Wetlands are under increasing stress due to urbanization and other anthropogenic activities, leading to their over exploitation and degradation. Deeporbeel wetland a permanent fresh water lake in a channel of the river brahmaputra of assam state in India has great biological and environmental importance and is the only ramsar site in the state. One of the major threats faced by the wetland is deterioration of its water quality. This paper presents the results of physico-chemical parameters measured during the post monsoon (2005) and pre-monsoon seasons (2006) and the computation of National Sanitation Foundation - Water quality Index (NSF-WQI) at fixed locations and comparison with base year (1989) data available only for 3 locations. Besides, point and non-point pollution sources, erosion, silt deposition and gully erosion have been identified as the major sources of deterioration of water quality. The results indicated that the wetland has reached medium water quality over the years from good quality in the year 1989. The conservation measures in respect of point and non-point sources as well as remedial measures for silt deposition and gully erosion are suggested.