Variability of Soil Moisture in the Walawe River Basin: A Case Study in Sri Lanka Using Low-Resolution Satellite Data

Limited availability of freshwater and increasing demand for food require careful management of available resources. However, information on water utilization within river basins is often inadequate for comprehensive water management. Therefore, researchers are developing new tools and methodologies to overcome these data problems. A major concern for land use planning is the identification of suitable areas for different types of activities to enable optimal management of natural resources. Satellite remote sensing technology opens new paths for studies on the management of river basins. Through information derived from satellite data, it is possible to monitor land surface conditions and the status of the water resources on daily basis. NOAA-AVHRR sensor supplies data at a relatively low resolution for every part of the world, also on a daily basis. By integrating these low-cost images in physically based models, soil moisture was estimated for every part of Sri Lanka at 1-km resolution. This paper endeavors to show the relevance of soil moisture variation for water basin characterization, and ultimately for natural resources management. Walawe basin, one of the IWMI benchmarked basins in Sri Lanka has been selected for soil-moisture characterization and for the delineation of classes. Results show time variations and amplitude differences between different zones in the basin. When compiled with the vegetation growth zones of Walawe, the soil moisture highlights relevant land and water management lessons.