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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #86212
Title: SEASONAL FLOW AND NUTRIENT PATTERNS FOR AN AGRICULTURAL HILL-LAND WATERSHED

Author
item Pionke, Harry
item Gburek, William
item Schnabel, Ronald
item Sharpley, Andrew
item Elwinger, Gerald

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The patterns and concentrations of phosphorus and nitrate in streamflow were analyzed in terms of environmental impact. The analysis was structured so to identify the primary source areas, seasons, and storm events controlling the export of these nutrients from a typical hill land agricultural watershed located in the northeastern U.S. The results showed dmost losses to occur from relatively small areas within the watershed and during late winter-spring when flow rates were the highest. Most of the nitrate was exported in nonstorm flow, whereas most of the phosphorus was exported in storm flow, especially by the 5-7 largest storms per year. Thus, there are critical areas, times, and storm events that are most important to sample or treat for control purposes. In contrast, very large outlier events can contribute enormous P loss, but their impact and controllability can be greatly different. This paper develops a watershed scale perspective for perceiving and assessing the impact of critical areas, seasonality, and storm event size using stream export data.

Technical Abstract: The effects of seasonality on nutrient patterns and export in streamflow were determined for a 7.3 km2 agricultural hill-land watershed located in Pennsylvania. Dissolved phosphorus (DP) concentrations were highest in stormflow for all seasons, but especially in summer when flow was least. About two-thirds of the DP export was in stormflow, with two-thirds of this sexport occurring during winter and spring when five of the seven largest stormflow events within the year occurred. For larger stormflows, DP concentrations were positively correlated with flow rate, which contributed to storm dominance of DP export. Export of NO3, and to a lesser extent DP, by flow component and season were controlled by flow rate rather than concentration. Summer was least important, contributing only 7-8% of the annual export of water, DP, and NO3. The NO3 concentrations were lowest for baseflow and highest for elevated baseflow across seasons. More of the eNO3 export was in non-storm than stormflow and occurred mostly in winter and spring. A 50-year storm event dominated the DP exported (33%) over a 12-year period of record, but not water (10%) nor NO3 (6%) export. P management and control decisions for watersheds need to be developed in a storm-based, source-area framework, whereas N management and control decisions depend more on managing and balancing N use over the watershed.