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Surface water and energy budgets of the La Plata Basin

Surface water and energy budgets of the La Plata Basin. Fengge Su, Dennis P. Lettenmaier University of Washington, Seattle, WA. Background. The La Plata basin is the sixth largest in the world, and spreads over five South American countries.

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Surface water and energy budgets of the La Plata Basin

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  1. Surface water and energy budgets of the La Plata Basin Fengge Su, Dennis P. Lettenmaier University of Washington, Seattle, WA

  2. Background • The La Plata basin is the sixth largest in the world, and spreads over five South American countries. • It plays a critical role in economies and water resources of the region. Bolivia Brazil Paraguay Argentina Atlantic Ocean Uruguay Area: 3.1×106 km2 La Plata elevation (m)

  3. Scientific questions • How predictable is runoff in the la Plata Basin, and what are the limiting factors? • What is the spatio-temporal variability of the water and energy budgets of the La Plata? • Does the moisture convergence balance the surface runoff in the basin? • What are the closure status of the water and energy balances in the region?

  4. Data and methodology The water and energy budgets of the La Plata basin are evaluated using a combination of: • Offline simulations of a macroscale hydrology model (VIC), • European Centre for Medium-Range Weather Forecasts (ECMWF) 40-year Reanalysis (ERA-40), • P-E which is calculated from the ERA-40 atmospheric water balance, and • Available observations.

  5. The VIC macroscale hydrologic model • Model features: • multiple vegetation classes in each cell; • energy and water budget closure at each time step; • subgrid infiltration and runoff variability; • and non-linear baseflow generation.

  6. Precipitation stations for 1986 (2050) Temperature stations for 1986 (125). Paraguay Parana Paraguay Parana Uruguay Uruguay LowerBasin Lower basin

  7. Mean Monthly Streamflow (1979-1999) Paraguay Parana Parana at Jupia Area:478,000km2 Paraguay at Bermejo Area: 1,100,000km2 Paraguay Parana Uruguay Iguazu at EstreitoArea:63,236km2 Parana at Posadas Area:975,000km2 Uruguay at Paso de los Area:189,300km2 Simulated Observed

  8. Water balance equations • Atmospheric water balance: • Land surface water balance: • For long-term means the atmospheric vapor flux convergence should be balanced by runoff.

  9. Annual average precipitation over the entire La Plata basin (1979-1999) This study: derived from daily station data CRU: Climatic Research Unit global monthly half-degree data sets (New et al., 2002) Vasclim: Variability Analysis of Surface Climate Observations (VASClimO) global monthly half-degree data sets (Beck et al., 2005) ERA-40: ERA-40 reanalysis

  10. Annual average evaporation over the entire La Plata basin (1979-1999) Implied E = Observed P - (P-E)

  11. Annual average runoff over the entire La Plata basin (1979-1999) P-E: calculated from the atmospheric moisture flux convergence using ERA-40 wind and humidity fields

  12. Seasonal means of surface water balance components (mm)

  13. Monthly time series of surface water budget terms for entire the La Plata basin from the VIC model, and ERA-40 reanalysis for (1979-1999). VIC/OBS ERA-40

  14. Annual average water balance terms from the Observations, VIC Model, and ERA-40 reanalysis for the Uruguay, Parana, Paraguay, and the entire La Plata basins (1979-1999). Implied E = P – (P-E) Implied R = P-E

  15. Surface energy balance RH: Net radiation (w/m2) LH: Latent heat fluxes (w/m2) SH: sensible heat fluxes (w/m2) GH: Ground heat fluxes (w/m2) ΔH: Heat storage (w/m2)

  16. Annual average heat fluxes from the VIC model and ERA-40 reanalysis (1979-1999): RH: Net radiation (w/m2) LH: Latent heat fluxes (w/m2) SH: sensible heat fluxes (w/m2)

  17. Seasonal means of surface energy balance components (w/m2) Residual = RH-LH-SH

  18. Monthly time series of surface energy budget terms for entire the La Plata basin from the VIC model, and ERA-40 reanalysis for (1979-1999). VIC/OBS ERA-40

  19. Annual average energy balance terms from the Observations, VIC Model, and ERA-40 reanalysis for the Uruguay, Parana, Paraguay, and the entire La Plata basins (1979-1999). Residual = RH-LH-SH

  20. Conclusion • The lack of observed high resolution forcing data and the inadequate representation of the pantanal in the VIC model, are the main limiting factors in runoff simulation over the La Plata basin. • There is a spatial and temporal (seasonal and interannual) variation in both water and energy balance characteristics across the entire basin. • There are still large unresolved differences between observed R and the moisture convergence calculated from ERA-40. • The unclosure terms of both water and energy balance in the VIC model are much smaller than those in the ERA-40 reanalysis.

  21. Thank You!

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