On Water Quality Aspects of Manchanabele Reservoir Catchment and Command Area (karnataka)

Reservoirs and lakes occupy a prominent place in the history of irrigation in South India. Tanks are considered to be useful life saving mechanism in the water scarcity areas which are categorized as Arid and Semi-arid zones. The lakes and reservoirs, all over the country without exception, are in varying degrees of environmental degradation. The degradation is due to encroachments, eutrophication (due to the inflow of domestic and industrial effluents) and siltation. There has been a quantum jump in population during the last century without corresponding expansion of civic facilities resulting in deterioration of lakes and reservoirs, especially in urban and semi urban areas becoming sinks for the contaminants. The degradation of reservoir and lake catchments due to deforestation, stone quarrying, sand mining, extensive agricultural use, consequent erosion and increased silt flows have vitiated the quality of water stored in reservoirs and lakes. Infrastructure development, housing projects, and inflow of untreated wastewater into the water bodies have resulted in deterioration of urban and rural lakes and reservoirs. The paper discusses the physico-chemical and bacteriological studies carried out on surface and ground water in the reservoir catchment and the command areas .The results of analyses of water samples reveal that water is polluted at certain locations. The presence of total –Coliform and Faecal-Coliform in ground water and reservoir and lake water at certain locations indicates that water is polluted with waste water. The nitrate level varies between 0.6ppm to 135.8ppm, and exceeds the drinking water standards at 10 locations in the catchment and command area. The suitability of water for irrigation is evaluated based on SAR, %Na, RSC and Salinity hazards. Most of the samples fall in the suitable range for irrigation purpose. The inflow of urban runoff into the surface water bodies has resulted in pollution of reservoir and ground water at certain locations. The paper also discusses the measures proposed to reduce pollution levels in the reservoir, its catchment and command areas