The Limnology of Lake Pleasant Arizona and its Effect on Water Quality in the
Central Arizona Project Canal.
by
David Bradley Walker
Dissertation Submitted to the Faculty of the
DEPARTMENT OF SOIL, WATER, AND ENVIRONMENTAL SCIENCE
In Partial Fulfillment of the Requirements
For the Degree of
DOCTOR OF PHILOSOPHY
In the Graduate College
THE UNIVERSITY OF ARIZONA
2002
APPROVAL BY DISSERTATION DIRECTOR
This dissertation has been approved on the date shown below:
________________________________________________
R.J. Frye
Professor of Soil, Water and Environmental Science
___________
Date
2
STATEMENT OF AUTHOR
This dissertation has been submitted in partial fulfillment of requirements for an
advanced degree at the University of Arizona and is deposited in the University Library
to be made available to borrowers under rules of the Library.
Brief quotations from this dissertation are allowable without special permission,
provided that accurate knowledge of source is made. Requests for extended quotation
from or reproduction of this manuscript in whole or in part may be granted by the head
of the major department of the Dean of the Graduate College when in his or her
judgment the proposed use of the material is in the interests of scholarship. In all other
instances, however, permission must be obtained from the author.
SIGNED:___________________________________
3
ACKNOWLEDGEMENTS
(single spaced if needed, 1 pg max)
4
DEDICATION
(double spaced- 1 pg max)
TABLE OF CONTENTS
Page
5
LIST OF ILLUSTRATIONS
6
LIST OF TABLES
7
ABSTRACT
8
1
INTRODUCTION
9
2
MATERIALS AND METHODS
Site Description
Hydraulics of Re-Filling and Withdrawing Water from Lake
Pleasant
Sampling Sites
Field Data Collection
Lake Pleasant
CAP Canal
Laboratory Methods
11
11
RESULTS
Thermal Stratification and Mixing
Lake Pleasant Nutrient Data
CAP Canal Nutrient Data
Lake Pleasant Phytoplankton Dynamics
CAP Canal Periphyton Dynamics
Analysis of MIB and Geosmin in the CAP Canal
Correlations Between Cyanophyte Species and MIB/Geosmin
Levels in the CAP Canal
Principal Component Analysis of Lake Pleasant Hypolimnetic
Conditions and MIB, Geosmin, and Periphyton in the CAP
Canal
17
17
19
23
27
28
32
4
DISCUSSION
40
5
CONCLUSIONS
45
APPENDIX A - DIGITAL IMAGES
91
LITERATURE CITED
104
3
LIST OF ILLUSTRATIONS
12
13
13
13
14
33
36
6
Figure
Page
2-1
Lake Pleasant operational data showing relationship between the
old and new Waddell Dams
50
2-2
Sampling Sites within Lake Pleasant, AZ.
51
2-3
Sampling sites within the CAP canal showing approximate
distances from Lake Pleasant.
52
3-1
The relationship between dissolved oxygen and depth in Lake
Pleasant during August-October of 1996 and 1997.
53
3-2
Mean dissolved oxygen levels (mg/L) by stratified layer in Lake
Pleasant.
54
3-3
Oneway analysis of hypolimnetic ammonia-N levels (mg/L) in
Lake Pleasant by year.
55
3-4
Oneway analysis of hypolimnetic total phosphorous levels (mg/L)
in Lake Pleasant by year.
56
3-5
Oneway analysis of hypolimnetic orthophosphate levels (mg/L) in
Lake Pleasant by year.
57
3-6
Oneway analysis of nitrate/nitrite-N Levels (mg/L) in the CAP
canal by year.
58
3-7
Oneway analysis of ammonia-N levels (mg/L) in the CAP canal
by year.
59
3-8
Oneway analysis of total-P levels (mg/L) in the CAP canal by
year.
60
3-9
One-way analysis of orthophosphate levels (mg/L) in the CAP
canal by year.
61
3-10
Mean numbers of algae by division observed in Lake Pleasant
during 1996 and 1997.
62
LIST OF ILLUSTRATIONS - Continued
7
Figure
Page
3-11
Mean numbers of phytoplankton (in units/mL) by site in Lake
Pleasant for 1996 and 1997.
63
3-12
Bivariate fit of depth (m) by units/ml while withdrawing water from
Lake Pleasant during 1996 and 1997.
64
3-13
Bivariate fit of algal units/mL by depth (m) while pumping water
into Lake Pleasant during 1996 and 1997.
65
3-14
Bivariate fit of algal units/mL by depth (m) at site A while pumping
water into Lake Pleasant during 1996 and 1997.
66
3-15
Bivariate fit of algal units/mL by depth at site B while pumping
water into Lake Pleasant during 1996 and 1997.
67
3-16
Bivariate fit of algal units/mL by depth at site C while pumping
water into Lake Pleasant during 1996 and 1997.
68
3-17
Bivariate fit of units/mL by depth at site D while pumping water
into Lake Pleasant during 1996 and 1997.
69
3-18
Divisions of algae (in units/mL) found below 10 meters depth at
sites A, B, and C during the period of re-filling.
70
3-19
Cyanophyte abundance by site during the summers of 1996 and
1997.
71
3-20
One-way analysis of cyanophyte abundance (units/mL) during the 72
Summers of 1996 and 1997 in Lake Pleasant.
3-21
One-way analysis of periphyton abundance (units/cm 2) for all
sites in the CAP canal during 1996 and 1997.
73
3-22
Abundance of algal divisions found within the periphyton of the
CAP canal during the summers of 1996 and 1997.
74
LIST OF ILLUSTRATIONS - Continued
8
Figure
Page
3-23
Divisions of Algae by Distance from Lake Pleasant During the
Summer of 1996.
75
3-24
Oneway analysis of numbers of periphytic cyanophytes by year in
the CAP canal at 70-78 Kilometers from Lake Pleasant.
76
3-25
Oneway analysis of numbers of periphytic cyanophytes by year in
the CAP canal at 0-45 kilometers from Lake Pleasant.
77
3-26
Mean levels of 2-methylisoborneol in the CAP canal by distance
from Lake Pleasant during periods of release for 1996 and 1997
collectively.
78
3-27
Oneway analysis of mean MIB levels (ng/L) by distance from
Lake Pleasant during times of release for 1996 and 1997
collectively.
79
3-28
Oneway analysis of MIB levels by year for all sites in the CAP
canal.
80
3-29
Mean levels of MIB by distance from Lake Pleasant during
periods of release into the CAP canal during 1996 and 1997.
81
3-30
Mean levels of geosmin in the CAP canal by distance from Lake
Pleasant during periods of release for 1996 and 1997 collectively.
82
3-31
Cyanophyte abundance by site during the summers of 1996 and
1997.
83
3-32
Correlations between numbers of Anabaena sp. (units/cm2) to
levels of MIB and geosmin (ng/L) in the CAP canal during 1996.
84
3-33
One-way analysis of periphyton abundance (units/cm 2) for all
sites in the CAP canal during 1996 and 1997.
85
3-34
Correlations between numbers of Oscillatoria sp. (units/cm2) to
levels of MIB and geosmin (ng/L) in the CAP canal during 1996.
86
LIST OF ILLUSTRATIONS - Continued
9
Figure
Page
3-35
Correlations between numbers of Oscillatoria sp. (units/cm2) to
levels of MIB and geosmin (ng/L) in the CAP canal during 1997.
87
3-36
Correlations between numbers of Lyngbya sp. (units/cm2) to
levels of MIB and geosmin (ng/L) in the CAP canal during 1996.
88
3-37
Correlations between numbers of Lyngbya sp. (units/cm2) to
levels of MIB and geosmin (ng/L) in the CAP canal during 1997.
89
3-38
Principal component analysis of nutrient and dissolved oxygen
data from the hypolimnion of Lake Pleasant and MIB/geosmin
data from 70-78 km down-canal during 1996.
90
3-39
Principal component analysis of nutrient and dissolved oxygen
data from the hypolimnion of Lake Pleasant and MIB/geosmin
data from 70-78 km down-canal during 1997.
91
3-40
Principal component analysis of site B dissolved oxygen levels,
MIB/geosmin and periphyton growth in the CAP canal at 70-78
km down-canal from Lake Pleasant during 1996..
92
3-41
Principal component analysis of site B dissolved oxygen levels,
MIB/geosmin and periphyton growth in the CAP canal at 70-78
km down-canal during 1997. .
93
10
LIST OF TABLES
11
ABSTRACT
Recent changes in the management strategy of water released from Lake
Pleasant into the Central Arizona Project canal have substantially reduced taste and
odor complaints among water consumers. Most of the taste and odor complaints were
likely caused by 2-methylisoborneol (MIB) and geosmin produced by periphytic
cyanobacteria growing on canal surfaces. Most years, Lake Pleasant consists almost
exclusively of water brought in via the CAP canal. The location of the inlet towers and
the Old Waddell Dam influence sedimentation of material brought in by the CAP canal.
In-coming water was found to contain large amounts of periphyton of the type
commonly found growing on the sides of the CAP canal. Withdrawal of hypolimnetic
water early in the spring of 1997 decreased the time that sediments were exposed to
anoxic conditions, potentially decreasing the amount of nutrients released into the CAP
canal and therefore available for periphytic cyanobacteria. Utilizing this management
regimen since 1997 has resulted in a substantial reduction (or elimination) of consumer
complaints of earthy/musty tastes and odors.
CHAPTER 1
12
INTRODUCTION
In the first few years after Lake Pleasant, a reservoir in Central Arizona, was
used to store water from the Colorado River via the Central Arizona Project Canal
(CAP) to several municipalities in the Phoenix Valley, many consumers complained of
earthy or musty tastes and odors in drinking water delivered by utilities (pers.comm.
Tom Curry, Central Arizona Water Conservation District). Earthy or musty tastes and
odors often are associated with certain species of cyanobacteria that are capable of
producing 2-methylisoborneol (MIB) or geosmin (Izaguirre et al., 1983, Naes et al.,
1988, Izaguirre & Taylor 1995). Treatment of this water with powdered activated carbon
(PAC) was extensively used to remove chemicals causing tastes and odors, often at
great expense to utilities.
Anecdotal information suggested that complaints about tastes and odors
decreased dramatically when the CAP canal contained water directly from the Colorado
River as opposed to water that had been stored in Lake Pleasant. Also, it appeared that
complaints of tastes and odors increased among utilities in the Phoenix Valley that were
farthest from Lake Pleasant.
This research addresses methodologies of releasing water from Lake Pleasant
and the consequent changes in water quality in the CAP canal for the years 1996 and
1997. Prior to and during 1996, water was released from the surface layer (epilimnion)
of Lake Pleasant during the summer into the CAP canal. Due to preliminary findings
from our research, we recommended releasing water from the bottom layer
13
(hypolimnion) in addition to epilimnetic release during the summer of 1997. This
research compares and contrasts the different release strategies to determine if our
recommendation and its subsequent implementation resulted in an alleviation of tastes
and odors in drinking water supplied by the CAP down-canal of Lake Pleasant.
