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Evapotranspiration in a lotic wetland ecosystem G. Milton Ward

Evapotranspiration in a lotic wetland ecosystem G. Milton Ward Department of Biological Sciences and Center for Freshwater Studies University of Alabama Tuscaloosa, Alabama, USA. Water Budget. Evapotranspiration. Storage. Surface Outflow. Precipitation. Groundwater Flow. Alnus

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Evapotranspiration in a lotic wetland ecosystem G. Milton Ward

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  1. Evapotranspiration in a lotic wetland ecosystem G. Milton Ward Department of Biological Sciences and Center for Freshwater Studies University of Alabama Tuscaloosa, Alabama, USA

  2. Water Budget Evapotranspiration Storage Surface Outflow Precipitation Groundwater Flow

  3. Alnus serrulata Juncus effusus Talladega Wetland in October Beaver Dam Nymphaea odorata

  4. Talladega Wetland hydrologic installation

  5. Preliminary Water Budget for Talladega Wetland Evapotranspiration (mm) 879 64 % Storage = -3 301 22% 1367 Precipitation Surface Outflow 28621% Groundwater Flow

  6. Evapotranspiration- The E-T component of this budget was a spatially integrated average calculated from a modified Penman-Monteith equation. Spatial Mean = 75% of Pan estimate Because of the inherent uncertainty of such calculations, and the need to refine our ET estimate, we installed an eddy covariance system in the wetland. Evapotranspiration (ET) is an important component of wetland water budgets. A preliminary budget for the Talladega Wetland Ecosystem (Fig. 1 a, b) suggested that ET accounted for 64% of water losses from the system (Fig. 2). The ET component of this budget was calculated based on Penman-Monteith equations. Because of the inherent uncertainty of such calculation and the need to refine our ET estimate, we installed the eddy covariance system (Campbell Scientific, Inc.).

  7. Measurement of E-T using eddy covariance techniques Krypton Hygrometer Surface Energy Budget Rn= LE + H ± G Net Radiometer 3-D Anemometer Campbell Scientific, Inc.

  8. Equipment is deployed on a tower that rises above the canopy

  9. Equipment is deployed on a tower that rises above the canopy • 10 m tower in a stand of alder, Alnus serrulata • Surface energy budget data collected 10x per second and averaged over 30 min • ET (mm) calculated from effluxes of latent energy • Daily ET was calculated as the sum of daytime (Rn>0) 30 min ET • When necessary, data were corrected for closure of energy balance using the Bowen Ratio

  10. Surface Energy Budget Closure Is Needed !!! Advection can be a source of error

  11. 2002 2003 Daily Variation ranged between 0.46 to 4.4 mm/d in 2003 and 0.40 to 6.0 mm/d in 2002. The slightly higher rate in 2002 was attributed to a somewhat warmer and less humid growing season.

  12. Monthly E-T fluxes from Talladega Wetland

  13. Can ET be indexed to PET? Our longer term measurement of evaporation is that of potential ET, using a class-A evaporation pan. A comparison of actual ET versus PET in 2002 revealed that pan evaporation measurements tended to capture only 84% of AET as measured by Eddy Covariance.

  14. E- T at Talladega Wetland in comparison with similar habitats in the SE US

  15. Beaver pond exposed!!!! Where are those beaver when you really need them? Research support by funding from NSF EPSCoR and NSF IGERT programs

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