Physicochemical Analysis of Surface Water in Rohri Canal from Sukkur Barrage to Mehrabpur

Abstract

The purpose of this study was to assess the effect of domestic and industrial waste discharge on the surface water quality of Rohri Canal in the stretch of the canal from Sukkur Barrage to Mehrabpur town. Eight sampling points were selected along the canal focusing on canal locations near major settlements. The parameters studied were temperature, pH, turbidity, hardness, alkalinity, total dissolved solids and suspended solids, chlorides, biochemical oxygen demand (BOD), chemical oxygen demand (COD) and E-coli. The average value of BOD and COD at the sampling stations were recorded as 212 mg/L and 423 mg/L respectively, which exceed the permissible surface water limits for drinking and irrigation purposes. The results indicate significantly higher value of BOD in sampling locations where there are major settlements and there is a continuous inflow of untreated sewage into the canal. The pH values at all the sampling sites were found within the drinking and irrigation water quality standards whereas the TDS values at only sampling stations (3 and 4) exceeded these limits. The turbidity values of the samples ranged from 237 to 821 NTU, exceeding the WHO drinking water quality standards for this parameter. The values of the water quality parameters including hardness (range 146 to 300 mg/L), chlorides (range 36 to 103 mg/L) and alkalinity (range 120 to 230 mg/L) were found well below the limits of WHO drinking water quality standards. The turbidity values of the samples ranged from 237 to 821 NTU and exceeded the WHO drinking water quality standards for this parameter. At all the sampling sites located near major settlements low levels of dissolved oxygen and the presence of E.coli were recorded. The results revealed that the continuous inflowing of untreated or un-treated sewage and industrial effluents into the canal has changed its physicochemical and biological characteristics, which make it unfit for human consumption and can have long-term irrevocable ecological threats if left unmanaged