Previous studies that have dealt with MIB/geosmin production by cyanobacteria
in source waters have tended to examine the role of reservoirs (Izaguirre et al., 1982;
Berglind et al., 1983; McGuire et al., 1983; Slater & Blok 1983; Yagi et al., 1983;
Negoro et al., 1988; Izaguirre 1992), or canals emanating from these reservoirs
(Izaguirre & Taylor, 1995) as separate ecosystems. In contrast, we propose that
nutrients released from Lake Pleasant may promote the growth of periphytic taste and
odor causing organisms within the CAP canal.
CHAPTER 2
14
Materials and Methods
Site Description
Lake Pleasant is located about 48 km northwest of Phoenix, Arizona and is used
as a storage reservoir for water transported from Lake Havasu on the Colorado River to
Central Arizona via the Central Arizona Project (CAP) canal system. Water is pumped
into Lake Pleasant during winter and released during summer when it is needed for
irrigation and drinking water. Prior to CAP water being stored in Lake Pleasant, the
Agua Fria River, an intermittent stream entering from the north was the primary water
source to Lake Pleasant. Smaller, ephemeral streams flowing into the reservoir are
Castle Creek and Humbug Creek. Construction of the new Waddell Dam increased the
surface area of Lake Pleasant from 1,497 to 4,168 hectares (AZ. Game and Fish Dept.
unpublished report to U.S. Bureau of Reclamation, 1990). The old Waddell Dam was
left submerged within the reservoir approximately 0.5 km north of the new dam (Fig. 21). The primary water source for Lake Pleasant is now the CAP canal. At maximum
capacity, Lake Pleasant contains about 811,000 acre-feet (324,000 hectare-feet) of
water.
Hydraulics of Re-filling and Withdrawing Water From Lake Pleasant
15
The hydrology of Lake Pleasant is such that the majority of water now enters or
leaves the reservoir via a penstock pipe that penetrates the new Waddell Dam
terminating in a tower with 2 gates at heights approximately 18 meters apart. Either gate
can be used separately or in combination. The maximum flow that the Waddell Dam
Forebay and the CAP canal can accommodate is approximately 3500 cfs.
Lake Pleasant is unique in that most of the water now enters in the lacustrine
zone of the reservoir instead of the more typical situation of entering via a river
(Thornton, Kimmel, and Payne 1990). The impact of the Agua Fria River entering from
the North on water quality leaving the reservoir is relatively minimal except possibly
during flood events. The proximity of the old Waddell Dam to the CAP inlet/outlet towers
(Fig. 2-1) may divide the lacustrine zone creating an area that enhances sedimentation,
stratification, dissolved oxygen depletion, and primary production. Breaches in The Old
Waddell Dam approximately 50 meters wide and 400 meters apart allows some mixing
of this area with the rest of the reservoir however, the area between the Old Waddell
Dam and the CAP towers may be sufficiently separated from the rest of the lacustrine
zone to be considered unique. We believe this area may have the greatest effect on
water quality leaving the reservoir and entering the CAP canal due to all of the water
exiting the reservoir having to pass through this zone.
Sampling Sites
We established four sampling sites within Lake Pleasant (“A”, “B”, “C”, and “D”;
Fig 2-2), chosen according to an idealized model from upstream to downstream of
reservoir zonation as proposed by Thornton, Kimmel, and Payne (1990). Locations
16
were determined with a Global Positioning System (GPS) unit. Site A (33 o 50’ 57” N and
112o 16’ 18” W) was closest to incoming CAP water. Site B (33o 51’ 04 N and 112o 17”
W) was between the New and Old Waddell Dams. Site C (33o 51’ 26” N and 112o 16’
21” W) was north of the old dam and Site D (33o 52’ 20” N and 112o 16’ 11” W) was
farthest north from the CAP inlet and the site most influenced by water entering from the
Agua Fria River. (Fig. 2-2).
Five additional sampling sites were established within the CAP canal. The sites,
including approximate distance downstream from Lake Pleasant, were; Waddell
Forebay (0 km), 99th Ave (6 km), Scottsdale Water Treatment Plant (45 km), Granite
Reef (70 km), and Mesa Water Treatment Plant (78 km) (Fig. 2-3).
Field Data Collection
Lake Pleasant
Samples were collected at each of the four sites every 2 weeks when the
reservoir was stratified (May – November) and monthly when it was de-stratified
(December – April) from May 1996 to March 1998. When the reservoir was thermally
stratified, samples were collected 0.5 meters below the surface, immediately above the
thermocline, and 1.0 meter above the sediment. When the reservoir was not thermally
stratified samples were collected 0.5 meters below the surface, at the mid-point of the
water column, and 1.0 meter above the sediment.
Water samples were collected in a 2.2-L Van Dorn-style sample bottle and
transferred to two 500-mL, and one 100-mL plastic bottle (Nalgene Corp). One of the
17
500-mL bottles contained 2 mL of sulfuric acid for preservation of ammonia-N, nitrate-N,
and total phosphorous. The other 500-mL sample was used for phytoplankton
identification and enumeration and contained 25 mL of formaldehyde. Samples
collected for analysis of orthophosphorous were field filtered using a 0.45 m cellulose
acetate sterile syringe filter and a sterile 100-mL syringe and stored in a 100-mL bottle.
All samples were kept on ice for transport to the laboratory. Dissolved oxygen, pH,
temperature, specific conductance, and turbidity levels were recorded through the water
column at each of the 4 sites during every sampling trip using a HydroLab Surveyor 3
data recorder and sonde (HydroLab Corp).
CAP Canal
Each of the 5 CAP canal sites was sampled approximately every 14 days when
water from Lake Pleasant was the primary source (May – November) and monthly when
Colorado River water taken from Lake Havasu was the predominant source in the CAP
canal (December – April). Samples were collected in the CAP canal for nutrient
analyses in the same manner as those collected from Lake Pleasant. Water samples
collected in 1-liter glass amber bottles for MIB and geosmin analysis were kept on ice
for transport back to the University of Arizona. Periphyton was collected from the sides
of the canal at a depth of 0.5 m. The area scraped was measured and the sample
diluted with 250 mL of distilled water and 12 mL of formaldehyde.
Laboratory Methods
18
Water samples were analyzed for NH3-N (Standard Method 417 B), NO3- -N
(Standard Method 4500-NO3-), orthophosphate (Standard Method 4500-P), total
phosphorous (Standard Method 4500-P.5), ferrous iron (Standard Method 3500- Fe D),
and total iron (Standard Method 3030 D followed by 3500-Fe D). Results were
determined colorometrically using a Hach DR/890 colorimeter.
Phytoplankton and periphyton were enumerated with a Sedgwick-Rafter counting
chamber with an ocular micrometer (Standard Method 10200 F) on a calibrated
Olympus BH2 phase contrast light microscope (Olympus Corp.) at a total magnification
of 200X. Identifications were made to genus and natural unit counts were recorded as
units/ml for phytoplankton and units/cm2 for periphyton (Standard Method 10200 F)
MIB and geosmin were determined by GC/MS at the University of Arizona's Mass
Spectrometry Facility. The procedure was:
1) Sorbent and glass fiber filters were washed with 10-mL CH2CL2 then 3-mL methanol.
2) Samples were warmed to room temperature and 100g of NaCl added to the
1-L sample. Bottles were then capped and rotated to dissolve. Methanol (5-mL) and 10
L internal standard solution (5 ng/L 1-chlorodecane in MeOH) were then added.
3) Samples were pulled through the sorbent bed by vacuum. The sample bottle was
rinsed with 5-mL methanol that was then diluted to 50 mL with organic-free water and
pulled through the sorbent bed. The sample volume was recorded.
4) The sorbent bed was eluted with 4-mL dichloromethane, which was pulled through a
bed of anhydrous sodium sulfate (to remove water). The extract was concentrated by
evaporation under a stream of nitrogen to a volume of ca. 100 L. Dimethylglutarate
19
was added as a standard to the final concentrate that was analyzed by GC/MS with
selected ion monitoring.
Statistical analyses were performed with JMP 4.0.3 statistical software (SAS
Institute Inc.).
CHAPTER 3
RESULTS
Thermal Stratification & Mixing
Thermal stratification was evident at all sites beginning in May and lasting until
mid– to late November of both years. The mean epilimnetic and hypolimnetic
temperature for 1996 was 25.2 oC and 15.8 oC respectively while for 1997 they were
26.4 oC and 13.5 oC respectively. While mean epilimnetic temperatures were lower in
1996 than 1997 (x = 25.2 and 26.4 oC respectively, F1,317 = 20.7438, p <0.0001) mean
hypolimnetic temperatures were higher (x = 15.8 and 13.5 oC respectively, F1,578 =
20
196.4797, p <0.0001). When the reservoir was not stratified, mean temperatures were
lower in 1997 than 1996 (x = 14.25 oC and x = 16.05 oC respectively; F1,912 = 111.6136,
p <0.0001).
Dissolved oxygen levels were inversely correlated with depth among all sites
during the time of peak stratification (Aug-Oct) in 1996 and 1997
(R = 0.82, Fig. 3-1). Dissolved oxygen levels were not significantly different among sites
(F3, 1808 = 0.4160, p = 0.7416), but were significantly different (F2, 895 = 433.5019, p
<0.0001) among vertical strata (epilimnion, x = 7.5 mg/L; hypolimnion, x = 3.19 mg/L;
metalimnion = 5.06 mg/L, Fig. 3-2). The hypolimnion became anoxic during late summer
and early fall 1996. In 1996, mean dissolved oxygen levels were 5.2 mg/L and in 1997,
7.7 mg/L (F1,896 = 325.7442, p <0.0001). Summer hypolimnetic dissolved oxygen levels
between 1996 (x = 1.2 mg/L) and 1997 (x = 4.6 mg/L) showed even larger differences
(F1, 578 = 375.1382, p <0.0001).
When the reservoir was stratified the hypolimnion had significantly lower mean
pH levels (x = 7.94) than shallower strata (epi- and metalimnion x = 8.73 and 8.26
respectively, F1,895 = 938.9329, p <0.0001). Differences in pH values were not
significant between sites in either the non-stratified or stratified condition (F3, 913 =
0.1455, p = 0.9327 and F3, 896 = 0.2682, p = 0.8487 respectively). There were however,
significant differences in hypolimnetic pH values between 1996 (x = 7.72) and 1997 (x =
8.04) (F1, 578 = 257.8011, p <0.0001).
