ABSTRACT:

Flood infrastructure that uses pipes and culverts, also called gray infrastructure, collects and conveys stormwater to receiving areas, typically oceans, inland lakes, and wetlands. Gray infrastructure increases stormwater runoff volume and exposure to pollutants and prevents infiltration to groundwater. Green infrastructure is increasingly proposed to reestablish ecosystem services that are lost from urban development. This study uses QUAL2Kw to simulate streamflow, stream temperature, dissolved oxygen concentration, and total phosphorus concentration in the Jordan River Watershed in Salt Lake City, UT, USA with and without implementation of grass swales, bioretention cells, and rain gardens at the reach, small watershed, and large watershed scales. Sixty-four model runs simulated streamflow and water quality effects if 10%, 50%, and 100% of the available watershed area converted to green infrastructure. As an example, the 100% implementation of rain gardens for roofs alternative reduced streamflow by 5.6% and 4.6% in the May and June models, respectively. Secondly, the 100% implementation of bioretention cells for parking lots alternative leads to a decrease of 5.8% in total phosphorus load to adjacent surface water bodies. Overall, it takes implementation of green infrastructure on the large watershed scale to see measurable changes downstream. When green infrastructure is implemented on the large watershed scale, total phosphorus concentrations are reduced by 3-6% in reaches that total phosphorus is a pollutant of concern. These findings quantify the potential of green infrastructure to maintain ecosystem services such as water quality improvement, flood mitigation, and water supply.