Augustana Digital Commons

In spring 2013, the Upper Mississippi Center initiated a Sustainable Urban Watersheds Project in partnership with Rock Island County.

The primary goal of Phase I of the project is to assess the overall ecological health of the approximately 13 urban watersheds and associated urban riparian forests that are dominant features of city landscape (i.e. known as “the ravines”). In collaboration with the cities, the project established approximately 40 samples sites (about three per watershed) in summer 2013. There has been a sampling for a wide range of water quality parameters monthly since June 2015 and is intended to continue the sampling program through at least August of 2015.

Findings:

• Significant degradation in water quality once urbanization reaches a threshold of 10-percent upstream impervious surface.
• Upstream land use is a poor predictor of downstream water quality for a diverse array of pollutants.
• We observed strong watershed-specific differences in water quality within an urbanization gradient ranging from 25-percent to 60-percent upstream impervious surface.

Our findings suggest that water quality within an urbanized setting is dependent on fine-scale differences in the type and intensity of land use and related disturbance and the spatial relationship between such uses and streams. High impervious surface can cause these streams to flow only during rain events, limiting our results.

The primary goal of Phase II is to get a clearer understanding of predictors of water quality by honing in on one watershed in Rock Island in summer 2015. The findings from these projects will contribute substantially to the ongoing Sustainable Urban Watersheds Projects and provide decision-makers with critical knowledge necessary to more effectively conserve and restore these important urban ecosystems.