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Using AGWA and the KINEROS2 Model-to-Model Green Infrastructure in Two Typical Residential Lots in Prescott, AZ
Guertin, D., Y. Korgaonkar, I. Burns, C. Unkrich, D. Goodrich, AND W. Kepner. Using AGWA and the KINEROS2 Model-to-Model Green Infrastructure in Two Typical Residential Lots in Prescott, AZ. AWRA Summer Specialty Conference, Sacramento, CA, July 11 - 13, 2016.
This work provides environmental protection managers and practitioners with an ability to evaluate a selected set of Green Infrastructure (GI) features relative to low impact development in arid and semi-arid regions. Specifically, the Automated Geospatial Watershed Assessment (AGWA) hydrologic modeling and watershed assessment tool has been modified to help facilitate environmental assessment related to GI practices at multiple scales (lot, subdivision, and small watershed). The AGWA GI tool can be a used to inform planning decisions related to urban development and storm water management and will be useful in understanding expected differences in storm water runoff between neighboring developments or natural environments. (www.awra.org/meetings/Sacramento2016/)
The Automated Geospatial Watershed Assessment (AGWA) Urban tool provides a step-by-step process to model subdivisions using the KINEROS2 model, with and without Green Infrastructure (GI) practices. AGWA utilizes the Kinematic Runoff and Erosion (KINEROS2) model, an event driven, physically-based model, to represent an urban parcel (or lot) using seven interconnected subcomponents which drain water onto a street half. These include indirectly-connected pervious and impervious surfaces which drain onto connecting impervious and pervious surfaces, respectively; directly-connected pervious and impervious surfaces; and retention basins. These seven subcomponents allow the flow of water towards a street half, while an eighth subcomponent represents a non-contributing area which acts as a water sink.Consider a typical residential lot. The roof can be represented using the indirectly-connected impervious surface, which drains to a front yard (represented by the connecting pervious surface). The driveway can be represented using the directly-connected impervious surface, whereas the side yard can be presented by the directly-connected pervious surface. Swimming pools and backyards can be represented using the non-contributing area. KINEROS2 can be used to model GI practices using these subcomponents. Rainwater harvesting can be modeled by allowing the roof to capture rainwater into a cistern with a user-defined storage capacity. Retention basins can be modeled by providing capacity and conductivity parameters to allow the retention of water in the retention basin subcomponent. Finally, permeable pavements can be modeled by providing a user-defined hydraulic conductivity to the directly-connected impervious surface and/or the street half to determine infiltration rates.The AGWA Urban tool was utilized to model the effectiveness of various GI practices in two typical residential lots in Prescott, Arizona. One of the lots was an acre in size with a 2500 square-foot house and two car driveway, and the other lot was 0.17 acres in size with a 1500 square-foot house and a single car driveway. GI practices included: water harvesting cisterns of capacities ranging from 50 to 2000 gallons; retention basins with surface areas ranging from 1 – 30% of the lot area and filled with gravel; and permeable driveways with an hydraulic conductivity equivalent to gravel driveways. Five rainfall events of 1-hour duration were evaluated; 1-year return period (19.9 mm), 2-year return period (25.7 mm), 5-year return period (35.1 mm), 10-year return period (42.4 mm) and 25-year return period (52.8 mm). Simulation results indicated higher effectiveness of GI practices on the 0.17 acre lot as compared to the acre lot. Effectiveness was measured as a percent reduction of runoff due to the addition of GI practices. For both lots, simulation results showed that GI practices were highly effective for the smaller rainfall events. Results indicated that retention basins were the most effective GI practice. A retention basin that is 5% of the total lot area, resulted in almost 100% capture of the runoff produced.