1) Identify candidate reference stream reaches of wadeable streams in Missouri using existing landscape-level data.
2) Develop a quantitative, scientifically-defensible method to determine candidate reference site conditions in Missouri wadeable streams for each MORAP stream size classification.
3) Validate reference site methodology and selection using on-site physical habitat and biological sampling.
Streams and their biota are influenced by in-stream habitat alterations, as well as disturbances occurring at a landscape level. The past two centuries have seen immense growth in urban and agricultural development, resulting in highly degraded stream conditions and subsequent losses in aquatic biodiversity. We summarized landscape-level disturbance metrics for 92,500 headwater stream segments in Missouri, a size class greatly underrepresented in our existing stream biota databases. We selected metrics detrimental to water quality and habitat condition (e.g., agricultural land cover, urban land cover, stream crossing density, confined animal feeding operations density). Streams showed substantial variation in disturbance type and intensity within and across major physiographic boundaries. While headwater drainages in the Mississippi Alluvial Basin had the least amount of urbanization (1.7% impervious surfaces), they exhibited the highest percentage of agricultural crop cover (68.7%), followed by the Central Plains (37.4%) and Ozark (3.9%) Regions. Although Ozark catchments generally showed the least amount of landscape alteration, lead mine densities were the highest within the Ozarks (0.015/square Km), and confined animal feeding operation densities were greatest within the Ozark’s Neosho drainage (0.021/square Km). These marked differences in land-use support the conclusion to establish stream reference criteria at the subregion level or smaller.