I Report Title

Historical Physical and Chemical Data for Water in Lake 

Powell and from Glen Canyon Dam Releases, Utah-Arizona, 

1964–2013

Data Series 471

Version 3.0, February 2015

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the Bureau of Reclamation
COVER:

Photograph of the San Juan River arm of Lake Powell downstream of Wilson Creek, Utah (USGS photograph by William Vernieu.)
Historical Physical and Chemical Data for 

Water in Lake Powell and from Glen Canyon 

Dam Releases, Utah-Arizona, 1964–2013

By William S. Vernieu

Data Series 471

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the Bureau of Reclamation

Version 3.0, February 2015
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia

First release: 2009

Revised: October 2013 (ver. 2.0)

Revised: February 2015 (ver. 3.0)

For product and ordering information: World Wide Web: http//www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS (1-888-275-8747)

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual

copyright owners to reproduce any copyrighted material contained within this report.

Suggested citation:

Vernieu, W.S., 2015, Historical physical and chemical data for water in Lake Powell and from Glen Canyon Dam 

releases, Utah-Arizona, 1964–2013 (ver. 3.0, February 2015): U.S. Geological Survey Data Series 471, 23 p., http://

dx.doi.org/10.3133/ds471.

ISSN 2327-638X (online)
iii

Contents

Abstract ..........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Physical and Geographic Setting.......................................................................................................1

Hydrologic History ................................................................................................................................3

Information Sources and Monitoring History ..................................................................................4

Goals and Objectives of Monitoring Program.........................................................................4

Monitoring History.......................................................................................................................5

Phase 1 .................................................................................................................................5

Phase 2 .................................................................................................................................5

Phase 3 .................................................................................................................................5

Phase 4—Current Monitoring Program..........................................................................5

Quarterly Reservoir-Wide Sampling.......................................................................5

Monthly Forebay Sampling ......................................................................................5

Tailwater Monitoring.................................................................................................6

Field Methods.................................................................................................................................................6

Sample Locations and Site Identification.........................................................................................7

Initial Observations...............................................................................................................................9

Physicochemical Profiles....................................................................................................................9

Objectives......................................................................................................................................9

Historical Methods, 1964–90....................................................................................................10

Current Methods, 1990–2013.............................................................................................................10

Chemical Sampling and Processing................................................................................................11

Objectives....................................................................................................................................11

Historical Methods, 1964–90....................................................................................................11

Current Methods, 1990–2013....................................................................................................11

Sample Collection.............................................................................................................11

Sample Filtration ...............................................................................................................12

Preservation ......................................................................................................................12

Transportation and Shipment..........................................................................................12

Documentation..................................................................................................................12

Quality Assurance/Quality Control..........................................................................................12

Blank Samples ..................................................................................................................12

Replicate Samples ...........................................................................................................13

Known-Addition Samples................................................................................................13

Analytical Methods ...................................................................................................................13

The WQDB ....................................................................................................................................................13

Site Locations......................................................................................................................................14

Site Visits..............................................................................................................................................15

Secchi-depth Transparency..............................................................................................................15

Physical Profiles..................................................................................................................................15

Chemical Analyses .............................................................................................................................15

Sample Catalog ..........................................................................................................................15
iv

Alkalinity Determinations .........................................................................................................15

Major Ion Concentrations ........................................................................................................15

Nutrient Concentrations ...........................................................................................................15

Acknowledgments.......................................................................................................................................16

References Cited..........................................................................................................................................16

Appendix—Database Table Descriptions ...............................................................................................18

Stations Table ......................................................................................................................................18

Surface Table.......................................................................................................................................18

Secchi Table ........................................................................................................................................19

Profiles Table .......................................................................................................................................20

Samples Table .....................................................................................................................................20

Alkalinity Table ....................................................................................................................................21

Major Ions Table .................................................................................................................................21

Nutrients Table ....................................................................................................................................21

Figures

1. Lake Powell geographic setting, major tributaries, and water-quality sampling sites.....2

 2. Lake Powell historical surface elevation..................................................................................3

 3. Glen Canyon Dam historical water releases............................................................................4

 4. Entity-relationship diagram for the WQDB (water-quality database).................................7

Tables

 1. Major features of Lake Powell monitoring program phases.................................................6

 2. Initial Lake Powell monitoring locations...................................................................................7

 3. Listing of the primary station groups in the WQDB (water-quality database) ...................8

 4. Detection limits, units, and U.S. Environmental Protection Agency methods for 

Lake Powell chemical analyses ...............................................................................................14

A-1. Data fields and attributes of tblStations .................................................................................19

A-2. Data fields and attributes of tblSurface..................................................................................19

A-3. Data fields and attributes of tblSecchi....................................................................................20

A-4. Data fields and attributes of tblProfiles ..................................................................................20

A-5. Data fields and attributes of tblSamples.................................................................................21

A-6. Data fields and attributes of tblAlkalinity................................................................................21

A-7. Data fields and attributes of tblMajor Ions.............................................................................22

A-8. Data fields and attributes of tblNutrients ...............................................................................22
Historical Physical and Chemical Data for Water in Lake 

Powell and from Glen Canyon Dam Releases, UtahArizona, 1964–2013

By William S. Vernieu

Abstract 

This report presents the physical and chemical 

characteristics of water in Lake Powell and from Glen Canyon 

Dam releases from 1964 through 2013. These data are available 

in a several electronic formats. Data have been collected 

throughout this period by various offices of the Bureau of 

Reclamation and U.S. Geological Survey and are compiled 

to represent the existing body of chemical and physical 

information on Lake Powell and Glen Canyon Dam releases. 

From this record, further interpretation may be made concerning 

mixing processes in Lake Powell, the movement and fate of 

advective inflow currents, effects of climate and hydrological 

variations, and the effects of the operation and structure of Glen 

Canyon Dam on the quality of water in Lake Powell and from 

Glen Canyon Dam releases.

Introduction

This report presents the physical and chemical data 

collected and the methods of data collection used by the 

Bureau of Reclamation (Reclamation) and U.S. Geological 

Survey (USGS) throughout a 50-year history of Glen Canyon 

Dam and Lake Powell, from 1964 through 2013. The ongoing 

monitoring program remains in current operation. The data from 

this monitoring program are organized in separate tables of the 

WQDB (a nominal acronym for “water-quality database”). The 

WQDB is a Microsoft Access relational database, consisting 

of tables of similar information linked by common fields and 

was developed to store data and assist in organizing, analyzing, 

and interpreting this information. Individual data tables contain 

sampling site information, a catalog of site visits, ambient 

observations associated with a site visit, depth profiles of 

physicochemical parameters through the water column, and 

results of chemical analyses for water samples for major ionic 

and nutrient constituents. Data from the biological component 

of the Lake Powell monitoring program will not be presented in 

this report. Results of continuous monitoring of water-quality 

conditions below Glen Canyon Dam are reported by Voichick 

and Wright (2007).

The WQDB and associated files are available at http://

pubs.usgs.gov/ds/471/. These files contain the WQDB Microsoft 

Access database (WQDB.mbd), comma-separated-values 

(CSV) files of each of the eight database tables, and CSV files 

representing the output of predefined sample queries, which 

combine data from select tables. Further assistance and other 

data formats are available from the author.

Physical and Geographic Setting

Glen Canyon Dam was completed on March 13, 1963, 

and represents the primary storage unit of the Colorado River 

Storage Project. Glen Canyon Dam, constructed and operated 

by Reclamation, impounds the Colorado River to form Lake 

Powell. Lake Powell is located on the border of Utah and 

Arizona within Glen Canyon National Recreation Area, 

upstream of Glen Canyon Dam, 2 miles northwest of Page, 

Ariz. (fig.1). At a full pool elevation of 1,128 m (3,700 ft), Lake 

Powell has a capacity of 32.336 km3 (26.214 MAF) (Ferrari, 

1988), a surface area of 65,069 ha (160,784 acres), and extends 

290 km (180 miles) upstream, with an estimated shoreline length 

of 3,057 km (1,900 mi). The drainage area above Lake Powell is 

279,000 km2 (108,000 mi2) (Stanford and Ward, 1991). 

Glen Canyon Dam can discharge water from three different 

release structures, located at different elevations. During normal 

operations, virtually all water is released from Glen Canyon Dam 

through eight powerplant penstocks, located across the face of 

the dam at an elevation of 1,058 m (3,470 ft), with a maximum 

release capacity of 934 m3/s (33,000 cfs). An additional 425m3/s 

(15,000 cfs) can be released through the river outlet works, 

which withdraw water at an elevation of 1,028 m (3,374 ft) 

through four penstocks controlled by hollow jet valves; this 

water bypasses the Glen Canyon Dam powerplant. As much 

as 7,815 m3/s (276,000 cfs) may also be discharged from two 

spillway structures, which route water from near the surface of 

the reservoir at an elevation of 1,112 m (3,648 ft) to the river 

below the dam, at an approximate elevation of 956 m (3,135 ft), 
2 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013 Figure 1. Lake Powell geographic setting, major tributaries, and water-quality sampling sites.
Introduction 3

through tunnels in the bedrock on either side of the dam (Bureau 

of Reclamation, 1981). 

Hydrologic History

Lake Powell began filling on March 13, 1963, when the gates 

of Glen Canyon Dam were closed. The reservoir experienced a 

prolonged filling period until the full-pool elevation of 1,128 m 

(3,700 ft) was reached on June 22, 1980 (fig. 2). From 1980 to 

1987, Lake Powell remained relatively full during a period with 

above-average inflows. Prolonged drought conditions, in which 

inflow volumes to Lake Powell were below normal, persisted in 

the upper Colorado River Basin from 1987 to 1992, and again 

from 1999 to 2007. As a result, Lake Powell’s surface level 

steadily declined during those periods. During the period from 

2000 to 2013, the unregulated inflow to Lake Powell was above 

average in only 3 of the 14 years, the lowest 14-year period since 

the closure of the Glen Canyon Dam in 1963. The reservoir 

reached a minimum level of 1,101.08 m (3,612.46 ft) on February 

19, 1993, and a lower minimum level of 1,083.57 m (3,555.02 ft) 

on April 8, 2005. The 2005 minimum was Lake Powell’s lowest 

level since 1969. This resulted in a reduction of Lake Powell’s 

volume to 12.166 km3 (9.863 MAF), or 38 percent of its full 

capacity of 32.335 km3 (26.214 MAF). At the end of 2013, the 

reservoir was at a level of 1,092.54 m (3,586.46 ft).

Annual and monthly releases from Glen Canyon Dam 

are determined by the Annual Operating Plan for Colorado 

River Reservoirs, which takes into account hydrologic and 

climatic conditions, most probable water-supply conditions, and 

downstream delivery requirements. 

