N. Toride et Fj. Leij, CONVECTIVE DISPERSIVE STREAM TUBE MODEL FOR FIELD-SCALE SOLUTE TRANSPORT .2. EXAMPLES AND CALIBRATION, Soil Science Society of America journal, 60(2), 1996, pp. 352-361
The use of the stream tube model developed in the first part of this s
tudy is illustrated for several examples with a stochastic pore-water
velocity, nu, and distribution coefficient, K-d, The model allows quan
tification of the concentration variance in the horizontal plane to ev
aluate models for transport in heterogeneous fields, Increased vertica
l solute spreading due to stochastic local-scale parameters is accompa
nied by increased horizontal variations of the held-scale mean concent
ration. Solute application at the surface is modeled as a boundary val
ue problem (BW) and an initial value problem (IVP), The field-averaged
concentration vs. depth exhibits more spreading for the BVP than the
IVP since a variable solute mass is applied to each stream tube in the
latter case, Flow is also modeled by a lognormal probability density
function for the saturated conductivity, K-s, and the unit gradient as
sumption instead of nu. The use of a random nu instead of K-s is prefe
rable for small variations in water content, Results of the stream tub
e model are compared with those of a one-dimensional macroscopic conve
ction-dispersion equation (CDE) with effective parameters (i.e., depth
-dependent constants), When these constants are determined from time m
oments of the held-scale flux-averaged concentration, (c) over cap(f),
for the BVP, the stream tube model and the macroscopic CDE will give
different results if the effective parameters are used to model other
transport scenarios, Finally, the stream tube model was fitted to the
concentrations obtained from a detailed numerical simulation of flow a
nd transport in a (hypothetical) heterogeneous field, The (simple) str
eam tube model appears to provide a sensible description of the held-a
veraged concentration and variance.