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C. West Return Ditchl - Flow and Quality <br /> 1. Site SW-N7 <br /> Site SW-N7 is located on the West Return Ditch upstream of <br /> mining as shown on Exhibit 1. Flow and quality data have routinely <br /> been collected from this site since March of 1986; these data are <br /> presented in, Appendix B and statistically summarized in Table 14. <br /> A hydrograph constructed from monthly instantaneous flow <br /> measurements is shown in Figure 8. A trilinear plot of the major <br /> ions is depicted in Figure 2. <br /> Monitoring at this site did not begin until March of 1986 because <br /> the need to collect baseline data on the West Return Ditch upstream <br /> of the triangle area (which lies between SW-N7 and SW-N6) was not <br /> apparent until this time. The triangle area was planned to be <br /> mined in early 1987 but this plan has temporarily been abandoned; <br /> however, monitoring at this site will continue for the purpose of <br /> obtaining baseline data in the case that mining may occur in the <br /> future in the triangle area. <br /> Again, for previously discussed reasons, flow at this site is <br /> reflective of the seasonal use of irrigation water. From the <br /> record to date, flow was at a low of 0.006 cfs in April rising to a <br /> peak of 0.856 cfs in June. <br /> Perusal of the data in Table 14 and Figure 2 indicates that the <br /> quality of the water at this site can be classified a Ca-HCO3-SO4 <br /> type. The relatively high percentage of HCO3 reflects its origins <br /> from the San Miguel River via the Second Park lateral . San Miguel <br /> River water as sampled from the West Lateral irrigation ditch this <br /> spring (1986) shows this water to be a Ca-HCO3 type (see Appendix <br /> 6) ; Second Park lateral water is assumed to be closely similar to <br /> 1Note: The drainages referred to as the "West and East Return Ditches" <br /> are part of the natural surrounding drainage pattern. Return water from <br /> irrigation flows into these drainages because of their location and the <br /> rather inefficient method of flood irrigation used upstream. The <br /> "ditches" were never designed as ditches, per se, or for irrigation <br /> purposes. <br /> 41 <br />