Before June 1990, daily releases from Glen Canyon 

Dam were designed to maximize revenues from hydropower 

production. As a result, discharges from Glen Canyon Dam 

were generally characterized by large daily fluctuations with 

maxima at turbine capacity of 892 m3/s (31,500 cfs), and 

minima of 28.3 m3/s (1,000 cfs) in winter and 85.0 m3/s (3,000 

cfs) in summer (National Research Council, 1996). High release 

volumes above powerplant capacity, using the river outlet works 

and spillway structures, occurred during periods of high inflows 

and full-reservoir conditions in 1980, 1983, 1984, and 1985.

From June, 1990, through July, 1991, a series of research 

flows was conducted to determine the effects of various operations 

on Grand Canyon resources. These flows consisted of various 

discharge regimes with durations of 2 to 5 weeks, separated by 

3-day periods of 142 m3/s (5,000 cfs) (Stanford and Ward, 1991). 

Interim operating criteria were established in August, 1991, which 

restricted daily minimum and maximum releases and daily and 

hourly release fluctuations. The 1996 Record of Decision (U.S. 

Department of the Interior, 1996) adopted these criteria, with 

slight modification, as the modified low fluctuating flow (MLFF) 

Figure 2. Lake Powell historical surface elevation. ft, feet; m, meters.






	
























             


















4 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

Figure 3. Glen Canyon Dam historical water releases. cfs, cubic feet per second; cms, cubic meters per second.

alternative. These release criteria have remained in place to the 

present, with occasional experimental high-flow releases occurring 

in 1996, 1997, 2000, 2004, 2008, 2012, and 2013 (fig.3).

In 2007, the Secretary of the Interior signed the Record of 

Decision for the Interim Guidelines for the Operation of Lake 

Powell and Lake Mead (Bureau of Reclamation, 2007). Section 

6.C.1 of the Interim Guidelines sets criteria by which annual 

required releases from the Glen Canyon Dam may be reduced, 

depending on projected system storage and reservoir water surface 

elevations. A minimum of 10.15 km3 (8.23 MAF) must be released 

from Glen Canyon Dam each year, except for reductions specified 

by Interim Guidelines. 

Information Sources and Monitoring History

Goals and Objectives of Monitoring Program

Reclamation and USGS have monitored the water quality 

of Lake Powell and Glen Canyon Dam releases since 1964. The 

objectives of this monitoring program have changed during this 

period, reflecting changes in scientific interest in a filling reservoir, 

responsibilities of Reclamation for maintaining salinity levels 

in the Colorado River, and more recent environmental concerns 

related to the Grand Canyon Protection Act, the Glen Canyon 

Dam Environmental Impact Statement and subsequent Record 

of Decision, and the establishment of the Glen Canyon Dam 

Adaptive Management Program.

Objectives of this long-term monitoring program include:

• Status-and-trend determination;

• Documentation of the historical record of Lake Powell 

water quality during various climatological and hydrological patterns;

• Documentation of the effects of the structure and 

operation of Glen Canyon Dam on the quality of water 

in Lake Powell and Glen Canyon Dam releases;

• Integration with Glen Canyon Dam Adaptive Management Program;

• Documentation of the density structure of the water 

column in the Glen Canyon Dam forebay and other 

locations in the reservoir;

• Assessment of distribution and patterns of major ionic 

constituents;

• Assessment of distribution and patterns of nutrient 

constituents; and

• Assessment of the community structure and status and 

trends of plankton populations and primary production.

Year

1968 2008

2,382

2,144

1,906

1,667

1,429

1,191

953

476

238

0

1992 1996 2000 2004 2012 2016

715

1964 1972 1976 1980 1984 1988

100,000

90,000

80,000

70,000

60,000

50,000

40,000

20,000

10,000

0

30,000

Discharge (cfs)

Discharge (cms)
Introduction 5

Monitoring History

Reclamation initiated a water-quality monitoring program 

on Lake Powell in 1964, which has continued to the present, 

to gather information to describe water-quality conditions and 

to observe changes in water quality as the reservoir filled and 

matured. Based on sampling frequency, spatial resolution of 

measurements, and changes in instrumentation, four distinct 

phases of monitoring activity can be identified (table 1). 

Studies related to Lake Powell were conducted in the 

1970s by educational consortiums and Federal and State 

agencies on topics that include sedimentation, circulation 

patterns, trace-element chemistry, remote sensing, and publichealth issues (Potter and Drake, 1989). Various agencies and 

institutions have conducted additional research and monitoring 

during Lake Powell’s recent history (Hart and Sherman, 1996; 

Marzolf, 1998; Hart, and others, 2005). 

Phase 1

From 1964 to 1971, monthly sampling was conducted 

in the Glen Canyon Dam forebay and quarterly surveys were 

conducted throughout the entire reservoir for temperature 

and salinity. Measurements and samples were collected at 

50-ft depth intervals, corresponding to even 50-ft increments 

in elevation above mean sea level (for example, 3,500 ft, 

3,550 ft, 3,600 ft), at seven locations in the reservoir. 

Phase 2

From 1972 to 1981, monthly forebay sampling continued; 

however, the frequency of lake-wide surveys was increased 

to a monthly interval. Dissolved oxygen was measured 

electrometrically.

Phase 3

From 1982 to 1990, sampling activity steadily declined to 

one reservoir-wide survey per year in 1988 and 1989. Despite 

the decline in sampling frequency, advances in instrumentation 

allowed the collection of higher quality data at finer depth 

resolution. Continuous monitoring of temperature and salinity in 

the Glen Canyon Dam tailwater was initiated during this period. 

Phase 4—Current Monitoring Program

In 1990, Glen Canyon Environmental Studies (GCES), a 

science program initiated in 1982 by Reclamation to examine 

the effects of dam operations on downstream resources, began 

conducting water-quality monitoring of Lake Powell, with the 

goal of understanding how physical and chemical processes in 

Lake Powell and the operation of Glen Canyon Dam influence 

the quality of water released to the Colorado River in Grand 

Canyon. Monitoring frequency was returned to monthly forebay 

surveys and quarterly lake-wide surveys. Forebay monitoring 

was conducted by the USGS Water Resources Division during 

the GCES research flow period from 1990 to 1991 (Hart and 

Sherman, 1996). Sampling for nutrient chemistry and biological 

conditions was also initiated in 1990. GCES conducted 

monitoring from 1990 to 1996. After 1996, the USGS GCMRC 

conducted Lake Powell water-quality monitoring.

Quarterly Reservoir-Wide Sampling

Because of characteristic seasonal patterns in the 

physical and chemical conditions in Lake Powell, reservoirwide sampling was conducted on a quarterly basis. The goal 

of this monitoring was to describe the physical, chemical, and 

biological conditions of the major strata of the reservoir in 

the main Colorado River channel and the primary tributary 

arms of the San Juan and Escalante Rivers.

Each reservoir survey took place over a weeklong 

period and consisted of measurements and collection of 

chemical and biological samples at 21 to 37 established 

stations, depending on reservoir elevation, along the main 

channel and major tributary arms. During each site visit, 

initial observations were recorded (depth, meteorological 

conditions, Secchi-depth transparency). A profile of the 

physicochemical parameters of temperature, specific 

conductance, dissolved oxygen, pH, oxidation-reduction 

potential, and turbidity was then collected throughout the 

water column at variable intervals sufficient to define vertical 

patterns. This information described stratification patterns 

that separate the layers of the reservoir, location of inflow 

currents, dissolved oxygen patterns, and overall chemical 

conditions in the reservoir. Results were recorded on portable 

data-logging equipment for immediate viewing in the field 

and automated transfer to data-management systems.

Samples for chemical analysis of major ion and nutrient 

constituents were collected at designated sites in Lake Powell. 

Based on the stratification patterns seen from the physical 

profile, depths for discrete chemical sampling were determined, 

with the objective being to characterize the major ion and 

nutrient concentrations in the major layers of the reservoir. Water 

samples were filtered and preserved immediately in the field for 

later laboratory analysis. Field alkalinity determinations were 

performed on water samples collected from 1995 through 2005.

Biological sampling consisted of the collection of 

surface samples for chlorophyll a and phytoplankton analysis 

and vertical tows for zooplankton analysis. Data from these 

activities are not discussed in this report.

Monthly Forebay Sampling

Monitoring of the forebay of Lake Powell was 

performed monthly at the Wahweap station (fig. 1), 

LPCR0024. This site has been sampled throughout Lake 

Powell’s history and was located in the main channel at 

the confluence with Wahweap Bay, 2.4 channel kilometers 

upstream of Glen Canyon Dam. Physicochemical profiling 

was performed and chemical and biological samples, similar 

to those for designated stations on quarterly surveys, were 

also collected.
6 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

Tailwater Monitoring

Sampling of the Glen Canyon Dam tailwater was 

performed on a monthly basis, immediately below Glen Canyon 

Dam and at Lees Ferry, 24.9 km (15.5 mi) downstream of 

Glen Canyon Dam. Measurements of temperature, specific 

conductance, dissolved oxygen, pH, oxidation-reduction 

potential, and turbidity were made, and chemical and biological 

samples similar to those collected at designated reservoir 

stations on quarterly surveys were collected.

Continuous water-quality data collection was conducted 

at three locations in the Glen Canyon Dam tailwater. 

The longest operating station is located immediately 

downstream of the Glen Canyon Dam powerplant. At this 

site, a submersible multiparameter sonde was deployed in 

a perforated pipe on the river-left (the left side of the river 

when the viewer is facing downstream) wall in the dam’s 

tailrace below the river outlet works. This site has been in 

operation since August 1988 measuring temperature and 

specific conductance at intervals of 2 hours or less. Other 

constituents were gradually added to this collection program: 

dissolved oxygen monitoring was added in November 1990, 

and pH measurements began in July 1995. Continuous 

monitoring at Lees Ferry began in October 1991, recording 

temperature, specific conductance, and dissolved oxygen. 

Measurements of pH were added in August 1996. Data from 

continuous monitoring in the Glen Canyon Dam tailwater 

are not reported in this report. Tailwater temperature data are 

described by Voichick and Wright (2007).

Field Methods

Field activities associated with the Lake Powell monitoring 

program were generally conducted at established main-channel 

stations throughout the reservoir from a 31-ft Uniflite sedan 

powered by twin inboard engines, in use since 1970. This vessel 

provided workspace for sampling activities on its aft deck and 

living quarters for a crew of four to six people for weeklong 

reservoir surveys. 

At each station, several activities were conducted to 

gather information and collect samples representative of the 

reservoir at that location. Initial observations characteristic 

of the location and time of sampling were recorded. A depth 

profile of physical water-quality parameters was recorded. 

