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• z.oa.7 <br />RESPONSE continued <br />The siz sites (S-1 through 4. 7 and 8) were located such that <br />they could provide baseline data from all areas to be permitted <br />and continue to provide operational and poet-operational surface <br />water resource data. The sites on Dry Creek provide data from <br />the mountainous pastures (S-7) and the cultivated flats (S-8). <br />The sites were also selected to provide data on the effects of <br />different geological features upon surface water resources. The <br />amount of recharge to or discharge from the Trout Creek sand- <br />stone may be approrimated by canparing simultaneous observa- <br />tions at flow at S-1 with those at S-z or S-3 with S-a. Dry <br />Creek's changes in water quality caused by runoff or seepage <br />from the Lewis Shale may be approximated by comparing data <br />from S-7, which is isolated from the shale's outcrop, with data <br />from S-8 which is not. The data for streamflow within the <br />• adjacent area, as observed at the sin sites, is presented in <br />Table 3. <br />These observations, as well ae other literature (USDI-BLM, <br />1976), indicate that the three streams are not perennial. At <br />best, all could possess intermittent reaches. However, it is most <br />likely that they are ephemeral. Hayden and Dowden Gulches <br />probably flow for the shortest duration; from one to two months <br />during spring runoff. Dry Creek has the larger drainage area <br />and greatest use of water (storage in reservoirs) indicating <br />flows for a longer periods of time.. Perhaps for four months <br />each year. Observations indicate that flow on Dry Creek's main <br />stem occurs during appro~mately the same period ae for the <br />other two streams. It is possible that upstream regulation of <br />Temple, Emrich and Dill Gulches by storage reservoirs may alter <br />the natural seasonal variability of flow in Dry Creek. All three <br />drainages may flow briefly during their normally dry periods as <br />• a result of runoff from intense convective precipitation. Esti- <br />mates of peak flow rates associated with precipitation events of <br />various recurrence intervals are provided on Table 4 for each <br />site. <br />