DWQ-2004-003001

NAVAJO LAKE

Limnological Assessment of Water Quality

Prepared by

James Harris
Project Manager

Harry Lewis Judd
Project Supervisor

Utah Division of Water Quality

Utah Department of Water Quality, Division of Water Quality
TMDL Section

Waterbody ID Navajo Lake
Location Kane County; South-Central Utah
Pollutants of Concern Dissolved Oxygen
Impaired Beneficial Uses Class 3A: Cold water fishery
Loading Assessment Not Applicable
Defined Targets/Endpoints No endpoints identified. Recommended for de-listing due to natural
conditions.
Implementation Strategy No implementation strategy.

I. INTRODUCTION

Waterbody Description

Navajo Lake is a small lake located in southwestern Utah on the Markagunt
Plateau in the northwest comer of Kane County, about 40 kilometers (25 mi) east of
Cedar City, Utah (Map 1). The lake formed when a lava flow cut off the uppermost part
of the natural surface drainage of Duck Creek, a headwater tributary of the Sevier River.
Navajo Lake has a maximum surface area of 290 hectares (714 ac) and an average depth
of 3.7 meters (12.1 ft), and is at an altitude of 2754 meters (9035 ft). The topographic
basin containing Navajo Lake is about 1600 hectares (4000 ac). The lake is primarily
used for recreational purposes, although outflow from the lake contributes to flows in
both the Sevier River in the Great Basin drainage and the Virgin River in the Colorado
River drainage. The lake's alpine setting makes the area a highly-valued summer
recreation area. The lake is entirely surrounded by the Dixie National Forest with some
private in-holdings developed with summer homes. Facilities near the lake include three
Forest Service Campgrounds, a privately owned lodge and boat ramp, and 34 private
summer homes along the southwest side of the lake.

Duck
C r e e k
NavajoLake
Watershed BoundaryStreams
Lakes N
EW
S
Map 1. Navajo Lake Watershed and Major Streams

The main water problems in the lake are fairly heavy vascular water plant
(macrophyte) growth, which clogs much of the lake by late summer during some years,
and low dissolved oxygen during winter months from the decay of macrophytes under the
ice. This situation is worsened by the shallowness of the lake which limits fish habitat
and is exacerbated by low water years. Although the lake is primarily oligotrophic (based
on chlorophyll a TSI) and nutrient sources are minimal, the primary impairment is the
potential for fish mortality during conditions of low dissolved oxygen.

This document represents the findings of an EPA Clean Lakes Study (1996)
submitted by the Division of Water Quality which fully assessed the conditions of the
lake and determined nutrient sources and loadings from the watershed. The conclusions
of the study found that nutrients sources in the watershed and in the lake were minimal
and recommended options in-lake treatments for fishery maintenance.

Surface and Groundwater hydrology

Navajo Lake was created several thousand years ago after a lava flow cut off the
natural surface flow of the uppermost part of Duck Creek in the Sevier River Drainage.
The lake is unique in that groundwater accounts for most of the inflow and all of the
outflow. Sinks located on the east end of the lake are the principal outlets; no surface
outflow exists for the lake. Sinkholes in the east end of the lake drained the lake
completely in low water years before construction of a north-south dike, just west of
major sinkholes on the east end of the lake basin (see Photo 1).

Photo 1. View of Navajo Lake and dike.

