HomeMy WebLinkAboutCosmos Hills Hydroelectric Hydrology Report - May 2012 - REF Grant 2195413Cosmos Hills Hydrologic Network
Installation and Operation,
August 2010-December 2011
View from outcrop bluff location near Kogoluktuk River
Winter Supplemental Station.
by
Michael R. Lilly, David Brailey,
Kristie Hilton, Ron Paetzold,
and Austin McHugh
May 2012
Cosmos Hills Hydrology Network Project
FERC Preliminary Permit # P-13286-000
Report GWS.TR.12.01
Cosmos Hills Hydrologic Network Installation and Operation,
August 2010-December 2011
by
Michael R. Lilly1, David Brailey
2, Kristie Hilton
1, Ron Paetzold
1 and Austin
McHugh1
A report on hydrologic investigations sponsored by:
Alaska Energy Authority
Alaska Village Electric Cooperative, Inc.
NANA Development Corporation
Geo-Watersheds Scientific
May 2012
Cosmos Hills Hydrology Network Project
Report Number GWS.TR.12.01
1Geo-Watersheds Scientific, Fairbanks, AK
2Brailey Hydrologic, Anchorage, AK
i
Recommended Citation:
Lilly, M.R., Brailey, D., Hilton, K., Paetzold, R., and McHugh, A. 2012. Cosmos Hills
Hydrologic Network Installation and Operations, August 2010-December 2011. Geo-
Watersheds Scientific, Report GWS.TR.12.01. Fairbanks, Alaska. 55 pp (plus
appendices).
Fairbanks, Alaska
May 2012
For additional information write to:
Geo-Watersheds Scientific
PO Box 81538
Fairbanks, Alaska 99708
mlilly@gwscientific.com
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TABLE OF CONTENTS
TABLE OF CONTENTS...................................................................................................ii
LIST OF FIGURES..........................................................................................................iii
LIST OF TABLES............................................................................................................ v
LIST OF APPENDICES................................................................................................... v
DISCLAIMER..................................................................................................................vi
CONVERSION FACTORS, UNITS, WATER QUALITY UNITS, VERTICAL AND
HORIZONTAL DATUM, ABBREVIATIONS AND SYMBOLS.........................................vii
PROJECT COOPERATORS...........................................................................................xi
ACKNOWLEDGEMENTS ...............................................................................................xi
1.0 INTRODUCTION...................................................................................................1
1.1 NETWORK INSTALLATION OBJECTIVES.......................................................3
1.2 BACKGROUND HYDROLOGY..........................................................................4
2.0 PROCEDURES.....................................................................................................8
2.1 SITE SELECTION..............................................................................................8
2.2 GAUGING STATION INSTALLATION AND OBJECTIVES................................9
2.3 LEVATION SURVEYING AND WATER LEVEL MEASURMENTS..................11
2.4 WATER CHEMISTRY MEASUREMENTS.......................................................11
2.5 DISCHARGE MEASUREMENTS.....................................................................12
2.5.1 ACOUSTIC DOPPLER DISCHARGE MEASUREMENTS.........................12
2.5.2 CURRENT METER DISCHARGE MEASUREMENTS..............................13
2.6 SNOW SURVEY MEASUREMENTS...............................................................14
3.0 SITE DESCRIPTIONS.........................................................................................15
3.1 UPPER COSMOS CREEK STATION..............................................................16
3.2 LOWER COSMOS CREEK STATION.............................................................17
3.3 UPPER WESLEY CREEK STATION...............................................................18
3.4 LOWER WELSEY CREEK STATION..............................................................19
3.5 UPPER DAHL CREEK STATION ....................................................................20
3.6 MIDDLE DAHL CREEK STATION...................................................................21
3.7 UPPER KOGOLUKTUK RIVER STATION.......................................................22
3.8 UPPER KOGOLUKTUK FALLS WINTER SUPPLEMENTAL STATION..........23
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3.9 LOWER KOGOLUKTUK RIVER STATION......................................................25
4.0 SELECTED RESULTS AND DISCUSSION........................................................26
4.1 DISCHARGE MEASUREMENTS.....................................................................26
4.2 STREAMFLOW COMPUTATIONS..................................................................28
4.2.1 CORRECTION OF PRESSURE TRANSDUCER DATA............................29
4.2.2 PRELIMINARY RATING CURVE DEVELOPMENT ..................................35
4.2.3 MEAN DAILY FLOW COMPUTATIONS....................................................44
4.2.4 STREAMFLOW MEASUREMENT DISCUSSION.....................................44
4.3 WATER TEMPERATURE MEASUREMENTS.................................................46
4.3.1 WATER TEMPERATURE RESULTS........................................................46
4.4 SPRING SNOW MEASUREMENTS AND FIELD OBSERVATIONS...............50
5.0 SUMMARY..........................................................................................................53
6.0 REFERENCES....................................................................................................54
LIST OF FIGURES
Figure 1. Map of Cosmos Hills Hydrologic Network. Some stations decommissioned in
Fall 2011. .................................................................................................................2
Figure 2. USGS Dahl Creek gauge mean daily mean discharge, in cubic feet per
second. ....................................................................................................................6
Figure 3. USGS Dahl Creek gauge daily mean-discharge period-of-record range, in
cubic feet per second...............................................................................................6
Figure 4. USGS Dahl Creek gauge mean and low daily mean discharges for the period
of record, in cubic feet per second...........................................................................7
Figure 5. USGS Dahl Creek gauge daily mean discharges for the 11-year period 1999
through 2009, in cubic feet per second....................................................................7
Figure 6. Website plotting example of data logger temperature, battery bank voltage and
solar panel output voltage for the Upper Wesley Creek Station.............................16
Figure 7. Site picture of the Upper Cosmos Creek Station (8/18/10, M. Lilly). The station
was located on the west bank and the picture is looking upstream........................17
Figure 8. Site picture of the Lower Cosmos Creek Station, looking downstream from
east bank (8/18/10, M. Lilly)...................................................................................18
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Figure 9. Site picture of the Upper Wesley Creek Station, looking across the stream
from the west bank (8/20/10, M. Lilly). ...................................................................19
Figure 10. Site picture of the Lower Wesley Creek Station, looking downstream from an
old bridge on a regional trail (8/21/10, M. Lilly). .....................................................20
Figure 11. Site picture of the Upper Dahl Creek Station looking downstream from the
station on the west bank (8/12/10, M. Lilly)............................................................21
Figure 12. Site picture of the Middle Dahl Creek Station, looking south and downstream
(8/21/10, M. Lilly)....................................................................................................22
Figure 13. Site picture of the Upper Kogoluktuk River Station, taken on the east bank,
and looking slightly upstream (8/18/10, M. Lilly).....................................................23
Figure 14. Site picture of the Upper Kogoluktuk Falls Repeater Station (9/30/11, M.
