Hydrologic Modeling of a Retention Irrigation System

Urbanized watersheds produce instantaneous response to rainfall, resulting in storm-water runoff exceeding the carrying capacity of drainage systems—the management of which is important to prevent flooding and erosion of streams. Management can be achieved using structural storm-water best management practices (BMPs). The city of Austin, Texas, envisioned a plan to mitigate future scenarios for flooding and erosion, resulting in the development and integration of storm-water BMP algorithms into the subhourly version of the soil and water assessment tool (SWAT) model. Algorithms were developed to simulate the physical processes governing the flow transport mechanisms through these BMPs. They were tested using a previously flow-calibrated watershed in the Austin, Texas, area. The retention irrigation (RI) system is one such BMP commonly found in Austin, Texas. This paper describes the development of a modeling tool for the RI system and its potential applications. From the test results obtained, it appears that the RI algorithm functions rationally. The algorithm developed could be used to evaluate the functionality of an individual BMP structure to analyze the benefits of such structures at a watershed scale and as a design tool.