The dike has been raised in stages beginning in about 1933. It was last raised to
5.2 m (17 ft) in 1945. The dike allows the lake to be maintained near 4 to 5 m (13-16 ft)
deep; however evaporation and seepage, and release of irrigation water via a pipe outlet,
still drop the water level a few feet below the dike spillway level by late summer in most
years.
Subterranean flow from a considerably large area to the north contributes flow
into the lake via seepage, solution channels in limestone, and perhaps tubes and fractures
in basalt layers. A large portion of the annual inflow enters during spring snowmelt and
runoff. Several springs along the north shore are solution-channel springs which appear
to be connected to sinkholes in basins immediately to the north, which flow mainly
during snowmelt or heavy storm runoff and add large quantities of water during wet
years. These springs and seeps dry up rapidly after the peak of spring runoff. Navajo
Lake Spring on the west end, and Elderberry Spring and Larson Spring on the southwest
side of the lake are the only perennial springs feeding the lake. By late summer in a
normal year, flowrates are less than 0.1 cfs in Elderberry and Larson Springs and less
than 1 cfs in Navajo Lake Spring.
The entire subsurface area of Navajo Lake is interlaced with limestone solution
cavities and solution channels and lava tubes. Water flows not only out of the east end
sink holes but likely feed small seeps and springs located west of Cascade Spring on the
steep face at the head of the Virgin River basin. The outlet of the lake is via sinkholes
east of the dike and other seepage from the lake bottom; there is no surface outflow from
the lake basin. The flow into the Navajo Lake sinks reappears in Cascade Spring to the
south and Duck Creek Spring to the east. The percentage of flow is approximately 60% to
Duck Creek Spring and 40% to Cascade Spring. The amount of flow into the sinks is
dependent on the water's elevation head above the sinks. The flow is approximately 30
cfs when the elevation of the water above the sinks is 9 m (30 ft) (about the maximum
lake depth in historical times). The basin drainage into the lake, as alluded to before,
consists of subsurface travel from areas lying outside of the basins topographical
boundaries. Since inflow and outflow of Navajo Lake basin is mostly subterranean, a
normal water budget is not possible. During maximum spring runoff in 1993, it is
estimated that approximately 80 cfs was coming into the lake. Of this, only about 25%
was in measurable surface inflow.

II. Water Quality Standards

This document addresses water quality impairments for Navajo Lake through the
assessment of pollutants of concern and their sources. Navajo Lake been listed on the
2002 303(d) list of impaired waters. The State of Utah has designated Navajo Lake as
coldwater (3A) fisheries and impairment of this designated uses exist due to low
dissolved oxygen. The primary cause of the low dissolved oxygen is a combination of
morphological conditions and excessive growth of macrophytes which decay under the
winter ice and results in oxygen depletion.

Impaired Waters
Utah's Year 2002 303(d) list identifies Navajo Lake as being impaired due to water
quality numeric exceedences of the minimum dissolved oxygen criteria for the support of
a coldwater fishery (see Table 1).

Table 1. Impaired Waterbodies and pollutants of concern.

Navajo Lake was originally listed on the 303d list as a low priority for TMDL
development. However, the Sevier River TMDL was targeted for completion in 2004
due to the active planning efforts in the watershed guided by local stakeholder groups and
the establishment of the watershed as one of the USFS Large-scale Watershed Projects.
The completion of this assessment will not preclude the development of high priority
TMDLs that are scheduled for completion.

The listing is based on the findings of the Phase I EPA Clean Lakes Study (1993). The
beneficial uses, as designated by the State of Utah (DWQ, 2000b), for Navajo Lake are:
2B – Protected for secondary contact recreation such as boating, wading, or
similar uses;
3A – Protected for cold water species of game fish and other cold water aquatic
life, including the necessary aquatic organisms in their food chain;
4 – Protected for agricultural uses including irrigation of crops and stock
watering

II. Water Quality Standards and Impairments
Utah water quality standards (UAC R317-2, ) and the 303(d) listing criteria (UDEQ -
DWQ, 2002) provide the criteria to make an initial assessment of water quality
conditions. The Utah water quality standards establish a narrative criteria for coldwater
fishery ( Class 3A) waters (Table 6.). While additional designated uses exist for Navajo
Lake, 3A classification carries the strictest criteria for the pollutants of concern (POCs).

Table 2. Utah Water Quality Criteria for Class 3A Waters
Parameter Criterion Minimum Concentration

Dissolved Oxygen 4.0 mg/l
-Lakes (in 50% of water column)

DWQ lists any waterbody assessed as ‘partially supporting’ or ‘not supporting’ its
beneficial uses on the 303(d) list with the exception of those waterbodies for which a
Waterbody Waterbody ID
Impaired
Designated
Use
Cause of
Impairment Priority
Navajo Lake UT16030001-005 3A Low Dissolved
Oxygen Low
TMDL study has already been completed and approved by the EPA. According to
DWQ's assessment Navajo Lake is not meeting beneficial uses associated with its
coldwater fishery (3A) designation. The 303(d) listing criteria provide guidance on
evaluating beneficial use support status based on the number of violations of the water
quality criterion as listed in Table 3.