Water samples from several discrete depths were collected and 

processed for later analysis. Finally, measurements and samples 

of biological conditions were taken at selected locations in 

the water column. With the exception of biological sampling 

activities, these activities are described in detail below.

Throughout this discussion, references will be made to the 

WQDB, a database that contains the information from the Lake 

Powell monitoring program. Data from various components 

of the monitoring program are stored in separate tables of 

the database. The linkages that exist between the various 

tables are graphically represented in figure 4. Further details 

of the structure and content of each of the specific tables are 

discussed in the appendix.

Monitoring program 

component

Phase 1

1965–1971

Phase 2

1972–1981

Phase 3

1982–1990

Phase 4

1990–2013

Frequency:

 Forebay

 Reservoir

monthly

quarterly

monthly

monthly

quarterly to yearly

quarterly to yearly

monthly

quarterly

Number of sampled stations 8 8 8–10 21–37

Physicochemical parameters temperature, DO 

(Winkler titration), 

occasional SC, and pH

temperature, DO 

(electrometric)

multiparameter profiling

(T, SC, DO, pH, ORP)

multiparameter profiling 

with datalogger (T, SC, 

DO, pH, ORP, turbidity)

Chemical sampling major ions major ions major ions (field processing 

initiated)

major ions, nutrients

Sampling interval 50 ft 50 ft 50 ft variable, representative of 

stratification

Biological sampling none none qualitative zooplankton 

sampling

chlorophyll, phytoplankton, 

zooplankton

Inflow monitoring none none selected sites depending 

on reservoir level

selected sites depending on 

reservoir level

Tailwater monitoring none none below dam T, SC below dam, Lees Ferry

T, SC, DO, pH

Table 1. Major features of Lake Powell monitoring program phases. 

[DO—dissolved oxygen, T—temperature, SC—specific conductance, ORP—oxidation-reduction potential; ft, feet]
Field Methods 7

Figure 4. Entity-relationship diagram for the WQDB (water-quality database).

Sample Locations and Site Identification

The Lake Powell monitoring program began in 1964 at six 

locations in the Colorado River channel and at one location in the 

San Juan River channel. These sampling locations, the original site 

identifier codes that were used until 1995, and the current identifier 

codes that have been used since 1995 are listed in table 2.

In 1992, additional stations were added to the monitoring 

program to provide greater spatial resolution, especially in the 

inflow areas of the major tributary arms of the reservoir (Colorado, 

San Juan, and Escalante Rivers), and to provide regular monitoring 

of major tributary inflows and Glen Canyon Dam releases. In most 

cases, sample locations were selected to represent major distinct 

areas of the reservoir and are located in the thalweg of the original 

river channel at or near channel constrictions. Thirty-one primary 

stations have been established at which quarterly monitoring has 

been or is currently performed (table 3). Some primary stations 

were not always sampled because of low reservoir elevations, 

and, occasionally other nonprimary stations were sampled where 

interesting or unusual conditions existed. Currently, 21 to 37 

stations may be sampled on a given quarterly survey. 

Historically, sampling locations were numbered sequentially 

in the order of their establishment (column 3, table 3). Under this 

numbering scheme, there was no information in the station name or 

code to locate a particular station in reference to another. A revised 

site-coding scheme was developed in 1995 (column 2, table 3), 

which allows the location of a station within a particular tributary 

arm to be determined from its station code. This station-coding 

scheme and station-group identifiers are described in the appendix.

Original

station ID

Name Current

station ID

SCUCLP12 Wahweap LPCR0024

SCUCLP13 Crossing of the Fathers LPCR0453

SCUCLP14 Oak Canyon LPCR0905

SCUCLP15 Cha Canyon (San Juan River) LPSJR193

SCUCLP16 Escalante LPCR1169

SCUCLP17 Bullfrog LPCR1692

SCUCLP18 Hite LPCR2387

Table 2. Initial Lake Powell monitoring locations.

[Original Site ID refers to the site identifier in use from 1964 to 1992. Current 

Site ID refers to the revised site identifier and primary station group in place 

since 1992]
8 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

Table 3. Listing of the primary station groups in the WQDB (water-quality database). 

[Chemical samples are collected at all FULL, LT, TW and INF sites. RKM— river-channel kilometers; Channel Codes: CR—Colorado River, SJR— San Juan 

River, ESC—Escalante River; Type Codes: INF—inflow site, LT—long-term site, FULL—full sampling site, PRO—profile-only site, TW—tailwater site]

Station 

group

Station ID Original

station ID Site name Latitude Longitude Channel RKM Type

No. of 

site 

visits

LPCR0000 LPCR0000 Glen Canyon Dam draft 

tubes

Variable Variable CR 0 TW 265

LPCR-249 LPCR-249 Colorado River at Lees 

Ferry

36.865241 -111.584485 CR -24.9 TW 236

LPCR0024 LPCR0024 SCUCLP12 Wahweap 36.955278 -111.482778 CR 2.4 LT 667

LPCR0250 LPCR0250 Romano Narrows 37.005474 -111.3606156 CR 25.0 PRO 31

LPCR0453 LPCR0453 SCUCLP13 Crossing of the Fathers 37.039333 -111.256944 CR 45.3 LT 263

LPCR0905 LPCR0905 SCUCLP14 Oak 37.134444 -110.952222 CR 90.5 LT 266

LPCR1001 LPCR1001 San Juan River Confluence 37.172744 -110.904269 CR 100.1 PRO 73

LPCR1080 LPCR1080 Colorado River above 

Llewellyn Gulch

37.722259 -110.88178 CR 108.0 PRO 10

LPCR1169 LPCR1169 SCUCLP16 Escalante 37.283056 -110.874444 CR 116.9 LT 253

LPCR1395 LPCR1395 Iceberg 37.332731 -110.762581 CR 139.5 PRO 69

LPCR1587 LPCR1587 Lake 37.422500 -110.703056 CR 158.7 PRO 71

LPCR1679 LPCR1679 SCUCLP17 Bullfrog 37.470556 -110.725000 CR 169.2 LT 256

LPCR1799 LPCR1799 Moki 37.484492 -110.645733 CR 177.2 PRO 65

LPCR1933 LPCR1933 Knowles 37.579247 -110.598806 CR 193.3 PRO 67

LPCR2085 LPCR2085 Lower Good Hope Bay 37.657222 -110.514167 CR 208.5 FULL 85

LPCR2255 LPCR2255 Scorup 37.767222 -110.436389 CR 225.5 PRO 83

LPCR2387 LPCR2387 SCUCLP18 Hite Basin 37.805278 -110.436944 CR 238.7 LT 250

LPCR_INF LPCR_INF Colorado River inflow 

stations

Variable Variable CR 999 INF 151

LPESC030 LPESC030 Escalante below Indian 

Creek

37.29718 110.88255 ESC 3.0 PRO 6

 LPESC069 LPESC069 Escalante above Clear 

Creek

 37.30846 -110.8984 ESC 6.9 PRO 60

LPESC119 LPESC119 Escalante at Davis Gulch 37.324167 -110.917222 ESC 11.9 FULL 78

LPESC200 LPESC200 Escalante at Willow Creek 37.346389 -110.938056 ESC 20 PRO 62

LPESC273 LPESC273 Escalante Inflow above 

Garces Island

37.370510 -110.944223 ESC 27.3 PRO 48

LPESCINF LPESCINF Escalante River inflow 

stations

Variable Variable ESC 999 INF 59

LPSJR070 LPSJR070 San Juan at RKM 7.0 37.18246 -110.86967 SJR 7.0 PRO 10

LPSJR193 LPSJR193 SCUCLP15 San Juan at Cha Canyon 37.170000 -110.813889 SJR 19.3 LT 255

LPSJR329 LPSJR329 San Juan at Lower Piute 

Bay

37.188889 -110.719167 SJR 32.9 PRO 80

LPSJR431 LPSJR431 San Juan at Upper Piute 

Bay

37.218889 -110.673056 SJR 43.1 FULL 87

LPSJR530 LPSJR530 San Juan at Alcove Canyon 37.267758 -110.696148 SJR 53 PRO 38

LPSJR625 LPSJR625 San Juan at Lower Zahn 

Bay

37.229444 -110.623611 SJR 62.5 PRO 53

LPSJRINF LPSJRINF San Juan River inflow 

stations

Variable Variable SJR 999 INF 87
Field Methods 9

Initial Observations

On arrival at a sampling location, the current date and 

time were recorded, which were used to nominally identify the 

site visit, depth profile, and all samples collected during the 

site visit. This information is stored in the DATE field of the 

SURFACE table in the WQDB. Because sampling activities 

at a given site may occur over a period as long as 2 hours, 

the time value is approximate and should be not construed to 

represent the actual time that a specific sample was collected. 

General meteorological observations were recorded describing 

cloud cover, wind speed and direction, air temperature, and 

wave height. The surface elevation of the lake was obtained 

from daily National Park Service (NPS) or Reclamation 

reports and the bottom depth was determined using a 

Lowrance X-16 sonar depth sounder. 

These observations are descriptive of conditions at 

the surface of a reservoir site or at a stream location during 

a single site visit. They were recorded on the header of 

the field data sheet and form one observation in the data 

table SURFACE in the WQDB. Each observation in the 

SURFACE table is uniquely identified by the STATION_ID 

of the location being sampled and the DATE identified for 

the site visit, which are the key fields of the SURFACE data 

table. 

Secchi-depth transparency observations were made by 

using both the unaided eye and a subsurface viewing scope. 

Secchi-depth readings were recorded using a standardized 

20-cm disk with alternating quadrants of black and white. 

The Secchi disk was attached to a metric surveyor’s tape 

with gradations in centimeters. Secchi-depth transparency 

was determined by lowering the disc from the shady side 

of the boat to a depth at which it disappeared from view 

and the depth was then recorded to the nearest decimeter. 

This observation was made over a sufficient time to allow 

for variations in surface disturbance and glare. Frequently, 

several measurements were made by different observers to 

compensate for variations in the subjective observations made 

by individuals (Wetzel and Likens, 1991).

Secchi-depth transparency observations in Lake Powell 

began in 1984. After 1994, a subsurface viewing scope (Lawrence 

Enterprises, Aqua Scope II) was employed to eliminate effects of 

glare or surface disturbances, and all Secchi depth observations 

more than 1 m in depth were recorded with both the viewing scope 

and the unaided eye. Secchi depths observed with the viewing 

scope are usually greater than those obtained by the unaided eye 

and show less variation under different conditions. The Secchi 

depth, observer’s initials, whether or not a viewing scope was 

used, and a condition code describing the quality of observation 

conditions (for example, water glare, wave action, sun angle) were 

noted on the field data sheet. Several Secchi-depth transparency 

observations may be recorded during each site visit at a reservoir 

sampling location and are stored in the SECCHI table of the 

WQDB, which is linked to the SURFACE site visit table by 

STATION_ID and DATE. See the appendix for further details 

about the SECCHI table.

