21. Hydrological Change Detection Mapping and Monitoring of Ramganga Reservoir, Pauri Gharwal, Uttarakhand, Using Geospatial Technique

Wetlands serve an essential role in conserving the ecological balance of both biotic and abiotic lives in both inland and coastal environments. Hence, understanding their existence and the spatial extent of change in the wetland ecosystem is vital and monitored using remote sensing technology. A study was performed for the Ramganga reservoir, located in Uttarakhand, India, one of the important wetlands in Uttarakhand that comes under Ramsar sites with many bird species and is rich in biodiversity. The present study modeled the spatiotemporal changes of the reservoir using the multi-temporal Landsat TM (1992, 2000, and 2010) and Landsat OLI-TIRS (2020) imageries. While performing spatiotemporal analysis, the applicability of various satellite-derived indexes such as the Normalized Difference Water Index (NDWI), Modified NDWI (MNDWI), Normalized Difference Vegetation Index (NDVI), and Normalized Difference Turbidity Index (NDTI) has been employed for retrieval of wetland elements including the wetland extent boundary, water-spread area, aquatic vegetation, and turbidity level of the reservoir during pre- and post-monsoon seasons by using remote sensing and hierarchical decision tree algorithm. In the post-monsoon season, the minimum and maximum water-spread areas were 59.98 km² in 1992 and 74.30 km² in 2010, respectively. Similarly, in the pre-monsoon season, the reservoir had a minimum, and the maximum water-spread area was 28.697 km² in 2010 and 58.536 km² in 2020, respectively. The total aquatic vegetation of wetland was increased from 3.41 to 4.14 km² in the years 1992 and 2020 during post-monsoon. Throughout the study period, the medium turbidity level in the reservoir was observed to be less than 1 km². The result indicates that these different satellite-derived spectral indices are less time-consuming and provide more accurate mapping and wetlands monitoring. This requires constant monitoring of the structural components of wetlands and urgently focuses on wetland conservation, rehabilitation, and management.