Table 3. 303 (d) Criteria for Assessing Beneficial Use Support
Degree of
Use Support
Conventional Parameter

Non-Support (3A Lakes) Any lake profile with >50% of water column below the 4.0
mg/l DO criterion.

While some historic dissolved oxygen data exist for Navajo Lake, most sampling has
occurred during the summer months when the lake is well mixed and exhibits high DO
values. However, according to the Utah Divison of Wildlife Resources, some degree of
fish mortality occurs each year during the winter months as the shallow lake ices over
and macrophyte decay depletes the dissolved oxygen (Hepworth, 2003). Management of
the fishery has included the piping of spring water into the lake to increase dissolved
oxygen levels and create a refuge for trout to over-winter. However, measurements of
dissolved oxygen near the spring outfall which range between 4-6 mg/l drop rapidly
within a 50 foot radius of the spring to below 1 mg/l. Trout survival is highest during
years when spring flow is high and more oxygen rich water is entering the lake and when
Utah chub populations are low. Rotenone treatment of the chub population has resulted
in higher trout survival over the winter months (Hepworth, 2003).

III. Pollution Assessment

Human Sources

The Navajo Lake watershed is 100% Forest Service Land with some private in-holdings
utilized for summer home development. General recreation use and grazing are a
potential, but limited, source of nonpoint nutrient pollution. The campgrounds and
summer homes around the Lake are on total containment systems for waste disposal. The
Navajo Lodge, however, has a septic system with leach fields which are submerged
during unusually high lake levels.

Point Sources

Currently, no point sources exist within the Navajo Lake watershed.

IV. Linkage Analysis

The main problem experienced at Navajo Lake is oxygen depletion under winter ice. This
problem stems largely from decomposition of macrophytes and algae; macrophytes grow
rather profusely during most summers. The dissolved oxygen depletion under winter ice
is not a recent problem in Navajo Lake; it dates back to initial formation behind the dike
over 60 years ago (DWQ, 1996).

V. Water Quality Analysis

As mentioned earlier, there are very few measurable sources of inflow to the lake. The
few surface tributaries were monitored when significant flow existed. The
outflow is entirely seepage and subterranean flow, largely through the natural sinks in the
east end of the lake. Cascade and Duck Creek Springs were sampled to add more
information to the USGS studies showing these as major outflow recipients via Navajo
Lake sinks. Major springs were also sampled to determine the water quality of inflows to
the lake. These include the following STORET sites:

Cascade Spring (495125) – Located over the ridge approximately 2 km (1.2 mi) south of
the Navajo Lake Sinks. The flow in Cascade Spring is largely from the Navajo Lake
Sinks.

Duck Creek Spring (594675). Located adjacent to Highway 14, 4.8 km (3 mi) east of
Navajo Lake. Part of this flow originates from the Navajo Lake Sinks.

Boy Scout Spring (594689). Located on the west end of Navajo Lake. Only one flow
measurement, 0.5 cfs, was recorded during the study period in June 1993. Flow was less
than 0.1 cfs after that time and was not sampled.

Navajo Lake Spring (594691). Spring just to west of Navajo Lake. A pipeline captures
most of the flow after inlet renovation in 1994. It was submerged during most of 1993 by
the high lake level.

Larson Spring (594695). Located on east side of Navajo Lake Lodge. Provides potable
water to the lodge and rental cabins. Continuous flow year- round, but less than 0.2 cfs
except during the spring and early summer when it flows up to 1 cfs.

