The present investigation was conducted in the remnants of old channel of Jia Bharali called as Mara Bharali at Tezpur in the Sonitpur district of Assam during the period from January to December, 2017. Five sampling stations were selected from Pumpani village (N-26º45'10.52" and E-92º50'07.93") to Maithan (N-26º37'05.69" and E-92º49'34.34"), Tezpur where Mara Bharali meets the river Brahmaputra. The 05 sampling stations has been demarcated as MB5 (Pumpani village, N-26º45'10.52" and E-92º50'07.93"), MB4 (Amlopam village, N-26º41'16.84" and E-92º48'58.88"), MB3 (Dolabari village, N-26º40'00.65" and E-92º49'43.64"), MB2 (Porowa Bridge, N-26º39'10.05" and E-92º47'49.28") and MB1 (Maithan, N-26º37'05.69" and E-92º49'34.34") that covers a stretch of 16.5 km. The mean water temperature, transparency, TDS, dissolved oxygen, free CO2, hardness, alkalinity and pH were found to be within the WHO permissible limits. However, turbidity was found to range between 58 NTU and 228.5 NTU which is above WHO permissible limits. Twenty (20) species of aquatic insects belonging to 13 families and 7 orders were identified from five sampling stations. Laccotrephes sp., Notonecta sp., Hydaticus sp. and Hydrophilus sp. were the most abundant species. Insect species were dominated by the orders Hemiptera and Decapoda with 4 and 5 representatives of each respectively. Moreover, six (6) molluscan species belonging to 5 different families, Viviparidae, Planorbidae, Pachychilidae, Ampullariidae and Bithyniidae were identified with most dominant species being Gyrulus convexiusculus, Brotia costula and Pila globosa.