Background: Freshwater is not only a finite resource but also essential for agriculture, industry and even human existence. The present investigation on seasonal water quality parameters was conducted in the remnants of old channel of river Jia Bharali called as Mara Bharali at Tezpur in the Sonitpur district of Assam from December, 2017 to November, 2020. Methods: Five sampling stations were selected that covers a stretch of 16.5 km. Physico-chemical parameters were determined seasonally by following the standard methods of APHA (1998) and Trivedy et al., 1987. The statistical analyses of the data were done by one way ANOVA using Statistical Package for Social Scientists. Result: TDS in monsoon in all the locations remained lowest (171.33a±3.059 mg/L at MB2) and highest in winter (320.11c±2.441 mg/L at MB3). The pH value is within the permissible limit except for site MB4 during the winter and post monsoon when the values were 6.38±0.146 and 6.44±0.039 respectively. Maximum DO of 7.878d±0.074 mg/L was observed at site MB1 during the winter season and minimum DO of 5.444a±0.047 mg/L was observed at site MB4 during the monsoon season. BOD was recorded below the tolerance limit of 3 mg/L in all sampling stations.

Background: Rapid industrialization, water abstraction and the extensive use of pesticides in agriculture have severe strains on rivers and resulted in deterioration of water quality. The present investigation on certain geomorphological aspects and fish fauna was conducted in the remnants of old channel of river Jia Bharali called as Mara Bharali at Tezpur in the Sonitpur district of Assam from December, 2017 to November, 2019. Methods: Five sampling stations were selected that covers a stretch of 16.5 km. River width, river depth, bank type and riparian vegetation were assessed following Armantrout (1999) and statistical analysis were conducted. Fish species were collected and identified following Talwar and Jhingran (1991). Result: Maximum value of river-width was found at site MB5 (12.821±6.067 m). Mean water current velocity was found to be maximum at site MB5 (0.645±0.056 ms-1) followed by MB1 (0.433±0.045 ms-1). The river depicts riffle-pool morphology and consisted of substrates in the form of pebbles, sand and silt. Thirty four fish species belonging to 25 genera, 08 orders and 17 families has been recorded. Moreover, random sampling analysis shows the presence of 14 rare species in Mara Bharali.