Laserfiche WebLink
<br />. <br /> <br />002891 <br /> <br />. <br /> <br />whether flows measured during these studies were representative of typical <br />"low" and "high" flow periods, the measured flows were compared to the <br />historical 7-day 10-year low and high flows at several stream gaging stations. <br />This comparison is shown in Table 5. It is evident that neither the "low <br />flows" nor the "high flows" measured during these studies approach the <br />7-day average low or high flows expected to occur once each ten years at <br />the various stations. This indicates that the measured flows were neither <br />extremely lower nor higher than what might be considered an average flow <br />rate for each study period. This conclusion is supported by the fact that <br />the recurrance interval, indicating the most probable elapsed time period <br />before a flow similar to the measured flow occurs, averaged only slightly <br />more than one year for both the "low flow" and "high flow" rates. If <br />determination of baseline water quality at truly "low flow" and "high flow" <br />conditions is desired, the recurrahce interval should probably be at least <br />ten years or more. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />As shown by the profile map in Fig. 2, flows measured during the <br />Spring, 1976 "high flow" study generally averaged from three to ten times <br />higher than flows measured during the "low flow" study in the Fall of 1975. <br />Exceptions to this range of flows were observed at several sampling stations <br />located on streams affected by irrigation diversions and return flow (CC-8, <br />LBC-9, MC-19) or by other undetermined natural hydrologic characteristics <br />(YC-3, MC-lO). <br /> <br />. <br /> <br />Tempe ra tu re <br /> <br />Temperature profiles for the White River are presented in Fig. 3. <br />The profiles show that water temperatures during the Spring runoff period <br />averaged approximately 20 C higher than during the Fall sampling period. <br />The colder water temperatures observed during the Fall study were Simply <br />due to colder weather present during the late September - early October <br />sampling period. Past records show that the warmest stream temperatures <br />are usually recorded during July, August, and early September. The <br />temperature profiles also show the gradual increase in water temperature <br />in the downstream direction. The reason for the relatively high average <br />temperature recorded during the Fall study at station WR-6 (RM 144.3) <br />near Meeker is because these measurements were made during warmer weather <br />two weeks earl ier than any of the downstream measurements. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />The dependence of water temperature upon the time of day during whjch <br />samples were collected is also an important consideration in evaluating <br />temperature data. For example, in Appendix A, water temperatures at <br />WR-4 (RM 116.1) varied from 7.50 C at 0915 on 10/2/75 to 14.00 C at 1515 <br />on 9/29/75. In summary, all of the measured water temperatures were less, <br />than the cold water criterion of 200 C during the two study periods. <br /> <br />pH <br /> <br />. <br /> <br />pH measurements were generally within the acceptable range of 6.5-9.0 <br />standard units (S.U.) except for one measurement of 6.4 recorded at the <br /> <br />17 <br /> <br />. <br /> <br />.1: '.it <br />