Physicochemical Profiles

Objectives

The main objective of the profiling effort was to 

characterize the major limnological strata in the water 

column with sufficient resolution to accurately define 

boundaries of the strata and identify other significant 

phenomena such as inflow density currents and depths at 

which dissolved oxygen minima or maxima occur.

Measurements of common physical and chemical 

water-quality parameters were routinely collected during 

the reservoir surveys, continuously in the tailwater below 

Glen Canyon Dam, and in conjunction with the collection 

of all chemical samples. Until April 2009, most of these 

measurements were collected using a multiparameter 

instrument, such as a Hydrolab 8000 Surveyor II or Surveyor 

3/H20. These measurements included temperature in degrees 

Celsius (°C), specific conductance, in microSiemens per 

centimeter (μS/cm), pH in standard units, dissolved oxygen 

in milligrams per liter (mg/L), turbidity in Nephelometric 

Turbidity Units (NTU), and oxidation-reduction potential 

in millivolts (mV) (table 4). From June 2009 to June 2010, 

depth profiles were collected with a Eureka Environmental, 

Inc., Manta/Amphibian profiling system recording the same 

parameters. After 2009, reservoir profiles were collected 

with a Seabird Electronics SBE19plus-V2. This instrument 

collects a continuous profile of the above parameters at a 

rate of four measurements per second during its descent and 

ascent through the water column. Post-processing of the 

collected data yields a profile of values at 0.5-m intervals 

throughout the water column. These measurements are stored 

in the PROFILES table of the WQDB. See the appendix for 

further details about the PROFILES table.

Temperature and specific conductance are important 

in reservoir surveys for defining the density-controlled 

stratification patterns and determining the depth at which 

inflow currents enter and flow through the reservoir. 

Temperature is also a major regulatory factor in determining 

the rates of chemical and biological processes. Specific 

conductance is an indirect measure of salinity and is an 

indicator of the amount of dissolved minerals in the water. 

Dissolved oxygen is important for biological processes 

in aquatic systems. Most aquatic organisms require adequate 

concentrations of dissolved oxygen to maintain life. 

Anoxia, or the absence of dissolved oxygen, can result in 

chemically reducing conditions, the generation of hydrogen 

sulfide, and the release of contaminants from the sediments. 

In the reservoir, dissolved oxygen concentrations help 

indicate the relative age of inflow currents, the amount 

of primary productivity, the amount of decomposition of 

organic and inorganic matter in a particular stratum, and the 

suitability of the water for release to downstream organisms. 

Oxidation-reduction potential (ORP) can be used to 

determine when chemically reducing conditions form after 

anoxia develops.
10 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

The pH of water is affected by biological and chemical 

processes such as respiration and photosynthesis and is 

directly related to the amount of dissolved carbon dioxide 

and the degree of buffering in the water from biological 

or atmospheric processes. Turbidity is used to track inflow 

currents, indicating the concentration of organic or inorganic 

particles and the amount of light available underwater. 

Historical Methods, 1964–90

During phases 1 and 2 (1965–81, table 1), original 

field notes were not maintained. Available information from 

field sampling is limited to a list of samples collected for 

each station and usually exists as type written information. 

It is difficult to determine exactly what methodologies 

and instrumentation were used during this time. Samples 

were collected from near the surface, near the bottom, 

and at standardized 50-ft depth intervals, corresponding 

to even 50-ft increments in elevation above mean sea 

level, throughout the water column. Measurements were 

made in vitro aboard the sampling vessel from collected 

samples. Water temperature was measured with a handheld 

thermometer to the nearest degree Fahrenheit. Dissolved 

oxygen was determined by Winkler titration. After February 

1973, an electrometric dissolved oxygen meter was used. 

Occasional pH determinations were made by unknown 

methods. Specific conductance was determined in the 

laboratory with analysis of major ion concentrations.

During phase 3 (1982–90, table 1), sampling frequency 

was gradually reduced from monthly reservoir-wide surveys 

to a single annual survey. During this period, the number of 

measurements within a profile was occasionally increased to 

provide more definition between depths in areas of rapidly 

changing conditions, while maintaining the measurements at 

50-ft depth intervals described above. This period coincided 

with a series of extremely high-flow years in the Colorado 

River Basin, with high inflows into Lake Powell and high 

releases from Glen Canyon Dam.

Beginning in March 1982, a Hydrolab System 8000 was 

used, allowing multiparameter measurements to be made 

throughout the water column. This instrument recorded 

temperature, specific conductance, pH, dissolved oxygen, 

and oxidation-reduction potential; however, oxidationreduction potential was not consistently recorded until April 

1988. For much of this period, problems were encountered 

with dissolved oxygen measurements, often resulting in 

abnormally high readings. In April 1988, the profiling 

instrument was replaced with a Hydrolab Surveyor II 

multiparameter profiling system. This system resolved the 

previous dissolved oxygen measurement problems.

Current Methods, 1990–2013

During the initial part of phase 4 (1990–94) (table 1), 

the Hydrolab Surveyor II was used to collect depth profiles 

for common physicochemical parameters. During this period, 

a Hydrolab 5100A datalogger was occasionally used to 

electronically transfer data to data-management systems. The 

number of sampling stations was increased to provide greater 

longitudinal resolution in the reservoir and its larger tributaries. 

From August 1990 to September 1991, monthly depth profiles 

were collected in the forebay of the reservoir by the USGS 

(Hart and Sherman, 1996). Those measurements are included in 

this report and the WQDB.

From March 1994 to April 2009, depth profiles were 

collected with the Hydrolab Surveyor 3/H20 multiparameter 

measurement system. This system measured temperature, 

specific conductance, dissolved oxygen, pH, oxidation-reduction 

potential, and turbidity. Formal calibration procedures were 

followed, according to established protocol and manufacturers 

guidelines, in a controlled laboratory setting before and after use 

in the field. Accuracy checks were occasionally made while in 

the field, but field calibration was avoided due to the relatively 

unstable field environment that could affect the equilibrium of 

the individual sensors. The Hydrolab H20 sonde was connected 

to the Surveyor 3 display unit, which received a signal from 

the sonde for shipboard display and storage of the profile 

readings. These units were connected by a 165-m underwater 

cable mounted on a 110 VAC motorized reel. A small handheld 

computer (HP 200LX) was connected to the Surveyor 3 and was 

used to view the readings from the display unit and temporarily 

store those readings for immediate display after the profile was 

completed. Immediately reviewing these data allowed for the 

identification of specific depths for chemical sampling in the 

water column. Permanent readings were stored in the Surveyor 

3 for subsequent downloading and processing.

After the initial surface observations (for example, bottom 

depth, Secchi depth, weather observations) were made, the depth 

profile was collected. The Hydrolab H20 sonde was lowered to 

selected depths throughout the water column, and readings were 

stored in the Surveyor 3 datalogger after equilibration at a given 

depth was achieved and readings had stabilized. 

Initial readings were taken immediately below the surface 

and at approximately 0.5- to 1.0-m intervals below the water 

surface for the first few meters to document surface warming 

phenomena. Below these near-surface measurements, the 

“Rule of Fives” was observed to determine intervals between 

measurements. This guideline states that if the value of any 

parameter changes by more than a decimal fraction of five (that 

is, 0.5°C for temperature, 0.5 mg/L dissolved oxygen, 0.05 

units for pH, or 50 μS/cm for specific conductance), a smaller 

depth interval should be chosen, with 0.5 m being the minimum 

interval. If parameters were not changing at this rate, a larger 

interval (as much as 5 m) was selected. This guideline resulted 

in sufficient vertical resolution in the profile while allowing for 

a reasonable time at each station to collect the profile and allow 

full equilibration between measurements. Efforts were made to 

obtain measurements as close to the bottom as possible without 

disturbing bottom sediments that could foul sensors and cause 

ambiguous readings. This was accomplished by the vessel 

operator viewing the sonde on the sonar depth sounder as it was 

lowered through the water column.
Field Methods 11

From June 2009 to June 2010, depth profiles were collected 

with a Eureka Environmental, Inc., Manta/Amphibian profiling 

system. Methods remained similar to those employing the 

Hydrolab Surveyor 3 during this period.

After October 2009, depth profiles were collected with the 

Seabird Electronics SBE19plus-V2 conductivity/temperature/

depth (CTD) profiler. This instrument pumps water at a constant 

rate through its temperature, conductivity, and dissolved 

oxygen sensors. Sensors for turbidity, pH, ORP, and chlorophyll 

florescence are positioned external to the CTD. Sensors are 

scanned at 0.25-second intervals as the instrument is lowered 

and raised through the water column. Post-processing of the 

data collected by this instrument results in a profile of downcast 

readings averaged in 0.5-m depth intervals. 

After the profile was collected, the stratification of the 

water column was determined and major strata (epilimnion, 

metalimnion, hypolimnion, inflow layers) were identified 

from the tabular and graphical display of data recorded on the 

handheld computer. From this information, discrete chemical 

sampling depths were determined, based on the sampling 

objectives described below.

The values recorded at a specific depth are descriptive of the 

physical conditions at that point in the water column and form one 

observation in the WQDB table PROFILE, uniquely identified 

by STATION_ID, DATE, and DEPTH of the reading. The entire 

depth profile for a given site is composed of many PROFILE 

observations, which are associated with the SURFACE table by 

the common fields of STATION_ID and DATE. See the appendix 

for further details about the PROFILE table.

Chemical Sampling and Processing

Objectives

Water samples were collected at various depths at designated 

sites on Lake Powell for the determination of major ion and 

nutrient concentrations. The main objective of the sampling 

effort was to characterize chemical conditions near the surface, 

near the bottom, and in each major stratum of the water column. 

A secondary objective was to describe unusual phenomena that 

may occur at specific depths such as a metalimnetic oxygen 

deficit or an inflow plume flowing into an intermediate layer in 

the reservoir. Water samples for major ion and nutrient analysis 

were collected to characterize the overall chemical makeup and 

nutrient concentrations of the water being sampled. Nutrient 

compounds support primary productivity in the reservoir and the 

downstream aquatic ecosystem.

Historical Methods, 1964–90

During phases 1, 2, and 3 (1964–90) (table 1), 

samples were only collected for the analysis of major ion 

concentrations, specific conductance, total dissolved solids, 

pH, hardness, and alkalinity. Samples were collected from 

near the surface, near the bottom, and at 50-ft depth intervals, 

corresponding to even 50-ft increments in elevation above 

mean sea level, throughout the water column at each of seven 

original stations listed in table 2. No filtration, refrigeration, or 

preservation were performed. Approximately 65 to 70 samples 

were collected for a single reservoir-wide survey. These 

samples were analyzed by Reclamation’s Upper Colorado 

Regional Laboratory in Salt Lake City, Utah.

