Stream dwelling organisms are subject to numerous environmental stresses. Solar ultraviolet radiation (UVR) has been indicated as an important stressor in lakes and oceans, but has previously received little attention in stream ecosystems. Here, 16 small streams are monitored in the Lehigh Valley, Pennsylvania from June to October, primarily during base flow conditions. Land use/land cover ranged from primarily agriculture to primarily forest. Urban land use and wetlands were negligible in all watersheds studied. Optical properties, such as absorbance of dissolved and particulate material as well as fluorescence are monitored in addition to several other chemical and water quality parameters. Geographical Information Systems analysis is used to investigate the relationship between the optical properties and the characteristics of each individual watershed...