Helmand River Hydrologic Studies Using ALOS PALSAR InSAR and ENVISAT Altimetry

Abstract

The Helmand River wetland represents the only fresh-water resource in southern Afghanistan and one of the least mapped water basins in the world. The relatively narrow wetland consists of mostly marshes surrounded by dry lands. In this study, we demonstrate the use of the Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) Interferometric SAR (InSAR) to detect the changes of the Helmand River wetland water level. InSAR images are combined with the geocentric water level measurements from the retracked high-rate (18-Hz) Environmental Satellite (Envisat) radar altimetry to construct absolute water level changes over the marshes. It is demonstrated that the integration of the altimeter and InSAR can provide spatio-temporal measurements of water level variation over the Helmand River marshes where in situ measurements are absent.

Keywords:

• Helmand River
• water level change
• InSAR
• satellite altimetry

Acknowledgments

This research is partially supported by grants from the National Geospatial-Intelligence Agency's University Research Initiatives Program, HM1582-07-1-2024; the Climate, Water, and Carbon Program at the Ohio State University; and the U.S. Geological Survey Land Remote Sensing Program. PALSAR data are copyrighted by JAXA/METI 2006–2008 and are provided by ASF. Envisat radar altimetry data are provided by ESA/ESRIN. We also thank two anonymous reviewers for their constructive comments which have improved the manuscript.