Degradation Status of Certain Urban Lakes of Coimbatore, India

Urbanization has profound long-lasting impact on lakes and leads to the total retardation of the ecosystem. This complex and dynamic problem needs in depth understanding before the implementation of conservation or mitigation measures. As an initial step, the present study was carried out during 2008-2009 on typical four urban lakes of Coimbatore, India which are facing threats from varying degrees of urbanization and related anomalies. Physico-chemical analyses of lakes water revealed that the increased degradation in water quality was observed in those lakes which were in close proximity with the urban centers. Ukkadam lake was suffered highest degradation showing Water Quality Index (WQI) of 123, followed by Kurchi lake (WQI=97), Chinnakulam lake (WQI=84) and Perur lake (WQI=75). However, a slight different trend was observed in the case of littoral benthic fauna of these lakes. Diversity indices and community composition of benthic fauna were used as an indicator of degradation status of the lakes
studied. Shannon Wiener diversity for macro-invertebrates was highest in Chinnakulam lake (H=2.2531) followed by Perur lake (H=2.0771), Kurchi lake (H=2.0636) and Ukkadam lake (H=1.2141). Land use changes and spatial analysis carried out in geographical area of these lakes using Landsat satellite temporal imagery indicated that there was an unprecedented increase in urban area (more than 50%) during 1989-1999. Spatial analyses using Landsat imagery also gave the similar results as that by water quality. From all these analyses it is understood that these lakes are facing varying degrees of pressures due to urbanization and require immediate implementation of conservation and management plans before such threats turn into irreparable / irreversible impacts.