There are other sources of inflow to the lake which, in general, cannot be sampled. These
consist of underlake springs and springs adjacent to the lake which flow only during
heavy snow melt. Four of these springs deserve mention. First, Roaring Spring comes
from a solution channel about 20 m (70 ft) up the hillside. It is located along the north
shore approximately 0.5 km (0.75 mi) east of the lodge. Roaring Spring may flow up to
20 cfs or so during spring runoff. This spring drains a considerable portion of the
watershed just above the lake as the flow is short-lived each spring. West of Roaring
Spring is another similar solution channel spring which flowed about 2 cfs during the first
two sampling trips in June. Another spring, Breathing Spring, is located about 0.9 km
(1.5 mi) from the lodge along the north shore. Breathing Spring is submerged and appears
to be an important source of oxygenated water under the winter ice. It has been observed
that fish congregate around this spring to escape from the low oxygen conditions which
sometimes occur in the lake during ice cover. The fourth spring is located near the dike
on the north shore. It is also submerged and is reported to be foul smelling and devoid of
oxygen. A sulfide smell is sometimes detectable around this part of the lake. Both of the
last two springs were submerged beneath 6 to 9 m (20 to 30 ft) of water during the
sampling period and could not be identified nor sampled.

Table 4 gives the averages for samples collected from Cascade Spring and Duck Creek
Spring. The 1964 USGS report identified Navajo Lake Sink outflow water as dividing
about 40% to Cascade Spring and making up essentially all of the flow there, and 60% to
Duck Creek Spring and making up half or less of the flow there.

Table 4. Water Quality in Cascade Spring, and Duck Creek (Averages for 1993)
Parameter Cascade
Spring
Duck Creek Lake Site #1
Temperature ( C ) 10.58 8.37 13.8
Dissolved Oxygen (mg/l) 7.63 7.8 8.5
Field pH 8.0 7.74 8.4
Sp. Conductivity
(umhos/cm)
235 249 212.3
Flow (cfs) 12.5 14.8 N/a
Total Alkalinity (mg/l) 136.6 122.2 108.3
Total Hardness (mg/l) 134.5 119.2 97.4
Nitrate + Nitrite (mg/l) 0.09 0.1 0.04
Total Kjeldahl Nitrogen
(mg/l0
0.3 0.25 0.27
Total Nitrogen (mg/l) 0.39 0.35 0.31
Total Phosphorus (mg/l) 0.01 0.02 0.01
Dissolved Phosphorus
(mg/l)
0.01 0.02 0.01

In general, water quality in the lake and in the outflows of the lake are good with Total
Phosphorus (TP) and Total Nitrogen (TN) concentrations typical of a high quality
oligotrophic lake. Since most of the inflows could not be measured or sampled
accurately, nutrient loadings to the lake can not be determined. However nutrient levels
in two perennial springs, Navajo Lake and Larson Springs are probably indicative of the
water quality of the inflows; generally TN was less than 0.22 mg/l and TP was less than
0.02 mg/l.

Lake data.

The Clean Lake Study summarizes the dissolved oxygen concentration for the years of
1993-1994 and found that DO did not drop below 7 mg/l. The mean concentration was
8.5 mg/l for all three stations on the lake. These stations include “Above the Dam”
(594681), “Mid-Lake” (594682), and the “Upper End” (594683). Data from the years
1997-2003 compare with data from the Clean Lakes study and are summarized in Table
5.

Table 5. Water quality for all three lake sites by year 1997-2003
Year Total Phosphorus Dissolved Oxygen Chlorophyll a
Mean Min Max Mean Min Max Mean Min Max
1997 0.029 0.005 0.058 8.92 7.95 10.49 1.67 1.4 1.8
1999 0.01 0.01 0.01 9.63 8.7 11.4 2.42 1.8 3.6
2001 0.01 0.01 0.01 9.0 7.38 10.5 0.2 0.2 0.2
2003 0.012 0.01 0.029 8.7 6.46 9.9 0.3 0.2 0.5

Overall, dissolved oxygen was stable for all sampling dates since the lake does not
stratify but remains well mixed due to its shallow depth. Often during the summer
months, the oxygen concentrations demonstrate super-saturation due to the macrophytes
actively producing oxygen in the shallow lake. No data exist to confirm whether diel
fluctuations occur in the water column when plants respire at night, nor are there recent
winter data to demonstrate conditions of low dissolved oxygen. As mentioned
previously, continual observation by DWR personnel has established that few refuges
with sufficient DO exist for overwintering trout and that Navajo Lake frequently exhibits
winter fish kills (Hepworth, 2003).

