic models were compared in this study. In order to determine the best‐fitting equation, the coefficient of determination (r²), the sum of the squares of the errors (SSE), sum of the absolute errors (SAE), average relative error (ARE), hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), and the Chi‐squared test (χ²) were used as error analysis methods. Results showed that the non‐linear forms of pseudo‐first‐order and pseudo‐second‐order models were more suitable than the linear forms for fitting the experimental data. Non‐linear method is thus more appropriate for estimating the kinetic parameters and should primarily be used to describe adsorption kinetics.