Abstract:
Sustainability of desert ecosystem is highly dependent upon water availability from different sources. Palaeochannels are important sources of groundwater, and exploiting such resources involves their identification / mapping and subsequent investigation for fresh groundwater. In this study multi-sensor (Landsat 8 OLI & active microwave Envisat ASAR) images of the Cholistan desert of Pakistan were processed and analyzed to identify and map Hakra River palaeochannels. Radiometrically corrected optical and SAR datasets were fused using Principal Components image fusion method. The palaeochannels were delineated from the analysis of this fused data, and using Normalized Difference Vegetative Index (NDVI) values from Landsat 8 OLI (atmospheric corrected images) were used as supportive information. Identified alignment of palaeochannel was validated with geophysical ground measurements (electrical resistivity & conductivity surveys) and historical records. The presence of high apparent electrical resistivity with corresponding low soil water conductivity values intersect well with the identified palaeochannels from the remote sensing data. The results were also confirmed with historical evidences like old wells, forts and previously identified ground water harvesting sites. These measurements additionally helped in distinguishing zones of fresh groundwater from brackish and saline in underground aquifers. The proposed methodology in this study could be adopted in other parts of the world deserts for the mapping of palaeochannels.
