Report Number: 109
Year: 2005

Environmental Assessment for Non-Point Sources of Pollution for Ugum Watershed

The existing physical and environmental components of the 4,672.6-acre Ugum Watershed in Southern Guam were studied and their potential impacts on the streams were discussed. The overall goal was to review natural resources for better understanding the potential for protecting and improving water quality of the streams within the Ugum Watershed. For this study we used Geographic Information System (GIS) and ArcHydro programs to organize and register all available information about the Ugum Watershed. The projection that was used for this study was WGS 84 (Latitude/Longitude World Grid System 84). To locate areas of interest, such as farms, badland, and riverbank erosion sites, etc., we took a set of low-elevation, geo-referenced, non-corrected aerial photos from a helicopter from altitudes ranging from 1500 to 2500 feet.

The sites that have potential to be considered as non-point sources of pollution (contributing sediment particles into the streams) were identified in the aerial photos that were taken above the Ugum and Bubulao rivers. Sites were selected based on the steepness of the river section, changes in river direction, bank erosion and land slumping (observed from aerial photos). The impacts of the badlands, off-road vehicle excursions, and sheet and rill erosion were discussed. Badlands could contribute a large amount of the sediment into the waterways. They need to be monitored and an effective revegetation method should be applied. The off-road vehicle excursions and sheet and rill erosion (mostly due to intended fire) are mostly due to human activities. The public should be informed of the impacts and programs to reduce impacts should be in place.

Shahram Khosrowpanah
John M. U. Jocson