This study used monitoring in the waterways of agricultural fields to understand the use of the runoff curve number (CN) in continuous simulation models. The CN has a long history as a design tool for estimating runoff volumes for large, single storms on small watersheds, but its use in continuous simulation models to describe runoff from smaller storms and relatively small areas is more recent and controversial. We examined 788 nonwinter rainfall events on four agricultural fields over five years (2004‐2008) during which runoff was generated in 87 events. The largest 20 runoff events on each field generated approximately 90% of the total runoff volume. The runoff event CNs showed an inverse correlation with storm depth that could not consistently be explained by previous precipitation. We review how small areas of higher runoff generation within larger areas will systematically increase the apparent CN of the larger area as the storm size decreases. If this variation is not incorporated into a model explicitly, continuous simulation modelers must understand that when source areas are aggregated or when runoff generation is spatially variable, the overall CN is not unique when smaller storms are included in the calibration set.

After graduating from the University of Wisconsin-Madison, Gavin worked for a government research nonprofit and since obtaining her master's degree has worked for a variety of nonprofits in various roles. Currently, she is the Program Manager for Graduate and Collaborative Programs at the University of Wisconsin-Platteville. Gavin also teaches MEDIA 3010/5010 Business Communication and APC 3300 Technical and Professional Communication. Randy Mentz, University of Wisconsin-Platteville Randy Mentz joined the University of Wisconsin-Platteville staff in 2003 as a field technician for the university's Pioneer Farm in the Agro-Ecosystem Research program. Mentz's main duty was operating and maintaining edge-of-field runoff monitoring stations that were designed to measure and sample storm and snowmelt runoff water from farm fields. With experience, he took on additional responsibilities, such as data management, quality assurance, methods development, data analysis, presenting at conferences, grant writing support, grant administration, training and supervision, outreach, and project management. Mentz joined the Division of Professional Studies in June 2017 as the Research and Compliance Manager overseeing research projects associated with assessment, student services, marketing, and faculty development. He supports grant writing activities, grant administration, and data analysis. He also oversees compliance with regulations that affect programming and research administered by the Center for Distance Learning, the Continuing Education Institute, and the School of Graduate Studies.

No abstract