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Nanjing Hydraulic Research Institude (NHRI) Hohai University (HHU)

5 th International Symposium on IWRM 3 rd International Symposium on Methodology in Hydrology. Experimental study on mechanism of the nutrient export in a small watershed. Hongwei Liu. Nanjing Hydraulic Research Institude (NHRI) Hohai University (HHU) 2010.11.21, Nanjing, Hohai University.

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Nanjing Hydraulic Research Institude (NHRI) Hohai University (HHU)

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  1. 5th International Symposium on IWRM 3rd International Symposium on Methodology in Hydrology Experimental study on mechanism of the nutrient export in a small watershed Hongwei Liu Nanjing Hydraulic Research Institude (NHRI) Hohai University (HHU) 2010.11.21, Nanjing, Hohai University

  2. How does the non-point sources pollution get into the environment? TOPIC NPSP Eutrophacation Rain-Runoff

  3. Study Area Meilin Watershed • closed watershed • area: 69 hm² • 9 km west to the Taihu Lake • subtropical monsoon climate • precipitation averages: 1177 mm • evaporation averages: 950 mm

  4. Methodology Field + Lab experiment Computer Simulation

  5. Field Observation Design Discharge measuring and water sampling at the outlet • Weather station • Temperature • Windspeed • Humidity • Solar radiation

  6. Sampling & Analyzing Items

  7. N, P export at the outlet • The concentrations of the nutrients are pretty high at the beginning of the flow processes • The nutrients concentration peeks turn up earlier than the flow peeks • There is a second nutrients’ peek after the flow peek • Nitrate concentrations are quite steady

  8. N, P export at the outlet A C B • The nutrients who are easy to be eluviated have a thinner B&C zone • The nutrient who are easy to be absorbed has a broader B&C zone • Total nitrogen is between

  9. N, P export on different landuse N(5/28/2008) P(5/28/2008) N(6/9/2008) P(6/9/2008) • Significantly • Complex • Random

  10. Regression analysis xrunoff is runoff (mm) xss is total suspended solid produced on unit area (kg·ha-1) , pollution load vector, (g·ha-1) , impact factors vector C0, constant term, C0=O; M, regression coefficient matrix

  11. Surface nutrients load in the watershed

  12. Conclusions Agricultural nutrients output from the small watershed depends on rainfall erosion, runoff eluviation, and landuse. In the same landuse area, the nutrients output processes are influenced significantly by the hydrologic processes. The erosion effect of the rainfall tends to be higher in the early nutrients output process, but the eluviation effect would be more important when the quantity of the runoff larger than some threshold. It seems nitrate nitrogen is mainly influenced by the eluviation effect while the ammonia nitrogen and phosphate phosphorous are more influenced by the erosion effect. The results show that most of the nutrients load comes from the ground surface and carried out by the runoff. Generally, 70~80% or more nitrogen load output is consist of the surface load in the Meilin watershed, while the number of the phosphorous is 80~90% or more. 1 2 3

  13. More Research — Rain-runoff process

  14. More Research — Soil water movement Hydrus 2D simulation

  15. More Research — SWAT2005 Landuse HRU DEM Soil type TSS Organic P Dissolved P Organic N Nitrate

  16. 谢 谢! Thanks for your attention!

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