Predicting and Verifying Physiological Performance of Plants in a Bioretention System in an Arid Climate

The Arid West is the fastest growing region of the country and expanding development in this harsh environment brings new stormwater management challenges. Bioretention presents unique engineering and ecological challenges that are different than more mesic regions of the country. To address these challenges, two bioretention cells are being constructed in Salt Lake City to test performance in an arid climate. Factors driving plant selection and design are expected delivery of annual precipitation as well as physiological traits of native plant species. First, expected precipitation amounts and pattern of delivery are reviewed for Salt Lake City. Second, physiological benefits and restraints of selected upland species from the area are explored to determine suitability for use in bioretention stormwater facilities. Traits examined include carbon to nitrogen ratios of biomass, rooting depth, salt tolerance, soil preferences and season of growth. In arid climates timing of precipitation plays a larger role in plant physiology than total precipitation inputs. Third, water demands are estimated for native species and wetland species traditionally used in bioretention of more mesic climates. Irrigation demands needed to sustain these plants and costs of these demands will be measured. Transpiration, respiration, evaporation, and percent removal of nitrogen and phosphorus are measured in the bioretention cells over one growing year; results of the establishment phase are compared to the literature and presented. Special consideration must be given to these local factors when planning sustainable Low Impact Development stormwater management in these harsh climates.