干旱区生态环境知识资源中心

Aim: Vegetation status analysis is the best technique to assess the impact of watershed development activities. However, this approach often ignores biomass changes which are not due to the watershed management intervention in arid/semi-arid regions. The present study focused on the biomass vigour change detection to assess the impact of watershed management measures in arid Arjuni and semi-arid Morva-Hadaf watersheds from Gujarat state, India.

Methodology: The study was carried out by multi-temporal remote sensing data for the year, 2002 & 2012 and 1997 & 2011 for the corresponding watersheds. The changes in biomass vigour were identified using the Normalized Difference Vegetation Index (NDVI) approach at watershed and sub-watershed levels for Arjuni watershed and watershed and mini-watershed levels for Morva-Hadaf watershed. The identified biomass changes were precisely tested with respect to already treated areas under watershed management programmes.

Results: The NDVI values increased in both watersheds representing an overall increase in the biomass vigour. However, the sub-watershed level study of Arjuni watershed and mini-watershed level study of Morva-Hadaf watershed showed negative relationship between the percentage increase in NDVI, and percentage of treated area under different programmes.

Interpretation: The results inferred that the increase in biomass vigour does not solely explain the implementation of watershed management measures. This clearly indicates that other than human induced factors (viz., micro-irrigation system adopted by farmers), seasonal factors (i.e., rainfall, temperature) have also influenced the NDVI values throughout the study area. Looking into the current micro-watershed clustering approach, the future work is required to distinguish between climate and human induced factors as a part of impact assessment studies.