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<br />ranged from 8.110 8.6 during the sampling period. Dis-
<br />solved-oxygen concentrations and pH were largest
<br />near the lake surface as a result of photosynthesis and
<br />smallest near the lake bottom, where respiration
<br />occurs. Specific conductance in Lake Henry ranged
<br />from 8891IS/cm on June 29 to 1,010 lIS/cm on October
<br />6 but did not vary vertically and areally in the lake. Sec-
<br />chi-disk measurements indicated unifonn light trans-
<br />parency throughout the lake. On May I, Secchi-disk
<br />depths were 1.5 ft, and during the remainder of the
<br />study period Secchi-disk depths were 0.5 ft. Light
<br />transparency in Lake Henry is affected by phytoplank-
<br />ton biomass and nonalgal suspended material.
<br />Total-nitrogen concentrations ranged from 0.86
<br />to 1.4 mgIL, and total-phosphorus concentrations
<br />ranged from 0.030 to 0.106 mg/L during the sampling
<br />period. Dissolved-solids concentrations ranged from
<br />598 to 704 mg/L, and calcium and sulfate comprised
<br />the largest percentage of the major chemical constitu-
<br />ents. At site HEW2, concentrations of total-
<br />recoverable iron occasionally exceeded the Colorado
<br />Department of Health water-quality standard of
<br />1.000 IJgIL. On August 19, total-recoverable iron con-
<br />centrations were 1,000 1Ig/L near the lake surface and
<br />6,300 IJgIL near the lake bottom; on October 6, concen-
<br />trations of total-recoverable iron were 1,900 1Ig/L near
<br />the lake surface and 2,500 lIglL near the lake bollom.
<br />Concentrations of other trace elements were less than
<br />the water-quality standards or less than the detection
<br />limits for the analysis.
<br />The groups of phytoplankton sampled in Lake
<br />Henry during the sampling period were diatoms, green
<br />algae, golden-brown algae, cryptomonads, blue-green
<br />algae, and euglenoids. The concentrations of phy-
<br />toplankton collected at site HEW2 ranged from 33,000
<br />cells/mLon June 29to 930,OOOcells/mL on August 19.
<br />On each sampling date, blue-green algae accounted for
<br />the greatest percentage of the phytoplankton density.
<br />The trophic status of Lake Henry is eutrophic as indi-
<br />cated by the trophic-state index and the fixed-boundary
<br />system.
<br />During the sampling period, water temperatures
<br />in Lake Meredith ranged from 15.3 to 27.90C. The lake
<br />was thermally stratified on May I and was not stratified
<br />on June 30. Concentrations of dissolved oxygen
<br />ranged from 1.4 to 10.3 mgIL. CDncentrations of dis-
<br />solved oxygen less than the 5.0 mg/L water-quality
<br />standard were measured near the lake bollom on
<br />May I, June 30, and August 20 and 21. The pH of the
<br />water in Lake Meredith ranged from 7.9 tD 8.7. Dis-
<br />solved-Dxygen cDncentrations and pH in Lake
<br />Meredith were largest near the lake surface as a result
<br />of photosynthesis and smallest near the lake bollom
<br />
<br />where respiratiDn occurs. Specific cDnductance in the
<br />lake ranged from 2,520 lIS/cm on June 30 tD 3,040 lIS/
<br />cmon August21 but did not vary vertically and areally.
<br />Secchi-disk measurements ranged frDm 0.5 to 1.5 ft
<br />and were largest on May I. Light transparency in Lake
<br />Meredith is affected by phytoplankton biomass and
<br />nonalgal suspended material.
<br />Concentrations of total nitrogen at site M2B
<br />ranged from less than 1.3 mg/L to less than 2.0 mgIL
<br />during the sampling period. At sites M2B, M1B, and
<br />M4B, concentrations of total phosphorus ranged from
<br />0.062 to 0.148 mg/L. Dissolved-solids concentrations
<br />at site M2B ranged from 1,870 tD 2.370 mg/L, and
<br />sDdium and sulfate comprised the largest percentage of
<br />the major chemical constituents. At sites M1B and
<br />M4B on June 30 and August 21, concentrations Df
<br />total-recDverable iron ranged frDm 1,300 to
<br />1,800 lIglL, which exceeded the 1,000 1Ig/L Colorado
<br />Department of Health water-quality standard. Concen-
<br />trations of total-recoverable boron at site M2B on
<br />August 20 and October 6 ranged from 770 to 810 lIg/L,
<br />which exceeded the 750 1Ig/L water-quality standard.
<br />Concentrations of other trace elements were less than
<br />the water-quality standards or less than the detection
<br />limits for the analysis.
<br />The groups of phytoplankton sampled at site
<br />M2B during the sampling period were diatoms, green
<br />algae, golden-brown algae, cryptomonads, blue-green
<br />algae, euglenoids, and dinoflagellates. The concentra-
<br />tions of phytoplankton collected at site M2B ranged
<br />from 58,000 cells/mL on May 1 to 3,900,000 cells/mL
<br />on October 6. On each sampling date, blue-green algae
<br />comprised the largest percentage of the phytDplankton
<br />density. The trophic status of Lake Meredith as deter-
<br />mined using the trophic-state index and the fixed-
<br />boundary system indicates Lake Meredith is a
<br />eutrophic lake.
<br />During the sampling period, the thennal proper-
<br />ties of Lake Henry and Lake Meredith were similar.
<br />Dissolved-oxygen concentrations and pH values in
<br />Lake Henry and in Lake Meredith were larger near the
<br />lake surface and smaller near the lake bollom because
<br />of the effect of photosynthesis and respiration by phy-
<br />toplankton. Average specific conductance in Lake
<br />Henry was about one-third the average specific con-
<br />ductance in Lake Meredith.
<br />Nutrient concentrations varied between Lake
<br />Henry and Lake Meredith. Nutrient concentrations
<br />were generally smaller in Lake Henry than in Lake
<br />Meredith. The predominant chemical constituents
<br />were calcium and sulfate in Lake Henry and sodium
<br />and sulfate in Lake Meredith. Concentrations of total-
<br />recoverable iron in Lake Henry and total-recoverable
<br />iron and total-recoverable boron in Lake Meredith
<br />
<br />30 Reconnaissance of Water Quality of Lake Henry and Lake Meredith Reservoir, Crowley County, Southeastern
<br />Colorado, April-October 1987
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