Current Methods, 1990–2013

During phase 4 (1990–2013), sampling for nutrient 

concentrations began. Filtration and preservation were 

performed at each site, and samples were refrigerated 

immediately after collection. The sample collection was 

changed from even 50-ft depth intervals described above to 

variable depths so that fewer samples were collected at depths 

that more accurately represented major strata in the water 

column. The number of sampling sites during this period 

was increased to provide greater longitudinal resolution; 

however, chemical sampling was confined to a subset of these 

stations (approximately half of the 31 primary sites that are 

listed in table 3). Sampling for chlorophyll a, phytoplankton, 

zooplankton, and organic carbon began during this time; 

however, this information is not included in this report. From 

February 1995 to November 2005, alkalinity was determined 

in the field concurrently with the collection of water samples.

Sample Collection

Water samples were collected using Van Dorn samplers 

attached to a 160-m stainless-steel cable connected to a 

motorized winch. This task involved two people, one to operate 

the winch and one to attach and remove the samplers. The 

cable was marked at 1-m intervals to identify specific sampling 

depths. Samplers were lowered in a series to specified depths 

and were activated by a weighted messenger that travels down 

the cable. As one sampler was tripped, it released a second 

messenger that, in turn, actuated the sampler below, and so on.

From each water sample, four subsamples were 

obtained, which included two unfiltered 250-ml samples and 

two 125-ml filtered samples. The unfiltered subsamples were 

used for the laboratory determination of physicochemical 

properties (total suspended solids, pH, specific conductance, 

and alkalinity) and total nutrients (total phosphorus and total 

Kjeldahl nitrogen). The filtered subsamples were used for 

the determination of major dissolved ion concentrations and 

dissolved nutrient compounds of phosphorus and nitrogen. 

Both nutrient samples were preserved with sulfuric acid in 

the amount described below.

All samples for chemical analysis were collected in highdensity polyethylene bottles that had been precleaned to U.S. 

Environmental Protection Agency (EPA) Contract Laboratory 

Program specifications (I-Chem 300 Series). The precleaning 

process involved acid washing and deionized water rinsing 

under controlled conditions to remove any impurities from 
12 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

storage conditions or the manufacturing process that may have 

affected the determination of low-level analytes.

Sample Filtration

All samples to be analyzed for the determination 

of dissolved substances were filtered through a 0.45-μm 

polycarbonate-membrane filter in the field as soon as 

possible after collection (U.S. Environmental Protection 

Agency, 1983). This was accomplished using a peristaltic 

pump (Geotech Series II) with silicon tubing connected 

directly to the Van Dorn sampler. A segmented flow of air 

and water was used to thoroughly rinse the pump tubing 

before connecting to the filter apparatus. The filter apparatus 

was a 47-mm inline filter holder (Millipore Swinnex 47) 

housing a 47-mm, 0.45-μm polycarbonate-membrane filter, 

low in water extractable compounds (Poretics #1035, lo 

extractable). After approximately 50 to 100 ml passed 

through the filter apparatus, the filtered subsamples were 

collected. 

Preservation

All samples for water-quality analysis were stored on 

ice. In addition, the nutrient samples were acidified with 

1.2 N H2SO4 in a proportion of 1 ml of acid per 250 ml 

sample. The acid preservation solution was supplied by the 

laboratory performing the sample analysis. The purpose of 

preserving samples was to (1) retard biological activity, (2) 

reduce chemical changes occurring between collection and 

analysis, (3) reduce volatility of constituents, and (4) reduce 

adsorption affects with the sample container. 

Transportation and Shipment

Samples were stored on ice in coolers for the duration 

of the reservoir survey. On return from the field, samples 

were checked to ensure all samples were accounted for and 

proper documentation has been performed. The coolers were 

re-iced and shipped overnight to a designated laboratory for 

analysis. 

Documentation

The depths of all samples collected at a specific station 

were noted on the field sheet. The four bottles representing 

the nutrient and major-ion subsamples were treated as a 

single sample. Quality-assurance samples collected at a 

given station were treated and numbered in the same manner 

as all other samples.

Starting with the first sample of the trip, a sequential 

field number was assigned to each sample for identification 

and tracking purposes. This number was recorded on the cap 

of each bottle as well as on the field sheet and sample labels. 

Each subsample received a label that identified the station 

code and name, sampling time and depth, field number, type 

of analysis requested, and the presence of any preservative. 

Water-resistant label materials and inks were used to prevent 

damage from submersion.

The combination of station code, time, and depth of 

sampling uniquely identify each sample collected. These 

fields and other information pertaining to the sample, such 

as laboratory ID numbers for each analysis, constitute one 

observation in the WQDB SAMPLES table. The SAMPLES 

table is used to link sample collection information with site 

visit information in the SURFACE table, over the common 

fields STATION_ID and DATE. Analytical results from 

the laboratory, which are contained in the tables MAJOR 

IONS and NUTRIENTS, are linked to the SAMPLES table 

through laboratory identification numbers (LAB#MAJ and 

LAB#NUT). See the appendix for further details about the 

SAMPLES table.

Quality Assurance/Quality Control

Quality-assurance/quality-control (QA/QC) procedures are 

a critical part of the Lake Powell chemical sampling program 

to verify the accuracy and precision of laboratory analyses and 

verify the absence of contamination from the sampling process. 

Three types of QA/QC samples were collected: blank samples, 

blind replicates, and known-addition (spike) samples. Throughout 

the course of a reservoir survey, QA/QC samples made up 

approximately 10 percent of the total number of collected 

samples. 

Blank Samples 

Blank samples are used to determine the presence of, or 

verify the absence of, any contamination in the sampling or 

sample-processing efforts. Two types of blank samples were 

collected. An equipment blank was used to determine the 

amount of contamination from any aspect of the sampling 

or sample processing steps. For this sample, reagent-grade 

water was passed through every step of the sample processing 

process. The Van Dorn sampler was rinsed three times with 

reagent-grade water and then filled with a sufficient volume 

to fill all sample bottles. This water was used to rinse the 

filter apparatus in the same manner that an actual sample was 

processed and finally collected in precleaned sample bottles. 

Equipment blanks for nutrient analysis were preserved with 

sulfuric acid; unfiltered blanks were not passed through the 

filtration apparatus. Any detectable analyte measured in 

equipment-blank samples indicates contamination occurring 

somewhere in the sampling process. These samples are 

identified and stored in the WQDB with a STATION_ID 

value of “LPQC-EB.”

A reagent blank is used to verify the presence or 

absence of contamination in the precleaned sampling bottles, 

rinse water, or the acid solution used to preserve samples. 

Reagent-grade water was transferred directly into precleaned 

sample bottles and preserved as appropriate for the analysis. 

The water did not come into contact with any sampling 

equipment, and no filtration step was performed (although the 
The WQDB 13

bottles for dissolved-constituent analysis were still labeled as 

being filtered). Any detectable analyte measured in reagentblank samples indicates contamination from sources other 

than the sampling or filtration apparatus. These samples are 

identified and stored in the WQDB with a STATION_ID 

value of “LPQC-RB.”

Replicate Samples 

Replicate samples are used to determine the precision 

of a sampling or analytical technique. Replicates resulting 

from multiple sampling efforts at a given location are 

used to evaluate the variability or precision of sampling 

activities. This type of replicate, however, was not routinely 

collected as part of the Lake Powell monitoring program. 

Because of the large volume of the horizontally stratified 

reservoir represented by a sample collected from a site at a 

given depth, it was assumed that the variability of samples 

collected from repeated efforts at that site and depth was low.

Replicates resulting from a single sampling effort, 

referred to as laboratory replicates, are used to evaluate 

the precision of the laboratory analytical process. These 

samples were collected from a continually mixed sampler 

and identified as two separate samples. Both samples were 

identified by the actual STATION_ID and DATE of the site 

visit; however, the first sample collected was identified by 

the actual DEPTH of the collected sample, and the second 

sample was identified by a fictitious depth (greater than the 

site depth) and identified as a replicate on the field sheet. By 

use of this means of identification, the two samples appeared 

to the analytical laboratory as two discrete samples, although 

they were identical replicates.

Known-Addition Samples

Known-addition (spike) samples are used to determine 

the accuracy of an analytical process and to ascertain the 

loss of a particular analyte from volatilization or adsorption. 

To evaluate these characteristics, a field spike was prepared 

by collecting a known volume of a laboratory replicate of 

the sample and adding a specific volume of a solution of 

known concentration. This spike solution, usually prepared 

by the laboratory performing the analysis, was prepared with 

known concentrations of the nutrient compounds that were 

to be determined. The solution contained concentrations of 

10 mg/L soluble reactive phosphorus (SRP) (PO4 as P), 100 

mg/L nitrate nitrogen (NO3 as N), and 10 mg/L ammonia 

nitrogen (NH4 as N). Volumes of the spike solution were 

added to a measured volume of filtered or unfiltered sample 

such that the resulting concentrations were within the 

detectable range of the analysis and not more than 10 times 

the concentration of the sample itself. The resulting spiked 

sample was then transferred directly to sample bottles. When 

possible, a large Van Dorn or other type sampler (Wildco 

6.2 l Beta Bottle #1900) was used for this type of sample 

so that the original sample, the laboratory replicate, and the 

spike could be collected from the same sampler. As with the 

laboratory replicate, the spike sample was identified by the 

actual STATION_ID and DATE of the site visit but was given 

a fictitious depth and identified as a spike sample with the 

sample volume, concentration of spike solution, and volume 

of spike solution on the field sheet.

Another type of known-addition sample, a reagent spike, 

was prepared by adding a known amount of spike solution 

to reagent-grade water. The purpose of this type of spike 

sample is to provide a measurement of analytical accuracy 

in the absence of any sample matrix effects and to verify the 

concentration of the spike solution being used. These samples 

are identified and stored in the WQDB with a STATION_ID 

value of “LPQC-RS.”

Analytical Methods

During phases 1, 2, and most of phase 3 of the 

monitoring program (1965–87) (table 1), all samples collected 

from Lake Powell were analyzed by Reclamation’s Upper 

Colorado Regional Soils Laboratory in Salt Lake City, Utah. 

From September 1987 to November 2004, most samples 

for chemical constituents were analyzed by Reclamation’s 

Environmental Chemistry Laboratory at the Technical Service 

Center in Denver, Colorado. Beginning in December 2004, 

all samples were analyzed by Reclamation’s Lower Colorado 

Regional Laboratory in Boulder City, Nevada.