Turbidity was significantly higher when the reservoir was not stratified than when
thermally stratified (F1,742 = 40.3337, p = 0.0008). When the reservoir was not stratified
21
turbidity levels increased with depth (F2, 412 = 23.4621 p <0.0001) and differed between
sites (F3, 742 = 18.0206, p = <0.0001). Site B had the highest levels (x = 10.9 NTU’s)
followed by site C (x = 9.12 NTU’s), site A (x = 5.85 NTU’s) and site D (x = 4.17 NTU’s).
Thermal stratification persisted longer in the fall of 1996 compared to 1997
especially in the area between the old and new Waddell Dams. In 1997, de-stratification
occurred at site B in October but persisted until late November during 1996. Mean
hypolimnetic dissolved oxygen levels at site B during 1996 and 1997 were 1.19 and
5.28 mg/l, respectively. At site B in 1996 the hypolimnion was often completely anoxic
from 16.5 m to the bottom (35 m). At this site in 1997, the lowest dissolved oxygen level
over the sediment was 2.53 mg/l.
Lake Pleasant Nutrient Data
Nutrient levels for Lake Pleasant were divided into 3 treatments based upon
temporal variances (year), spatial variances (site), and layer (epi- meta- or
hypolimnion). Since the taste and odor problems primarily occur when water is being
released from Lake Pleasant into the CAP canal, analysis will focus on this period.
Nitrate and nitrite levels were summed for analysis and showed significant
differences between layers, site, and years as well as for all of the interaction terms
except for site*year (Table 3-1). By layer, the epilimnion had the highest nitrate levels (x
= 0.06 mg/L) followed by the metalimnion (x = 0.05 mg/L) and hypolimnion (x = 0.03
mg/L) (F2, 103 = 61.7547, p <0.0001). Overall nitrate levels within Lake Pleasant were
higher in 1997 (x = 0.05 mg/L) than 1996 (x = 0.03 mg/L) (F1, 103 = 70.8291, p <0.0001).
There was a significant difference in nitrate levels for the interaction term layer*site
22
(Table 3-1) and univariate analysis revealed that the epilimnion of sites A and B
collectively had higher levels of nitrate (x = 0.068 and 0.067 mg/L respectively) than the
epilimnion of sites C and D collectively (x = 0.052 and 0.048 mg/L respectively) (F1, 103 =
6.9554, p = 0.0002). Hypolimnetic and metalimnetic nitrate values by site showed
similar trends; site B had the highest levels (x = 0.056 and 0.067 mg/L respectively)
followed by sites C (x = 0.051 and 0.063 mg/L), A (x = 0.047 and 0.061 mg/L), and D (x
= 0.041 and 0.044 mg/L) (F3,103 = 6.2068, p = 0.0004 and F3,103 = 10.9, p <0.0001
respectively).
Table 3-1. 3-way ANOVA testing for treatment effects on nitrate/nitrite-N levels within
Lake Pleasant.
Treatment
df
SS
F-ratio
p-value
Site
3,103
0.008399
3.603
0.0051
Layer
2,103
0.030053
12.890
<0.0001
Year
1,103
0.026191
8.024
<0.0001
Site*Year
4,103
0.000723
1.552
0.2160
Site*Layer
5,103
0.005722
6.136
0.0031
Layer*Year
3,103
0.003774
4.403
0.0207
Site*Layer*Year
6,103
0.001787
3.832
0.0533
Ammonia levels showed significant differences among all treatment effects and
their interactions (Table 3-2). Ammonia levels were highest at site B
23
(x = 0.019 mg/L) and lowest at site D (x = 0.005 mg/L, F3, 103 = 4.0533, p = 0.004). The
hypolimnion of all sites had significantly higher levels of ammonia (x = 0.028 mg/L) than
did the meta- (x = 0.005 mg/L) or epilimnion (x = 0.002 mg/L) (F2, 103 = 8.37, p =0.0004).
Mean hypolimnetic ammonia levels were higher in 1996 (x = 0.06 mg/L) compared to
1997 (x = 0.01 mg/L) (F 1, 53 = 20.2862, p <0.0001, Fig. 3-3).
Table 3-2. 3-way ANOVA testing for treatment effects on ammonia levels within Lake
Pleasant.
Treatment
df
SS
F-ratio
p-value
Site
3,103
0.014849
4.478
<0.0001
Layer
2,103
0.030635
14.782
<0.0001
Year
1,103
0.051376
15.494
<0.0001
Site*Year
4,103
0.006623
7.990
0.0006
Site*Layer
5,103
0.003861
4.656
0.0119
Layer*Year
3,103
0.018404
22.201
<0.0001
Site*Layer*Year
6,103
0.002593
6.256
0.0142
Levels of total phosphorous showed no significant differences between sites
(Table 3-3). This trend was carried over to the interaction terms of site*year, site*layer,
and site*layer*year. There was however, a significant difference between years and
layers. Analysis of mean hypolimnetic total phosphorous levels showed that these were
higher in 1996 (x = 0.21 mg/L) than 1997 (x = 0.14 mg/L) (F1,53 = 4.8175, p = 0.03)
(Figure 3-4).
24
Table 3-3. 3-way ANOVA testing for treatment effects on total phosphorous levels within
Lake Pleasant.
Treatment
df
SS
F-ratio
p-value
Site
3,103
0.020382
0.8233
0.4426
Layer
2,103
0.065473
5.3033
0.0239
Year
1,103
0.080324
6.8269
0.0147
Site*Year
4,103
0.012819
0.5192
0.5970
Site*Layer
5,103
0.057049
0.9242
0.4697
Layer*Year
3,103
0.204502
16.5647
<0.0001
Site*Layer*Year
6,103
0.036679
0.5942
0.7044
Dissolved orthophosphate levels followed the same trend as total phosphorous
with no significant difference between sites or any interaction term involving this
treatment effect (Table 3-4). Again, the treatment effects of year and layer exhibited
significant differences in orthophosphate levels. The hypolimnetic orthophosphate levels
between 1996 (x = 0.18) and 1997 (x = 0.06) were even more significant than those of
total phosphorous (F1,54 = 22.7184, p = <0.0001) (Figure 3-5). This indicates that most
25
of the phosphorous in the hypolimnion of Lake Pleasant is in a dissolved and bioavailable form.
Table 3-4. 3-way ANOVA testing for treatment effects on orthophosphate levels within
Lake Pleasant.
Treatment
df
SS
F-ratio
p-value
Site
3,103
0.011376
0.4607
0.6325
Layer
2,103
0.452959
36.6897
<0.0001
Year
1,103
0.385675
30.5639
<0.0001
Site*Year
4,103
0.004205
0.1703
0.8473
Site*Layer
5,103
0.063453
1.0279
0.4069
Layer*Year
3,103
0.234849
19.0220
<0.0001
Site*Layer*Year
6,103
0.032299
0.5232
0.7580
CAP Canal Nutrient Data
The nutrient data for the CAP canal was divided into 2 treatments based upon
spatial (site) and temporal (year) variances. Like the nutrient data from Lake Pleasant,
analyses focused upon the time of the year when water was being released from Lake
Pleasant. For clarity of reporting univariate responses, the sites were grouped into 2
categories based upon distance from Lake Pleasant. The 6-45 km group includes the
26
CAP Canal at 99th Ave. and Scottsdale WTP sites and the 70-78 km group consisted of
the CAP Canal at Granite Reef Dam and Mesa WTP.
Nitrate and nitrite-N data (grouped together as nitrate/nitrite-N) showed
significant differences for site and year but not for the interaction term site*year (Table
3-5). During the summer of 1996, levels of nitrate/nitrite were highest farther away from
Lake Pleasant (70-78 km, x = 0.104 mg/L) compared to sites closer to the reservoir (645 km, x = 0.060 mg/L) (F1,32 = 10.2363, p = 0.0039). This trend was still evident in
1997 (6-45 km, x = 0.039 mg/L; 70-78 km, x = 0.058 mg/L; F1,32 = 8.1181, p = 0.0075),
however, comparison of means between years revealed significantly lower overall
numbers among all sites during 1997 (x = 0.049 mg/L) as compared to 1996 (x = 0.082
mg/L, F1,63 = 16.3993, p = 0.002, Fig. 3-6) The fact that the same spatial trend was
evident for both years, but that overall nitrate/nitrite numbers were lower in 1997 than
1996, may explain the non-significance in the interaction term site*year.
Table 3-5. 2-Way ANOVA testing for treatment effects on nitrate-nitrite levels within the
CAP Canal.
Treatment
df
SS
F-ratio
p-value
Site
4,64
0.906977
14.965
<0.0001
Year
1,64
0.418749
27.637
<0.0001
Site*Year
4,64
0.088421
1.4590
0.2247
27
Levels of ammonia-N were significantly different by site, year, and the interaction
term site*year (Table 3-6). Spatial trends were opposite those for nitrate/nitrite during
the summer of 1996 i.e. levels of ammonia-N were higher at sites closer to Lake
Pleasant (6-45 km, x = 0.15 mg/L) than those farther away (40-45 km, x = 0.06 mg/L)
(F1,32 = 13.8992, p = 0.0010). This same trend was evident in the summer of 1997 (6-45
km x = 0.06 mg/L, 40-45 km x = 0.02 mg/L, F1,32 = 12.3682, p = 0.0013). Similar to
nitrate/nitrite, levels of ammonia-N were significantly lower at all sites during 1997 (x =
0.04 mg/L) than 1996 (x = 0.11 mg/L, F1,66 = 22.0415, p <0.001, Fig. 3-7).
Table 3-6. 2-Way ANOVA testing for treatment effects on ammonia-N levels within the
CAP Canal.
Treatment
df
SS
F-ratio
p-value
Site
4,66
0.200309
66.451
<0.0001
Year
1,66
0.183651
60.924
<0.0001
Site*Year
4,66
0.060408
40.128
<0.0001
Levels of total phosphorous differed by all treatment effects with the differences
between years exhibiting the most significance (Table 3-7). Levels of total phosphorous
were much lower during the summer of 1997 (x = 0.09 mg/L) compared to the summer
of 1996 (x = 0.27 mg/L, F1,64 = 135.9570, p <0.0001, Fig. 3-8). During the summer of
1996, total phosphorous levels were higher at sites farthest from Lake Pleasant (70-78
km x = 0.31 mg/L) compared to closer sites (6-45 km x = 0.26 mg/L,F1,31 = 5.1552, p =
0.0342). This trend was not evident during the summer of 1997 and no significant
28
difference between sites based upon distance from Lake Pleasant was observed (6-45
km x = 0.09, 70-78 km x = 0.09, F1,32 = 0.0919, p = 0.7636).
Table 3-7. 2-Way ANOVA testing for treatment effects on total phosphorous levels
within the CAP Canal.