Appendix A contains the lake profiles for all 3 monitoring sites for the years 1997-2003.
In short, very little fluctuation in temperature or dissolved oxygen occurs in the profiles,
again due to the lake being shallow and well-mixed. No recent winter data exist to
determine if winter depletion of dissolved oxygen is occurring.

The Carlson Trophic Status Index is often used to classify or predict the productivity of a
lake compared to typical lakes and is determined by three indicators, chlorophyll a,
secchi depth and total phosphorus concentrations. The latter two are typically used as
surrogates for the most important indicator of lake productivity which is chlorophyll a.
Historically, TSI values for Navajo Lake have demonstrated that it is primarily an
oligotrophic lake, with very little primary production in the form of phytoplankton
(measured as chlorophyll a). The Clean Lakes Study determined that total phosphorus is
sufficient to support higher phytoplankton growth but that long winters and a short
growing season may limit their growth. Typically, the TSI values for TP indicate the
lake to be somewhat mesotrophic while the chlorophyll a TSI demonstrates a
predominantly oligotrophic system. Figure 1 summarizes the chlorophyll a TSIs for all
available data at the three sampling locations.

Figure 1. Chlorophyll a TSI by year for three sampling locations.
Carlson Chlorophyll a TSI Values for Navajo Lake from 1991
to 2002 - Site #1 Above Dam, 594681
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Carlson Chlorophyll a TSI Values for Navajo Lake from
1991 to 2002 - Site #2 Mid-lake, 594682
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Carlson Chlorophyll a TSI Values for Navajo Lake
from 1991 to 2002 - Site #3 Upper End, 594683
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In summary, the water quality of Navajo Lake is very good; it is oligotrophic to slightly
mesotrophic year to year as nutrient, water depth and other conditions vary. The major
management problem is the occasional depletion of oxygen under winter ice from the
decomposition of abundant macrophytes. During the sampling period of the Clean Lakes
Study, low DO levels were found only near the bottom under ice in February of 1994, but
fair to good levels of oxygen were still available in the water column due to deeper than
normal water depth and limited macrophyte growth the prior summer.

VI. Water Quality Assessment

Since the conditions in Navajo Lake and the potential for winter fish kills are independent
of nutrient loads, in-lake or inflow water quality, no nutrient loading targets are
recommended for this Navajo Lake. The primary water quality target is to meet the 4.0
mg/l dissolved oxygen minimum criteria in the water column to ensure that suitable habit
is provided to support the fishery during ice-free periods. Currently, Navajo Lake is
meeting this criteria and is in full support of its water quality standards during this
designated period. Since winter fish kills are not a function of human caused pollution
but a natural occurrence due to lake morphology and macrophyte abundance, it is
recommended that Navajo Lake be de-listed for dissolved oxygen. The Division of
Wildlife Resources may decide to manage the lake as a year-round fishery and implement
strategies to mitigate for the loss of adequate fish habitat, however, this assessment does
not recommend endpoints to that effect. Options for achieving such fishery management
goals are discussed below in the implementation strategy. In order to facilitate de-listing,
this study recommends the development of site-specific language in Utah’s water quality
standards exempting the dissolved oxygen criterion for Navajo Lake as such action is
required.

VII Allocations

No allocations are recommended for Navajo Lake since the endpoints are not determined
by measurable loads but by the attainment of the minimum concentration of 4.0 mg/l DO
necessary to support the fishery. It has been determined that sources of pollutants in the
watershed are minimal and are not a contributing factor to impairment.

VIII. Monitoring Plan
Navajo Lake was listed as impaired for low dissolved oxygen. The data used to establish
the listing is not currently available for the winter months. However, fishery managers
have observed frequent fish kills as a result of low dissolved oxygen in the winter. In the
future it will be useful to obtain DO profiles to assess the management strategies which
may be put in place to maintain the fishery, characterize the situation and assess progress
towards meeting water quality goals. Future monitoring is also recommended to ensure
that water quality criteria are met during other times of the year.

IX. Public Participation
The public participation process for this assessment was addressed through a series of
public meetings with the Upper Sevier River Watershed Committee. The Watershed
Committee is comprised of individuals who represent the interest of stakeholders in the
watershed. The committee has participated in this study since the inception of the
project, has supported the collection of relevant data and information, and has assisted
with the development of best management practices.

