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Site SW-N102 is located on the lower end of a small return ditch that flows into Calamity <br />• Draw approximately one quarter mile downstream of Site SW-N101. When flowing, water <br />quality samples have been collected at this site since July of 1986 (see Appendix 7-9). <br />Table 7-49 presents a statistical summary of all water quality data collected at this <br />site. Figure 7-30 shows the means of milliequivalent values for the major ions during <br />both seasons. <br />The water type at SW-N102 during the two seasons is a calcium sulfate. Figure 7-30 <br />demonstrates that, even as levels of each major ion increase after the irrigation season <br />ends, the relative proportions of each ion remains consistent (see Appendix 7-8 ). The <br />mean value of pH during irrigation is 7.7, while averaging slightly lower during periods <br />of no irrigation (7.39). <br />Mean TDS also increases after the irrigation season ends, averaging 1900 mg/1 during this <br />period in comparison to a mean TDS of 1,176 mg/1 during the irrigation season. <br />After the irrigation season has ended, TSS, FeT and FeD all average slightly higher (12.5 <br />• mg/1, .88 mg/7 and .39 mg/1, respectively) than during the irrigation season (6.8 mg/1, <br />.49 mg/1 and .OB mg/1, respectively). These higher averages for these constituents at <br />SW-N102 after the irrigation season ends probably reflect the gradual recession of tail <br />water discharge (hence, higher concentrations) after irrigation ceases. <br />Surface water Site SW-N103 is situated in Calamity Draw about 6 miles downstream of <br />SW-N101, It is the furthest downstream monitoring site Peabody routinely monitors for <br />water quality in Calamity Draw. Monitoring for water quality at SW-N1D3 began in July of <br />1986 (see Appendix 7-9). Table 7-50 is a statistical summary of water quality data <br />collected at this site. Figure 7-31 presents a Schoeller diagram of mean milliequivalent <br />values for the major ions during both seasons at Site SW-N103. <br />The water type at Site SW-N103 for both seasons is a calcium magnesium sulfate (see <br />Appendix 7-8). This water type is very similar to waters sampled upstream in Calamity <br />Draw at Site SW-N101. Figure 7-31 shows an identical trend of increased levels of the <br />major ions during the non-irrigation season as depicted in Figure 7-29 for Site SW-N701. <br />Interestingly, if one overlaid each figure, it is evident that, during periods of <br />• irrigation, the major ions at SW-N103 are slightly lower than shown at SW-N1~01. This <br />suggests that contributions to flow in Calamity Draw between these sites due to irrigation <br />tail water provides a dilution effect. <br />7-147 Revised 04/11/88 <br />