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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #30401

Title: FLOW AND NUTRIENT EXPORT PATTERNS FOR AN AGRICULTURAL HILL-LAND WATERSHED

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

Submitted to: Clean Water Clean Environment 21st Century Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/8/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Interpretive summary not required

Technical Abstract: Nutrient patterns and export in streamflow were determined for a 3-mi-sq agricultural hill-land watershed in Pennsylvania. Data included mostly nutrient export in the water phase (soluble P, orthophosphorus, NO3) routinely collected for 9 yr, and in the suspended phase (labile P, algal- available P, total P) composited for 37 large storms. The data set was subdivided into storm flow, baseflow, and elevated baseflow categories. P export, whether associated with sediment or water phase, was dominated by storm flow. Even though storm flow periods accounted for less than 10% of the time, 65-80% of the dissolved P (soluble or ortho P) export occurred during storm flow. The proportion of P exported with sediment during storms ranged from 40-90%, depending on whether the sediment-associated P was the labile, algal-available, or total P fraction. Soluble P accounted for 30-50% of the algal-available P exported by all flows. Dissolved P concentrations were very low for non-storm periods, substantially higher for storm periods, and overall exceeded EPA standards for ortho P (10 ppb) less than 25% of the time. The EPA soluble P standard for lakes (50 ppb) was exceeded infrequently, and then only during storm flow. NO3 export was mostly in non-storm flow (60%), with the higher concentrations in elevated baseflows. The significantly higher NO3 concentration in elevated baseflow result from increased drainage from the shallow fracture layer that underlays cropland. Only about 2% of all flows exceeded the 10 ppm NO3-N standard. Because storm flow dominates P export, control of the hydrologically active P source areas within the watershed provides the greatest opportunity for controlling export of algal-available P.