Dissertation
Understanding tile drainage’s effect on streamflow in the agricultural Midwest
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2025
DOI: 10.25820/etd.008141
Abstract
Understanding the movement of water across the land surface and into channel networks is critical for accurate flood prediction, effective water resource management, and the protection of water quality. In agricultural regions such as Iowa, subsurface tile drainage systems— networks of perforated pipes installed beneath fields—play a key role in regulating soil moisture and routing water to streams, influencing both the timing and magnitude of runoff. There is a growing interest in the scientific community in understanding the effect of tile drainage on the transport of agricultural nutrients and other pollutants across a basin’s river network. This study builds upon a recent study where a tile drainage module for the WRF-Hydro model was calibrated automatically at large regional scales (e.g., the Upper Mississippi River basin) to estimate streamflow. Here we addressed the underexplored model applicability to a smaller domain: the South Fork Iowa River basin, a heavily tile-drained watershed. Here is proposed a novel approach where model calibration is performed manually, with a dual focus on reproducing observed streamflow hydrographs and aligning modeled runoff partitioning with expected hydrologic behavior. The model is also forced with more refined local tile drainage maps. Model simulations were produced at hourly temporal resolution over a 14-year period between 2008 and 2021, and include outputs of streamflow, soil moisture, and all necessary elements to calculate water budget. Results indicate that tile drainage accounted for approximately 24% of the total runoff volume over the simulation period and contributed up to 30% of total streamflow during peak flow events. These findings underscore the hydrologic significance of tile systems and highlight the need for accurate representation of their behavior in fine-scale watershed models.Improving WRF-Hydro’s ability to simulate tile drainage dynamics in small agricultural basins enhances its utility for flood forecasting and water quality assessment. This framework also lays the groundwork for evaluating the hydrologic impacts of conservation practices and informing land and water management strategies under future climate and land use scenarios in the agricultural Midwest.
Details
- Title: Subtitle
- Understanding tile drainage’s effect on streamflow in the agricultural Midwest
- Creators
- Kaleb Young
- Contributors
- Larry J Weber (Advisor)Felipe Quintero (Committee Member)Humberto Vergara (Committee Member)Keith E Schilling (Committee Member)Witold F Krajewski (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Civil and Environmental Engineering
- Date degree season
- Summer 2025
- DOI
- 10.25820/etd.008141
- Publisher
- University of Iowa
- Number of pages
- xi, 100 pages
- Copyright
- Copyright 2025 Kaleb Young
- Language
- English
- Date submitted
- 07/23/2025
- Description illustrations
- illustrations (some color), color maps
- Description bibliographic
- Includes bibliographical references (pages 94-100).
- Public Abstract (ETD)
Understanding how water moves across the land and into rivers is essential for predicting floods, managing water resources, and protecting water quality. This research focuses on improving a computer model called WRF-Hydro, which is used by the National Weather Service to forecast streamflow across the United States. One important part of the water system in agricultural areas like Iowa is tile drainage a network of underground pipes that help remove excess water from farm fields. These systems have a major impact on how much water flows into rivers and when that water arrives.
While work has been done to study the current WRF-Hydro model including a tile drainage module, it was designed and tested at very large scales, like the Upper Mississippi River basin. This study takes a closer look by testing and improving the tile drainage model in a smaller watershed: the South Fork of the Iowa River. Using real-world weather data and computer simulations, this work compares how the model performs with and without tile drainage and examines how water is partitioned between different flow pathways, like surface runoff and groundwater.
The goal of this research is to make the WRF-Hydro model more accurate by adjusting it to better match conditions in smaller, tile-drained watersheds. This will help improve flood forecasting and provide better information about how water and nutrients move through farmed landscapes. In the future, this approach could be used to evaluate conservation practices and support more effective land and water management in the Midwest.
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984948238402771
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