Soil-vegetation-atmosphere transfer in regional scale climate modeling. R.A. Feddes, K. Metselaar, l.wipfler and J.C. van Dam

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1 Soil-vegetation-atmosphere transfer in regional scale climate modeling R.A. Feddes, K. Metselaar, l.wipfler and J.C. van Dam

2 Water balance components P E R D root q p

3 Global circulation

4 Atmosphere Processes schematization rain/irrigation interception Plant Unsaturated zone transpiration soil evaporation surface runoff Surface waters Saturated zone seepage/ percolation Deep Groundwater drainage/ infiltration Flow / transport of: soil water soil heat solutes Influenced by: hysteresis soil spatial variability water repellency shrinkage cracks drainage/ infiltration

5 Atmosphere Processes schematization rain/irrigation interception Plant Unsaturated zone transpiration soil evaporation surface runoff Surface waters Saturated zone seepage/ percolation Deep Groundwater drainage/ infiltration Flow / transport of: soil water soil heat solutes Influenced by: hysteresis soil spatial variability water repellency shrinkage cracks drainage/ infiltration

6 Soil water flow equation Darcy Continuity dz q S q q K H z t q z S

7 Water uptake by roots T act 0 T S z act D root D root s s s s s

8 Distribution root water extraction Root length density L root (cm cm -3 ) Potential root water extraction rate S p (d -1 ) Actual root water extraction rate S (d -1 ) z root Sp() z T 0 p D root L () z L () z z root S( z) S ( z) rw p 0 D root S z T p p

9 Actual root water extraction 1.0 T low rw T high h 4 h 3l h 3h h 2 h 1 Soil water pressure head 0.0 Actual root water extraction: S( z) S ( z) rw p

10 Effect root distribution Grass vegetation with 100% soil cover Loamy sand soil (B7 and O8 in Staring Series) Free drainage boundary condition at z = -200 cm At t = 0, h = -200 cm throughout soil profile No rainfall, potential transpiration T p = 4 mm d -1

11 Transpiration (mm/d) z (cm) Relative root density (-) Root1 Root2 4 Potential transpiration Root1 Root Time (days)

Soil depth z (m) Relative root density distribution 0.0 0.0 0.2 0.4 0.6 0.8 1.0-0.5 Steppe: c = 3.

12 Soil depth z (m) Relative root density distribution Steppe: c = 3.0 (Gruzis) Deciduous Forest: c = 3.0 (Kalisz) -1.0 Savanna: c = 2.17 (Le Roux) -1.5 Steppe: c = 1.6 (Akpo) -2.0 General: L root e cz

13 Cumulative root fraction Cumulative Root Fraction (Y) with Y 1 z

TESSEL-model for flow of water and heat Atmosphere Rain Interception Vegetation Transpiration Soil evaporation Surface runoff Root zone Unsaturated zone No groundwater table is

14 TESSEL-model for flow of water and heat Atmosphere Rain Interception Vegetation Transpiration Soil evaporation Surface runoff Root zone Unsaturated zone No groundwater table is present Soil is homogeneous over entire depth Root zone: entire profile (2.89 m) 4 numerical layers Water management absent (no irrigation or drainage) Percolation No Groundwater

15 Possible effects of modifications on soil water balance ET / ET p Precipitation P / Potential P/ETpevapotranspiration ET p

16 Groundwater dependent systems

17 Possible effects of modifications on soil water balance ET / ET p Precipitation P / Potential P/ETpevapotranspiration ET p

18 Tests with the detailed SWAP model Discretization Maximum rooting depth Leaf area index as a function of time Soil depth (shallow - deep) Root extraction Soil texture Bottom boundary condition (Groundwater)

19 Effects SWAP tests on evapotranspiration ET Location: Hungary continental climate LAI(time) Texture LAI max h and K Critical h transpiration Partitioning ET p Rooting depth (time) Maximum rooting depth Root density profile Root water uptake (h ) Discretisation soil profile Year Stones Groundwater depth

20 Modifications in Tessel for Hungary Discretization Soil Depth Groundwater Root water uptake Introduced changes

21 ET- Tower, RS-SEBAL, [ET act and ET pot ] -SWAP ET(mm/week) ETact ETpot ETtower SEBAL time (days)

22 SEBAL computations Application of SEBAL voor 2005 SEBAL: Surface Energy Balance for Land Basis inputs: - Satellite based products Vegetation-index (NDVI) Surface albedo Surface radiation temperature - Meteorological measurements - Air temperature - Relative humidity - Windvelocityd - Transmissivitty/incoming radiation

23 SEBAL computations Satellite products Derived from the MODIS satellite 1 km resolution (thermal) Daily recording Total of 19 cloudfree images Transformed in weekly valuesof evapotranspiration for Hungary

24 Validation 2 measuring locations in Bugac en Matra Pixel is not homogenous! Bugac (Agriculture) Matra (Forest)

25 SEBAL (W/m2) Validation Evapotranspiration flux MATRA y = 1.048x R 2 = y = x R 2 = Rn H LE Linear (LE) Linear (Rn) measured (W/m2)

26 ET, SEBAL (mm/day) Validation fluxes with Bowen ratio 7 y = 1.236x R 2 = y = x R 2 = BUGAC - grass MATRA - forest 01:01 Linear (BUGAC - grass) Linear (MATRA - forest) Linear (01:01) ET, corrected with Bowen-ratio (mm/day)

27 Validation with Energy balance

28 Comparison with Rainfall Tropical Rainfall Measurement Mission (TRMM) TRMM rainfall SEBAL ET

29 Comparison with rainfall Tropical Rainfall Measurement Mission (TRMM) and point measurements (meteorological stations)

30 Conclusions 1) Measured net radiation agrees well with SEBAL estimate 2) Measured energy balance does not close 3) Corrected measurements agree well with the spatial SEBAL data 4) The spatial patterns of rainfall as measured by TRMM are reflected by the evapotranspiration values computed by SEBAL

Water Saving Technology

Water Saving Technology Water Demand & Irrigation Miguel Aguila aguila@gemuese-garten.com Prof. Dr. S. Kleisinger Project for Water and Fertilizer Use Efficiency November 6, 2009 EDUCATIONAL AND WORK HISTORY