C - Lublin
C - Lublin
C - Lublin
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0.4<br />
1000<br />
Moisture [Vol.]<br />
0.3<br />
0.2<br />
0.1<br />
moisture - 1 cm<br />
moisture - 2.5 cm<br />
moisture - 4 cm<br />
water potential - 1 cm<br />
water potential- 2.5 cm<br />
water potential - 4 cm<br />
900<br />
800<br />
700<br />
600<br />
500<br />
400<br />
300<br />
200<br />
100<br />
Water potential [hPa]<br />
0<br />
0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000<br />
Time [s]<br />
Fig. 2. Water content and water potential dynamic in soil column<br />
evaporation process<br />
Assuming that the process of water transport takes place under isothermal conditions<br />
and is one-dimensional, the Darcy’s low is valid for the proposed experimental<br />
conditions. The water flow can be described with the use of the following<br />
equation:<br />
⎛ ∂ψ<br />
( z,<br />
t)<br />
⎞<br />
q(<br />
z,<br />
t)<br />
= −k(<br />
ψ ) ⎜ −1⎟<br />
(1)<br />
⎝ ∂z<br />
⎠<br />
Alternatively the flux can be calculated from the equation:<br />
z<br />
∂θ<br />
( z,<br />
t)<br />
q(<br />
z,<br />
t)<br />
= − ∫ dz<br />
(2)<br />
t<br />
∂<br />
z= z<br />
0<br />
Comparing these equations it is possible to calculate the hydraulic conductivity<br />
k(ψ) from the equation:<br />
z<br />
∂θ<br />
( z,<br />
t)<br />
∫ dz<br />
∂t<br />
z=<br />
z0<br />
k( ψ ) =<br />
(3)<br />
⎛ ∂ψ<br />
( z,<br />
t)<br />
⎞<br />
⎜ −1⎟<br />
⎝ ∂z<br />
⎠<br />
Using this method it is possible to determine relationship between hydraulic<br />
conductivity coefficient and water potential (see Fig. 3) and so called dynamic<br />
retention curve (see Fig. 4).<br />
156<br />
0
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