Abstract—The assessment of Environmental Flow is river-specific, as each catchment has its own hydrological character, and each river may have a different blend of ecosystems that provide a wide range of valuable services to the society. Environmental flow assessments should be made for a river where development is planned or, equally, for an impacted one where an improvement in river ‘health’ (i.e. condition) is desired. Bhadra river, which flows through Shivamogga and Davanagere districts of Karnataka, is one of the tributary of river Krishna which faces acute problems of water pollution due to major industries like Visvesvaraya Iron and Steel Limited and Mysore Paper Mills located in the Bhadravathi taluk, downstream of Bhadra reservoir. According to the local public, both surface and ground water quality are affected due to the inadequate treatment of wastes generated from the above mentioned industries. It is also reported that the river does not carry enough flow during the lean season due to which the water quality issues have become severe. Thirty five years of inflow and outflow data (1972-2007) of Bhadra Reservoir Project were analyzed and compared with the French fisheries law method and Montana method of environmental flow assessment. The study revealed the fact that the flow is altered significantly over the years due to unscientific methods of agriculture and encroachment of riparian land which resulted in massive loss of aquatic habitat and ecological imbalance. Further, the surface and ground water quality studies carried out in the Bhadravathi area indicated that there is a considerable decline in water quality status of the river due to the discharge of both domestic and industrial wastes without adequate treatments. Water Quality Index (WQI) shows a wide variation among all the water samples (39 to 169) indicating that the quality of water is deteriorated in major part of the selected stretch and also in the surrounding ground water. This is substantiated with the observed DO-BOD relationship and also by using QUAL2K model. The average flow analysis of the Bhadra reservoir showed that the major part of the water is released to canals for irrigation and river receive only limited quantity of water during the lean period. Flow is completely negligible during the lean season. From the present study it is estimated that about 5m3/s of water is required to maintain the self-purification capacity of the river in Bhadravathi area. The present investigations and observations indicated that there is a significant decline in the flow level during the lean season due to which number of species (fish genera and plant species) reduced significantly over the years.

Index Terms—Environmental flow, Dissolved oxygen, WQI, Self purification

Cite:B.K. Purandara, N. Varadarajan, and J. V. Tyagi, "Assessment of Environmental Flow Requirement and Ecosystem Analysis of Bhadra River, Karnataka, India," International Journal of Geology and Earth Science, Vol. 5, No. 2, pp. 105-115, June 2019. doi: 10.18178/ijges.5.2.105-115