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, ,'-- ' . 002835 . furthest upstream station on the White River (RM 192.6) during high flow. As shown in Fig. 4, pH values during the Fall exhibited a smooth trend of increasing pH in the downstream direction with lowest values near the headwaters (RM 187.1, pH = 7.1) and highest values downstream near Rangely (RM 78.2, pH = 8.1). During Spring runoff, this trend was much more irregular, with highest pH measurements occurring in the intermediate stream reach near Pi ceance Creek. The pH measurements made during "low flow" ranged from 0.2 to 1.0 SU higher than measurements made during "high flow". . Dissolved Oxygen . As shown in Fig. 5 most dissolved oxygen measurements averaged greater than 7.0 mg/l. The only exceptibn' was Yellow Creek, which averaged approx- imately 4 mg/l D.O. during both study periods. These concentrations were well below the minimum criteria/standard values of 5-6 mg/l. However, some difficulties were encountered in field preserving these water samples because of the foaming action caused by the reaction of the preservative reagents with the minerals in the water (TDS~4000 mg/l). The measured D.O. concentrations may, therefore, not be truly representative of the actual in-stream D.O. in Yellow Creek. Published data for D.O. concentra- tions at this location have been generally higher (7-9 mg/l) for these same time periods (GS, 1974). The dissolved oxygen profiles shown in Fig. 5 for the mainstem White River indicate similar concentrations in the upstream reach during both study periods, while downstream concentrations were consistently higher during the Fall "low flow" study. These higher D.O. concentrations during "low flow" are probably related to the colder water temperatures measured during the Fall study in the lower White River drainage. . . . Hardness . Hardness of surface waters is composed primarily of calcium and magnesium ions. Other metal ions, such as iron, manganese, and strontium may con- tribute to water hardness if they are present in appreciable amounts. Although not necessarily an indicator of water quality itself, the amount of hardness present in stream water has been shown to be a significant factor in the toxicity of various metals to aquatic life. Profiles of water hardness in the White River, in selected tributaries, and in Milk Creek are shown in Fig. 6. Hardness concentrations ranged from 35 mg/l to 265 mg/l in the mainstem \~hite River while tributary concentrations greater than 500 mg/l were measured in Yellow Creek (566 mg/l), Little Beaver Creek (500 mg/l), and Miller Creek (514 mg/l). These measure- ments are indicative of very hard water and are due primarily to high concentrations of calcium and magnesium ions. Water hardness was significantly greater during the "low flow" study due at least partially to the presence of higher concentrations of dissolved minerals (see Fig. 8- for the TDS profile). Hardness concentra- tions also showed a steady increase in the downstream direction in all . . 21 . lL