Lilly)........................................................................................................................24
Figure 15. Site picture of the Lower Kogoluktuk River Station, looking downstream from
the west bank (8/18/10, M. Lilly).............................................................................25
Figure 16. 2010 Discharge measurement locations, Kogoluktuk River.........................27
Figure 17. Raw and corrected stage data for the Upper Dahl Creek Station.................30
Figure 18. Raw and corrected stage data for the Upper Wesley Creek Station............31
Figure 19. Raw and corrected stage data for the Upper Cosmos Creek Station...........32
Figure 20. Raw and corrected stage data for the Upper Kogoluktuk River Station. ......34
Figure 21. Preliminary rating for the Upper Dahl Creek Station. ...................................37
Figure 22. Surveyed cross section at the Upper Dahl Creek Station. ...........................38
Figure 23. Preliminary rating for the Upper Wesley Creek Station................................39
Figure 24. Ratios of annual minimums to flows on the previous October 15.................39
Figure 25. Surveyed cross section at the Upper Wesley Creek Station........................40
Figure 26. Preliminary rating for the Upper Cosmos Creek Station...............................41
Figure 27. Surveyed cross section at the Upper Cosmos Creek Station.......................42
Figure 28. Preliminary rating for the Upper Kogoluktuk River Station. ..........................43
Figure 29. Surveyed cross section at the Upper Kogoluktuk River Station. ..................44
Figure 30. Mean Daily Hydrographs..............................................................................46
Figure 31. Water-temperature data from the time of installation to the September 2011
field trip for the series of downstream stations.......................................................48
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Figure 32. Water-temperature data (15 minute averages) from the time of installation to
February 2012, for the series of upstream stations................................................49
Figure 33. Water-temperature data from the time of installation to February 2012, for the
Upper Kogoluktuk River Station.............................................................................50
Figure 34. Snow survey site locations during March 2011 field trip...............................51
LIST OF TABLES
Table 1. Surface-Water, Repeater, and Base Station Locations...................................15
Table 2. Summary of discharge measurements............................................................28
Table 3. Snow Survey Summary, March 24 to 27, 2011...............................................52
LIST OF APPENDICES
APPENDIX A. ELEVATION SURVEY FORMS
APPENDIX B. WATER-LEVEL MEASUREMENTS
APPENDIX C. CROSS-SECTION ELEVATION SURVEY FORMS
APPENDIX D. WATER-QUALITY SAMPLING FORMS
APPENDIX E. WATER-QUALITY METER CALIBRATION FORMS
APPENDIX F. SNOW SURVEY FORMS
APPENDIX G. STATION METADATA STANDARDS EXAMPLE
APPENDIX H. METADATA STANDARDS SUMMARY EXAMPLE
APPENDIX I. STATION METADATA STANDARDS QAQC
APPENDIX J. SUSPENDED SEDIMENT ANALYSIS
APPENDIX K. SELECTED DAILY UPDATES
APPENDIX L. MEAN DAILY FLOW
APPENDIX M. HOBO SENSOR TRACKING
APPENDIX N. METEOROLOGIC DATA PLOTS
APPENDIX O. HEALTH, SAFETY, AND ENVIRONMENTAL
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DISCLAIMER
This report was prepared as an account of work sponsored by the Alaska Energy
Authority, Alaska Village Electric Cooperative, Inc., NANA Development Corporation,
and Geo-Watersheds Scientific. Neither the agencies, nor any of their employees, make
any warranty, or assume any legal liability or responsibility for the accuracy,
completeness, or usefulness of any information disclosed, or represents that its use
would not infringe privately owned rights. Reference herein to any specific commercial
product, process, or service by trade name, trademark, manufacturer, or otherwise does
not necessarily constitute or imply its endorsement, recommendation, or favoring by any
agency.
The contents of this report reflect the views of the authors, who are responsible for the
accuracy of the data presented herein. The contents of the report do not necessarily
reflect the views or policies of the agency or any local sponsor. This work does not
constitute a standard, specification, or regulation.
