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Field and laboratory experiments for parameterizing soil variables at complex tarrain

Field and laboratory experiments for parameterizing soil variables at complex tarrain. Tae Hee Hwang, Seongwon Eum, and Dowon Lee Graduate School of Environmental Studies Seoul National University Seoul 151-742, Korea. Introduction.

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Field and laboratory experiments for parameterizing soil variables at complex tarrain

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  1. Field and laboratory experiments for parameterizing soil variables at complex tarrain Tae Hee Hwang, Seongwon Eum, and Dowon Lee Graduate School of Environmental Studies Seoul National University Seoul 151-742, Korea

  2. Introduction Some parameters of RHESSys are greatly variable at complex terrain. Can we estimate the parameters from easily measurable topological indices (slope, elevation, aspect, etc.)

  3. Introduction Parameters for vertical soil moisture fluxes in RHESSys Ksat_0 : Saturated hydraulic conductivity at surface Porosity_0: porosity at soil surface M_z : conductivity with actual soil depth Porosity_decay : porosity scaling parameter with depth

  4. Study Area Seoul Gwangneung Experimental Forest, Gyonggi-do, Korea

  5. Study area • Vegetation type : • deciduous broadleaf (Quercus serrata, Carpinus laxiflora community) • Elevation : 270 ~ 490 m • Avg. slope : 19.0 ° • Catchment area : 22 ha • Forest age : 80 years

  6. Sampling points

  7. Field measurements • Soil type • Effective soil depth • Soil color • Slope • Vegetation type • Aspect • Bedrock

  8. Soil type, soil depth, soil color

  9. Laboratory measurements • Hydraulic conductivity (L/T) • Hydraulic conductivity decay rate with depth (1/L) • Porosity (dimensionless) • Porosity decay rate with depth (1/L) • Soil texture • Bulk density (M/L3)

  10. Saturated hydraulic conductivity (Ksat) time

  11. Macroporosity (Φm)(pF 2.7) pF meter DIK-3340 Daiki Co. Ltd.

  12. Results Ksat Φm R, L: slope, A: Toe, B: middle slope, C: upper slope

  13. Results Ksat decay rate with depth Φm decay rate with depth R, L: slope, A: Toe, B: midle slope, C: upper slope

  14. Results Bulk density (Db)

  15. Correlation Analysis Φm vs. Ksat A Horizons B Horizons

  16. Correlation Analysis with Topological Index (Slope) Slope vs. Ksat A Horizons B Horizons

  17. Correlation Analysis with Topological Index (Slope) Slope vs. Φm A Horizons B Horizons

  18. Correlation Analysis with Topological Index (Slope) Slope vs. Φm decay rate Slope vs. Ksatdecay rate

  19. Correlation Analysis with Topological Index (Elevation) Elevation vs. Ksat Elevation vs. Φm

  20. Correlation Analysis with Topological Index (Elevation) Elevation vs. Φm decay rate Elevation vs. Ksatdecay rate

  21. Correlation Analysis with Bulk Density Db vs. Ksat Db vs. Φm

  22. Discussion • Correlation bet. Φm and Ksat : Kozency-Carman Eq. • (Giménez et al. 1997, Comegna et al. 2000, Gloaguen et al. 2001, Jarvis et al. 2002 ) • Ksat αΦmμ Correlation appears only in A horizons μ = -0.2662

  23. Discussion • Correlation bet. slope and Φm • Correlation bet. slope and Ksat only in A horizons • (Lee et al. 1999)

  24. Discussion • Correlation bet. slope and Φm decay rate • Correlation bet. slope and Ksat decay rate Further study needs

  25. Conclusions • Some soil variables (e.g., Ksat, Φm, Ksatdecay rate, Φmdecay rate) may be estimated from topological indices (ex. slope). • Topological index can be considered in patch partitioning

  26. References Comegna, V., P. Damiani and A. Sommella. 2000. Scaling the saturated hydraulic conductivity of a vertic ustorthens soil under conventional and minimum tillage. Soil and tillage research 54: 1-9. Gimenez, D., E. Perfect, W.J. Rawls, Ya. Pachepsky. 1997. Fractal models for predicting soil hydraulic properties: a review. Engineering geology 48: 161-183. Gloaguen, F. , M. Chouteau, D. Marcotte, and R. Chapuis. 2001. Estimation of hydraulic conductivity of an unconfined aquifer using cokriging of GPR and hydrostratigraphic data. Journal of applied geophysics 47: 135-152. Jarvis, N.J., L. Zavattaro, K. Rajkai, W. D. Reynolds, P. -A. Olsen, M. McGechan, M. Mecke, B. Mohanty, P. B. Leeds-Harrison, and D. Jacques. 2002. Indirect estimation of near-saturated hydraulic conductivity from readily available soil information. Geoderma 108: 1-17.

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