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<br />
<br />during December 1975, must be a reflection of oppos-
<br />ing mechanisms in operation. It is difficult to com-
<br />pletely assess these trends in the absence of a detailed
<br />statistical analysis of the data.
<br />
<br />Surface and spatial trends of particularly interesting
<br />parameters such as iron and manganese are discussed
<br />in greater detail in those sections.
<br />
<br />Depth Profiles
<br />
<br />The most common trend observed with depth was an
<br />increasing ion concentration for many parameters, the
<br />most obvious indicators being conductivity, hardness,
<br />sulfate, zinc, iron, sodium, and especially manganese.
<br />D.O. (dissolved oxygen) at times was observed to de-
<br />crease with depth, but only once to less than 50 percent
<br />of saturation at one site. A definite increasing concen-
<br />tration trend with depth was observed for at least one
<br />parameter during every month sampled at sites A and
<br />B during the period of July 1974 to May 1975. No
<br />obvious trends were observed at any other sites. The
<br />most clear case of localized stratification was observed
<br />the first sampling year during April 1975, at sites A
<br />and B where, for example, at site A the D.O. dropped
<br />from 10.2 to 5.1 mg/I, total conductivity rose from
<br />675 to 1200 J1S/cm, t-hardness rose from 272 to 560
<br />mg/I going from the surface to the bottom. Similar
<br />conditions prevailed at site B where, for example,
<br />manganese rose from not being detectable at the sur-
<br />face to 0.401 mg/I at the bottom.
<br />
<br />During the second year, depth trends were observed at
<br />sites A and B from June 1975 through September 1975,
<br />after which the depth trends seemed to disappear. How.
<br />ever, during the month of August, a very sharp depth
<br />profile was noted for several parameters, including an
<br />increase from 0,001 mg/I Mn at the surface to 0.627
<br />mg/I at the bottom, accompanied by a decrease in D,O,
<br />from 7.3 to 2.3 mg/1. Also, slight depth profiles were
<br />observed at this time at deep sites D and E. The pres-
<br />ence of the old Arkansas River diversion dam in the
<br />proximity of sites A and B may have a prominent ef.
<br />fect in causing stratification in that localized area. The
<br />trace metal that was most prominent in the observation
<br />of depth profiles was manganese and is discussed in
<br />that section of this report.
<br />
<br />Suspended Fraction Trends
<br />
<br />It is difficult to assess the trends in the suspended frac-
<br />tions other than the principal one that the concentra-
<br />tion of the trace metals increases with the total sus-
<br />pended matter. The data must be further refined statis-
<br />tically to give the trace metal concentration within the
<br />suspended matter before any trends can emerge,
<br />
<br />Preface to Individual Param ters
<br />
<br />The following sections disc ss and summarize the find-
<br />ings of this study with rega d to each of the individual
<br />parameters. Repeated refe ence and comparisons are
<br />made to the studies of Dur or and Becker [7], Durum
<br />and Haffty [8], Kopp an Kroner [9], and Durum,
<br />Hem, and Heidel [10]. Th se studies are described and
<br />the numbers with which c mparisons were made are
<br />discussed, Durfor and Bec er [7] surveyed the water
<br />supplies of the 100 largest cities of the United States,
<br />Values used for comparis n are the median values
<br />which are also used by Du um and Haffty [8]. Durum
<br />and Haffty surveyed the mi or elements content of the
<br />major streams of the world, but only the median values
<br />for North American rivers 're used. Kopp and Kroner
<br />[9] surveyed the trace met Is of the surface waters of
<br />the United States from 1 62-67, reporting both sus-
<br />pended and dissolved data In their summaries, how-
<br />ever, they report the freq ency of detection for an
<br />element and then the mea of the values of those sam-
<br />ples in which the element was detected. This would
<br />seem to produce higher val es than in this study and in
<br />comparison to the two oth r studies just cited. Durum,
<br />et al. [10] surveyed As, C , Cr, Co, Pb, Hg, and Zn in
<br />the surface waters of the U ited States, wh ich included
<br />three sites on the Arkansas River, one near the Pueblo
<br />waterworks (site H).
<br />
<br />Water Analysis - Field Mea urements
<br />
<br />Temperature. - The grand mean temperatures (oC) of
<br />the reservoir pool for 197475 and 1975-76 were 13.5
<br />(56.30 F) and 12.4 (54.30 ), respectively. The varia-
<br />tions in pool, inlet, and ou let values are illustrated in
<br />figure 4. The highest mont Iy means for 1974-75 and
<br />1975-76 were 22.9 (73.20 ) [July] and 21.3 (70.80F)
<br />[August], respectively. ecember had the lowest
<br />monthly mean of the mo hs in which samples were
<br />collected in each year, 4.4 ( 9.90F), 1974; 4.9 (40.80F),
<br />1975. Seasonal trends werEl observed during each year;
<br />depth trends were not evi' ent except on a few occa.
<br />sions; spatial and surface t ends were not pronounced
<br />(figs. 17 and 19), For mos. sampling periods, near-iso-
<br />thermal conditions prevail d. In terms of water use
<br />criteria [11], temperature recorded to date have not
<br />approached acceptable ma imums for recreation, pub-
<br />lic water suppl ies, or agric \ture. Mean surnmer maxi-
<br />mums slightly exceed the aximum temperatures rec-
<br />ommended for growth of salmonids [200C (680F)].
<br />Interestingly, growth rates, f rainbow trout in Pueblo
<br />Reservoir have been specta ular.3
<br />
<br />3 Wurm, D" Colorado Di ision of Wildlife, personal
<br />communication,
<br />
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