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Seasonal Variations of Chemical Properties of Water of the Kaptai Lake, Rangamati, Bangladesh

Mohammed Mukhlesur Rahman
Bangladesh Forest Research Institute, P.O. Box No-273, Chittagong 4000, Bangladesh

M. Mahfuzur Rahman*
Department of Botany, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh

Mohammed Kamrul Huda
Department of Botany, Chittagong University, Chittagong, Bangladesh

Abstract/ Executive Summary:

The chemical properties are the most important factors in the aquatic environment. The present study was carried out to analyze the chemical properties of the water of the Kaptai lake, Rangamati. The investigation was done from December, 2007 to November, 2008, during four seasons in two sites and three sub-sites. The main aim of the present research was to analyze the water quality of the Kaptai lake. Chemical properties of the water of this lake were determined by different standard methods. The chemical properties of water varied in different sites and seasons. The value of pH and dissolved oxygen (DO) was higher in undisturbed (UD) area than in less disturbed (LD) and disturbed (D) area (UD>LD>D). The nitrate (NO3) value was higher in disturbed area than undisturbed and less disturbed area (D>UD>LD). The phosphate (PO4) value was higher in less disturbed area than disturbed and undisturbed area (LD>D>UD). The electrical conductivity (EC), biological oxygen demand (BOD) chemical oxygen demand (COD) were higher in disturbed area than less disturbed and undisturbed area (D>LD>UD). The potassium (K) value was LD>UD>D. The pH value was higher in winter (W) than in late monsoon (LM), early monsoon (EM) and monsoon (M) (W>LM>EM>M). The NO3-1 value was EM>M>LM>W>EM. The PO4-2 value was LM>M>W>EM. The EC value was W>LM>M>EM. The biological oxygen demand (BOD) value was EM> W>LM>M. The DO value was higher in monsoon than late monsoon, early monsoon, and winter (M>LM>EM>W). The COD was EM>M>W>LM. The K value was EM>W>M>LM. The highest value of pH, K, NO₃ and BOD were recorded in the Kaptai hydroelectricity project area (site –A) and the highest value of the DO, EC and COD were recorded in the Longudu area (site-B). This study is the first initiative to assess the detail chemical properties of water of the Kaptai lake.

Keywords: Chemical properties, Water, Seasonal variations, Sites, Kaptai lake.

Location: In two different sites belonging to two Upzilas of Rangamati Hill Tracts district.

Start Date: 00-12-2007

End Date: 00-11-2008

Program Area: Crop-Soil-Water Management

Commodity: Water quality

Objectives:

An attempt has been made to assess the present condition of chemical properties of the water of the Kaptai lake.

Methodology:

The study was conducted from December, 2007 to November, 2008, in two different sites belonging to two Upzilas of Rangamati Hill Tracts district. One was in Longudu Upzila, nearest to Longudu Cantonment and another was in Kaptai Upzila, which was the front site of Kaptai hydroelectricity project area and located in western part of the Kaptai lake. The total area of the lake is 254 square miles and during the rainy season the area becomes to about 400 square miles. The Kaptai lake is the largest lake of the south Asia. Each study site was divided into three sub-sites on the basis of degree of disturbances and human interferences. These were distinguished as disturbed (D) less disturbed (LD) and undisturbed (UD) sites. Data were collected in in four seasons, viz. early monsoon (EM) (March to May), monsoon (M), (June to August), late monsoon (LM), (September to November), and winter (W) (December to February). Chemical properties were determined on the basis of seasons, sites, sub-sites. The water samples were randomly collected from three different sub-sites of each main site on the basis of topography for the chemical analysis in the laboratory. Each water sample was collected from three different depths, such as upper layer (0-10 cm), middle layer (10-25 cm), and the lower layer (25-40 cm). Normally the samples of top water, middle water and deep water were respectively collected into separate bottles (2.00liter plastic bottle). The temperature of water samples was measured at the time of water sampling with the help of mercury thermometer. Eighteen water samples were collected from the two different sites. These water samples were carried to the laboratory and preserved for determining the chemical properties. The value of pH was measured by HANNA digital pH meter (Model H198107). The inorganic nitrogen of water was measured by using the Kjeldahl distillation method (Jacobson, 1966). The phosphorous content of water was determined by ascorbic acid blue color method (Murphy & Riley, 1962). Electrolytic conductivity of water samples was determined by EC meter (Bennet 1, HI 3291, ATC- conductivity probe). Dissolved oxygen (DO) content sample water was determined by using DO meter (Portugal, Model). At five (5) days interval, Biological oxygen demand (BOD) was determined by the dilution method (APHA, 1989). Mohr’s solution was used for the determination of chemical oxygen demand (COD). Potassium content was estimated by Flame Photometric method (APHA, 1989). These results were expressed in mg/l.

Source of Information: Jahangirnagar University J. Biol. Sci. 6(2): 11-17, 2017 (December)

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

This study has exposed that, the total chemical properties of Kaptai lake were increased by different human activities in the study area. The variation in different chemical properties was statistically significant in different seasons and sites. Through this research, a comprehensive status of chemical properties of Kaptai lake water has been obtained. The total chemical properties of the lake water indicate that chemical substances have been added in the water due to the different disturbing interferences. The findings of the study will be useful for the conservation of aquatic flora and fauna of the lake and also for the environment friendly management of the Kaptai lake ecosystem. This study suggests to undertake further research on the influence of water chemical attributes to aquatic flora and fauna of the lake.

Knowledge Management: Journal