31
have given the same horizontal and vertical weighting, but with slightly different results
since the number itself indicates how much influence points farther away have on a node,
with larger numbers causing less influence from more distant points. The 2-2 model did not
produce the surface hydrofacies 1 deposits that are seen in the raw well data (Fig. 2.9). Also,
the model showed vertical tubes of sand and gravel (Fig. 2.10), which does not make
geologic sense. Therefore, all subsequent models were selected with more weighting in the
horizontal direction to reduce this effect.
Table 2.3. Hydrostratigraphic model runs in RockworksTM. The two numbers for each
model indicate the n values for horizontal-vertical weighting. The smaller number is the
direction of preferential weight, in this case the horizontal direction. The descriptions give
relative amounts of horizontal weighting and the major flaws in each model.
2-2        Base case; no weighting; vertical tubes, no eastern surface clay
0.2-3      Slight horizontal weighting; vertical tubes, no eastern surface clay
0.2-6      Slight horizontal weighting; vertical tubes, no eastern surface clay
0.2-10      Slight horizontal weighting; vertical tubes
1-3       Slight horizontal weighting; vertical tubes, no eastern surface clay
1-10       Slight horizontal weighting; vertical tubes
1-20       Average horizontal weighting; no extreme problems
1-30       Average horizontal weighting; no extreme problems
1-50       Average horizontal weighting; horizontal sand layers
1-65       Extreme horizontal weighting; horizontal sand layers
1-100       Extreme horizontal weighting; horizontal sand layers, no eastern surface clay
All of the models with slight horizontal-vertical weighting (Table 2.3) showed
vertical tubes (Fig. 2.10), while those with extreme horizontal weighting began to show
continuous horizontal layers of hydrofacies 3 (sand), inconsistent with the six cross sections
(Fig. 2.3. and Appendix 1) that indicated the sands are not well connected laterally. At the
extreme of 1-100 (Fig. 2.11), the deeper portions of the valley were almost entirely
hydrofacies 3 (sand) and once again hydrofacies 1 was not present at the surface. Based on
these observations, only two models (horizontal-vertical weighting of 1-20 and 1-30) were