Treatment
df
SS
F-ratio
p-value
Site
4,65
0.200309
66.451
<0.0001
Year
1,65
0.183651
60.924
<0.0001
Site*Year
4,65
0.060408
40.128
<0.0001
Orthophosphate levels, like total phosphorous, were significantly different for all
treatment effects (Table 3-8). The general trend was decreased levels of
orthophosphate with distance from Lake Pleasant during the summer of 1996 (6-45 km,
x = 0.16 mg/L, 70-78 km, x = 0.07 mg/L, F1,29 = 16.1259, p = 0.0005) and 1997 (6-45
km, x = 0.05 mg/L, 70-78 km, x = 0.03 mg/L, F1,29 = 11.0558, p = 0.0022).
Orthophosphate levels were much lower for all sites in 1997 than 1996 (F1,60 = 38.8166,
p <0.001, Fig. 3-9).
Table 3-8. 2-Way ANOVA testing for treatment effects on orthophosphate levels within
the CAP Canal.
Treatment
df
SS
F-ratio
p-value
Site
4,59
0.081828
25.693
<0.0001
Year
1,59
0.10258
48.313
<0.0001
Site*Year
4,59
0.021045
19.823
<0.0001
29
Lake Pleasant Phytoplankton Dynamics
Six divisions of algae were found in the phytoplankton of Lake Pleasant for the
years 1996 and 1997 (Fig. 3-10). Overall, chrysophyta was the most abundant division
followed by chlorophytes, cyanophytes, pyrrophytes, cryptophytes, and euglenophytes.
Spatial differences existed in overall algal biomass with sites B and C
having the highest overall mean followed by sites A and D respectively (Fig. 3-11). This
same trend was evident during both 1996 and 1997.
When water was being withdrawn from the reservoir (primarily during the
summer and fall), algal numbers decreased with depth at all sites (F1,546 = 83.1356, p
<0.0001, Fig. 3-12). This situation was reversed at sites A, B, and C when water was
being pumped into the reservoir and overall algal numbers actually increased with depth
(F1,285, = 21.4670, p <0.0001, Fig. 3-13). This was noticed at sites A (Fig. 3-14), B (Fig.
3-15) and C (Fig. 3-16) while site D, the site farthest from the in-coming water, had an
overall decrease in algal numbers with depth (Fig. 3-17).
A comparison of algal abundance above and below 10 meters at sites A, B, and
C shows that during the period of re-filling levels were significantly higher below 10
meters (x = 2763 units/mL) than above 10 meters (x = 623 units/mL, F1, 286 = 19.7248, p
<0.0001). During this same period at site D however, there was no difference in algal
abundance between samples collected above or below 10 meters depth (x = 100 and
43 units/mL respectively, F1, 64 = 3.1630, p = 0.0618).
30
The division of algae found in the highest abundance at sites A, B, and C at a depth of
below 10 meters during the period of re-filling was (in units/mL) chrysophyta (x = 9439),
followed by chlorophyta (x = 4383), pyrrophyta (x = 405), cyanophyta (x = 354), and
cryptophyta (x = 105) (Fig. 3-18).
Cyanophyte abundance differed between sites with site B having the highest
numbers (x = 373 units/mL) followed by site A (x = 348 units/mL), site C
(x = 293 units/mL), and site D (x = 103 units/mL) (Fig. 3-19). Mean numbers of
cyanophytes were significantly greater in Lake Pleasant during the summer of 1996 (x =
566 units/mL) compared to the summer of 1997 (x = 152 units/mL, F1, 66 = 16.1537, p
<0.0001) (Fig. 3-20).
CAP Canal Periphyton Dynamics
Generally, periphyton numbers tended to increase with distance from Lake
Pleasant. The exception to this was that periphytic algal abundance was slightly higher
in the Waddell Forebay (x = 2805 units/cm2) than it was 6 kilometers down-canal at the
99th Avenue Bridge (x = 1913 units/cm2, F1, 205 = 11.4276, p = 0.0009). The reason for
this is unknown however, the Waddell Forebay is morphologically different from the
other sites and this may have an influence on boundary layer effects. The remaining
sites showed a spatial trend of increasing periphytic biomass with distance from Lake
Pleasant (Table 3-9).
31
Table 3-9. Overall periphyton abundance (in units/cm2) by site including distance from
Lake Pleasant. Means are for 1996 and 1997 collectively.
Site
Units/cm2
Waddell Forebay (WFB)
2805
Distance from Lake
Pleasant (km)
0
CAP at 99th Ave. Bridge
1913
6
CAP at Scottsdale WTP
3205
45
CAP at Granite Reef
Dam
CAP at Mesa WTP
4762
70
9098
78
This spatial trend was evident for both years. Examining all sites collectively
however, revealed that 1996 had significantly higher overall levels of periphyton (x =
6866 units/ cm2) than 1997 (x = 2445 units/cm2, F1, 523 = 10.1582, p = 0.0015, Fig. 3-21).
Periphyton in the CAP was comprised of four divisions, chlorophyta, chrysophyta,
cyanophyta and pyrrophyta. During 1996, cyanophytes were the most abundant
member of the periphyton (x = 19,833 units/cm2) followed by chrysophytes (3377
units/cm2), chlorophytes (2109 units/cm2), and pyrrophytes (2103 units/cm2) (Fig. 3-22).
This hierarchy changed in 1997 with chrysophytes dominating the periphyton (x = 3132
units/cm2) followed by chlorophytes (2039 units/cm2), cyanophytes (1250 units/cm2),
and pyrrophytes (877 units/cm2) (Fig. 3-22).
There was a large degree of spatial and temporal variation in the periphyton
communities along the CAP canal. Dividing the canal into two categories based upon
distance from Lake Pleasant, 6-45 and 70-78 km, shows that cyanobacterial dominance
32
was much more evident in the 70-78 km category during the summer of 1996 (Fig. 3-23)
There was no significant difference in abundance between algal divisions 6-45
kilometers from Lake Pleasant during the same time period (F3,295 = 1.3736, p =
0.2510). Mean cyanophyte numbers were over 6 times greater than the next most
abundant division in the 70-78 km category during the summer of 1996. Chrysophytes
were the most abundant division found in the periphyton during the summer of 1997
however, there was a much more equitable distribution among all algal divisions during
this year compared to 1996.
Periphytic cyanophytes consisted of 5 species all of which are capable of
producing tastes or odors. In order of abundance these were Lyngbya sp. (x = 17,601
units/cm2), Anabaena sp. (x = 3691 units/cm2), Oscillatoria sp. (x = 3205 units/cm2),
Phormidium sp. (x = 2387 units/cm2), and Schizothrix.sp. (x = 290 units/cm2). Table 310 shows the relative number of times cyanophytes were observed in the periphyton of
the CAP canal by distance from Lake Pleasant. Cyanophytes were observed in the
periphyton a total of 112 times during 1996 and 1997 when water was being released
from Lake Pleasant into the CAP canal. Lyngbya sp. were observed most often (54
times) followed by species of Anabaena (29 times), Oscillatoria (23 times), Phormidium
(4 times) and Schizothrix (twice).
Table 3-10. Contingency analysis of periphytic cyanophytes in the CAP canal during
periods of release from Lake Pleasant.
33
Count
Total %
Col %
Row %
00
06
45
70
78
Anabaena
Lyngbya
Oscillatoria
Phormidium
Schizothrix
2
1.79
6.90
13.33
6
5.36
20.69
31.58
5
4.46
17.24
27.78
9
8.04
31.03
32.14
7
6.25
24.14
21.88
29
25.89
10
8.93
18.52
66.67
9
8.04
16.67
47.37
8
7.14
14.81
44.44
14
12.50
25.93
50.00
13
11.61
24.07
40.63
54
48.21
3
2.68
13.04
20.00
4
3.57
17.39
21.05
5
4.46
21.74
27.78
3
2.68
13.04
10.71
8
7.14
34.78
25.00
23
20.54
0
0.00
0.00
0.00
0
0.00
0.00
0.00
0
0.00
0.00
0.00
0
0.00
0.00
0.00
4
3.57
100.00
12.50
4
3.57
0
0.00
0.00
0.00
0
0.00
0.00
0.00
0
0.00
0.00
0.00
2
1.79
100.00
7.14
0
0.00
0.00
0.00
2
1.79
D
15
13.39
uring
19
16.96
18
16.07
28
25.00
times
when
water
was
32
28.57
112
being
relea
sed from Lake Pleasant into the CAP canal, numbers of periphytic cyanophytes were
significantly higher at all sites in 1996 than 1997 (F1,111 = 9.1036, p = 0.0032). This
difference was most pronounced with increasing distance from Lake Pleasant and the
largest change was in the 70-78 km compared to the 0-45 km group (F1,60 = 5.6637, p =
0.0206 and F1,51, p = 0.0996 respectively) (Figs. 3-24 and 3-25). The difference in mean
numbers of cyanophytes for the 0-45 km group between 1996 and 1997 was 4503 and
1120 units/cm2 respectively while the 70-78 km group dropped from 28,156 (1996) to
1335 units/cm2 (1997).
Analysis of MIB and Geosmin in the CAP Canal
Like periphytic cyanophyte abundance, levels of 2-methylisoborneol (MIB)
increased with distance from Lake Pleasant while water from the reservoir was released
34
into the CAP canal (Fig. 3-26). Again dividing the canal into 2 sections, 0-45 and 70-78
kilometers from Lake Pleasant, reveals a significant difference in levels of 2methylisoborneol with levels much higher in the 70-78 kilometer group compared to the
0-45 kilometer group (x = 5.52 and 1.68 ng/L respectively, F1,75 = 11.3902, p = 0.0012,
Fig. 3-27).
Levels of MIB exhibited significant differences between 1996 and 1997 (F1,75 =
5.3585, p = 0.0234, Fig. 3-28). The biggest difference was in the 70-78 kilometers from
Lake Pleasant group with the mean going from 9.46 ng/L in 1996 to 2.67 ng/L in 1997
(Fig. 3-29). The relatively low levels in the 0-45 kilometer group remained basically
unchanged between years with the mean going from 1.81 ng/L in 1996 to 1.56 ng/L in
1997 (Fig. 3-29).
Overall, levels of geosmin in the CAP canal for both years were lower than those
for MIB (x = 1.19 and 3.39 ng/L respectively) and like MIB, levels of geosmin also
decreased with distance from Lake Pleasant (Fig 3-30). Levels of geosmin did not
significantly decrease from 1996 to 1997 (F1, 75 = 0.7263, p = 0.3968). While there was
no statistical difference between years for geosmin, the mean did decrease from 2.50
ng/L in 1996 to 1.51 ng/L in 1997 in those areas most affected by tastes and odors e.g.
sites 70-78 kilometers from Lake Pleasant (Fig. 3-31). While this difference may not be
statistically significant (at the 95% confidence level), it may represent a significant
increase in water quality to managers, utilities, and consumers.
