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" and bottom types are very much as would be anticipated. Rock and heavy rubble through the steep canyons" gravels and course sands in the slouina reaches of water and silt in the areas of least grade. Figures la through ld shoy the general relief of the Green River thro1Jgh the MJnument and the types of bottom that is found. Fisure 2 at Island Park would 'be typical of the slower waters of the low gradient areas. Temperatures Daily records at stream temperatures in 'both the Green and Yampa Rivers at Echo Park (Figure 3) are contained in the daily log. Of con- siderable interest and possible importance in the distribution of fish and insects is the constantly cooler water (as much as 4 to 5 degrees) in the Green River. This factor of cooler water could be very important in the faUure to find squawfish" humpback suckers or the humpback chub" and possibly other fish for any great distance up the Yampa River. unfortunately' there are no good data to suggest the preferred temperatures of the endemic :fish. A job completion report from the State of Colorado (Baily and Alberti, 1952) confirms this observation in temperature difference.. This report suggests Lily Park on the Yampa to be the zone of highest average tempera- ture for that river. The influence extends downstream to the confluence with the Green. Correlation series tests were made between the air and water temper- atures at Island Park for the period September 23 through Qetober 28. As might be expected the calculated r == .85 indicates a strong tendency for the data to cluster around a str a1.ght line relationship. Variance was approximate.q ten to eleven degrees bet"reen water and air. A simUar correlation between water temperature and dissolved oxygen over the same time period produced an even stronaer indication of a linear relationship with an r = .95. High dissolved oxygen was 10.6 parts per million at 48oF. and the low was 8.1 parts at 620F. Turbidity Daily changes in turbidity and water volumes were important observa.. tions of the summer study. River depths would rise and fall as much as five to seven inches or more per day. Turbidity was equally as extreme. In Island Park for example" Secchi disc visibility depths varied :trom an unbelievable 1/4 inch to a maximum 13k inches in approximately one month o:f observation. It should be noted that these data as given in Table 1 were for a period when maximum vis ibUity would be expected. The degree ot turbidity during the high waters ot May" June and Ju1.y# is demonstrated in the fact that gill nets could not be used during those months" even in quiet l1aters" unless they were parallel to the shore. In 8.D7 other position they would completely silt under during the night. The problem of turbidity is without question ot great importance in the habitat selection and special adaptations of both aquatic invertebrates and fish. In the Lodore area (Figure 4) where the character at the stream cba:xges abruptlJr" the ability of the Mayfly, Lachlania powelli Edmunds I =3= ~111i