The Sundarbans is one of the productive mangrove wetland ecosystems in the Ganges-Brahmaputra delta in Bangladesh. The delta is undergoing rapid ecological changes due to human activity. In the present study, surface water salinity data from 13 rivers of the Sundarbans were collected in order to investigate the saline water intrusion in the mangrove wetlands. Results demonstrate that saline water has penetrated the upstream area as river water salinity has increased significantly in 1976 compared to the year 1968. The soil and river water salinity data also shows that it has crossed the water salinity threshold line in most parts of the Sundarbans wetlands. These observations are due to the construction of Farakka Barrage in 1975, which reduced the water discharge of the Ganges River from 3700 m 3 /s in 1962 to 364 m 3 /s in 2006. The shortage of freshwater discharge to the deltaic area is trailing active ecosystems function, especially in the dry season in the south western region in Bangladesh. The objective of this study is to understand and analyze the present degraded mangrove wetland ecosystems and their negative impacts. The findings of this study would contribute to the formulation of the mangrove wetland ecosystems management plan in the Ganges delta of Bangladesh.

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Data records with equidistant time intervals are fundamental prerequisites for the development of water quality simulation models. Usually long-term water quality data time series contain missing data or data with different sampling intervals. In such cases "artificial" data have to be added to obtain records based on a regular time grid. Generally, this can be done by interpolation, approximation or filtering of data sets. In contrast to approximation by an analytical function, interpolation methods estimate missing data by means of measured concentration values. In this paper, methods of interpolation and approximation are applied to long-term water quality data sets with daily sampling intervals. Using such data for the water temperature and phosphate phosphorus in some shallow lakes, it was possible to identify the process of phosphate remobilisation from sediment.

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