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CONVERSION FACTORS, UNITS, WATER QUALITY UNITS, VERTICAL
AND HORIZONTAL DATUM, ABBREVIATIONS AND SYMBOLS
Conversion Factors
Multiply By To obtain
Length
inch (in.) 25.4 millimeter (mm)
inch (in.) 2.54 centimeter (cm)
foot (ft) 0.3048 meter (m)
mile (mi) 1.609 kilometer (km)
Area
acre 43560 square feet (ft
2)
acre 0.4047 hectare (ha)
square foot (ft2) 3.587X10
-8 square mile (mi2)
square mile (mi2) 2.590 square kilometer (km
2)
Volume
gallon (gal) 3.785 liter (l)
gallon (gal) 3785 milliliter (ml)
cubic foot (ft3) 23.317 liter (l)
Acre-ft 1233 cubic meter (m
3)
Velocity and Discharge
foot per day (ft/d) 0.3048 meter per day (m/d)
square foot per day (ft2/d ) .0929 square meter per day (m
2/d)
cubic foot per second (ft3/s) 0.02832 cubic meter per second
(m3/sec)
Hydraulic Conductivity
foot per day (ft/d) 0.3048 meter per day (m/d)
foot per day (ft/d) 0.00035 centimeter per second
(cm/sec)
meter per day (m/d) 0.00115 centimeter per second
(cm/sec)
Hydraulic Gradient
foot per foot (ft/ft) 5280 foot per mile (ft/mi)
foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)
Pressure
pound per square inch (lb/in2 ) 6.895 kilopascal (kPa)
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Units
For the purposes of this report, both US Customary and Metric units were employed.
Common regulations related to water use in Alaska uses combinations of both US
Customary and Metric units. The choice of “primary” units employed depended on
common reporting standards for a particular property or parameter measured.
Whenever possible, the approximate value in the “secondary” units was also provided in
parentheses. Thus, for instance, snow depth was reported in inches (in) followed by the
value in centimeters (cm) in parentheses.
Physical and Chemical Water-Quality Units:
Temperature:
Water and air temperature are given in degrees Celsius (°C) and in degrees Fahrenheit
(°F). Degrees Celsius can be converted to degrees Fahrenheit by use of the following
equation:
°F = 1.8(°C) + 32
Snow Water Equivalent (SWE):
Water content of a given column of snow is determined by knowing the depth of the
snowpack and density.
SWE = d s s /p w
where:
d s = snow depth
s = snow density
p w = density of water.
Electrical Conductance (Actual Conductivity and Specific Conductance):
In this report conductivity of water is expressed as Actual Conductivity [AC] in
microSiemens per centimeter (µS/cm). This unit is equivalent to micromhos per
centimeter. Elsewhere, conductivity is commonly expressed as Specific Conductance at
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25°C [SC25] in µS/cm which is temperature corrected. To convert AC to SC25 the
following equation can be used:
Error! Bookmark not defined.)25(125 Tr
ACSC
where:
SC25 = Specific Conductance at 25oC, in µS/cm
AC = Actual Conductivity, in µS/cm
r = temperature correction coefficient for the sample, in oC
T = temperature of the sample, in oC
Milligrams per liter (mg/l) or micrograms per liter (g/l):
A milligram per liter is a unit of measurement indicating the concentration of chemical
constituents in solution as weight (milligrams) of solute per unit volume (liter) of water.
One thousand micrograms per liter is equivalent to one milligram per liter. For
concentrations less than 7,000 mg/l, the numerical value is the same as for
concentrations in parts per million (ppm).
Millivolt (mV):
A unit of electromotive force equal to one thousandth of a volt.
Vertical Datum:
“Sea level” in the following report refers to the National Geodetic Vertical Datum of 1929
(NGVD of 1929), a geodetic datum derived from a general adjustment of the first-order
level nets of both the United States and Canada, formerly called Sea Level Datum of
1929.
Horizontal Datum:
The horizontal datum for all locations in this report is the North American Datum of 1983
or North American Datum of 1927.
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Abbreviations, Acronyms, and Symbols
AC Actual conductivity
ADOT&PF Alaska Department of Transportation and Public Facilities
ADNR Alaska Department of Natural Resources
ASTM American Society for Testing and Materials
AVEC Alaska Village Electric Cooperative
atm Atmospheres
C Celsius (
oC)
cm Centimeters
DO Dissolved oxygen
DVM Digital voltage multi-meter
F Fahrenheit (
oF)
ft Feet
GWS Geo-Watersheds Scientific
in Inches
kg Kilograms
km2 Square kilometers
kPa Kilopascal
lb/in2 Pounds per square inch
m Meters
mg/l Milligrams per liter
g/l Micrograms per liter
mi2 Square miles
mm Millimeters
S/cm Microsiemens per centimeter
mV Millivolt
NGVD National Geodetic Vertical Datum
NRCS Natural Resources Conservation Service
NWIS National Water Information System
ppm Parts per million
QA Quality assurance
QC Quality control
SC25 Specific conductance at 25°C
SWE Snow water equivalent
USACE U.S. Army Corps of Engineers, Alaska District
USGS U.S. Geological Survey
WWW World Wide Web
YSI Yellow Springs Instruments
xi
PROJECT COOPERATORS
The Cosmos Hills Hydrology Network Project covers selected streams in the Cosmos
Hills area and the adjacent Kogoluktuk River and benefits from a number of positive
partnerships, all contributing to the overall project objectives.
Alaska Energy Authority (AEA)
Alaska Village Electric Cooperative, Inc. (AVEC)
NANA Development Corporation
WH Pacific
Geo-Watersheds Scientific
Brailey Hydrologic
Northwest Arctic Borough School District
Kobuk School
And coordination with NovaGold Resources Inc.
ACKNOWLEDGEMENTS
This material is based upon work supported by the Alaska Energy Authority. Field
coordination and logistics support were provided by NovaGold Resources Inc.
Additional support was provided by Alaska Village Electric Cooperative, Inc., NANA
Development Corporation, and Geo-Watersheds Scientific, in the form of financial and
in-kind match.