Correlations Between Cyanophyte Species and MIB/Geosmin Levels in the CAP Canal
35
Since it is believed that the major taste and odor causing organisms in the CAP
canal are periphytic cyanophytes, this section will examine correlations between these
species and the taste and odor causing compounds they can produce, MIB and
geosmin. The majority of taste and odor complaints have historically occurred when
water from Lake Pleasant was being released into the CAP canal and this analysis will
focus on this period only. Because species of Phormidium and Schizothrix were only
observed in the periphyton a combined total of 5 times, and the mean level of each was
relatively low (x = 2387 and 290 units/cm2 respectively), these species are excluded
from this analysis. This leaves 3 species of cyanophytes commonly found in the
periphyton of the CAP canal that were analyzed for correlations to MIB and geosmin;
Anabaena, Lyngbya, and Oscillatoria. Because of the apparent differences in MIB,
geosmin, and periphytic cyanophyte levels between 1996 and 1997, each species of
cyanophyte is analyzed by these years separately. This data should be carefully
interpreted because each species existed in a matrix of other potential taste and odor
causing species within the periphytic community each of which are able to produce
differing levels of MIB or geosmin depending upon optimum environmental rates of
production. Therefore, it is possible that species found in low abundance could have
produced larger levels of either geosmin or MIB than species found in higher numbers.
Species of Anabaena showed a more positive correlation to geosmin (R = 0.81)
than MIB (R = 0.66) during 1996 (Fig. 3-32). This was not the case for 1997 however
when numbers of Anabaena showed no significant correlation to geosmin (R = 0.40)
and an inverse correlation to MIB (R = -0.46, Fig 3-33). The fact that there is no
36
correlation between Anabaena and geosmin or MIB during 1997 could be because
numbers of all these variables were significantly less during this year than 1996.
Numbers of Anabaena dropped from 6058 units/cm2 during 1996 to 1482 units/cm2 in
1997 while numbers of MIB and geosmin similarly decreased. Another explanation
could be that Anabaena did not have optimum environmental conditions for the
production of taste and odor causing compounds during 1997.
Abundance of Oscillatoria sp. showed a positive correlation to both MIB (R =
0.89) and geosmin (R = 0.74) during 1996 (Fig. 3-34). Abundance of Oscillatoria
showed no correlation to levels of MIB (R = 0.32) or geosmin (-0.41) during 1997 (Fig.
3-35). Like Anabaena, a possible reason for the uncoupling of any correlation between
Oscillatoria and MIB and geosmin during 1997 may be due to environmental conditions
not conducive to the production of either compound during this year. Mean numbers of
Oscillatoria dropped from 5934 units/cm2 in 1996 to 227 units/cm2 in 1997.
There was a large, positive correlation between amounts of periphytic Lyngbya
sp. and MIB (R = 0.91, Fig. 3-36) during 1996. This correlation, like that of the other
species of cyanophytes, decreased dramatically during 1997 (R = 0.18, Fig. 3-37). The
correlation between Lyngbya and geosmin was not as pronounced as MIB during 1996
(R = 0.52, Fig. 3-36) and did not decrease as dramatically during 1997 (R = 0.43, Fig. 337).
Table 3-11 shows the mean numbers of each periphytic cyanophyte species by
year as well as their correlation to MIB and geosmin levels. During 1996, Lyngbya and
Anabaena were most closely correlated to levels of MIB and geosmin respectively.
37
During 1997 however, there were no significant correlations between cyanophyte
abundance and MIB or geosmin.
Table 3-11. Mean numbers of periphytic cyanophytes by year and their correlation to
taste and odor producing compounds.
Species by Year
1996
Anabaena
Lyngbya
Oscillatoria
1997
Anabaena
Lyngbya
Oscillatoria
Mean Units/cm2
Correlation to
MIB (R)
Correlation to
Geosmin (R)
6058
41,128
5934
0.66
0.91
0.89
0.81
0.52
0.74
1482
1493
227
-0.46
0.18
0.32
0.40
0.43
-0.41
Principal Component Analysis of Lake Pleasant Hypolimnetic Conditions and MIB,
Geosmin, and Periphyton within the CAP Canal
In order to better view the high-dimensional nature of all the variables
simultaneously, principal component analysis (PCA) was performed on the data from
Lake Pleasant simultaneously with the data from the CAP canal. It appears that among
the Lake Pleasant sites, site D is lower in nutrients (i.e. N and P) than sites A, B, or C,
so this site was excluded from the PCA analyses. It also appears that MIB, geosmin,
and periphytic cyanobacterial numbers were much lower closer to Lake Pleasant (0-45
km) than areas farther removed (70-78 km) therefore, the 0-45 km group was excluded
from PCA analyses. This was done in order to answer the question "what conditions (if
any) within Lake Pleasant may contribute the most to periphytic cyanobacterial growth
38
and subsequent MIB/geosmin production within areas of the CAP canal where taste and
odor problems were most pronounced?" PCA allowed us to distinguish maximum
variability in the data, what the most important gradients were, and what their position
was within the data. We performed standardized principal component analysis in which
the mean was subtracted from the data set and divided by the standard deviation. This
sets the centroid of the data cloud to zero and the standard deviation of all variables to
one. This is an eigenanalysis of the correlation matrix where the covariance of the
standardized variables equals the correlation. The Gabriel (1971) bi-plots associated
with each PCA reveal the correlations among the chosen variables by examination of
the principal component rays. These rays are orthogonal to one another in the original
high dimensional space that defines all of the variables, but as this space becomes
forced to approximate fewer dimensions it may become evident that not all of the rays
are truly orthogonal. When the higher dimensions are reduced the correlation between
all variables, even those originally thought to be orthogonal, come closer together with
those becoming the closest having the greatest correlation.
The variables from the hypolimnion of Lake Pleasant include total phosphorous
("P"), nitrogen (NO3-N + NH3-N labeled as "N"), and dissolved oxygen (D.O.) while
those from the CAP canal include MIB, geosmin and periphytic cyanobacteria numbers
(#/cm2).
PCA for 1996 shows a significant correlation between MIB, total phosphorous,
and nitrogen with geosmin showing less of a correlation to both nutrients (Fig. 3-38).
Dissolved oxygen and both N and P levels from the hypolimnion of Lake Pleasant were
39
inversely correlated. There was also an inverse correlation between MIB levels within
the canal and dissolved oxygen levels within the hypolimnion of Lake Pleasant. While
geosmin shared some degree of environmental space as the hypolimnetic nutrients and
MIB, the correlation was less apparent. The principal component rays for both MIB and
geosmin are relatively short indicating a large degree of variance for this year.
For 1997, the correlation among nutrient levels from the hypolimnion of Lake
Pleasant and MIB/geosmin production within the CAP canal are less evident (Fig. 3-39).
There is still an inverse correlation between dissolved oxygen and MIB, geosmin, and
total phosphorous, but this is not true for nitrogen, which now shows a positive
relationship with dissolved oxygen. The only clear correlation that exists for this year is
the inverse relationship between dissolved oxygen within the hypolimnion of Lake
Pleasant and both MIB and geosmin levels within the CAP canal. Dissolved oxygen
accounted for 45.4 and 41.3% of the total variation within the data clouds for 1996 and
1997 respectively.
Isolating the site with the highest hypolimnetic nutrient levels (site B) with the
MIB, geosmin, and periphytic cyanobacterial numbers within the CAP canal reveals a
strong correlation between cyanobacterial numbers and both MIB and geosmin during
1996 (Fig. 3-40). There was an inverse correlation among these variables and dissolved
oxygen levels. This would indicate that the lower the dissolved oxygen levels within the
hypolimnion of site B, the higher the periphytic cyanobacterial numbers and
MIB/geosmin levels within the CAP canal at those areas most affected by taste and
odor problems.
40
Analyzing the same sites and variables for 1997 did not show any correlation and
the principal component rays were nearly orthogonal to one another (Fig. 3-41). The
dissolved oxygen levels at site B were higher in the summer of 1997 than the summer
of 1996 (x = 1.19 and 5.28 mg/l respectively. F1,156 = 178.1413, p <0.0001). There was
an almost completely random scatter of data points within the cloud. The only way to
interpret PCA for 1997 is to say that conditions within the hypolimnion of site B had no
apparent correlation to numbers of periphytic cyanobacteria or MIB/geosmin levels
within those areas of the CAP that historically had the worst taste and odor problems.
41
CHAPTER 4
DISCUSSION
The correlation between anoxia and nutrient levels within the hypolimnion of
Lake Pleasant and the abundance of periphytic cyanobacteria and MIB/geosmin
production in the CAP canal may be the result of a causal relation. We propose that
nutrients are released from the sediment of Lake Pleasant during periods of anoxia
within the hypolimnion, and when this nutrient-rich water is released into the CAP canal,
it promotes the growth of periphytic taste and odor causing organisms within the canal.
What is less evident is why areas closest to the reservoir exhibit far less severe taste
and odor problems and support fewer periphytic cyanobacteria than areas farther downcanal. This pattern holds even when there is some detectable level of MIB and geosmin
production within Lake Pleasant (personal observation). We believe that most of the
MIB and geosmin produced within Lake Pleasant was degraded in the turbulent
conditions of the released water and that taste and odor problems farther down-canal
were the result of increased local periphytic cyanobacterial growth. This explanation
does not diminish the role of conditions within Lake Pleasant as the principle cause of
42
MIB or geosmin production within the CAP canal. Our data suggest that the relationship
between MIB and geosmin within the CAP canal is not a direct result of MIB or geosmin
produced within Lake Pleasant. A generalized model of MIB/geosmin production within
the CAP canal is:
1) Increased sedimentation of material (mostly periphytic algae from the sides of the
CAP canal upstream of Lake Pleasant) between the old and new Waddell Dams during
annual re-filling of Lake Pleasant with CAP canal water. The result may be that the
lacustrine area between the dams is now the most productive zone in terms of nutrients
and primary production. This model is different than the idealized model of reservoir
zonation as proposed by Thornton, Kimmel, and Payne (1990).
2) Under prolonged anoxia in the hypolimnion, this deposited organic material releases
nutrients (especially reduced forms of nitrogen and phosphorous) at a faster rate than
do sediments in other parts of the reservoir (Walker et al. in press).
3) These nutrients accumulate within the hypolimnion. If water is released into the CAP
canal from the top gate of the release tower, the hypolimnion remains undisturbed for
long periods and this stability leads to further nutrient accumulation within the
hypolimnion.
4) Geosmin or MIB formed within Lake Pleasant may be quickly degraded in the
turbulent release water. This may explain why taste and odor has never been a
significant problem at those water treatment plants closest to the reservoir. Taste and
odor problems increase linearly away from Lake Pleasant as a result of increased
periphytic cyanobacterial biomass, which in turn produces MIB or geosmin.
