Impacts of Climate Change on Water Quality in Selected Coastal Areas of Bangladesh

Abstract

A hydro-meteorological study was conducted at Kalapara Upazila in Patuakhali District to assess the impacts of climate change on water quality in coastal areas of Bangladesh. Some secondary meteorological data of Khepupara (now Kalapara) station from 1975 to 2017 from BMD and mean sea level and salinity data of few decades from BWDB, SRDI, and PSMSL have been collected for the present study. The water samples from the selected estuaries, rivers, canals, ponds, and tube-wells have also been collected during the pre-monsoon, monsoon, and post-monsoon seasons of 2016 and 2017. Some major water quality parameters, including water temperature, DO, pH, EC, TDS, TSS, Na+, K+, Ca2+, Mg2+, Fe, Cu, Pb, Mn, As, Zn, Cl-, SO42-, NO3-, HCO3 – and PO43- were analyzed and the interpretation was made to determine the present water quality of the area using various diagrams, indices, formulas, and graphs. The meteorological data showed significant positive increasing trends of annual average temperature, relative humidity, and rainfall. The annual average temperature increased to 0.7oC, and the projected trend line is likely to raise 1.2oC by the year 2050. The study estimated that the projected relative humidity and rainfall would be increased by 6.6 % and 234.7 cm, respectively, by the same period. The available secondary tide gauge data of four stations named the Cox’s Bazar, Khepupara, Hiron point, and Diamond Harbor were assessed and found a positive increasing trend. The higher increasing trend was observed at Khepupara station of the study area. The results showed that the water level of the Khepupara station would raise to 1.35 m by the year 2050. The EC level of the Andhermanik river increased 2.54 ds/m from 2000 to 2015 and will be increased by 8.09 ds/cm by the year 2050. The water samples of the estuaries, rivers, and canals showed a higher salinity during the pre- and post-monsoon seasons. The results showed higher EC, TDS, and TSS values during the dry seasons. The major ions, including Na+, K+, Cl-, SO42-, and HCO3- exceeded the permissible limit of the DoE, WHO, and FAO standards during the pre- and post-monsoon periods. The study observed the dominant water type during the pre- and post-monsoon periods was Na-Cl, whereas a mixed water type, Na-Cl-HCO3, was found in the monsoon period. The study evaluated the water quality for specific uses such as irrigation, domestic, and drinking purposes. The water quality of the estuaries, rivers, and canals was found to be poor to unfit for all purposes during the pre-monsoon season, furthermore, the water quality turned into good quality in the monsoon and post-monsoon seasons. The selected pond waters showed good quality for irrigation uses especially in the monsoon season, nevertheless, a few pond water showed poor quality during the pre and post-monsoon seasons. The tube-well waters showed good quality except for the few water samples of the estuarine areas during the pre-monsoon season. However, all of the groundwater samples were found good quality during both the monsoon and post-monsoon seasons. The study results illustrated that the humidity, rainfall, mean sea level, and EC of the coastal areas showed a positive correlation with temperature. It showed that the increased temperature remarkably influenced the seawater level and salinity in the coastal watershed. The study exhibited a good correlation with existing EC and WQI values, indicating that EC values have great influences on the water quality of the coastal areas. As the EC level of the coastal watersheds was increased from 2000 to 2015. Hence, it is expected that it would severely affect the water quality in the areas by the three to four decades. The study recommends the appropriate adaptation and mitigation options to reduce further degradation of the coastal water quality as well as the entire coastal environment.