1
Cosmos Hills Hydrologic Network Installation and
Operations, August 2010-December 2011
1.0INTRODUCTION
Alaska Village Electric Cooperative, Inc. (AVEC) and NANA Development Corporation
(NANA) are evaluating the potential for hydroelectric power generation in the Cosmos
Hills region. The objective is to reduce diesel power generation in the communities of
Ambler, Shungnak, and Kobuk. Fuel delivery issues, primarily decreasing barge access
due to gravel bars and shallow water have caused these villages to have some of the
highest power generation costs in Alaska. In 2009, AVEC was awarded a Renewable
Energy Grant from the Alaska Energy Authority to evaluate nearby hydropower
resources. The project included evaluation of 12 potential hydroelectric sites in the
upper Kobuk River valley. Of these, four sites were selected for further evaluation:
Cosmos Creek, Wesley Creek, Dahl Creek, and the Kogoluktuk River (Figure 1). These
sites are appropriately scaled for local energy needs, are close to existing roads and
power-line infrastructure, and are run-of-river projects with less environmental impact
than large dam-storage hydroelectric projects.
With support from NANA, a hydrologic monitoring network was installed to record
weather and streamflow data on the three Cosmos Hills streams and the Kogoluktuk
River. Although the primary goal of the monitoring network is to evaluate the potential
for hydroelectric power generation, the resulting data can also be used for
environmental assessments, design of stream and river crossings, and for general
water-resource, climate, river-transportation, and weather-forecasting applications.
The hydrologic monitoring network includes the following:
Four gauging stations located at the four potential hydroelectric plant intakes;
Four water temperature monitoring stations located in potential tailraces;
Four ridge-top repeaters transmitting data and camera images to an Internet
base station at the Kobuk School;
2
Air temperature, relative humidity, and summer precipitation sensors at the four
stream gauging stations;
Time-lapse digital cameras at the four gauging stations and the Upper
Kogoluktuk River Winter Supplemental Station; and
Air temperature sensors at the four ridge-top repeater sites.
Figure 1. Map of Cosmos Hills Hydrologic Network. Some stations decommissioned in
Fall 2011.
In addition to the four gauging stations at the potential hydroelectric plant intakes, a fifth
gauging station was added at the Upper Kogoluktuk River Falls. This station was added
in an effort to improve the quality or winter flow measurements. Complex river-ice
formation at the Upper Kogoluktuk Station makes winter flows difficult to measure and
estimate. The narrow bedrock cross section and confined under-ice winter flows at the
supplemental station will make both winter discharge measurements and flow
estimation between measurements more reliable.
3
The data-collection procedures used for the project were reported in Lilly and Derry,
2010. The design and installation of the gauging stations and field data-collection
approach was intended to help answer the hydropower evaluation questions and start
the collection of baseline data that would be required by regulatory agencies under the
Federal Energy Regulatory Commission (FERC) process. Both engineering design and
environmental assessments require adequate understanding of summer and winter flow
conditions and variability between these seasonal extremes. Alaska Department of
Natural Resources, Alaska Department of Fish and Game, and multiple Federal
regulatory agencies reviewed the project workplan before field work began and
indicated the approach would meet their criteria for hydropower-related water-resource
investigations. This approach was intended to reduce the potential time required to
meet both engineering and environmental evaluations that would be required for project
development. Given the high cost of working in remote arctic environments, significant
future cost savings and a shorter development timeline would lead to beneficial
outcomes for the communities in the region.
1.1 NETWORK INSTALLATION OBJECTIVES
The installation objectives for the Cosmos Hills Hydrologic Network (Network) in August
2010 included the initial setup of data collection stations, stream surveying, discharge
measurements, water chemistry, and general hydrologic observations to start the
watershed characterization process. The primary interpretative goal of the project was
the development of rating curves for the stage discharge relationship at each of the
primary gauging stations. Secondary objectives included basic water-quality
characteristics, such as water temperature and conductivity. This information is useful
for baseline characterizations, and understanding the processes taking place in each of
the surface-water systems, such as groundwater contributions to base flow.
Additionally, the region is lacking in background meteorological observations, so the
current collection of meteorological data is important to understanding the weather
(short-term) and climate (long-term) factors that impact stream conditions and the
quality of stage and discharge data. The collection of precipitation (summer rainfall) and
4
snow measurement are particularly important for later hydrologic modeling and flow
frequency estimates, as well as permitting and future environmental compliance efforts.
1.2 BACKGROUND HYDROLOGY
The study area is located in the interior region of Alaska, on the southern flanks of the
Brooks Range, in the Kobuk River watershed. It is in a sub-arctic environment, in the
transition zone from continuous to discontinuous permafrost. The lower portions of the
drainages are a mixture of forest and tundra, while the upper ridges are primarily
bedrock exposures. The Cosmos Hills are bounded on the south by the Kobuk River, on
the north and west by the Ambler River and Lowlands, and on the east by the
Kogoluktuk River eastern watershed boundary. More detailed descriptions of the
watersheds will be provided in subsequent reports.
The USGS maintains gauge stations on Dahl Creek (No. 15743850) and on the Kobuk
River near Kiana (No. 15744500). Both of these gauges are active and have relatively
long periods of record (1986-present for Dahl Creek; 1976-present for the Kobuk River).
If results of the present study show good daily flow correlations, it may be possible to
generate synthetic streamflow records at the new gauging stations using historic
records at one or both of the USGS stations. This practice is termed “record extension”
and is commonly used to estimate flood frequency distributions and daily flow statistics.