43
5) Release of nutrient-rich water from the hypolimnion into the CAP canal may lead to
the proliferation of taste and odor causing periphytic cyanobacteria within the canal,
especially in areas 70 km or more away from Lake Pleasant
The linear increase in periphytic cyanobacteria in the CAP canal moving away
from Lake Pleasant may be due to dampening of hydraulic disturbance of periphyton
with greater distance from the site of release. Many cyanophytes are not adapted to the
turbulent flow found at sites closer to the reservoir. During 1996, chlorophytes (mostly
Cladophora sp.) and pennate diatoms were dominant in the CAP canal until 70 km
down-canal from Lake Pleasant, where cyanobacteria began to dominate. During 1997,
numbers of cyanophytes were greatly reduced at all reaches of the CAP canal as it
crossed the Phoenix Valley. On average, flow decreases by 400 cfs between areas of
the CAP canal closest to Lake Pleasant and areas 70-78 km away where cyanobacteria
had begun to dominate during 1996 (pers. comm. Tim Kacerak, CAWCD). The higher
flows at sites closest to Lake Pleasant in 1996 may have favored species (i.e.,
Cladophora sp, pennate diatoms) that were adapted to faster-flowing water.
Cyanophytes (i.e., Lyngbya, Anabaena, Oscillatoria sp.) that could not survive in high
flow became dominant only when flow decreased enough to allow establishment.
Resource-ratio theory states that exploitative competition among taxa with
different optimal nutrient ratios will cause changes in plant community structure (Tilman
1977, 1982, 1985). This theory was originally constructed for phytoplankton, and not
until recently has it been applied to benthic algae (Bothwell 1989, Harvey et al. 1998,
Stelzer & Lamberti 2001). Periphytic communities in the southwestern U.S. may be N
44
limited at ambient levels of 50-90 g NO3-N L-1 (Grimm & Fisher 1986; Lohman et al.
1991). Based on the Redfield (1958) ratio, Lake Pleasant would be considered N
limited with an average N:P ratio for both years of 9.5:1. This is based upon molecular
weight ratios of NO3-N + NH3-N and total phosphorous levels. Hypolimnetic Redfield
ratios from Lake Pleasant for 1996 and 1997 reveal that N was less limiting in 1997
(N:P = 11.7:1) than in 1996 (N:P = 6:1). Stelzer and Lamberti (2001) found a strong
correlation between intracellular lotic periphyton N:P and N:P of dissolved nutrients in
the ambient stream water. Peterson and Grimm (1992) and Mulholland et al. (1995)
observed dominance by cyanophytes in streams that had low N:P ratios because of the
ability of cyanophytes to fix atmospheric N2.
Nutrient ratios alone not be sufficient for identifying limiting nutrients, and should
not be used without quantifying the total nutrient concentration (TNC). Overall
periphyton production may not be as affected by N:P as by TNC (Bothwell 1985). We
found that within the CAP canal, there were differences in both overall periphyton
abundance (based upon numbers/cm2) and assemblage (based upon dominant
divisions) between 1996 and 1997. Hypolimnetic TNC (NO3 + NH3 + total P) in Lake
Pleasant for 1997 (0.19 mg/L) were less than half of what they were during 1996 (0.32
mg/L) (F1,89 = 142.9567, p <0.0001). The decreased anoxia within the hypolimnion
during 1997 as compared to 1996, may have inhibited nutrient release from sediments,
especially in those areas shown to have the greatest amount of nutrient release during
anoxia (Walker et al. in press). We believe that withdraw of water from the hypolimnion
of Lake Pleasant for delivery to the CAP canal should occur as early as possible during
45
the season of stratification in order to lower of the TNC loading as well as increase the
N:P ratio of water delivered to the CAP canal. This may result in decreased periphyton
abundance and shift periphyton community structure away from taste and odor-causing
organisms (i.e., cyanobacteria) and toward chlorophytes and diatoms.
CHAPTER 5
CONCLUSIONS
We believe that reservoir hypolimnetic withdrawal from Lake Pleasant may be an
effective management tool in controlling nutrient loading and alleviating the growth of
46
taste and odor causing organisms in those areas of the CAP canal receiving this
released water. While the hypolimnion of Lake Pleasant has experienced periods of
anoxia in subsequent years (unpublished data), they have not been as severe or lasted
as long since releasing water from the lower gates almost exclusively since 1997.
Dissolved oxygen depletion within the hypolimnion of thermally stratified reservoirs is a
common phenomenon however, biologically and chemically there is a large difference
between dissolved oxygen levels of 0.5 and 0.1 mg/L, especially as it applies to
reduction and nutrients released from sediment. Generally, ferric iron (Fe+++) will reduce
to soluble ferrous iron (Fe++) only at dissolved oxygen levels of 0.1 mg/L or less. It is at
this point when phosphorous will lose its normally close association with iron and
solubilize from the sediment and accumulate within the hypolimnion. The response of
the periphyton communities in the CAP canal was predicted from resource-ratio theory
in that as the N:P ratio became higher due to less phosphorous released from Lake
Pleasant, any exploitative competition by species capable of N2 fixation (e.g.
cyanobacteria) was decreased which lead to dominance by chlorophytes and diatoms.
Of course, resource-ratio theory and its use as a management tool are only useful if
total nutrient concentrations are taken into consideration. The management plan in the
CAP canal and Lake Pleasant was to not only change the N:P ratio but also to lower the
total nutrient concentration. We propose that even very subtle changes of management
strategies in reservoirs can change the amount and type of nutrients released to
receiving waters, which may have profound effects upon not only problems with taste
and odor but issues such as disinfection by-products and algal toxins as well. The cost
47
associated with releasing water from only the lower gates of Lake Pleasant was
virtually, nothing. Since this recommendation was made and its implementation, the
taste and odor problems in the CAP canal have been eliminated resulting in a savings
of hundreds of thousands of dollars in carbon use for municipalities using this water.
Figure 2-1. Lake Pleasant operational data showing relationship between the old and new Waddell Dams
48
49
Figure 2-2. Sampling Sites within Lake Pleasant, AZ.
Figure 2-3. Sampling sites within the CAP canal showing approximate distances from Lake Pleasant.
50
51
Figure 3-1. The relationship between dissolved oxygen and depth in Lake Pleasant
during August-October of 1996 and 1997.
Multivariate Correlations
Depth
Depth
1.0000
D.O. (mg/l)
0.8199
D.O. (mg/l)
0.8199
1.0000
Scatterplot Matrix
0
-10
Depth
-20
-30
-40
9
8
7
6
5
4
D.O. (mg/l)
3
2
1
0
-40
-30
-20
-10
0 0 1 2 3 4 5 6 7 8 9
52
Figure 3-2. Mean dissolved oxygen levels (mg/L) by stratified layer in Lake Pleasant.
Layer
Epilimnion
Metalimnion
Hypolimnion
0
1
2
3
4
5
Mean D.O. (mg/L)
6
7
8
53
Figure 3-3. Oneway analysis of hypolimnetic ammonia-N levels (mg/L) in Lake Pleasant
by year.
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group.
Ammonia-N
0.2
0.15
0.1
0.05
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source Sum of
Squares
Year
0.02656761
Error
0.06813098
C. Total 0.09469859
0.280549
0.266714
0.036197
0.02763
54
Mean Square F Ratio
Prob > F
0.026568
0.001310
<0.0001
20.2774
Means for Oneway Anova
Level Number
Mean
Std Error
Lower 95%
1996 26
0.056550
0.00809
0.04031
1997 28
0.010618
0.00621
-0.0018
Std Error uses a pooled estimate of error variance
Upper 95%
0.07279
0.02307
54
Figure 3-4. Oneway analysis of hypolimnetic total phosphorous levels (mg/L) in Lake
Pleasant by year.
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group.
0.6
0.5
Total P
0.4
0.3
0.2
0.1
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
52
C. Total
53
0.112322
0.088962
0.109752
0.165875
54
Sum of Squares
0.05791838
0.45772600
0.51564437
Mean Square
0.057918
0.012045
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
26
0.215000
0.02834
0.15763
1997
28
0.136400
0.02195
0.09196
Std Error uses a pooled estimate of error variance
F Ratio
4.8083
Upper 95%
0.27237
0.18084
Prob > F
0.0345
55
Figure 3-5. Oneway analysis of hypolimnetic orthophosphate levels (mg/L) in Lake
Pleasant by year.
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group.
0.5
Ortho-P
0.4
0.3
0.2
0.1
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
53
C. Total
54
0.299935
0.286727
0.094604
0.105273
55
Sum of Squares
0.20322746
0.47434345
0.67757091
Mean Square
0.203227
0.008950
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
27
0.182619
0.02064
0.14121
1997
28
0.057500
0.01622
0.02496
Std Error uses a pooled estimate of error variance
F Ratio
22.7073
Upper 95%
0.22403
0.09004
Prob > F
<.0001
56
Figure 3-6. Oneway analysis of nitrate/nitrite-N Levels (mg/L) in the CAP canal by year.
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group
Nitrate/Nitrite-N )
0.15
0.1
0.05
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
62
C. Total
63
0.21748
0.204217
0.031267
0.063115
64
Sum of Squares
0.01603006
0.05767813
0.07370820
Mean Square
0.016030
0.000978
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
32
0.081923
0.00613
0.06965
1997
32
0.049143
0.00529
0.03857
Std Error uses a pooled estimate of error variance
F Ratio
16.3974
Prob > F
0.0002
Upper 95%
0.09419
0.05972
Figure 3-7. Oneway analysis of ammonia-N levels (mg/L) in the CAP canal by year.
57
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group.
0.3
0.25
Ammonia
0.2
0.15
0.1
0.05
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
64
C. Total
65
0.271978
0.259639
0.053411
0.069672
67
Sum of Squares
0.06287960
0.16831385
0.23119344
Mean Square
0.062880
0.002853
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
33
0.106923
0.01047
0.08596
1997
33
0.042000
0.00903
0.02393
Std Error uses a pooled estimate of error variance
F Ratio
22.0415
Prob > F
<.0001
Upper 95%
0.12788
0.06007
Figure 3-8. Oneway analysis of total-P levels (mg/L) in the CAP canal by year.
58
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group.
0.5
0.4
Total-P
0.3
0.2
0.1
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
64
C. Total
65
0.697369
0.69224
0.060178
0.171148
65
Sum of Squares
0.49235638
0.21366330
0.70601967
Mean Square
0.492356
0.003621
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
32
0.275385
0.01180
0.25177
1997
33
0.093714
0.01017
0.07336
Std Error uses a pooled estimate of error variance
F Ratio
135.9570
Prob > F
<.0001
Upper 95%
0.29900
0.11407
Figure 3-9. One-way analysis of orthophosphate levels (mg/L) in the CAP canal by year.
59
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group.