Laboratory analysis included determination of specific 

conductance, pH, total alkalinity, total dissolved solids, total 

suspended solids, dissolved major ions (sodium, calcium, 

magnesium, potassium, sulfate, chloride, carbonate, and 

bicarbonate), and nutrients (total phosphorus, soluble 

reactive phosphorus, dissolved ammonia nitrogen, dissolved 

nitrate plus nitrite nitrogen, total Kjeldahl nitrogen, and total 

nitrogen). These analytes, their reporting units, detection 

limits, and references to EPA analytical methods are listed in 

table 4. 

The WQDB 

The WQDB contains the information collected from the 

long-term water-quality monitoring program for Lake Powell 

and has been developed and maintained by the GCMRC. 

WQDB is a Microsoft Access database and has a relational 

structure, meaning that information pertaining to different 

types of data is stored in separate tables, which are linked 

by common fields to display various types of data from the 

monitoring program. The data presented in WQDB are in 

raw form and have undergone preliminary editing but have 

not been rigorously scrutinized or adjusted, and therefore, 

the data contained in WQDB are provisional and should be 

used with some degree of caution. A brief description of the 

included tables contains the general content of each table and 

how it relates to other tables. The linkages that exist between 

the various tables are graphically represented in figure 4. 
14 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

Further details of the structure and content of each of the 

specific tables are discussed in the appendix.

Site Locations

The STATIONS table (tblStations) contains information 

pertaining to current and historic sampling sites on Lake 

Powell and in Glen Canyon Dam releases. A sampling site 

must have a record in this table before any information 

can be stored in WQDB for that site. Each record in the 

STATIONS table is uniquely identified by the STATION 

ID field, an eight-character alphanumeric string. Under 

the current naming scheme, this station code identifies a 

sampling location and specifies the stream channel in which 

it is located and its distance from a given reference point. 

Each record in the STATIONS table contains other pertinent 

information, such as the name of the site (SITE NAME), 

geographical coordinates (LATITUDE and LONGITUDE), 

the tributary arm in which it is located (CHANNEL), and 

its river-channel distance in the tributary arm, in kilometers 

from a given reference point (RKM). Also included is the 

STATION GROUP field, which collectively groups various 

multiple records in the STATIONS table that represent a 

single sampling location, and the PRIMARY GROUP field, 

which identifies the 31 primary station groups of the current 

and long-term monitoring program. These sites are listed in 

table 3.

Details of the structure and content of the STATIONS 

table, the STATION ID naming conventions, and the 

STATION GROUP field are contained in the appendix.

Analyte Symbol Sample units Detection limit EPA method

Physicochemical (Hydrolab profiles)

Temperature T °C -- --

Specific conductance Sp. Cond. μS/cm -- --

pH pH pH -- --

Dissolved oxygen DO mg/L -- --

Oxidation-reduction ORP mV -- --

Turbidity Turb NTU -- --

Physicochemical and major ions (laboratory analyses)

Specific conductance Lab EC μS/cm 2.0 120.1

pH pH pH N/A 150.1

Total suspended solids TSS mg/L 4 160.2

Total dissolved solids TDS mg/L 10 160

Dissolved calcium Ca mg/L 0.03 200.7

Dissolved magnesium Mg mg/L 0.03 200.7

Dissolved sodium Na mg/L 0.03 200.7

Dissolved potassium K mg/L 1.0 200.7

Dissolved carbonate CO3

= mg/L 1.0 310.1

Dissolved bicarbonate HCO3- mg/L 1.0 310.1

Dissolved chloride Cl- mg/L 1.0 300

Dissolved sulfate SO4

= mg/L 1.0 300

Dissolved silica SiO2 mg/L 0.02 200.7

Total alkalinity CaCO3 mg/L Calc.

Nutrients

Total phosphorus TP-P mg/L 0.005 365.1

Soluble reactive phosphorous OP-P mg/L 0.005 365.1

Ammonia NH3-N mg/L 0.01 350.1

Nitrate + nitrite NO3 + NO2-N mg/L 0.03 353.2

Total Kjeldahl nitrogen TKN-N mg/L 0.05 351.4

Table 4. Detection limits, units, and U.S. Environmental Protection Agency (EPA) methods for Lake Powell chemical analyses.

[--, no data; N/A, not applicable]
The WQDB 15

Site Visits

The SURFACE table (tblSURFACE) contains a record of 

each site visit that has been made to a particular sampling location 

and contains general observations pertaining to that site visit. These 

observations include reservoir surface elevation, identification of 

observers and instrumentation, air temperature, wind direction 

and speed, and cloud cover. This table represents the primary 

information by which all other measurements and observations 

are linked. A record for a specific site visit must be present in the 

SURFACE table before any observations can be stored related to 

that site visit. Each site visit is uniquely identified by a STATION 

ID and DATE. The DATE field is the date and time of the site 

visit. The time is a nominal representation of when the site visit 

occurred. In other words, although a site visit may take place over a 

time span of up to several hours, one representative time is selected 

to identify that site visit. All other data collected as part of that site 

visit are identified with the nominal site visit time.

Details of the structure and content of the SURFACE table are 

contained in the appendix.

Secchi-depth Transparency

The SECCHI table (tblSECCHI) contains multiple 

observations of Secchi-depth transparency for a given site 

visit. Because of the subjectivity of this measurement, multiple 

measurements among different observers, with and without the 

aid of a viewing scope, are often recorded. This creates a oneto-many relationship (one site visit with many Secchi-depth 

measurements) and requires these data to be contained in a separate 

table that is linked to the SURFACE table over the common fields 

STATION ID and DATE. Observations are uniquely identified by 

the STATION ID and DATE fields, along with an identifier for the 

observer and whether a viewing scope was used.

Details of the structure and content of the SECCHI table are 

contained in the appendix.

Physical Profiles

The PROFILES table (tblPROFILES) contains the results 

of multiparameter depth profiles of water-quality conditions 

throughout the water column at each sampling location. This 

table also contains single observations made at well-mixed 

stream sites. Each measurement at a discrete depth in the water 

column constitutes a record in the PROFILES table. A one-tomany relationship exists between the SURFACE table and the 

PROFILES table, with records linked by the common fields 

STATION ID and DATE. Each record is uniquely identified 

by STATION ID, DATE, and DEPTH in the PROFILES 

table. Remaining fields in the PROFILES table include water 

temperature (T), specific conductance (COND), dissolved oxygen 

(DO), pH (PH), oxidation-reduction potential (REDOX), and 

turbidity (TURB).

Details of the structure and content of the PROFILES table 

are contained in the appendix.

Chemical Analyses

Sample Catalog

The SAMPLES table (tblSAMPLES) contains a listing 

of all water-quality samples for chemical analysis collected 

during a given site visit. Each record is uniquely identified by 

the fields STATION ID, DATE, and DEPTH and link to the 

SURFACE table. There is a one-to-many relationship between the 

SURFACE table and the SAMPLES table over common values 

of the STATION ID and DATE fields. Each record contains a 

field collection identification code (a sequential number for all 

samples collected as part of a given field survey) and laboratory 

identification numbers for major ion and nutrient analyses to link 

with the analytical results in the MAJOR IONS and NUTRIENTS 

tables for a given sample.

Details of the structure and content of the SAMPLES table 

are contained in the appendix.

Alkalinity Determinations

The ALKALINITY table (tblALKALINITY) contains the 

results field titrations for total alkalinity of samples collected 

for chemical analysis. Occasionally, more than one alkalinity 

determination was done for a given sample, creating a oneto-many relationship over the common fields STATION ID, 

DATE, and DEPTH, that link the SURFACE table with the 

ALKALINITY table. Field alkalinity determinations began in 

February 1995 and were discontinued after November 2005.

Details of the structure and content of the SAMPLES table 

are contained in the appendix.

Major Ion Concentrations

The MAJOR IONS table contains the results of laboratory 

analyses for determinations of major ionic constituents. It is linked 

with a one-to-one relationship with the SAMPLES table over 

the common field LAB#MAJ, which is also the unique identifier 

for any record in this table. This table includes concentrations 

for each of the commonly occurring cations and anions and 

laboratory-determined values for pH, specific conductance, total 

dissolved solids, and total alkalinity. Associated with each analyte 

is a flagging field. The flagging field (with a suffix of “_FLG”) 

contains a remark code indicating whether a value was below 

detection limits. In the case of a value reported below detection 

limits, the flagging field is given a remark code of “<” and the 

value for the particular analyte’s field is set to the stated detection 

limit value for that analyte at the time of analysis

Nutrient Concentrations

The NUTRIENTS table contains the results of laboratory 

analyses for nutrient concentrations. It is linked with a one-to-one 

relationship with the SAMPLES table over common values of 

the field LAB#NUT, which is also the unique identifier for any 
16 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

record in this table. This table includes concentrations for total 

phosphorus (TP), soluble reactive phosphorus (SRP), dissolved 

ammonia nitrogen (NH3-N), dissolved nitrate and nitrite nitrogen 

(NO23-N), total Kjeldahl nitrogen (TKN-N), and total nitrogen 

(TN). Associated with each analyte is a flagging field. The flagging 

field (with a suffix of “_FLG”) contains a remark code indicating 

whether a value was below detection limits. In the case of a value 

reported below detection limits, the flagging field is given a remark 

code of “<” and the value for the particular analyte’s field is set 

to the stated detection limit value for that analyte at the time of 

analysis.

Acknowledgments

Data presented in this report were collected by various offices 

of the Reclamation and the USGS with the cooperation of the 

NPS Glen Canyon National Recreation Area. The author wishes to 

acknowledge and thank the following people for their assistance and 

participation in this data-collection effort. Reclamation boat pilots 

Larry Sanderson, John Parlett, Rick Leightner, Clarence Herron, 

and Calvin Leach provided logistical support for field activities 

conducted from 1964 through 1992. Technical field support since 

1992 was provided by Robert Radtke, Nick Williams, Keri Stout, 

Jeanne Korn, and Mike Horn (Reclamation); Kevin Berghoff, 

Murph Doty, Mark Anderson, Jesse Granet, Carolyn Hackbarth, 

Jamie Pezja, and Sasha Rohde (NPS); and Susan Hueftle and 

Nick Voichick (USGS). Susan Hueftle provided direction of 

the biological component of this monitoring program, graphical 

analysis, and valuable insight into the hydrodynamic processes 

in the reservoir. Mentoring, guidance, and project leadership was 

provided by Jerry Miller and David Wegner (Reclamation); and 

Matthew Andersen, David Garrett, Barry Gold, Dale Robertson, 

Bob Hart, and Richard Marzolf (USGS). Many other people, too 

numerous to mention, also provided assistance and support; their 

participation and involvement is recognized and greatly appreciated. 

