A study of wetlands and their role in geoecological environment of the Bhogdoi basin, Jorhat, Assam, using remote sensing and GIS

For conservation of biodiversity, control of flood, production of fish as well as other aquatic resources and to maintain ecological balance, wetlands play a significant role. The Bhogdoi river basin contains a large number of wetlands, which have been neglected resulting in their degradation. This paper presents a discussion on the wetlands of the basin and their role in geo-ecological environment. The wetlands and its surrounding areas have undergone rapid changes in respect of agricultural activities, human settlement and industrialization resulting in an imbalance in the wetland ecosystem within the entire Bhogdoi river basin. Considering all these aspects, an effort has been made to provide an information base on the changes in area, land use pattern, etc. of the wetlands in five different years, viz. 1974, 1990, 1998, 2001 and 2005 and their impact on the wetland eco-system using visual interpretation technique for LISS III (1998, 2005), Landsat TM (1990, 2001), Survey of India topographical maps (1974) supplemented by ground verification. A study using GIS tools reveals that there has been significant change in the areas of the natural lakes and ponds in between the years 1974 (16.698 sq km.) and 1998 (8.554 sq km.). The number of the wetlands has increased but the area has been decreasing for the natural lakes and ponds. It is also clear that cut-offs 1974 (8), 1998 (19) and 2001 (21) respectively have caused considerable changes in the channel alignment and channel morphology and there is an increasing trend in the development of meander loops in the Bhogdoi river. Similarly the length of the river during 1974, 1998 and 2005 were 184 km, 186 km and 191 km respectively. However, though the cut-off process has been active in the lower reach, the river does not show a shortening effect as the measurement for 32 years show that the length of the river has increased although there is an increase in number of cut-offs.