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i• <br />The Eftaets of Irrigation on the Ground and Surface Water Chemistry. The Nucla Eaat area <br />is presently irri gatetl with water from the San Ml goal River, via the Hi ghlSne Canal, which <br />is locally celled the Second Park Irrigation' Ditch. Ybis water Ss of high Quality, <br />•intlteated by analyses of sampl as collected from monitoring sites SW-N105, and SW-N106. <br />The TDS of this water ranges trap approximately 115 to 275 mg/1. <br />Tha water qual lty Sn Calamity Draw has been measured et sites SW-N1D1 and SW-N103. Table <br />77-12 aunmart zee TDS data for these si tea, for irrigation and non-irrigation seasons. <br />Site SN-N101 is upstream of the proposed area to be ni ned, white SW-N103 is downstream. <br />The TDS eoneentrati one during the non-trri gation, base-flow season era ai mi tar to those <br />measured in ground water samples. An increase in TOS at the downstream sS Ces is apparent. <br />Dur{ng iha trri getian season, dilution with San Miquel RS ver Water decreaaea <br />concentrations to approximately one-third of concentrations durt ng the non-f rrtgation <br />season. <br />Table 17-73 presents calculated fluxes of sulfate (concentration times stream flow) past <br />the moni tor; ng stations (SW-N101 and SN-N703), the change in sulfate flux between the two <br />_ atati one, and astinated eombi netl ground water dl seharge and au rfaee runoff (celeul sled by <br />• auDtracti~ the measured flow at SW-N107 and SW-N102 (on an upstream tributary to Calamity <br />Draw) from the measured flow at SW-N103j. Tha {rrtgation ceason ran tram apProzimetely <br />May through Septenher. Ungauged influx Tnto Calamity Draw increases sharply (f ras 1.14 to <br />7.73 efs) with the beginning of irrt gati on in May 1987. (The di ache rge measurement at <br />SW-N701 for June 24 fa ineonaS ateni M th other data, so that the calculated fluxes are <br />. Ques ti onebi e). Nith cessatf on of irrigation, the ungaugetl Influx decreaaea over s pnri od <br />of several months. lrrT gati on causes sulfate coneentratlona 1n the stream to decrease, <br />while at the same time the flux of sulfate increases. The decrease Tn concentration is <br />offset Oy the increase in flow. Within the stretch between SW-N101 and SW-N103, the <br />stream picks up beMSen 8,000 end 33,000 (ar higher) kg 504 par day, dapendSng an She <br />season. This increase in 504 faux Ss partially due to ground water. For the July 18, <br />1986 sampling, the ungaugad inflow had a concentratton of about 900 to 950 m9/i <br />(Ca7eulatatl by di vTdi ng the lnerease to sulfate tiux by the increase In streamflow). This <br />coneentratt on is greater then the sulfate coneentrati on in the trrlgati on hater, <br />indteati ng a ground water component. A similar analysts for ADri 1, 1967 intlieatee an <br />• influx sulfate cancentratS on of shout 2,400 mg/1. Sulfate Concentrations in samples Of <br />overburden ground water near Calamity Drew range from 875 mg/1 (end of irri gation season) <br />to 2.650 mg/i (entl of non-irrtgatf on season). <br />17-52 Revised 04/tl /88 <br /> <br />REVISED MARCH 2006 Attachment 2.05.6(3}2-61 <br />