Since the inception of the Lake Powell Water Quality Monitoring 

Program, Reclamation has provided the primary funding for this 

program.

References Cited

Bureau of Reclamation, 1981, Water and Power Resources—

Project data: Denver, Colo., Bureau of Reclamation.

Bureau of Reclamation, 2007, Record of decision—Colorado 

River interim guidelines for lower basin shortages and the 

coordinated operations for Lake Powell and Lake Mead: 

Boulder City, Nevada, Bureau of Reclamation, 61 p., available at http://www.usbr.gov/lc/region/programs/strategies/

RecordofDecision.pdf.

Ferrari, R.L., 1988, 1986 Lake Powell Survey: Denver, Colo., 

Bureau of Reclamation.

Hart, R.J., and Sherman, K.M., 1996, Physical and chemical characteristics of Lake Powell at the forebay and outflow of Glen 

Canyon Dam, Northeastern Arizona, 1990–91: U.S. Geological 

Survey Water–Resources Investigations Report 96-4016, 78 p.

Hart, R.J., Taylor, H.E., Antweiler, R.C., Fisk, G.G., Anderson, 

G.M., Roth, D.A., Flynn, M.E., Peart, D.B., M. Truini, M., 

and Barber., L.B., 2005, Physical and chemical characteristics of Knowles, Forgotten, and Moqui Canyons, and effects 

of recreational use on water quality, Lake Powell, Arizona 

and Utah: U.S. Geological Survey Scientific Investigations 

Report 2004-5120, 43 p.

Marzolf, G.R., 1998, Depth profiles of temperature, specific 

conductance, and oxygen concentrations in Lake Powell, 

Arizona–Utah, 1992–95: U.S. Geological Survey Open-file 

Report 97-835, 119 p,

National Research Council, 1996, River resource management 

in Grand Canyon: Committee to Review the Glen Canyon Environmental Studies, Commission on Geosciences, 

Environment, and Resources: Washington, D.C., National 

Academy Press, 226 p.

Potter, L.D., and Drake, C.L., 1989, Lake Powell—Virgin flow 

to dynamo: University of New Mexico Press, 328 p.

Stanford, J.A., and Ward, J.V., 1991, Limnology of Lake Powell and the chemistry of the Colorado River, in Colorado 

River ecology and dam management: Washington, D.C., 

National Academy Press, p. 75–101.

U.S. Department of the Interior, 1996, Record of decision, 

operation of Glen Canyon Dam final environmental impact 

statement: Washington, D.C., Office of the Secretary of the 

Interior, 15 p.

U.S. Environmental Protection Agency, 1983, Methods for 

chemical analysis of water and wastes: Cincinnati, Ohio, 

U.S. Environmental Protection Agency, Environmental 

Monitoring and Support Laboratory, EPA-600/4-79-020.

Voichick, N., and Wright, S.A., 2007, Water-temperature data 

for the Colorado River and tributaries between Glen Canyon 

Dam and Spencer Canyon, Northern Arizona, 1988–2005: 

U.S. Geological Survey Data Series 251, 24 p., available at 

http://pubs.usgs.gov/ds/2007/251/.

Wetzel, R.G., and Likens, G.E, 1991, Limnological analyses, 

2nd ed: New York, Springer-Verlag, 391 p.
References Cited 17

Appendix
18 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

Appendix—Database Table 

Descriptions

This appendix contains a description of the various 

tables in the WQDB. Each section contains a brief description 

of each table, the fields and attributes of each table, notes 

about linkages to other tables, and summary statistics of each 

table. Under the FieldSize property for the data field in each 

table, “Single” refers to single-point precision, with a storage 

size of 4 bytes; “Double” refers to double-point precision, 

with a storage size of 8 bytes. Figure 4 shows the graphical 

relationships between the tables of the WQDB.

Stations Table

The Stations table (tblStations) describes the various 

sampling sites at which monitoring activities occur on Lake 

Powell. A single sampling site is identified by the 8-character 

STATION ID field, which uniquely identifies each record in the 

table. The fields in the STATIONS table are listed in table A-1.

The STATION ID field describes the location of a 

sampling site by including the stream channel in which it is 

located and the river-channel distance, in tenths of kilometers, 

from Glen Canyon Dam or a tributary confluence. Under 

the current naming convention, the first two letters reference 

the project (LP for Lake Powell), the next 2 or 3 characters 

designate the tributary arm or stream channel (CR for 

Colorado River, SJR for San Juan River, ESC for Escalante 

River), and the remaining 3 or 4 digits designate the riverchannel distance, in tenths of kilometers, of the station from 

a given reference point. That reference point is usually the 

confluence of a tributary arm with the main channel. For the 

Colorado River channel, the reference point is Glen Canyon 

Dam. For example, the Cha Canyon station, which is located 

19.3 river-channel kilometers from the pre-dam Colorado 

River channel on the San Juan River arm of Lake Powell, 

has a value for the STATION ID field of LPSJR193. For 

stations below Glen Canyon Dam, the river-channel distance 

is negative. For example, LPCR-249 represents the Colorado 

River at Lees Ferry station, 24.9 river-channel kilometers 

below Glen Canyon Dam. The specific location for a given 

station is listed in the STATIONS table as latitude and 

longitude coordinates in decimal degrees.

Information regarding sampling locations is stored in 

WQDB according to the specific STATION ID in effect at the 

time of sampling and the more general STATION GROUP. 

Sampling locations representative of a given general location 

on the reservoir (STATION GROUP) may have many different 

STATION IDs recorded in the database. This is because 

different naming conventions have been used during the 

monitoring history of Lake Powell and because the specific 

sampling location for a given site may have been slightly 

adjusted over time to facilitate sampling conditions (because 

of boat traffic, wind patterns, or local sedimentation). Multiple 

STATION ID values may also exist for tributary inflow 

sites on the reservoir and Glen Canyon Dam release sites. 

Depending on reservoir elevation at the time of sampling, 

the actual location of an inflow sampling site may vary over 

a relatively large distance. Releases from Glen Canyon Dam 

may be sampled from any of eight generating turbine draft 

tubes or from the tailrace immediately below Glen Canyon 

Dam. The STATION GROUP field is therefore used to 

collectively reference multiple STATION IDs to a single 

representative location on the reservoir. All records in the 

STATIONS table that are representative of a single location 

on the reservoir will have a common value for the STATION 

GROUP field. For example, the STATION GROUP values 

of LPCR_INF, LPSJRINF, and LPESCINF collectively 

group various inflow sites on the Colorado, San Juan, and 

Escalante River arms of the reservoir, respectively. The 

STATION GROUP value of LPCR0000 collectively groups 

all sampling locations representative of Glen Canyon Dam 

releases. By selecting all records in the STATIONS table for 

common values of a given STATION GROUP code, the entire 

history for that site can be retrieved, regardless of the specific 

STATION ID value in effect at the time of sampling.

There are 330 sampling sites described in the STATIONS 

table. Of this number, 234 correspond to the 31 primary station 

groups shown in table 3. The remaining 92 sites represent 

occasional sampling and are not part of the current routine 

monitoring program. The 31 primary station groups represent the 

current monitoring program and long-term sampling sites. These 

groups are designated by the PRIMARY GROUP field. The 

geographical coordinates, stream channel designation, and river 

channel distances for the 31 primary groups are listed in table 3.

Surface Table

The Surface table (tblSurface) contains a record of 

every site visit at which water-quality measurements have 

been made on Lake Powell. It contains observations made on 

arrival (DATE) at a given sampling site (STATION ID) and 

includes information about who collected the measurements 

and how they were collected, reservoir elevation and depth, 

general meteorological conditions and other comments. 

Each record is uniquely identified by the time of the site visit 

(DATE) and the location of the site visit (STATION ID). See 

table 3 for the number of Surface table entries or site visits for 

primary station groups. 

The Trip ID field is a useful way to group all site visits 

within a given monitoring survey. The value of the Trip ID 

field is in the format LPyymmdd, where yymmdd corresponds 

to the date of the first reservoir sample collected during the 

monitoring survey. The fields constituting the Surface table are 

listed in table A-2.

There are currently 4,360 observations or site visits in the 

Surface table. Of this number, 4,084 (93.7 percent) represent site 

visits related to the 31 primary station groups shown in table 3. 
Appendix—Database Table Descriptions 19

The remaining 276 (6.3 percent) site visits represent occasional 

sampling at sites not part of the current monitoring program.

Secchi Table

The Secchi table (tblSecchi) contains a record of multiple 

Secchi-depth transparency observations made during each site 

visit. For a given site visit, multiple observers (OBSERVER) 

may record observations and each observation is made 

with or without the aid of an underwater viewing scope 

(SCOPE.) The viewing scope reduces the effects of glare 

and surface disturbance on the Secchi-depth transparency 

observation. Each Secchi-depth transparency observation is 

also assigned a condition code (CONDITIONS), with four 

primary designations—E, excellent; G, good; F, fair; and P, 

poor—which indicate the observation conditions relating 

to surface glare, choppiness, boat movement, and others. 

Consistent documentation of observers, condition codes, and 

the use of the viewing scope began in 1995. Each record in 

the Secchi table is uniquely identified by the primary fields 

STATION ID, DATE, OBSERVER, and SCOPE. More than 

one Secchi-depth transparency observation may be made 

during a single site visit. The fields in the Secchi table are 

listed in table A-3.

There are currently 6,961 Secchi-depth transparency 

observations in the Secchi table, 6,530 of which have been 

recorded since 1995 and have relatively consistent documentation 

of observers, condition codes, and whether or not a viewing scope 

was used. Of the observations recorded since 1995, 6,168 (94.5 

percent) are associated with the 31 primary station groups shown 

Field Name Type FieldSize Description

*STATION ID Text 10 site identifier code

SITE NAME Text 50 descriptive site name

LATITUDE Number Double latitude (decimal degrees)

LONGITUDE Number Double longitude (decimal degrees)

CHANNEL Text 5 stream channel of site location

RKM Number Single river channel distance (km)

STATION GROUP Text 10 station grouping identifier

PRIMARY GROUP? Yes/No 1 primary group designation

*

 Indicates primary field that uniquely identifies each record in the table.

Field Name Type FieldSize Description

*STATION ID Text 10 site identifier code

*DATE Date/Time 15 date and time of site visit

TRIP ID Text 10 monitoring survey identifier

PROFILERS Text 24 names or initials of observers

INSTRUMENT Text 20 designation of profiling instrument

VESSEL Text 20 designation of sampling vessel

ELEVATION Number Single reservoir elevation (ft)

BOTTOM SOUNDING Number Single bottom sounding (m)

WAVE HEIGHT Text 20 wave height description (cm)

WIND Text 20 wind speed description (mph)

AIR TEMP Number Single numeric air temperature

AIR TEMP UNITS Text 1 air temperature units (°F or °C)

CLOUD COVER Text 10 cloud cover—verbal (%)

*

 Indicates primary fields that uniquely identify each record in the table.