0.3
0.25
Ortho-P
0.2
0.15
0.1
0.05
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
59
C. Total
60
0.39683
0.386607
0.048934
0.072787
61
Sum of Squares
0.09294810
0.14127813
0.23422623
Mean Square
0.092948
0.002395
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
30
0.118077
0.00960
0.09887
1997
30
0.039143
0.00827
0.02259
Std Error uses a pooled estimate of error variance
F Ratio
38.8166
Upper 95%
0.13728
0.05569
Prob > F
<.0001
60
Figure 3-10. Mean numbers of algae by division observed in Lake Pleasant during 1996
and 1997.
Euglenophyta
Cryptophyta
Pyrrophyta
Chrysophyta
Cyanophyta
Chlorophyta
0
Division
Chlorophyta
Chrysophyta
Cryptophyta
Cyanophyta
Euglenophyta
Pyrrophyta
Number
198
201
70
194
11
160
200
400
600
800
Mean(Units/ml)
Mean
682.97
1241.92
46.81
282.34
19.36
260.43
Std Error
156.03
154.86
262.41
157.63
661.96
173.57
1000
1200
Lower 95%
376.7
938.0
-468.3
-27.1
-1280.0
-80.3
Upper 95%
989.2
1545.9
561.9
591.7
1318.7
601.1
61
Figure 3-11. Mean numbers of phytoplankton (in units/mL) by site in Lake Pleasant for
1996 and 1997.
A
Site
B
C
D
0
Site
A
B
C
D
100
Number
212
219
206
197
200
300
Mean
390.25
1010.06
720.26
164.85
400 500 600 700
Mean(Units/ml )
Std Error
151.75
149.30
153.94
157.42
800
Lower 95%
92.39
717.01
418.10
-144.14
900 10001100
Upper 95%
688.1
1303.1
1022.4
473.8
62
Figure 3-12. Bivariate fit of depth (m) by units/ml while withdrawing water from
Lake Pleasant during 1996 and 1997.
0
Depth (m)
-10
-20
-30
-40
-50
-60
0
1000
2000
Uni ts/ml
3000
4000
Linear Fit
Linear Fit
Depth (m) = -19.76264 + 0.0132913 Units/ml
Summary of Fit
RSquare
RSquare Adj
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Model
1
Error
545
C. Total
546
0.132353
0.130761
14.65224
-16.1768
547
Sum of Squares
17848.25
117005.11
134853.36
Mean Square
17848.2
214.7
F Ratio
83.1356
Prob > F
<.0001
63
Figure 3-13. Bivariate fit of algal units/mL by depth (m) while pumping water into Lake
Pleasant during 1996 and 1997.
0
Depth (m)
-10
-20
-30
-40
-50
0
10000
Uni ts/ml
20000
Linear Fit
Linear Fit
Depth (m) = -17.01583 - 0.0011781 Units/ml
Summary of Fit
RSquare
RSquare Adj
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Model
1
Error
285
C. Total
286
0.070047
0.066784
15.84388
-18.4
287
Sum of Squares
5388.823
71543.097
76931.920
Mean Square
5388.82
251.03
F Ratio
21.4670
Prob > F
<.0001
64
Figure 3-14. Bivariate fit of algal units/mL by depth (m) at site A while pumping water
into Lake Pleasant during 1996 and 1997.
0
Depth
-10
-20
-30
-40
-50
0
1000
2000
3000
4000
Units/ml
5000
6000
7000
8000
Linear Fit
Linear Fit
Depth = -17.46802 - 0.0047047 Units/ml
Summary of Fit
RSquare
RSquare Adj
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Model
1
Error
76
C. Total
77
0.080071
0.067967
17.07819
-19.9705
78
Sum of Squares
1929.393
22166.509
24095.902
Mean Square
1929.39
291.66
F Ratio
6.6151
Prob > F
0.0121
65
Figure 3-15. Bivariate fit of algal units/mL by depth at site B while pumping water into
Lake Pleasant during 1996 and 1997.
0
Depth
-10
-20
-30
-40
0
10000
Uni ts/ml
20000
Linear Fit
Linear Fit
Depth = -14.19112 - 0.0010294 Units/ml
Summary of Fit
RSquare
RSquare Adj
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Model
1
Error
74
C. Total
75
0.170345
0.159133
13.52382
-16.5961
76
Sum of Squares
2778.831
13534.138
16312.969
Mean Square
2778.83
182.89
F Ratio
15.1937
Prob > F
0.0002
66
Figure 3-16. Bivariate fit of algal units/mL by depth at site C while pumping water into
Lake Pleasant during 1996 and 1997.
0
Depth
-10
-20
-30
-40
-50
0
10000
Uni ts/ml
20000
Linear Fit
Linear Fit
Depth = -17.41605 - 0.0016615 Units/ml
Summary of Fit
RSquare
RSquare Adj
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Model
1
Error
66
C. Total
67
0.142386
0.129391
15.43067
-20.1662
68
Sum of Squares
2609.081
15714.971
18324.052
Mean Square
2609.08
238.11
F Ratio
10.9577
Prob > F
0.0015
67
Figure 3-17. Bivariate fit of units/mL by depth at site D while pumping water into Lake
Pleasant during 1996 and 1997.
0
Depth
-10
-20
-30
-40
-50
0
100
200 300 400
Uni ts/ml
500
600
Linear Fit
Linear Fit
Depth = -21.57742 + 0.0556009 Units/ml
Summary of Fit
RSquare
RSquare Adj
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Model
1
Error
63
C. Total
64
0.128409
0.114574
15.50459
-16.7769
65
Sum of Squares
2231.229
15144.707
17375.935
Mean Square
2231.23
240.39
F Ratio
9.2816
Prob > F
0.0034
68
Figure 3-18. Divisions of algae (in units/mL) found below 10 meters depth at sites A, B,
and C during the period of re-filling.
Cryptophyta
Pyrrophyta
Chrysophyta
Cyanophyta
Chlorophyta
0
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Mean(Units/ml)
69
Figure 3-19. Cyanophyte abundance by site during the summers of 1996 and 1997.
400
Mean(Units/ml)
300
200
100
0
A
B
C
D
Site
Figure 3-20. One-way analysis of cyanophyte abundance (units/mL) during the
Summers of 1996 and 1997 in Lake Pleasant.
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group
70
Units/ml
2000
1000
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
65
C. Total
66
0.199051
0.186729
323.2651
226.597
67
Sum of Squares
1688069.6
6792522.6
8480592.1
Mean Square
1688070
104500
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
32
566.417
93.319
380.05
1997
35
152.455
43.589
65.40
Std Error uses a pooled estimate of error variance
F Ratio
16.1537
Upper 95%
752.79
239.51
Prob > F
0.0002
71
Figure 3-21. One-way analysis of periphyton abundance (units/cm2) for all sites in the
CAP canal during 1996 and 1997.
Blue lines represent the standard deviation from the mean at a 95% confidence interval.
300000
Units/cm2
250000
200000
150000
100000
50000
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
522
C. Total
523
0.019089
0.01721
15817.42
4461.49
524
Sum of Squares
2541499212
1.306e+11
1.33141e11
Mean Square
2.5415e+9
250190684
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
239
6866.42
1023.1
4856.4
1997
285
2444.72
936.9
604.1
Std Error uses a pooled estimate of error variance
F Ratio
10.1582
Upper 95%
8876.4
4285.4
Prob > F
0.0015
72
Figure 3-22. Abundance of algal divisions found within the periphyton of the CAP canal
during the summers of 1996 and 1997.
Pyrrophyta
1997 Chlorophyta
Chrysophyta
Cyanophyta
Pyrrophyta
1996 Chlorophyta
Chrysophyta
Cyanophyta
0
10000
Mean(Units/cm2)
20000
73
Division by Distance from Lake Pleasant (km)
6 - 45
70 - 78
Figure 3-23. Divisions of Algae by Distance from Lake Pleasant During the Summer of
1996
Pyrrophyta
Chlorophyta
Chrysophyta
Cyanophyta
Pyrrophyta
Chlorophyta
Chrysophyta
Cyanophyta
0
5000
10000
15000
20000
Mean(Units/cm2)
25000
30000
74
Figure 3-24. Oneway analysis of numbers of periphytic cyanophytes by year in the CAP
canal at 70-78 Kilometers from Lake Pleasant.
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group
300000
Units/cm2
250000
200000
150000
100000
50000
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
58
C. Total
59
0.088963
0.073255
43038.49
16980.5
60
Sum of Squares
1.04909e10
1.07434e11
1.17925e11
Mean Square
1.0491e10
1.85231e9
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
35
28156.0
7274.8
13594
1997
25
1334.8
8607.7
-15895
Std Error uses a pooled estimate of error variance
F Ratio
5.6637
Upper 95%
42718
18565
Prob > F
0.0206
75
Figure 3-25. Oneway analysis of numbers of periphytic cyanophytes by year in the CAP
canal at 0-45 kilometers from Lake Pleasant.
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group
50000
Units/cm2
40000
30000
20000
10000
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
Analysis of Variance
Source
DF
Year
1
Error
50
C. Total
51
0.053304
0.03437
6858.744
2397.308
52
Sum of Squares
132437765
2352118658
2484556423
Mean Square
132437765
47042373
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
25
4500.53
1573.5
1340.1
1997
27
1186.36
1194.0
-1211.8
Std Error uses a pooled estimate of error variance
F Ratio
2.8153
Upper 95%
7661.0
3584.5
Prob > F
0.0996
76
Km's From Lake Pleasant
Figure 3-26. Mean levels of 2-methylisoborneol in the CAP canal by distance from Lake
Pleasant during periods of release for 1996 and 1997 collectively.
78
70
45
06
00
0
1
2
3
4
Mean MIB (ng/l)
5
6
7
77
Figure 3-27. Oneway analysis of mean MIB levels (ng/L) by distance from Lake
Pleasant during times of release for 1996 and 1997 collectively.
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group.
30
Mean MIB (ng/l)
25
20
15
10
5
0
0 - 45
70 - 78
Distance from Lake Pleasant (km)
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum Wgts)
0.13339
0.121679
4.871177
3.244079
76
Analysis of Variance
Source
DF
Distance from
Lake Pleasant
(km)
Error
C. Total
Sum of Mean F Ratio Prob > F
Squares Square
1 270.2705 270.270 11.3902 0.0012
74 1755.8994 23.728
75 2026.1698
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
0 - 45
36
1.67889
0.72615
0.2320
70 - 78
40
5.51613
0.87489
3.7729
Std Error uses a pooled estimate of error variance
Upper 95%
3.1258
7.2594
78
Figure 3-28. Oneway analysis of MIB levels by year for all sites in the CAP canal.
The horizontal line across each means diamond represents the group mean and the vertical span of each
diamond represents the 95% confidence interval for each group.
