Assessment of Gar Gar River Water Quality by Macrobenthic Community and BMWP Index

This study was conducted to assess water quality of Gar Gar River based on macrobenthic communities and  BMWP index during January 2014 to 2015. By monthly sampling was done from 7 selected stations by using Peterson grab and surber with cross-sectional area of 225 cm2. For measuring to total organic matter physical method of burning in an electric furnace was used and to analyze Grain  size of sediment, the screen series method was used.  The total number of 19 class, 58 families (41 genus, 16 species)  of Macrobenthos identified and counted in this survey. The highest number of individuals belonged to different families of Arthropoda (52.6 %), Mullusca (25 %), Oligochaeta (22 %) and other groups (0.4 %) respectively. The maximum density belonged to Tubifex sp. (Oligochaeta), Astrosimulium sp. (Diptera) and Melanoides tuberculatus (Gastropoda) respectively. According to the results of annual mean of BMWP index the Gar Gar River stations are classified in three categories. During the study period, stations 1and 2 were moderate,  stations 6 and 7 were poor and stations 3, 4 and 5 were very poor. Also ASPT index showed all stations were classified as high-probable contaminated.