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<br />.I.~'.,.~ .0
<br />..()~O
<br />Table 3, Relations.of dissolved-solids and major-ion
<br />concentrations to specific conductance in Pueblo Reservoir
<br />
<br />fAil dependent variable concentrations in milligrams per liler; SC. specific
<br />conductance in microsiemens per centimeter at 25 degrees Celsius 1
<br />
<br /> Coefficient. In C08"~
<br />Dependent Num- regre..lon clentor
<br />variable berol equation deter"
<br />M values Y = a + b(5C) mln8tlon
<br /> a b (r')
<br />Dissolved solids 129 -21.8 0,666 0,99
<br />Calcium 132 8.45 ,em .89
<br />Magnesium 130 -2,95 ,038 .86
<br />Sodium 130 -5.56 ,056 ,92
<br />Potassium 132 -.0224 ,006 .88
<br />Bicarlxmate 71 23.5 ,232 .68
<br />Sulfate t28 -29,7 .305 ,85
<br />Chloride 132 -.593 .016 ,78
<br />
<br />Nitrogen and Phosphorus
<br />
<br />Nitrogen and phosphorus species, commonly
<br />referred to as major nutrients, often are the plant nutri-
<br />ents most likely to limit phytoplankton growth. As
<br />nutrient concentrations increase, lake and reservoir
<br />productivity increases during a process Icnown as
<br />eutrophication. Nutrient enrichment of a reservoir is
<br />greatly affected by the nature of the drainage basin,
<br />because the basin often is a major source of the nutri-
<br />ents, organic malter, and sediment that enters a reser-
<br />voir (Cooke and others, 1986), The application of
<br />fertilizers and discharges of municipal wastewater
<br />often are the sources of increased nutrient loads to
<br />many lakes and reservoirs. The major sources of nutri-
<br />ents in Pueblo Reservoir probably are the Arkansas
<br />River drainage basin and nutrient releases from the res-
<br />ervoir bottom sediments, The major sinks for nutrients
<br />in the reservoir include biological uptake and conver-
<br />sion, burial of nutrient-containing sediment and
<br />organic matter in reservoir bottom sediments, and out-
<br />flow from the reservoir.
<br />Nitrogen in freshwater occurs as dissolved
<br />molecular nitrogen, ammonia, nitrate, nitrite, urea, and
<br />dissolved organic nitrogen compounds. Dissolved
<br />inorganic nitrogen, which includes ammonia and
<br />nitrate, is the major nitrogen form that is readily avail-
<br />able to bacteria, fungi, and plant growth in aquatic eco-
<br />systems (Go]dman and Home, ]983). Wetzel (1983)
<br />reported that the tolal phosphorus content of lake water,
<br />which includes dissolved and particulate inorganic and
<br />organic fOnDS, is considered the most important phos-
<br />phorus quantity relative to the overall metabolic
<br />
<br />Table 4, Results of Mann-Whitney test of seasonal
<br />differences between dissolved-solids concentrations in
<br />Puebto Reservoir, 1986 through 1989
<br />IHS. highly significant (p < 0.01); S. significant (p < 0.10); NS. not
<br />significant (p > O.IO)}
<br /> Median concentration, 5lgnlll-
<br />Sampling In milligrams per liter C8nce or
<br />.lte1 p-v81U8 concan-
<br />May- Saplamber - tratlon
<br /> August April difference
<br /> Dissolved solids
<br />38 205 343 0,00 HS
<br />5C 232 292 ,00 HS
<br />78 260 289 .19 NS
<br /> Calcium
<br />38 41 63 ,00 HS
<br />5C 45 54 .00 HS
<br />78 50 55 ,24 HS
<br /> Magnesium
<br />38 10 18 ,00 HS
<br />5C 12 15 ,00 HS
<br />78 14 15 ,07 S
<br /> Sodium
<br />38 15 25 .00 HS
<br />5C 16 21 ,00 HS
<br />78 19 21 ,32 NS
<br /> Potassium
<br />38 2.4 3.5 ,00 HS
<br />5C 2,2 3,0 ,00 HS
<br />78 2,6 2,9 .16 NS
<br /> Bicarbonate
<br />38 91 155 ,01 S
<br />5C 105 140 .02 S
<br />78 120 140 .13 NS
<br /> SulCate
<br />38 75 125 .00 HS
<br />5C 86 110 ,00 HS
<br />78 100 110 ,29 NS
<br /> Chloride
<br />38 5.5 8.5 ,00 HS
<br />5C 5.2 6.4 ,01 S
<br />78 6.4 6,2 ,50 NS
<br />ISampling site location shown in Plale I.
<br />characteristics of a lake. But, with respect to reservoir
<br />productivity and eutrophication, orthophosphorus is
<br />the phosphorus fonn of most concern, because it is
<br />immediately available for algal production (Walter
<br />Rast, United Nations Environmental Programme, writ-
<br />ten commun" 1993).
<br /> CHEMICAL CHARACTERISTICS 29
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