Monthly summer data collection at the Dahl Creek USGS station began in 1986. By
1988 the USGS was reporting data for the whole summer period and by 1990 for the
complete water year (October 1 to September 30). The USGS Dahl Creek Station is
referred to as the Lower Dahl Creek station for this project, as it is downstream of the
other two stations established on Dahl Creek. The timing of flow events from year to
year will vary and has a direct impact on planning of field measurements. Figure 2
shows the mean daily mean discharge for Dahl Creek for the period of record. This plot
illustrates winter baseflow conditions which are typically are characterized by a slow
decline in flow. Spring snowmelt then increases discharge, followed by lower flow
conditions in early summer with late summer precipitation floods generally occurring in
5
August. Surface-water flow starts decreasing in September and continues to drop until
winter base flow conditions are reached in winter. Figure 3 shows the maximum, mean,
and minimum daily mean discharge for the period of record. This helps illustrate the
range in flow conditions over the period of record. Note the difference in the scales on
the y-axis for Figure 2 and Figure 3. The high daily mean flows are highest for early
snowmelt floods and late summer flooding with the highest discharge events (flooding)
occurring during late summer rainfall events. Timing of the snowmelt flood varies over
the period of a month or longer. This time period also illustrates the variability in
summer flow conditions that must be taken into account when planning a field
measurement program, or hydropower evaluations.
The mean and low daily mean discharge characteristics are important for hydropower
assessments. Figure 4 shows the mean and minimum daily mean discharge for Dahl
Creek USGS gauge for the period of record. It illustrates the range in low flow
conditions that can occur during summer months. Figure 5 shows the daily mean
discharge for 1999 through 2009 and illustrates the variability in flow conditions over the
last 11 years. Note the variability in timing of snowmelt breakup flooding events, which
are sensitive to the variability in spring weather conditions.
6
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0
20
40
60
80
100
120
140
Period of Record
USGS 15743850 Dahl Creek Gauge Near Kobuk
Figure 2. USGS Dahl Creek gauge mean daily mean discharge, in cubic feet per second.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0
250
500
750
1,000
1,250
1,500
Maximum Daily Mean Q
Mean of Daily Mean Q
Minimum Daily Mean Q
Period of Record
USGS 15743850 Dahl Creek Gauge Near Kobuk
Figure 3. USGS Dahl Creek gauge daily mean-discharge period-of-record range, in cubic
feet per second.
7
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0
25
50
75
100
125
150
Mean of Daily Mean Q
Minimum Daily Mean Q
Period of Record
USGS 15743850 Dahl Creek Gauge Near Kobuk
Figure 4. USGS Dahl Creek gauge mean and low daily mean discharges for the period of
record, in cubic feet per second.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0
100
200
300
400
500
600
700 2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
USGS 15743850 Dahl Creek Gauge Near Kobuk
Figure 5. USGS Dahl Creek gauge daily mean discharges for the 11-year period 1999
through 2009, in cubic feet per second.
8
The Lower Dahl Creek USGS Station is important in the Cosmos Hills region, as it
serves as a representative stream for south facing watersheds in the lower foothills. The
extent of the benefit from this station is dependent on the collection of supporting data
to help develop correlations with climate and hydrologic processes. The gauge has a
potential for serving as an index station for water-use permitting and hydropower
design. Instream water reservations for permitting normally require 4-5 years of data
collection. Correlation between the USGS gauging site and stations in the hydrologic
monitoring network may result in a shorter data collection period for permit applications,
depending on the correlations between surface-water systems. Collection of
comparative surface-water and meteorological data sets are critical for environmental
and engineering evaluations.
2.0PROCEDURES
The following sections describe the general procedures used during the reporting
period. As continued data collection activities are conducted, these procedures may be
changed to help meet current or future project objectives.
2.1 SITE SELECTION
The general site locations for the upper gauging stations in each of the study
watersheds were determined during preliminary hydropower assessments performed by
WH Pacific (2010). General locations of the plant intakes were identified, and then
gauging sites were selected that were at, or slightly upstream of, the location where flow
conditions appeared conducive for continuous stage measurements. The stability of
channel conditions and general site access was also taken into account for each
station. Downstream station locations were selected based on the location of potential
outlet structures for each hydropower plant. Water temperature was measured at, or
slightly downstream of, each intended discharge location from the planned hydropower
plants. The temperature data will be used to evaluate the baseline temperature
gradients in the streams during the anticipated hydropower-production season. Basic
hydrology observations will also be collected during station visits.
Canning
River
9
2.2 GAUGING STATION INSTALLATION AND OBJECTIVES
The data stations are solar and battery powered. Land use permitting applications and
associated documentation were prepared for AVEC and coordinated with their
permitting contractors. The data-collection platforms use Campbell Scientific equipment,
which is the standard used in a majority of the North Slope and western Alaska
hydrologic and climate networks. The primary data collection at each station is stream
stage, with supporting data collection including water temperature, air temperature,
relative humidity, and summer precipitation (unshielded). Early spring station visits will
be used to measure end-of-season snow conditions. The winter snowpack conditions
are important for both understanding the snowmelt flood hydrograph and summer base
flow conditions. There are currently no known snow measurements taking place in the
Cosmos Hills region.
Remote reporting of data provides cost savings in several areas, primarily in supporting
field logistics. Benefits are also gained by reducing data loss caused by animals,
flooding and other environmental factors. The station construction allowed operations
through winter and summer seasons, withstanding animal or other environmental
damage. A test of the station construction methods occurred in February 2011, when an
avalanche covered up the Upper Cosmos Station. The station continued to collect
stream water level and temperature data through the rest of the winter and during spring
snowmelt flooding at the avalanche area, even when most of the station was under
water. Real-time data reporting will also help support other logistical efforts in the area
and local communities. A base station is located at the local school in Kobuk, with radio
repeaters located on high ridges to allow communication to the gauging stations located
in stream and river drainages.