Table A-1. Data fields and attributes of tblStations.

 Table A-2. Data fields and attributes of tblSurface.
20 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

Field name Type Field size Description

*STATION ID Text 10 site identifier code

*DATE Date/Time 15 date and time of site visit

*OBSERVER Text 5 initials of observer

*SCOPE Yes/No 1 viewing scope designation

SECCHI DEPTH Number Single Secchi-depth transparency (m)

CONDITIONS Text 5 viewing conditions (e, excellent; g, good; f, fair; p, poor)

*

Indicates primary fields that uniquely identify each record in the table.

in table 3. The remaining 362 (5.5 percent) represent occasional 

measurements at sites not part of the current monitoring program. 

There were 431 observations recorded before 1995, consisting 

mainly of single observations.

Profiles Table

The Profiles table (tblProfiles) contains a record 

of every discrete water-quality measurement for water 

temperature, specific conductance, pH, dissolved oxygen, 

oxidation-reduction potential or turbidity collected during 

each site visit. This includes single observations from a 

hand-held thermometer or other instruments as well as 

depth profiles collected through the water column at a 

given location. Each record in the Profile table is uniquely 

identified by time of the site visit (DATE), the location of the 

observation (STATION ID), and the depth of the observation 

(DEPTH). The PTIME field identifies the instantaneous 

time at which an observation was recorded. The fields in the 

Profiles table are listed in table A-4.

There are currently 129,461 observations contained 

in the Profiles table. Of this number, 121,320 observations 

(93.7 percent) are associated with the 31 primary station 

groups shown in table 3. The remaining 8,141 observations 

(6.3 percent) represent occasional measurements at sites not 

part of the current monitoring program.

Samples Table

The Sample table (tblSamples) provides a catalog of all 

samples collected for chemical analysis during a given site visit 

and serves as a link between the Surface table (tblSurface) and the 

various tables representing the different categories of chemical 

analysis (tblAlkalinity, tblMajor Ions, and tblNutrients). Each 

record can be linked with a site visit record in the Surface table 

by the fields STATION ID, DATE, and DEPTH. Links with 

the corresponding analysis tables are made through laboratoryassigned sample identifier fields or, in the case of the Alkalinity 

table, through the STATION ID, DATE, and DEPTH fields. Each 

record in the Samples table is uniquely identified by time of the 

site visit (DATE), the location of the site visit (STATION ID), 

and the depth at which the sample was collected (DEPTH). A 

sequential sample number (FLD #) is recorded for every sample 

collected during a given field survey to aid in sample tracking. 

The fields comprising the Samples table are listed in table A-5.

There are currently 12,315 samples contained in the Samples 

table. Of this number, 12,119 (98.4 percent) represent samples 

collected from the 31 primary station groups shown in table 3. 

Table A-4. Data fields and attributes of tblProfiles.

Field Name Type FieldSize Description

*STATION ID Text 10 site identifier code

*DATE Date/Time 15 date and time of site visit

*DEPTH Number Single depth of observation (m)

T Number Single water temperature (oC)

COND Number Single specific conductance (μS/cm)

DO Number Single dissolved oxygen (mg/L)

PH Number Single pH (units)

ORP Number Single oxidation-reduction potential (mv)

TURB Number Single turbidity (NTU)

PTIME Date/Time 18 actual time of single observation

*

 Indicates primary fields that uniquely identify each record in the table.

Table A-3. Data fields and attributes of tblSecchi.
Appendix—Database Table Descriptions 21

Table A-5. Data fields and attributes of tblSamples.

Field Name Type FieldSize Description

*STATION ID Text 10 site identifier code

*DATE Date/Time 15 date and time of site visit

*DEPTH Number Single depth of sample (m)

FLD # Number Single trip-specific sample identifier

LAB#MAJ Text 10 major ion analysis sample identifier

LAB#NUT Text 10 nutrient analysis sample identifier

*

 Indicates primary fields that uniquely identify each record in the table.

The remaining 196 samples (1.6 percent) represent occasional 

sampling at sites not part of the current monitoring program.

Alkalinity Table

The Alkalinity table (tblAlkalinity) contains the 

results of field determinations of total alkalinity on samples 

collected for chemical analysis. Each record in the Alkalinity 

table links with a record in the Samples table (tblSamples) 

by the fields STATION ID, DATE, and DEPTH. Because 

more than one field alkalinity determination may be made 

for a given sample, one or more records in the Alkalinity 

table can be linked to a single record in the Samples table. 

Each record in the Alkalinity table is uniquely identified by 

time of the site visit (DATE), the location of the site visit 

(STATION ID), and the depth at which the sample was 

collected (DEPTH). The fields in the Samples table are listed 

in table A-6.

There are currently 1,908 field alkalinity sample 

determinations in the Alkalinity table. These determinations 

were performed on samples collected between 1995 and 

2005. Of this number, 1,843 (96.6 percent) represent samples 

collected from the 31 primary station groups shown in table3. 

The remaining 65 determinations (3.4 percent) represent 

occasional sampling at sites not part of the current monitoring 

program. No alkalinity determinations have been performed in 

the field since November 2, 2005.

Major Ions Table

The Major Ions table (tblMajor Ions) contains the results 

of chemical analyses for the major ionic constituents and other 

physical characteristics in water samples. Each record in the 

Major Ions table is uniquely identified by the LAB#MAJ field. 

The fields with the “_FLG” suffix designate analytical values 

that were below the laboratory’s stated detection limit for a given 

analyte. In those cases, the “_FLG” field for a particular analyte is 

given a remark code of “<”, and the field representing the actual 

concentration of the analyte is given the stated detection limit at 

the time of analysis. It is important that both fields are incorporated 

in any reporting or analysis to indicate values that are below 

detectible limits. The fields constituting the Major Ions table are 

listed in table A-7.

There are currently 12,210 major-ion analyses in the Major 

Ions table. Of this number, 12,018 (98.4 percent) represent 

samples collected from the 31 primary station groups shown 

in table 3. The remaining 192 analyses (1.6 percent) represent 

occasional sampling at sites not part of the current monitoring 

program.

Nutrients Table

The Nutrients table (tblNutrients) contains the results 

of chemical analyses for nutrient compounds of phosphorus 

and nitrogen. Each record in the Nutrients table is uniquely 

Table A-6. Data fields and attributes of tblAlkalinity.

Field Name Type FieldSize Description

*STATION ID Text 10 site identifier code

*DATE Date/Time 15 date and time of site visit

*DEPTH Number Single depth of sample (m)

*OBSERVER Text 5 initials of observer

ALKALINITY Number Double total alkalinity (mg/L as CaCO3)

*

 Indicates primary fields that uniquely identify each record in the table.
22 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1964–2013

Table A-7. Data fields and attributes of tblMajor Ions. 

Field Name Type FieldSize Description

*LAB#MAJ Text 10 laboratory sample identifier

COND Number Single lab-determined specific conductance

PH Number Single lab-determined pH

TSS Number Single total suspended solids (mg/L)

TSS_FLG Text 5 detection limit qualifier

TDS Number Single total dissolved solids (mg/L)

TDS_FLG Text 5 detection limit qualifier

CA Number Single dissolved calcium (mg/L)

CA_FLG Text 5 detection limit qualifier

MG Number Single dissolved magnesium (mg/L)

MG_FLG Text 5 detection limit qualifier

NA Number Single dissolved sodium (mg/L)

NA_FLG Text 5 detection limit qualifier

K Number Single dissolved potassium (mg/L)

K_FLG Text 5 detection limit qualifier

CO3 Number Single dissolved carbonate (mg/L)

CO3_FLG Text 5 detection limit qualifier

HCO3 Number Single dissolved bicarbonate (mg/L)

HCO3_FLG Text 5 detection limit qualifier

ALAKALINITY Number Single total alkalinity (mg/L as CaCO3)

ALKALINITY_FLG Text 5 detection limit qualifier

CL Number Single chloride (mg/L)

CL_FLG Text 5 detection limit qualifier

SO4 Number Single dissolved sulfate (mg/L)

SO4_FLG Text 5 detection limit qualifier

SIO2 Number Single dissolved silica (mg/L)

SIO2_FLG Text 5 detection limit qualifier

FE Number Single dissolved iron (mg/L)

FE_Flg Text 5 detection limit qualifier

*

 Indicates primary field that uniquely identifies each record in the table.

Table A-8. Data fields and attributes of tblNutrients.

Field Name Type FieldSize Description

*LAB#NUT Text 10 laboratory sample identifier

TP Number Single total phosphorus (mb/L)

TP_FLG Text 5 detection limit qualifier

SRP Number Single soluble reactive phosphorus (mg/L as P)

SRP_FLG Text 5 detection limit qualifier 

NH3-N Number Single ammonium nitrogen (mg/L as N)

NH3-N_FLG Text 5 detection limit qualifier 

NO23-N Number Single nitrate+nitrite nitrogen (mg/L as N)

NO23-N_FLG Text 5 detection limit qualifier 

TKN Number Single total Kjeldahl nitrogen (mg/L)

TKN_FLG Text 5 detection limit qualifier 

TN Number Single total nitrogen (mg/L)

TN_FLG Text 5 detection limit qualifier

*

 Indicates primary field that uniquely identifies each record in the table.
Appendix—Database Table Descriptions 23

identified by the LAB#NUT field. The fields with the 

“_FLG” suffix designate analytical values that were below 

the laboratory’s stated detection limit for a given analyte. In 

those cases, the “_FLG” field for a particular analyte is given 

a remark code of “<”, and the field representing the actual 

concentration of the analyte is given the stated detection 

limit at the time of analysis. It is important that both fields 

are incorporated in any reporting or analysis to indicate 

values that are below detectible limits. The fields in the 

Nutrients table are listed in table A-8.

There are currently 3,802 nutrient analyses in the 

Nutrients table. Of this number, 3,682 (96.8 percent) 

represent samples collected from the 31 primary station 

groups shown in table 3. The remaining 120 analyses (3.2 

percent) represent occasional sampling at sites not part of the 

current monitoring program.
This page left intentionally blank.
Produced in the Western Region, Menlo Park, California

Manuscript approved for publication February 12, 2015

Text edited by James W. Hendley II

Layout and design by Jeanne S. DiLeo and Cory Hurd
26 Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1965–2008

Vernieu—Historical Physical and Chemical Data for Water in Lake Powell and from Glen Canyon Dam Releases, Utah-Arizona, 1965–2013—Data Series 471, ver. 3.0

ISSN 2327-638X (online)

http://dx.doi.org/10.3133/ds471