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Transport of nitrogen and phosphorus from Rhode River watersheds during storm events

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  1. Transport of nitrogen and phosphorus from Rhode River watersheds during storm events David Correll, Thomas Jordan, and Donald WellerWater Resources Research, 1999. Vol. 35 No 8 pg 2513-2521

  2. Why this paper? • One of many papers from the SERC on the Rhode River Watershed since the 1970s • Effects of land use, season, and storm characteristics on nutrient transport

  3. Site Description Land Use effects: 4 watersheds Watershed 101 Mixed Use Land Use Watershed 109 Crops Watershed 110 Forest Watershed 111 Grazed Forest Row crops Pasture and Hay fields Residential Old Fields

  4. Site Description

  5. Chemistry • Phosphorus • PPi, Dpi, POP, DOP • Nitrogen • NO3-, NH4, PON, DON • Continuous baseflow samples and storm samples • Collected and returned w/in 24 hr • Filtered 0.45 m

  6. Discharge 120° and 150 ° V notch weirs Stilling wells, floats every 5 minutes

  7. Loads: Linear interpolation • Steps: • Connect the concentrations using a linear interpolation • Integrate the instantaneous load for the period between the first sample and the last using equation (1) (1)

  8. Base flow vs. Storm Storm Particulate + Dissolved Fractions added

  9. Characteristic Storms (WS 101)

  10. P and N Dynamics June storm (WS 101) P N

  11. Storm P & N Dynamics (all 4) P N

  12. Seasonal P Comparison WS 101: Mixed LU WS 109: Cropland LU

  13. Seasonal N Comparison WS 101: Mixed LU WS 109: Cropland LU Summer: Particulates

  14. P c-Q relationships

  15. N/P Relationships Mainly due to increases in Particulate P

  16. Discussion Particulate nutrients related to soil, soil erosion.

  17. Discussion Peak water discharge correlated to mean particulate nutrient concentrations • Eliminating need to know rainfall volume or intensity • Smaller 1st order catchments • Shorter, more intense storm discharges [NH4] increased with peak water discharge - slopes much lower

  18. Sampling implications 1 large summer storm 24% of TP for entire summer 18% of TPi for entire summer 30% of TOP for entire spring 18.5% of TON for entire spring 1 large spring storm 39% of TP for entire spring 41% of TPi for entire spring 38% of TOP for entire spring 12% of of TON for entire spring Discussion

  19. Questions????? • Why do storms increase particulate nutrient concentrations but do not influence dissolved concentrations? • If sediment related, why isn’t rain (detachment) as important as flow? • Implications for sampling: every storm? Or use different load estimation? • Internal validity- are differences really seasonal and land use related • External validity? – how is this applicable to other watersheds