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SOIL WATER GES175, Science of Soils. Water Movement - Surface water moves due to gravitational force Does water always flow downward? 3.2.

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Presentation on theme: "SOIL WATER GES175, Science of Soils. Water Movement - Surface water moves due to gravitational force Does water always flow downward? 3.2."— Presentation transcript:

1 SOIL WATER GES175, Science of Soils

2 Water Movement - Surface water moves due to gravitational force Does water always flow downward? 3.2

3 Capillarity Water moves into capillary soil pores Water moves into capillary soil pores - due to adhesive and cohesive forces 3.3

4 O H H O H H O H H O H H O H H O H H O H H O H H K+K+ Cl - O H H Osmotic Force Water movement across semi-permeable membrane 3.4

5 Energy Concept Water moves from high to low free energy wet soil dry soil wet soil dry soil H 2 O movement H 2 O free H 2 O free H 2 O free H 2 O free energy is energy is energy is energy is higher lower higher lower - difference in free energy causes H 2 O to move 3.5 Large PoresSmall Pores

6 Properties of Water Hydrogen bonding 3.6

7 Capillary Forces - smaller pores hold water with greater energy - nondirectional h = 0.15/r 2T cos r d g h = T = surface tension = wetting angle r = radius of pore d = density of water g = gravity 3.7

8 Water Movement by Capillary Action 3.8

9 3.9

10 Units cm H 2 ObarskPa , , , , , , see Table 5.1 in text atm = 760 mm Hg = 1020 cm H 2 O = 1 bar = 100 KPa

11 3.11 Sandy Soil Clayey Soil Water Content (%) Suction (bars) Water Retention Curves

12 Aggregated Soil Water Content (%) Suction (bars) Compacted Soil Water Retention Curves 3.12

13 Hysteresis drying wetting Suction (bars) 2r 2R drying wetting

14 Soil Water: Classification and Availability physicalbiological gravitational capillary vapor 3values are only semiquantitative unavailable (drainage) available unavailable (bars) 3.14

15 3.15 clayey sandy H2OH2O Concepts of Movement sandy clayey H2OH2O sandy H2OH2O

16 3.16 H pi H gi H inlet = H pi + H gi Reference level soil H po H go H o = H po + H go H H= H inlet - H outlet = H pi - H po Saturated Flow - Horizontal Column L

17 3.17 H1H1 L inlet Reference plain outlet H i = H 1 + L H o = Saturated Flow - Vertical Column H = H 1 + L


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