Irrigation and Drainage

Oral

395145 - Modeling Runoff from Terraced Fields with Tile Drain Systems

Wednesday, June 6
4:00 PM - 5:30 PM
Location: Skyway Room
Co-Authors: Edward Peltier, Lawrence, KS – University of Kansas; Pamela Sullivan, Lawrence, KS – University of Kansas; C. Bryan Young, Lawrence, KS – University of Kansas

Three treatment wetlands were constructed in the Upper Wakarusa watershed in Douglas County, Kansas to remove nutrients and suspended solids from tile drainage from terraced agricultural fields. A continuous hydrological model was created to predict runoff volumes and peak flow rates from the terraced fields draining to these wetlands as part of a larger project to estimate nutrient removal by these wetland systems. Models were developed using the Hydrological Engineering Center’s Hydrological Modeling System (HEC-HMS) software using the Soil Conservation Service Curve Number (CN) method. The most effective approach to modeling the terraced field was to treat each terrace as an individual catchment area with an attached reservoir to represent the water temporarily stored in the terrace during a storm event. These terraces were connected to discharge pipes which are modelled to be free of hydraulic losses and ultimately discharge the runoff water to the receiving wetlands. The runoff model was calibrated using measured flows from runoff events monitored during 2014 and 2015. Site surveys were performed to create a stage storage-discharge relationship for ponded water.
Results generated with initial models without the reservoir component were unable to match peak flow and total runoff volume simultaneously. The full model was able to produce similar results to those measured on site for both runoff volume and peak flow but with rather higher curve numbers than those typically expected for agricultural fields. This is likely due to the high slope of the terraces and water ponding in the terrace lowlands. A sensitivity analysis was performed to examine the impact of initial abstraction, the preceding rainfall ponding effect, and crop cover on model performance. Finally, the results were compared to an alternate Green-Ampt modeling method (based on soil parameters) to evaluate the pertinency of the SCS CN method on terraced watershed systems.

Daniyal Ahmed Siddiqui

Graduate Research Assistant, Environmental Engineering
University of Kansas

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395145 - Modeling Runoff from Terraced Fields with Tile Drain Systems



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