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2.4 Results and Discussion <br />2.4.1 Hydrogeologic Monitoring <br />Furcow irrigation practices at the site employ a series of ditches to divert water from Monument <br />Creek. The main diversion ditch carries water across an upper terrace located in the southeast <br />site area, elevated approximately 10 to 12 feet above site wetlands to the west. Irrigation inputs <br />to underlying groundwater in this pasture probably stem from direct application and ditch leakage. <br />Wells SE-1 and SE-2 were installed on either side of this main ditch but were too shallow to <br />intercept water table. Saturated sediments were noted when SE-1 was drilled possibly reflecting <br />descent of the irrigation water wetting front through these permeable sediments. <br />Macroscopic soil analyses, based on soil cores, indicate highly permeable sediments occur in the <br />upper 4 feet of ground surface. Site soils are dominantly red to brown sandy loams overlying a <br />gravel sequence up to 15 feet thick, outcropping at the surface in some areas. Clay loams occur <br />in the upper soil profile (0-1 ft) of low-lying areas occupied by wetlands. These soils typically <br />have 6 inches of organic material overlying silty sands with clay. <br />Crroundwater levels in all wells (not dry) show an overall decreasing trend in elevation over <br />monitoring period. Water table depths ranged from 0.3 to >3.6 R bgs in November 1998 and <br />dropped to >2.9 to >4 ft bgs by June 1998, leaving all wells dry except for 5E-20 (Appendix <br />A. I). In general, groundwater levels drop rapidly in the first three months (November - January), <br />recede more gradually during February -March period, and drop rapidly again towards end of <br />monitoring period April -June. Water table drop in this intermediate period is more gradual <br />probably as a result of shallow groundwater recharge via snowmelt infiltration. Wells SE-14 and <br />5E-15 reflect this recharge event showing a March increase in groundwater levels. <br />Shallow groundwater flows from east to west across the site. Temporal and spatial water table <br />fluctuations, as depicted by hydrographs (Appendix A.1), reflect how the pulse of artificial <br />recharge from irrigation input moves in the shallow (local) groundwater flow system. <br />Hydrographs for wells located in the southeastern portion of the site (wells SE-3 - SE-6) show <br />rapid decreases in water levels and go dry within two months once irrigation water is shut-off. <br />Whereas, wells located to the west (wells SE-I 1 - 5E-16) show a more gradual water-table <br />recession. The more gradual drop in water table observed in the western most wells reflects <br />longer travel times as the pulse of water from artificial recharge via irrigation discharges west <br />towards river. <br />Spring discharge could also account for some inputs to overall wetland water budget but are <br />minor in comparison with irrigation inputs. Wetlands located directly downgradient from the <br />springs receive some inputs to support small wet meadow areas but not enough to sustain larger <br />areas that functioned as discharge wetlands in the past (i.e., under irrigation). Spring discharge to <br />the local groundwater system could also be responsible for supporting groundwater levels in wells <br />4 <br />