MAPPING AND MONITORING ENVIRONMENTAL DEGRADATION IN MANCHAR LAKE AND ENVIRONS

摘要

Environmental degradation in the sweet water lakes is a serious problem, which needs urgent attention of hydrologists and environmentalists. Study of lake environment is an application area of water resources for which satellite remote sensing data have been used. This paper describes mapping and monitoring of Manchar lake and environs. Multitemporal SPOT XS data pertaining to near infrared band covering the period from 1997 to 1999 in dry and wet seasons have been used Siltation and growth of uncontrolled natural vegetation (aquatic weeds) in Manchar lake is one of the serious environmental problems which limits the water holding capacity of the lake and reduces the water supply to adjoining areas. It is therefore, essential to address such environmental problems through satellite remote sensing. Both visual and digital image interpretation techniques based on differences in surface reflectance of ground features have been employed to identify different terrain features including water bodies as well as aquatic weeds. The temporal variation of water surface area and natural vegetation in the entire lake was determined. Water surface area of the lake can easily be calculated if water level is known by applying suitable statistical analysis. Delineation of land-water boundaries leads to valuable topographic details, which yields useful information on geomorphological conditions such as process of deposition of silt or erosion in the lake. The satellite based thematic image maps provide the level of pertinent information on different aspects of lake environment. This information is useful for effective planning and management besides environmental mapping and monitoring of the lake by irrigation engineers and environmentalists.