30
Mean MIB (ng/l)
25
20
15
10
5
0
1996
1997
Year
Summary of Fit
Rsquare
Adj Rsquare
Root Mean Square Error
Mean of Response
Observations (or Sum
Wgts)
Analysis of Variance
Source
DF
Year
1
Error
74
C. Total
75
0.067522
0.054921
5.052907
3.244079
76
Sum of Squares Mean Square
136.8119
136.812
1889.3579
25.532
2026.1698
F Ratio Prob > F
5.3585 0.0234
Means for Oneway Anova
Level
Number
Mean
Std Error
Lower 95%
1996
34
4.73529
0.86657
3.0086
1997
42
2.03690
0.77968
0.4834
Std Error uses a pooled estimate of error variance
Upper 95%
6.4620
3.5905
79
Figure 3-29. Mean levels of MIB by distance from Lake Pleasant during periods of
release into the CAP canal during 1996 and 1997.
70 - 78
1997
0 - 45
70 - 78
1996
0 - 45
0
1
2
3
4
5
6
7
Mean MIB (ng/l)
8
9
10
11
80
Km's From Lake Pleasant
Figure 3-30. Mean levels of geosmin in the CAP canal by distance from Lake Pleasant
during periods of release for 1996 and 1997 collectively.
78
70
45
06
00
.0
.5
1.5
1.0
Mean Geosmin (ng/l)
2.0
2.5
81
Figure 3-31. Mean levels of geosmin by distance from Lake Pleasant (km's) during
periods of release into the CAP canal during 1996 and 1997.
70 - 78
1997
0 - 45
70 - 78
1996
0 - 45
.0
.5
1.0
1.5
Mean Geosmin (ng/l)
2.0
2.5
82
Figure 3-32. Correlations between numbers of Anabaena sp. (units/cm2) to levels of
MIB and geosmin (ng/L) in the CAP canal during 1996.
Multivariate Correlations
Units/cm2
Units/cm2
Mean MIB (ng/l)
Mean geosmin
(ng/l)
1.0000
0.6611
0.8058
Mean MIB Mean geosmin (ng/l)
(ng/l)
0.6611
0.8058
1.0000
0.7086
0.7086
1.0000
Scatterplot Matrix
25000
20000
15000
10000
5000
0
30
25
20
15
10
5
0
Units/cm2
Mean MIB (ng/l)
10
8
6
4
Mean geosmin (ng/l)
2
05000 1500025000 0 5 10 15 20 25 30
2
4
6
8 10
83
Figure 3-33. Correlations between numbers of Anabaena sp. (units/cm2) to levels of
MIB and geosmin (ng/L) in the CAP canal during 1997.
Multivariate Correlations
Units/cm2
Units/cm2
Mean MIB (ng/l)
Mean geosmin (ng/l)
1.0000
-0.4636
0.3962
Mean MIB (ng/l) Mean geosmin
(ng/l)
-0.4636
0.3962
1.0000
0.3376
0.3376
1.0000
Scatterplot Matrix
10000
7500
5000
2500
Units/cm2
0
6
5
4
3
2
1
Mean MIB (ng/l)
7
6
5
4
3
2
Mean geosmin (ng/l)
0 2500
7500
1 2 3 4 5 6
2 3 4 5 6 7
84
Figure 3-34. Correlations between numbers of Oscillatoria sp. (units/cm2) to levels of
MIB and geosmin (ng/L) in the CAP canal during 1996.
Multivariate Correlations
Units/cm2
Mean MIB (ng/l)
Mean geosmin (ng/l)
Units/cm2 Mean MIB (ng/l) Mean geosmin (ng/l)
1.0000
0.8899
0.7412
0.8899
1.0000
0.6539
0.7412
0.6539
1.0000
Scatterplot Matrix
15000
10000
5000
Units/cm2
30
25
20
15
Mean MIB (ng/l)
10
5
10
7.5
5
Mean geosmin (ng/l)
2.5
5000 10000
5 10 15 20 25 30
2.5
5 7.5 10
85
Figure 3-35. Correlations Between Numbers of Oscillatoria sp. (units/cm2) to Levels of
MIB and Geosmin (ng/L) in the CAP Canal During 1997.
Multivariate Correlations
Units/cm2 Mean MIB (ng/l)
Units/cm2
1.0000
0.3226
Mean MIB (ng/l)
0.3226
1.0000
Mean geosmin
-0.4067
-0.1078
(ng/l)
Mean geosmin (ng/l)
-0.4067
-0.1078
1.0000
Scatterplot Matrix
500
400
300
Units/cm2
200
100
5
4
3
Mean MIB (ng/l)
2
1
1
0.5
Mean geosmin (ng/l)
0
100 200 300 400 500
1
2
3
4
5
0
.5
1
86
Figure 3-36. Correlations between numbers of Lyngbya sp. (units/cm2) to levels of MIB
and geosmin (ng/L) in the CAP canal during 1996.
Multivariate Correlations
Units/cm2 Mean MIB (ng/l) Mean geosmin (ng/l)
Units/cm2
1.0000
0.9119
0.5221
Mean MIB (ng/l)
0.9119
1.0000
0.7388
Mean geosmin
0.5221
0.7388
1.0000
(ng/l)
Scatterplot Matrix
300000
250000
200000
150000
100000
50000
Units/cm2
0
30
25
20
15
10
5
0
Mean MIB (ng/l)
10
8
6
4
Mean geosmin (ng/l)
2
0
0 100000
250000
0 5 10 15 20 25 30
0
2
4
6
8 10
Figure 3-37. Correlations between numbers of Lyngbya sp. (units/cm2) to levels of MIB
and geosmin (ng/L) in the CAP canal during 1997.
87
Multivariate Correlations
Units/cm2 Mean MIB (ng/l)
Units/cm2
1.0000
0.1853
Mean MIB (ng/l)
0.1853
1.0000
Mean geosmin
0.4349
0.2031
(ng/l)
Mean geosmin (ng/l)
0.4349
0.2031
1.0000
Scatterplot Matrix
3000
2500
2000
1500
Units/cm2
1000
500
6
5
4
3
Mean MIB (ng/l)
2
1
7
5
3
2
Mean geosmin (ng/l)
0
500
1500
2500
1
2
3
4
5
6
0 1 2 3 4 5 6 7
88
Figure 3-38. Principal component analysis of nutrient and dissolved oxygen data from
the hypolimnion of Lake Pleasant and MIB/geosmin data from 70-78 km down-canal
during 1996.
y
D.O.
N
P
x
MIB
Geosmin
z
Principal Components
EigenValue Percent Cum Percent
2.2695 45.391
45.391
1.7580 35.160
80.550
0.7309 14.617
95.168
0.2339
4.679
99.846
0.0077
0.154
100.000
Eigenvectors
D.O.
P
N
MIB
Geosmin
-0.41280
0.64283
0.63296
0.10132
0.07391
0.09699
-0.06435
-0.06534
0.69924
0.70231
0.90314
0.26385
0.32874
0.01092
-0.08085
0.04966
0.01632
0.04692
-0.70740
0.70331
0.04538
0.71607
-0.69629
-0.01602
0.01051
89
Figure 3-39. Principal component analysis of nutrient and dissolved oxygen data from
the hypolimnion of Lake Pleasant and MIB/geosmin data from 70-78 km down-canal
during 1997.
y
P
N
x
MIB
D.O.
Geosmin
z
Principal Components
EigenValue Percent Cum Percent
2.0665 41.330
41.330
1.0071 20.142
61.471
0.7440 14.880
76.352
0.7349 14.698
91.049
0.4475
8.951
100.000
Eigenvectors
D.O.
P
N
MIB
Geosmin
-0.49375
0.34140
-0.35736
0.44340
0.56156
0.03727
0.72941
0.68278
0.01640
0.01089
0.28993
-0.06904
0.04272
0.87893
-0.36991
0.67799
0.47438
-0.54168
-0.13182
0.06709
0.45945
-0.34874
0.33295
0.11505
0.73702
90
Figure 3-40. Principal component analysis of site B dissolved oxygen levels,
MIB/geosmin and periphyton growth in the CAP canal at 70-78 km down-canal from
Lake Pleasant during 1996.
y
D.O.
#/cm2
Geosmin
x
MIB
z
Principal Components
EigenValue Percent Cum Percent
1.8574 46.436
46.436
0.9496 23.740
70.176
0.9240 23.099
93.275
0.2690
6.725
100.000
Eigenvectors
D.O.
#/cm2
MIB
Geosmin
-0.26519
0.33117
0.67379
0.60498
0.94268
0.26258
0.06719
0.19465
-0.14872
0.88230
-0.10177
-0.43482
0.13750
-0.20718
0.72879
-0.63799
91
Figure 3-41. Principal component analysis of site B dissolved oxygen levels,
MIB/geosmin and periphyton growth in the CAP canal at 70-78 km down-canal during
1997.
D.O.
y
MIB
x
Geosmin
#/cm2
z
Principal Components
EigenValue Percent Cum Percent
1.4875 37.189
37.189
1.0000 25.000
62.189
0.9651 24.128
86.317
0.5473 13.683
100.000
Eigenvectors
D.O.
#/cm2
MIB
Geosmin
-0.00000
0.68684
0.67765
-0.26276
1.00000
0.00000
-0.00000
0.00000
0.00000
0.14782
0.22372
0.96338
-0.00000
0.71162
-0.70053
0.05349
92
APPENDIX A
DIGITAL IMAGES
93
Digital image 1. CAP inlet towers in relation to the new Waddell Dam in Lake Pleasant.
.
Digital image 2. CAP inlet towers showing the top gate exposed.
94
95
Digital image 3. The old Wadell Dam exposed during a time of low water level.
96
Digital image 4. View looking north toward the breach in the old Wadell Dam
97
Digital image 5. View looking south showing the breach in the old Waddell Dam in
relation to the CAP inlet towers and the new Wadell Dam.
98
Digital image 6. The Wadell Dam forebay from which water in Lake Pleasant is released
into the Wadell canal which then empties into the CAP canal.
99
Digital image 7. View looking east at the CAP canal near Granite Reef.
100
Digital image 8. The CAP canal near the city of Mesa water treatment plant
intake.
101
Digital image 9. Image of Anabaena sp. a potential taste and odor causing cyanophtye
commonly found growing periphytically on the sides of the CAP canal.
Magnification = 200 X
102
Digital image 10. Image of Lyngbya sp. a potential taste and odor causing cyanophtye
commonly found growing periphytically on the sides of the CAP canal.
Magnification = 200X
103
Digital image 11. Image of Oscillatoria sp. a potential taste and odor causing
cyanophtye commonly found growing periphytically on the sides of the CAP canal.
Magnification = 200X
104
Digital Image 12. Image of the chrysophyte species Cocconeis and Gomphonema
growing epiphytically on the chlorophyte Cladophora.
None of these species produce tastes or odors and were commonly found in the
periphyton of the CAP canal during 1997.
Magnification = 250X
105
LITERATURE CITED