Hydro-Morphological and Water Quality Changes of Shitalakhya River and their Effects
Shitalakhya, one of the main circulating rivers of Dhaka city, has ample importance in navigation, industrial purpose and economy of Bangladesh. The parent river of Shitalakhya is Old Brahmaputra. The main purpose of this study is to analyze hydrological and morphological characteristics and about the quality of water and its effects. All data for several parameters of Shitalakhya River were collected for specific years from Bangladesh Water Development Board (BWDB). By collecting and analyzing the hydrological data for the discharge at station SW179(Demra) and for the water level at station SW177(Lakhpur) & SW179(Demra) showed a declining trend in the maximum annual discharge and water level. From the Flow Duration Curve, the flow at 5.88% exceedance, it is 2587.2 m3/s(maximum) for the month of September, this is the higher flow rate, so basically the flow is at this flow or at a higher flow for 5.88% of the time. Using the graph of Flood Frequency Curve , the flow value corresponding to 5-year return period event for the Shitalakhya River at Demra (SW179), is approximately equal to 1700 m3/s. Observing the variations of cross sectional area, top width, average width and minimum bed level at eight (L-4, L-6, L-8, L-10, L-12, L-14, L-16 and L-18) sections for 2001, 2009 and 2015, Shitalakhya River is not changing its course with time rapidly. But the cross-section of the river showed slightly increased during 2001 to 2015 and from 1981 to 2003 showed a decreasing trend. The water quality with different parameters such as Dissolved Oxygen, Salinity, pH, Total Dissolved Solids, Electrical Conductivity and Concentration of Iron have been examined for several years (2012 to 2017) at Narayanganj station. Studying the parameters, we can say that the mean value of DO in the year 2017 was 1.57 mg/L. High levels of Salinity, TDS, EC were found in Shitalakhya from January to April and conversely tends to decrease from May to December. Water quality data analysis reveals that river water deteriorates in December and reaches the worst condition in April as well as in May and then starts to improve.
Hopefully, the present study on hydro-morphology and water quality of Shitalakhya River will possess a great importance in taking any necessary steps to protect this river.
Keywords - Shitalakhya River, Hydrological Analysis, Morphological changes, Water quality trend.