ABSTRACT
The coastal people have to sustain facing severe natural disasters, which are very frequent and caused by enormous natural and manmade events. The Government of Bangladesh (GOB) has undertaken the implementation of the Coastal Embankment Improvement Project with the loan assistance of World Bank (WB) and grant assistance of the Climate Investment Fund’s Pilot Program for Climate Resilience (PPCR). The project is likely to involve significant adverse environmental impacts that are sensitive, diverse, or unprecedented, which may affect an area broader than the facilities subject to physical works. The aim of the present research study was to know the quality of water for aquatic and irrigation purposes. So, the study was conducted with the water samples from adjacent surface water sources, where Polder up-gradation work is being implemented by Bangladesh water development board (BWDB). Water samples collected from adjacent rivers and khals (cannels) were analyzed against National/International permissible limits for aquatic and irrigation water quality. Water pH, Turbidity, Total dissolved solids (TDS), Dissolved oxygen (DO) and Biochemical Oxygen demand (BOD5). The results revealed that in most cases water bodies of Polder areas had the pH range within the standards of Department of Environment Bangladesh (DoE), The Environment Conservation Rules-1997 (ECR) and World Health Organization (WHO) for irrigation purposes. In most cases, the value of Turbidity was less than 25 Nephelometric Turbidity Unit (NTU), indicating that the water sample was not harmful for irrigation purposes. The TDS values of the water samples in the study area ranged from 1502.40 to 2630.40 mg/l, with an average value of 2044.27 mg/l. The levels of BOD5 ranged from 2.30 to 14.98 mg/l with an average value of 7.39 mg/l, which meets the ECR standards. It is well known that if the dissolved oxygen levels in the water bodies decreased by less than 6.00 mg/l life in the water bodies around the research area can come under pressure for aquatic ecosystem according to the standard from ECR (1997) ( but secure according DoE, 1997).
Key words: water quality, coastal, construction work, polder.
Introduction
The coastal area of Bangladesh is composed of the plain sea part of the Ganges Delta, which is shrunk by large tidal rivers flowing into the Bay of Bengal. The alluvial and aquatic river systems of the coastal region are formed by long periodic deltaic recognition that was transformed into the Ganga and Brahmaputra or historical patterns. The main estuarial rivers in the south-central region are connected and fed by numerous small channels. The coastal region has an estimated population of 40 million and they are very much vulnerable to the natural disaster along with an area of about 720 km coastline. The people of coastal region have to sustain their livelihood facing severe natural disasters which are very frequent and cause d enormous damages. As a result, the livelihoods of coastal people become uncertain as they have to struggle with nature throughout the whole year. They cannot lead a happy and peaceful life since frequent natural disasters tend to sweep away their means of living and other properties (Akter, 2009). Water logging condition in coastal area are becoming a regular dilemma day by day, so many people cannot afford to cultivate crops in a major portion of land every year. Most of the phenomenons are vulnerable with the changing conditions, but climatic circumstances are sets of difficulties that cannot be controlled through a program (Ferdousi, 2010; Yesmin et al., 2013). The cultivable lands in these coastal areas are being affected with varying degrees of soil salinity and other natural hazards. To combat the worst situations, Polderization began in the early sixties to protect land and other human resources from the tidal floods. It also provides to control the salinity infiltration and sedimentation.
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