| Description |
Bioretention is a stormwater management best management practice (BMP) designed to treat small yearly occurring storms. Bioretention is typically used on the East Coast, which is a mesic climate, with significant precipitation (500 to 750 mm precipitation annually). For Salt Lake City, UT, a semiarid climate with lower precipitation (250 to 500 mm precipitation annually), a different bioretention design is used that is better suited for this climate. In order to improve bioretention design in the semiarid west and to understand its limitations a performance assessment is needed by designers. A hydrologic performance evaluation is performed on a bioretention garden installed on the University of Utah campus. There are three main methods for water movement out of the bioretention garden including evapotranspiration, vertical infiltration and lateral water movement. Sensors installed on site, and a finite element software that simulates water movement through a variably saturated media (HYDRUS 2D/3D) are used to determine the percentage of water movement through the three methods. Sensors measure water depth in the storage layer, inflow volume, and meteorological conditions on site such as relative humidity, temperature, precipitation, wind speed, and direction. The meteorological conditions estimate evapotranspiration rates by using the Penman-Monteith equation, for nonwater limited conditions. Evapotranspiration accounts for approximately 5% of the total inflow volume for storms from April to September. HYDRUS is not effective at modeling this bioretention garden, and more information is needed on the individual process before bioretention gardens can be effectively simulated. From the data, exfiltration (lateral and vertical soil water movement) and soil water storage account for the other 95% of the inflow volume. The majority of water movement is through vertical infiltration, which is affected by initial soil water content and water temperature. |
