Spatio-temporal variation of water quality and bio indicators of the Badulu Oya in Sri Lanka due to catchment disturbances

Safe and ample supply of freshwater is fundamental to humans and for the sustainability of ecosystem function. Therefore, impacts of catchment disturbances on surface water quality have been given special attention currently. The Badulu Oya sub-catchment of the Upper Mahaweli catchment area in Sri Lanka is one of the landscapes affected by intensive agricultural activities and urban development. This study was aimed at evaluating the spatial and temporal variation of water quality, stream physical habitat quality and macroinvertebrate bioindicators in the Badulu Oya catchment area in relation to disturbances due to agricultural and urban practices. Physicochemical water quality parameters and macroinvertebrate indices were evaluated at ten sampling sites in the Badulu Oya catchment area within a one year period. The results revealed that water quality variables such as electrical conductivity (EC), total solids (TS), total dissolved solids (TDS), dissolved oxygen (DO), alkalinity, nitrate-N(NO3-N) and physical variables such as stream channel quality index (CQI) and riparian quality index (RQI) are significantly influenced by the degree of catchment disturbances. Among the macroinvertebrate indices tested, total abundance and family richness significantly varied with the degree of catchment disturbances. The findings of the present study revealed that the land use practices of Badulu Oya catchment result in significant impacts on stream ecological health. Similarly the study also revealed the prospect of using attributes such as water quality, physical habitat quality and macroinvertebrate bioindices for river health monitoring programmes.