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-14- Algae taken at this station was predominately C~.adophora sp.9 large amounts of this algae is found floating through this section of the river during the late summer. The sampling site was approximately 300 feet above the Big Island Bridge on the west side of the river, The bottom consisted of rock from 1 to 4 inches in diameter, Alight layer of silt is present at this staticn during most of the year. Development of diatom populations was heavier at this station than any of the stations previously described, ~abellaria and Gomphonema were present in-large amounts on the sampling slides from the diatometer. Gymbella and Cocconeis were present in smaller numbers, and an occasional Navicula was found. Zooplankton populations were also higher at this staticn. The average number of organisms being 7.2 per liter, The organisms found in the plankton samples were primarily rotifers and ostracods. The bottom fauna was not noticeably higher than at the other stations. Representatives from all of the orders listed on Table V, Eottam Fauna, page 29, were taken except Annelida and Odanata. The change in chemical composition of the water was not great> An increase in total solids gives the only indicatian, i.n those analysis run, of a change in quality. Colifor?n counts were slightly 'higher than the previous station. Of the three plate counts made in November, 1958, two of the plates developed two colonies each, and the third plate developed one colony during incubation. The area between Stations No. 3 and No. 4 is not as ogen as previously described areas, The river, for much of the distance, is confined in a valley from 1/2 to 1 1/2 miles wide, .any bluff areas are present along the east side of the river where no vegetation growth is possible. The river alternates between shallow riffle areas of gravel and long deep holes. No tributaries enter the river between Stations No. 3 and No. 4. The surrounding hillside vegetation in this area is sagebrush, Artemisia frigida. Bottom lands are covered with greasewood, Sarcobatus vermiculatus; scattered stands of narrowleaf cottonwood are present along the river. Pre- dominate streamside vegetation is the sandbar willow, Salix Exigua. The physical and chemical data present in .Graph I on the following page was taken from the records of a sodium carbonate plant operated by the Inter- mountain Chemical Company. This plant, located approximately 20 miles east of Green River, Wyoming, utilizes one million gallons of water per day in its operation. The water is pumped from the Green River to a stand tank which has approximately one million gallon capacity. Water for plant use is fed into the powerhouse from this tank, and samples for chemical analysis are taken between the tank and the powerhouse. Temperature data varies somewhat from river temperatures because of the time spent in the tank. Turbidities and Si02 would also be slightly conservative.