A public hearing on the assessment was held on January 26th, 2004 with notification of
the hearing published in the local newspapers. The comment period was opened on
February 1st, 2004 and closed on March 1st, 2004. In addition, the assessment and dates
for public comment were posted on the Division of Water Quality’s website at
http://waterquality.utah.gov/TMDL/TMDL_WEB.HTM

Coordination Plan

Lead Project Sponsor
The Upper Sevier Soil Conservation District (the District) will be the lead project
sponsor. The District is empowered by the State of Utah to devise and implement
measures for the prevention of nonpoint water pollution. Additionally the District is able
to enter into contracts, receive and administer funds from agencies, and contract with
other agencies and corporate entities to promote conservation and appropriate
development of natural resources. Memoranda of Understanding with state, federal, and
local agencies along with individual cooperator agreements empower the District and
individual cooperators to accomplish this work.
The Upper Sevier River Watershed Committee (Local Work Group) has brought
together citizens who are concerned about the future condition of the Upper Sevier River
and its tributaries. They are the primary stakeholders in the future value and future
problems that affect this watershed. Utah Association of Conservation Districts is a non-
profit corporation that provides staffing for project coordination and financial
administration to the Districts of the State of Utah, and specifically to the Upper Sevier
Soil Conservation District.
The Upper Sevier River Watershed Committee or an empowered subcommittee,
will provide oversight of project conceptualization, cooperator selection, volunteer efforts
during implementation, and sharing of information generated by this project with others.
The Upper Sevier Soil Conservation District and the Upper Sevier River Watershed
Committee will oversee detailed project development, planning, implementation,
approval, creation of fact sheets and educational materials, administration and reporting.
Some of these duties will be transferred to UACD, NRCS, DEQ, USU Extension Service
and others as per Memoranda of Understanding. The Upper Sevier River Watershed
Committee will be responsible for writing the final project report pursuant to EPA and
State requirements.
UACD will oversee project administration, match documentation, and contracting
with agencies and individuals. They will also provide staffing assistance at the direction
of the District.

Local Support
The Upper Sevier River Watershed Committee is coordinating with local stakeholders
and agencies to develop a watershed plan to further define water quality problems in the
Upper Sevier River watershed and to proceed with a coordinated approach to improve
water quality within the watershed. The Watershed Committee, working with a
Technical Advisory Committee will establish criteria and select cooperators for
implementation of projects. This project will be used to show landowners and
cooperators Best Management Practices (BMPs) for minimizing land use impacts on
water quality in the Upper Sevier River and its tributaries.
Coordination and Linkages
The District and Upper Sevier River Watershed Stewardship Committee anticipate
coordinating efforts with the following other entities, agencies, and organizations:
Cooperators - provide match for cost share, implementation of water quality plans
Utah State University Extension - I&E, Technical assistance
NRCS - Technical planning design and oversight
Dixie National Forest- Technical, planning and financial assistance
Utah Department of Agriculture & Food - Technical assistance, I&E assistance
Utah Division of Water Quality - Standard program monitoring, Technical assistance
EPA - Financial assistance
Utah Association of Conservation Districts - Administration, contracting, staff and
technical assistance
Utah Division of Water Rights- Permits advisory, and monitoring assistance
Utah Division of Water Resources - Advisory
Upper Sevier County Irrigation Companies - Advisory and TAC coordination

X. Implementation Options

The following implementation options are provided as a reference to efforts in assessing
and mitigating water quality impacts to Navajo Lake. The Clean Lakes Study (1996)
identified several feasible implementation strategies to minimize the impacts of excessive
macrophyte growth in Navajo Lake and include the following options:

