Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2008
Publication Date: 4/30/2009
Citation: Buda, A., Kleinman, P.J.A. , Srinivasan, M. S., Bryant, R.B., Feyereisen, G.W. Factors influencing surface runoff generation from two agricultural hillslopes in central Pennsylvania. Hydrological Processes. 23(9):1295-1312. Interpretive Summary: Identifying agricultural soils prone to surface runoff is essential for controlling nutrient pollution. This study examined runoff generation mechanisms on two contrasting hillslopes, finding a strong relationship between subsurface soil properties and runoff quantity and generation. Results point to the need to identify these soil features in the landscape to improve the accuracy of existing nutrient management metrics that rely on surface runoff prediction.
Technical Abstract: The variable source area (VSA) concept provides the underlying paradigm for managing phosphorus losses in runoff in the northeastern U.S. This study sought to elucidate factors controlling runoff along two hillslopes with contrasting soils, including characterizing runoff generation mechanisms and hydrological connectivity. Runoff monitoring plots (2 m x 1 m) were established in various landscape positions. Foot-slope positions were characterized by the presence of a fragipan that contributed to seasonally perched water tables. In upslope positions without fragipans, runoff primarily was generated via the infiltration-excess mechanism (96% of events) and largely was disconnected from downslope runoff. Roughly 80% of total runoff originated from the north foot-slope landscape position via saturation-excess (46% of events; 62% of runoff) and infiltration-excess (54% of events; 38% of runoff) mechanisms. Runoff from the north hillslope was substantially greater than the south hillslope despite their proximity and apparently was a function of the extent of fragipan representation. Results demonstrate the influence of subsurface soil properties (e.g. fragipans) on surface runoff generation in variable source area hydrology settings, which could be useful for improving the accuracy of existing runoff prediction tools.