Remote sensing and GIS-based assessment of urbanisation and degradation of watershed health

Water resources, ecological quality, i.e. vegetation, flora-fauna, native plants, etc., and geo-morphological characteristics are some of the important elements that represent health of a watershed. Watershed health can be assessed through some of the indirect metrics, such as change in rainfall-runoff response, depletion of groundwater, groundwater pollution and degradation of geo-morphological characteristics. In the present study, application of remote sensing and geographic information system (GIS) technologies have been demonstrated for assessment of health of two urbanised sub-watersheds over a period of last 29 years (1977-2005). Investigation includes estimation of urbanisation and resulting changes in the watershed characteristics representing heath of watershed, such as change in surface runoff response, groundwater level, groundwater quality and morphological characteristics. Remote sensing images of eight years (1977-2005) have been used for extraction of land use/cover and urban growth. Change in surface runoff characteristics have been estimated using a physically based distributed storm water management model (SWMM). Groundwater analysis has been carried out in GIS to determine the change in groundwater level and quality over a period of 1992 to 2005. Results reveal that rate of land development in Ajmer is higher as compared to the population growth. Significant changes have been found in important watershed characteristics leading to deterioration of its health. Remote sensing and GIS technologies have been found to be useful for such studies.