Impact assessment of watershed management programmes on land use/land cover dynamics using remote sensing and GIS

The semi-arid study area, which is the part of Khan-Kali watershed and Anas River from Gujarat, India, was intensely targeted for land reclamation by various government and non-government organizations since last decade. The present study aims at impact assessment of watershed management measure and determines the dynamics of land use/land cover (LU/LC) and vegetation cover in the agricultural area using multi-temporal Remote Sensing (RS) data and Geographical Information System (GIS). The entire study is divided into two parts. The first part deals with LU/LC classification, post classification analysis and change detection over 2001-2011. The ancillary data of both Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) were applied at during supervised classification stage and agricultural masks were applied at post supervised classification stage to improve the classification accuracy. In the second part of the study the RS data of the years 2001 and 2012 were used to calculate NDVI, and subsequently the NDVI differencing to detect the change of vegetation cover in agricultural land. Both the changes were estimated at watershed and mini-watershed levels. Specifically, the mini-watershed level changes were evaluated with respect to treated area. The results indicated that the integration of ancillary data with supervised classification has improved the classification accuracy of LU/LC maps by 91.8% and 95.5% for 2001 and 2011, respectively. The key LU/LC changes at watershed level were increased in both the water body and scrub forest areas and decrease in the forest/dense vegetation, barren land and riverine sand areas. At mini-watershed level, for the mini-watersheds treated- (1) less than 25% indicated decrease in forest/dense vegetation and increase in scrub forest area (2) between 25-50% increase in water body and decrease in scrub forest area; and (3) more than 50% indicated increase in water body and decrease in forest/dense vegetation area. To mitigate the observed localised deforestation, the immediate natural vegetation conservation is required. In spite of aridity remain present over the years 2011-2012, the area under agricultural crops showed an increase in high NDVI and decrease in low NDVI values at both watershed and mini-watershed levels. The ground water levels were also increased from 2001 to 2011. The study inferred that the watershed management programmes showed the overall positive impact on the study area.