Field work in the project area is costly due to its remoteness and difficult logistics. The
Kobuk area is nearly two hours away from Fairbanks or over an hour away from
Kotzebue in a small plane. At least two of the gauging stations require helicopter access
(Cosmos Creek, Kogoluktuk River). Stations were accessed by field crews via
helicopters, ATVs, snowmachines or on foot. Over four hundred pounds of cabling,
10
conduit, batteries, photovoltaic panels and cameras were required at each station. Most
of the field stations were accessed by helicopter in the summer and by snow machine in
the winter. During the summer season, hydrologists were sheltered in huts at the Dahl
Creek camp. In the fall, winter and spring seasons, floor space at the school in the
village of Kobuk was utilized and had to be periodically vacated to accommodate school
sessions. Due to poor weather, there were times during field visits when the helicopter
was unable to fly and workers were on standby waiting to fly out to the sites. All of these
factors contributed to the expense of the remote hydrology fieldwork.
The data collection objectives at each of the primary gauging stations includes
parameters to measure surface-water stage, unshielded precipitation, bank
temperatures, shielded air temperature and relative humidity, and station diagnostics.
Detailed descriptions of the data collection parameters are available in Appendix G and
H for an example station. Each station uses the same data collection standards. The
only exception is that one station (Upper Cosmos Creek Station – discontinued) also
measures barometric pressure (NOT adjusted to sea level elevation for aviation
applications). Barometric pressure is generally a regional property and cost
considerations supported only one station having this measurement. Additionally, the
surface-water gauging stations include cameras to help record visual observations of
stream conditions, important for the general understanding of stream conditions, snow
and winter icing conditions, and support of transportation logistics. Additional data for
the sensor specifications and other station information is available on the project
website.
There are also repeater stations, used to help transmit data from the surface-water
stations (normally in low-lying areas) back to a base station in Kobuk. The repeater
stations also record shielded air-temperature and station diagnostics. The primary data
reporting period is during summer months. Station data is normally updated every 1 to 3
hours. Adverse weather, animal damage (bears, foxes, etc.) and other environmental
factors may impact station reporting. The Campbell data loggers provide 150 or more
11
days of onsite storage so no information is lost during periods when the telemetry
network is not functioning.
2.3 LEVATION SURVEYING AND WATER LEVEL MEASURMENTS
Local survey control, temporary benchmarks (TBM’s), and stream cross sections were
surveyed each field trip. The TBM’s were established during the station installations in
August 2010. Depending on ground conditions, benchmarks (generally rebar or bolts in
stream boulders) may move on a seasonal basis, so a set of three to five benchmarks
were installed at each site. TBM’s were established to provide multiple balanced shots
to help track potential seasonal movement of TBMs and make any required elevation
adjustment. Reference marks (RMs) were also established to primarily provide easy
measuring points for surface-water elevations at varying stage levels. Closed loop
surveying was used to measure any changes in TBMs and RMs during each station visit
in spring and summer months (Kennedy, 1990). Elevation-survey measurement forms
are included in Appendix A. Water-level measurements and adjusted gauge heights
made during the field trips in August and October 2010 and May, August, September,
and October 2011 are reported in Appendix B.
It is important to characterize stream cross-sections for establishing stream gauging
stations and rating curves. During the August 2010 field trip, cross-section surveys were
conducted at the Cosmos Creek, Dahl Creek, Wesley Creek, and Kogoluktuk River
Stations and during the August 2011 field trip a cross-section survey was conducted at
the Upper Kogoluktuk River Station. This data is reported in Appendix C. Cross-section
surveys include surveys perpendicular to the channel and surveys upstream and
downstream of the station to establish the water slope. Subsequent cross-section
surveys may be made as needed when signs of erosion or other changes are noted
during field visits.
2.4 WATER CHEMISTRY MEASUREMENTS
The general water-quality measurements made for this project include temperature and
conductivity. Appendix D reports the basic water-quality data measured at various creek
12
and river locations. The supporting water-quality meter calibration forms and resulting
quality assurance results are provided in Appendix E. Additionally the station data
collection systems measure and store water temperature information from the pressure
transducers and stream-bank thermistors. The downstream sites located near the
proposed hydropower outfalls use Hobo instream data loggers that measure stream
temperature. The Hobo sensors have to be manually downloaded during station visits,
or sensors are swapped with replacement sensors and downloaded at a later time. This
data is reported in Appendix M.
2.5 DISCHARGE MEASUREMENTS
Discharge measurements were performed using an acoustic doppler current profiler
(ADCP) and by conventional current meter methods. These techniques are described in
the following sections.
2.5.1 ACOUSTIC DOPPLER DISCHARGE MEASUREMENTS
Except for a low-flow measurement on October 15, 2010, all of the discharge
measurements on the Kogoluktuk River were performed using either a 2.0 kHz
StreamPro or a 3.0 kHz Sontek RiverCat ADCP. Both of these devices are designed for
shallow-water operation, with a maximum depth range of about 17 feet. The ADCP
integrates water depths and velocities along transects extending from bank to bank,
and computes a total discharge for each transect. Measurement of multiple transects
improves the accuracy of each measurement and allows evaluation of overall
measurement precision.
Whereas Sontek’s data acquisition software accepts both bottom-track and GPS
positioning, the StreamPro software accepts only bottom-track positioning. For the
Sontek ADCP, a Geneq differential GPS (DGPS) receiver was used to collect position
information via the Federal Aviation Administration’s Wide Area Augmentation System
(WAAS). Poor satellite reception prevented accurate WAAS positioning during the
August 2010 trip therefore ADCP measurements relied solely on bottom-track
positioning, however the clear water and shallow depth of each transect (less than 4.5
13
feet) permitted visual observation of the sand to cobble-sized bed material. No bed
movement was observed (nor is expected) based on the water velocities and bed
materials encountered.