1. Mechanical removal especially during low water when the beds of macrophytes
are accessible especially since water conditions favor macrophyte growth and the
subsequent low dissolved oxygen in the winter months.
2. Chemical control once every few years when lake levels are low and midsummer
macrophyte growth is appearing to become too profuse.
3. Grazing with herbivorous triploid grass carp, which are a sterile, long-lived, and
hardy species. Proper stocking rate would have to be observed to avoid complete
grazing of macrophytes which would disrupt the lakes ecosystem and food chain.
It is also possible that herbivory by carp would result in a more uniform release of
nutrients via fish excreta, increasing and moderating algal productivity which in
turn may increase fish productivity.
4. Aeration via mechanical aerators and pipelines from the Navajo Spring and the
Forest Service culinary system. Aeration with generators has been successful in a
number of lakes, but has drawbacks in the case of Navajo associated with power
supplies, and access during the harsh winters. Extension of the spring outlet and
the diversion of the culinary pipeline into the lake would produce a small zone of
open and aerated water to sustain fish during the winter months.

The recommended plan contained in the Clean Lakes Study was a combination of the
introduction of grass carp, pipelines of the Navajo Spring and the Forest Service culinary
water and the chemical or mechanical removal of macrophytes in emergency years of low
water and profuse plant growth. The Department of Wildlife Resources has since
adopted alternative 4 and has piped spring sources into the lake to create an aerated zone
for fish to over winter. In addition, they have found that rotenone treatment for Utah
Chub when populations increase and compete with trout for winter habitat increases the
success of trout survival (Hepworth, 2003).

Appendix A. Lake Profiles

Temperature and Dissolved Oxygen
Profile of Navajo Lake Above Dam
(594681) - 6/11/1997
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 5 10 15 20
De
p
t
h

(
m
)
Temp. (C)
DO (mg/l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Midlake (594682) - 6/11/1997
0
0.5
1
1.5
2
2.5
3
3.5
051015
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Upper End (594683) - 6/11/1997
0
0.4
0.8
1.2
1.6
2
2.4
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake
Above Dam (594681) - 6/19/1999
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 5 10 15
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake
Above Dam (594681) - 7/29/1999
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 5 10 15 20 25
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Midlake (594682) - 6/19/1999
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 5 10 15
Temp. (C)
DO (mg/ l)
Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Midlake (594682) - 7/29/1999
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Upper End (594683) -6/19/1999
0
0.4
0.8
1.2
1.6
2
2.4
2.8
051015
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Upper End (594683) - 7/29/1999
0
0.4
0.8
1.2
1.6
2
2.4
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake
Above Dam (594681) - 7/4/01
0
0.5
1
1.5
2
2.5
3
3.5
4
0 5 10 15 20 25
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake
Above Dam (594681) - 8/2101
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Midlake (594682) - 7/4/01
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 5 10 15 20 25
Temp. (C)
DO (mg/ l)
Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Midlake (594682) - 8/2101
0
0.5
1
1.5
2
2.5
3
3.5
4
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Upper End (594683) - 7/4/01
0
0.4
0.8
1.2
1.6
2
2.4
2.8
0 5 10 15 20 25
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Upper End (594683) - 8/21/01
0
0.4
0.8
1.2
1.6
2
2.4
2.8
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved Oxygen
Profile of Navajo Lake Above Dam
(594681) - 6/4/03
0
0.5
1
1.5
2
2.5
3
3.5
4
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake
Above Dam (594681) - 9/3/03
0
0.5
1
1.5
2
2.5
3
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved Oxygen
Profile of Navajo Lake At Midlake
(594682) - 6/4/03
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Midlake (594682) - 9/3/03
0
0.5
1
1.5
2
2.5
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved Oxygen
Profile of Navajo Lake At Upper End
(594683) - 6/4/03
0
0.4
0.8
1.2
1.6
2
0 5 10 15 20
Temp. (C)
DO (mg/ l)

Temperature and Dissolved
Oxygen Profile of Navajo Lake At
Upper End (594683) - 9/3/03
0
0.5
1
1.5
2
2.5
0 5 10 15 20
Temp. (C)
DO (mg/ l)

REFERENCES

Hepworth, Dale. 2003. Personal Communication. Utah Department of Natural
Resources. Division of Wildlife Resources. Cedar City, UT. December, 2003.

Utah Department of Environmental Quality. 1996. Navajo Lake Phase I EPA Clean Lake
Study Diagnostic and Feasibility Report. Division of Water Quality. Salt Lake City, UT.