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CI & VA lMDLs 0254 . . hup:/lwww.kdhe.st3le.ks.us/tmdlluastream having the largest average concentrations among samples, also had the lowest average loads. The average load seen in 1963-1969 was 788 tons per day, By 1990-1999. the average was 1533 tons per day, Given that more flows around 200 cfs have crossed thc stateline recently. the constant conccntrations within those !lows have driven up the mass of sulfate entering Kansas, Some dilution is seen on a plot of concurrent sulfate concentrations at Coolidge and Pierceville (Figure 8), Considerably more dilution is seen at sulfate levels above 1700 mgll. A regression line plots below the I: I line csscntially beyond thc 1500 mglllevel. Ovcrall, conccntrations near Gardcn City arc 94% of those at the stateline, Of interest, however. are the six outliers seen at Coolidge concentrations of 1100-1300 mg/1. The elevatcd sulfate conditions seen at Pierceville rdati ve to concentrations crossing the stateline correspond to dales of no or low flow at the Garden City gage in 1988 and 1990, Prior to these incidents. pcrsistent flow IVent past the gagc from 1986 to mid-April of 1988, Sporadic f10lV then occun'ed in May and June of 1988 as well as June of 1990, July and August of 1988 saw no flow during those Illonths, The heightened sulfate at Pierceville during April to June of 1988 and June 1990 may retlect discharge from bank storage of high sulfate water below Garden City after recent flow events, The incidence of high sulfate dllling July and August of 1988 may be local groundwater seepage in the vicinity of Pierccville. or wastewater frolll Garden City which made it to Piercevi lie in a more concentrated condition after evaporative loss. There are no ditches present between Garden City and Pierceville and the power plant in Garden City, while having cftlucnt high in sulfatc, was not operating during this timc petiod, Analysis of the remaining conculTent data, indicate sulfate levels at Pierceville remain near or below the concentrations seen upstream Finally, initial analysis of ground watcr quality by Kansas Geological Survey indicates cvidence of increased total dissolved solid concentrations and sulfate in the ground water profile over the last 3-4 decades. CUlTent data hint that recent tlows with lower sulfate concentrations may result in improved water quality in the upper layers of the alluvium, Levels of higher sulfate and dissolved solids may migrate downward through the alluvial matelial into the underlying High Plains Aquifer over time, The indication is as long as the river loses water to the alluvial deposits and remains high in sulfate. some degradation in ground water quality should be expected to occur, notwithstanding CUlTcnt water quality standards pertaining to ground water recharge, Desired Endpoint Condition of Water Quality at Station 286 over 2005 -2010 While the ultimate goal of a TMDL is attainment of the applicable criteria associated with the water quality standards and designated uses of the segment in question; 250 mg/l in this case, the historic data taken over the range of flows indicates that such a goal is unallainable. Similarly, the standard for livestock watering (1000 mgl)) cannot be reliably met, given elevated background conditions seen in the liver. There are two conditions which indicate the inability of any cOITective actions to bring about achievement of the 250 mgll cliterion. The first occurs at high flows ahove ~50 d's and represcnts the typical sulfate condition while the watershed is in a diluted state, Sulfate levels average 1570 mgfl over 1987-1999 at flows over 250 cfs, ranging from 767-2392 mgl!. This condition probably represents the contemporary background level which might bc reached with the cessation of inigation activity in the basin, Such conditions are infrequent, occurring less than 15% of (he time, They do, however, indicate the unlikelihood that the 250 mgll critelion can be achieved, The second background level occurs below ~OO cfs, representing the long term impact of water use and reuse within the Arkansas River valley, As seen before, there is little change in concentration with flow within the I 0-~50 cfs range, averaging 2000 mg/!. Cessation of irrigation would not notably reduce sulfatc levels until sufficient time had passed to purge accumulated salts within the valley ground water and soil profiles. Even then. natural geologic contributions from Cretaceous shales along the tivcr would maintain .d""101 i-n-