The Sontek ADCP was not available for the May 2011 measuring event. As a result, the
StreamPro was used, and each discharge measurement was accompanied by a loop
moving bed test. Although the StreamPro provided acceptable results on May 28 and
May 30, higher flows on May 23 and May 25, 2011 resulted in signal loss due to
excessive turbidity and/or bed motion. As a result, the May 23 and May 25 discharge
measurements were not usable. In the future, GPS positioning could help reduce ADCP
data loss during spring breakup flow measurements.
Upon completion of the ADCP measurements, the data were reviewed for internal
consistency and acceptable precision measures. A subsequent office review included
the following:
Reprocessing of each transect to confirm that the proper edge distances,
transducer depths, and stream temperatures were used;
Review of each transect to identify lost or invalid ensembles;
Review of ship tracks and velocity vectors to identify bottom-track positioning
problems;
Moving bed test processing and corrections; and
Comparison of multiple transects to evaluate precision.
2.5.2 CURRENT METER DISCHARGE MEASUREMENTS
Following procedures outlined by Rantz, et al., (1982), discharge measurements on
Cosmos Creek, Wesley Creek, and Dahl Creek were made using conventional current
meter methods. A surveyor’s tape was used to divide the stream width into at least 25
partial vertical sections (termed “verticals”). The widths of the verticals were spaced
such that no vertical contained more than 10 percent of the total discharge. For depths
less than 2.5 feet, the velocity was measured at 60 percent of the water column height,
and for depths over 2.5 feet the velocity was measured at 20 and 80 percent of the
water column height. The velocity measurements were made with a Marsh-McBirney
14
Flow Mate 2000 flow meter mounted on a top-setting wading rod. Water depths were
recorded to the nearest 0.05 feet.
2.6 SNOW SURVEY MEASUREMENTS
Snow is an important part of the hydrologic cycle in the Cosmos Hills. Very few if any
historical snow measurements exist. The development of baseline snow conditions
began in March 2011, with the first spring snow surveys made for this project. Snow
surveys are conducted by selecting sites that will help define the regional snow
distribution. These would include sites in forested, tundra, and open environments. A
typical site involves performing a snow-course, which includes collecting snow depth as
well as snow density, using a method sometimes referred to as “double sampling”.
Snow-course data collected for the Cosmos Hills Hydrologic Project follows procedures
as described by Derry, et al., 2009. Snow-depth measurements are performed in “L”
shaped patterns with a T-handle probe approximately every 3.3 ft (1 m) for 82 ft (25 m),
then turning 90 degrees, and continuing for another 82 ft (25 m). Five snow density
samples are collected with an Adirondack snow sampler at each site. To calculate
average snow water equivalent (SWE) for a snow-course, the average of 50 snow
depths are multiplied by the average of 5 snow density samples. The heterogeneous
Arctic snowpack is more variable in depth than in density (Benson and Sturm, 1993);
hence, more depth-measurement locations are required relative to density-
measurement locations.
15
3.0SITE DESCRIPTIONS
This section describes the locations and general characteristics of each of the stations
in the network. Table 1 lists the general elevations, latitude and longitude for each
station. The table also lists the series of stations discontinued in September 2011. The
elevations were measured with GPS units and not tied into any local datum control.
Table 1. Surface-Water, Repeater, and Base Station Locations.
Station Elevation
North
Latitude
West
Longitude
Ft NAD 83 NAD 83
Upper Wesley Creek Station 615 66° 58.945’ 156° 58.824’
Lower Wesley Creek Station 260 66° 57.235’ 157° 01.364’
Lower Dahl Creek USGS Station 244 66° 56.737’ 156° 54.795’
Upper Kogoluktuk River Station 321 66° 59.706’ 156° 41.969’
Upper Kogoluktuk River Falls Station 339 66° 59.151’ 156° 41.531’
Lower Kogoluktuk River Station 279 66° 58.965’ 156° 41.862’
Wesley Creek Repeater Station 2010 66° 59.744’ 156° 59.880’
Kogoluktuk River Repeater Station 1707 66° 57.096’ 156° 47.888’
Kogoluktuk Falls Repeater Station 320 66° 59.225’ 156° 41.535’
Kobuk Base Station 147 66° 54.482’ 156° 52.997'
Stations Discontinued in September 2011
Upper Cosmos Creek Station 684 67° 00.287’ 157° 06.534’
Lower Cosmos Creek Station 336 66° 58.836’ 157° 11.170’
Upper Dahl Creek Station 405 66° 57.628’ 156° 52.950’
Middle Dahl Creek Station 287 66° 57.019’ 156° 54.217’
Cosmos Creek Repeater Station 1629 66° 59.421’ 157° 07.022’
Dahl Creek Repeater Station 1850 66° 57.919’ 156° 51.055’
Data plots for the stations are also available on the project website. Figure 6 is an
example of the datalogger panel temperature, battery bank voltage for the station, and
solar panel output voltage. This graph is for the Upper Wesley Creek Station and is
representative of the other creek stations. The data indicates the station battery banks
stayed at a high charge capacity during winter months and solar charging started to
increase in February and was meeting the daily energy consumption in March. When
16
the battery banks are fully charged (will not accept additional amps), the solar panel
voltages will exceed 20 volts during clear sky conditions.
Figure 6. Website plotting example of data logger temperature, battery bank voltage and
solar panel output voltage for the Upper Wesley Creek Station.
3.1 UPPER COSMOS CREEK STATION
The Upper Cosmos Creek Station was located in the upper portion of the Cosmos
Creek watershed, at an approximate elevation of 684 feet above sea level. The station
was located on the west bank of the creek, also called the “right bank” as viewed by an
observer looking in the downstream direction. The station was located a few hundred
feet to the east and southeast of the primary helicopter landing zone. The general
channel conditions appear to be well anchored cobbles and boulders. Some boulders
are over 3 feet (~1 meter) in diameter. There is brushy vegetation along both banks and
signs of overflow channels in the right overbank area. The left bank is located against a
talus slope from the adjacent Cosmos Mountain. The stage levels were measured in the
creek just upstream from the large rock shown in Figure 7. The survey control points
17
were located both upstream and downstream of the station location. The discharge
measurement locations varied upstream and downstream based on flow conditions at
specific water level conditions. This station was discontinued in September 2011.
