PERMFILE116661

• Permit No: C1981008A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: Pages 7-154 to 7-204
• Section_Exhibit Name: NH1 TAB 7 Part 4
• Media Type: D
• Archive: Yes

along the West Lateral. Exhibit 7-6 presents the ditch course and the locations of known
• diversions along the West Lateral irrigation ditch. The labels for each surface water
site presented on Exhibit 7-6, 580104, 580105 and SB0106, correspond to Sites SW-N104,
SW-N105 and SW-N106, respectively.
From Table 7-54 it is evident that 62 percent of the ditch water was either diverted or
lost (due to evapotranspiration and seepage) from the West Lateral splitte flume to Site
SW-N106 (see Exhibit 7-1). The greatest percentage of lost flow (30 percent) occurred in
the reach between the "Benson's Corner" box (13) and SW-N105 (14). Along this reach, a
significant portion of the ditch banks are heavily vegetated with willow, wild rose and a
variety of grasses that commonly exhibit high rates of transpiration.
Interestingly, two reaches showed a gain in discharge. Between Site SW-N104 (5) and the
"cemetary" box (8), an increase in flow of 1.5 percent (from 19.4 to 19.7 cfs) was
observed. Also, between the "halfway" box (10) and the "bend" box (11), a 12.6 percent
increase in flan was observed (from 15.9 cfs to 17.9 cfs).
• Most
and reaches along the West Lateral lose irrigation
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being withdrawn along each reach through diversions on the day the study was performed, as
well as significant lengths of heavily vegetated ba nk sides. Seepage of irrigation water
occurs along the entire reach of the West Lateral, probably occurring at higher rates and
volumes along the "ridge top" reach where the ditch was excavated through the shallow
sails into the highly fractured sandstone.
The two reaches where the ditch featured gains in flow are portions of the general
"ridge top" segment of the West Lateral (see Exhibit 7-6). The ditch channel bottom in
this reach is largely fractured and weathered sandstone, and likely results in relatively
large amounts of seepage. This seepage, in combination with localized intensive
"flooding-type" irrigation, travels laterally through the shallow soils and fractured
sandstone eventually flowing back into the West Lateral slightly downstream. The
combination of fractured, weathered sandstone channel bottoms in the ditch and localized
"flood-type" irrigation along these two gaining reaches likely resulted in the measured
gains in flow.
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7-174 Revised 04/11/88