Effects of salinity intrusion and pollution on the carps sanctuary Halda river

The Halda River is located in the Ramgarh Upazila under Khagrachari district, Bangladesh, which is one of the most important natural fish breeding grounds in Bangladesh from where carp fish (Catla, Labeo rohita, Labeo calbasu and Cirrhinus mrigala) eggs are collected by local fishermen generally during May to June every year. But due to salinity and pollution occurred by domestic and industrial wastes disposal, open defecations beside river, pesticide and fertilizer mixed discharge from different irrigation fields, spilled oil from various water vehicles, illegal sand mining, etc., this carp sanctuary is under threat. Thus, this research aims to deal with the investigation of salinity intrusion and water pollution of the river. Salinity tests during high tide, low tide and during rainfall have been performed from 17 sampling locations at about 500 m interval from the confluence of the Karnuphuli River. Based on the experimental results, from station number 11 to 17 the salinity concentration is over the standard value (600mg/l) and it increased accordingly. Moreover, the worst value found in the sample station 17 at Mohona and the value is 2,000 mg/l during high tide, which is over three times of standard value. But on the other hand, during low tide the salinity concentration (max. 375 mg/l) is below the standard value. Water quality parameters tests, such as, pH, Alkalinity, Chloride, CO2, Turbidity, Hardness, TS, TDS, TSS, DO, BOD5, Heavy metal tests were carried out by taking water samples from confluence point, salinity free location during low tide and high tide, respectively. The test results are compared with World Health Organization (WHO) and Bangladesh Environmental Conservation Rules (BECR) standards and a few parameters are found to be unsatisfactory for the carps. Among them Turbidity value was 62.70 NTU and Alkalinity was 186.67 mg/l, which is higher than the standard limit. Hygienic sanitation system, controlled use of fertilizers and pesticides, establishment of central ETP, enforcement of existing regulations and construction of tidal regulators are suggested to be practiced to save this sanctuary.