Sunlight can have a significant impact on freshwater aquatic communities. Using Geographic Resources Analysis Support System (GRASS) geospatial analysis software, a previously generated 18.2 m resolution forest canopy height grid for the State of North Carolina was used as a base elevation layer for calculation of daily total irradiance (Watt-hours/square meter/day) grids. Daily calculations were aggregated annually and overlaid on rasterized 1:24000 scale USGS quadrangle hydrology delineations with forest canopy type and seasonal filters (spring, summer, fall and winter) to quantify annual solar irradiation input to streams and rivers in North Carolina. Bare earth calculations of solar irradiation for the aquatic habitats were compared to the canopy filtered calculations. As expected, there was substantially less solar irradiation in aquatic habitats under the canopy filtered model.
Total solar irradiation for subbasins created from point locations of occurrences of dwarf wedgemussel (Alasmidonta heterodon) were compared to total solar irradiation for watersheds created from locations with no mussels for the full subbasin, 1km, and 500m upstream from the sampling point. There was no significant difference in the amount of total solar irradiation modeled for the subbasins with dwarf wedgemussel and watersheds with no mussels.
Annual solar irradiation model for North Carolina derived from lidar imagery
Sunlight exposure for a section of North Carolina streams derived from lidar imagery