Perspectives on the potential for hydropedology to improve watershed modeling of phosphorus loss

Predicting P loading to surface water bodies requires accurate partitioning of infiltration and runoff from potential source areas and portrayal of spatial landscape relationships between source areas and surface water bodies. This paper presents perspectives on the potential for hydropedology to improve watershed modeling of phosphorus (P) loss as it affects water quality. Calibrating the Soil and Water Assessment Tool (SWAT) and similar watershed models to the hydrograph at the watershed outlet may not reflect accurate partitioning of runoff among hydrologic response units (HRUs), and default runoff parameters for HRUs are often a poor representation of reality. Hydropedology combines knowledge and skills from the disciplines of hydrology, pedology, and soil physics to address this problem. While there are untapped data and existing knowledge within these disciplines that can be brought to bear, there is also a need for additional interdisciplinary collaboration. Issues that affect process modeling at field, farm, subcatchment, and watershed scales need to be addressed through combined knowledge of the structure of the system as related to the specific objective of better linking runoff generation from potential source areas to surface water bodies. Improved watershed modeling as applied to nutrient loss and water quality issues affords both challenges and opportunities for hydropedology if scientists are willing to bridge disciplines, data, and scales to address current limitations.