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<br />1938 <br /> <br />;"'" ~ :-~~'vi ~t\JF.~i"l A 1...'':':: ,-::.:::" '.' ,- <br />:3U8JECT TO REVIS~;C.' <br /> <br />Arkansas River al Carion City <br /> <br />. <br /> <br />Station 07096000 (Arkansas River at Canon City) is located in the upper Arkansas River Basin about 28 mi <br /> <br />upsrream from Pueblo Reservoir (fig. I). Discharge and specific-conductance trends were analyzed at this site to <br /> <br />detennine if the quantity and quality of water flowing from the upper basin into the lower basin were different dur- <br /> <br />ing the period before the completion of Pueblo Reservoir (pre-1975) versus the period after the completion of <br /> <br />Pueblo Reservoir (post-l 974). Discharge and specific-conductance data were available for the 3 I-year period <br /> <br />1964-94. Discharge and specific-conductance data from 1964-74 were compared to data from 1975-94. <br /> <br />The median annual discharge at station 07096000 increased from about 520.800 acre-ft in 1964-74 to about <br /> <br />538.600 acre-ft in 1975-94: however, this difference in discharge was not statistically significant (p = 0.92). <br /> <br />Although there was no significant change in the median annual discharge. rhe daily discharge changed substantially <br /> <br />in several months of the two periods (fig. 5). Daily discharge increased significantly between the 1964-74 and <br /> <br />1975-94 periods in January. February. March, April, June, October, November. and December (table 2). Most of <br /> <br />. the increases occurred during the low-flow months when natural baseftow is supplemented by upper basin reservoir <br /> <br />releases. Daily discharge decreased significantly in July. August. and September (table 2). <br /> <br />Figure 5 near here. <br /> <br />Table 2 near here. <br /> <br />The monthly discharge trends might bave been caused by differences in the quantity of native runoff or by <br /> <br />differences in the quantity ofimporred western-slope water for the two periods of analysis. Historic snowpack data <br /> <br />from six locations in the upper basin (fig. I) were evaluated to detennine if differences in the magnitude ofche <br /> <br />snowpack for the two periods coincided with rbe differences in discharge. Snowpack is highly correlated with <br /> <br />native runoff and as used in this report, is a measure of the amount of water being held in storage as snow for poten- <br /> <br />. tial runoff. The annual April I snowpack was utilized in this analysis, because the April I snowpack typically rep- <br /> <br />180. <br />