Additional station information is available on the following Internet link:
http://www.cosmoshydro.org/stations/UCosmosCrk/
Figure 7. Site picture of the Upper Cosmos Creek Station (8/18/10, M. Lilly). The station
was located on the west bank and the picture is looking upstream.
3.2 LOWER COSMOS CREEK STATION
The Lower Cosmos Creek Station was located on the east bank (left-hand bank), just
downstream of a regional trail (Figure 8). The location was chosen on a deep cut bank
so that there would be a greater chance of the sensor being under ice and not frozen in
during winter months. The general stream conditions are well mixed so the temperature
data should be representative of the general stream reach. There is thick vegetation on
both sides of the stream and the stream bed is primarily composed of gravel and
cobbles. Data collection at this station used a Hobo stream temperature sensor and
18
manual general stream observations. There was no real-time reporting from this station.
This station was discontinued in September 2011.
Figure 8. Site picture of the Lower Cosmos Creek Station, looking downstream from east
bank (8/18/10, M. Lilly).
3.3 UPPER WESLEY CREEK STATION
The Upper Wesley Creek Station is located just upstream of the Bornite Road bridge
crossing. The station is on the west (right) bank (Figure 9). Stage levels are measured
in a pool on the west side of the creek. Survey control is primarily on the west bank. The
general discharge measurement location is just downstream of the station. The west
bank is fairly high above creek water levels and the right bank will be underwater during
flood events. There are thick alders on both banks, with some birch intermingled. There
are some large boulders along the creek edges, but less than in Cosmos Creek. The
general bed material is composed of gravels and cobbles. Additional station data is
available at the following Internet site:
http://www.cosmoshydro.org/stations/UWesleyCrk/
19
Figure 9. Site picture of the Upper Wesley Creek Station, looking across the stream from
the west bank (8/20/10, M. Lilly).
3.4 LOWER WELSEY CREEK STATION
The Lower Wesley Creek Station is located on the west bank (right-hand bank), just
downstream of a regional trail and old 4-wheeler bridge (Figure 10). The location was
chosen on a deep cut bank (center of photograph) so that there would be a greater
chance of the sensor being under ice and not frozen in during winter months. The
general stream conditions are well mixed. There is thick vegetation and scattered
spruce trees on both sides of the stream and the stream bed is primarily composed of
gravel and cobbles. Data collection at this station uses a Hobo stream temperature
sensor and manual general stream observations. There is no real-time reporting from
this station.
20
.
Figure 10. Site picture of the Lower Wesley Creek Station, looking downstream from an
old bridge on a regional trail (8/21/10, M. Lilly).
3.5 UPPER DAHL CREEK STATION
The Upper Dahl Creek Station was located in the middle portion of the Dahl Creek
watershed, at an approximate elevation of 405 feet above sea level. The station was
located on the west bank (right-hand bank) of the creek. The station was also located
downstream of Wye Creek, which is approximately 1 mile upstream of the station. The
general channel conditions appear to be well anchored cobbles and boulders. Some
boulders are over 3 feet (~1 meter) in diameter. There is thick brushy vegetation along
both banks with scattered birch and spruce trees. The east bank is located against a
talus slope from the adjacent southern ridge of Asbestos Mountain. The survey control
points were located on the west bank near the station and also downstream of the
station location. The discharge measuring locations were downstream of the station and
varied in location based on flow conditions at specific water levels. This station was
21
discontinued in September 2011. Additional station information is available on the
following Internet link:
http://www.cosmoshydro.org/stations/UDahlCrk/
.
Figure 11. Site picture of the Upper Dahl Creek Station looking downstream from the
station on the west bank (8/12/10, M. Lilly).
3.6 MIDDLE DAHL CREEK STATION
The Middle Dahl Creek Station was located on the west bank (right-hand bank), just
downstream of a bend and clearing along the creek (Figure 12). The location was
chosen on a deep cut bank so there would be a greater chance of the sensor being
under ice and not frozen in during winter months. The general stream conditions are
well mixed so the temperature data should be representative of the general stream
reach. There is thick vegetation and abundant spruce trees on both sides of the stream
and the stream bed is primarily composed of gravel and cobbles. Data collection at this
station used a Hobo stream temperature sensor and manual general stream
observations. There is no real-time reporting from this station. The USGS Dahl Creek
22
gauge is located downstream of this location. This station was discontinued in
September 2011.
.
Figure 12. Site picture of the Middle Dahl Creek Station, looking south and downstream
(8/21/10, M. Lilly).
3.7 UPPER KOGOLUKTUK RIVER STATION
The Upper Kogoluktuk River Station is located in the lower portion of the Kogoluktuk
River watershed, at an approximate elevation of 321 feet above sea level. The station is
located on the east bank (left-hand bank) of the river. The station is also located
downstream of the Ambler Lowlands and upstream of the Kogoluktuk Falls reach. The
east bank is higher and steeper than the west bank. There is thick brushy vegetation
along both banks with scattered birch and spruce. There are also areas of black spruce
indicating poorly drained or shallow permafrost soils. The station is located east of
Asbestos Mountain. The survey control points are located on the east bank near the
station and upstream and downstream of the station location. Some survey control
points are located down the steep eastern bank. The discharge measuring locations are
23
near the station or upstream and may vary in location based on flow conditions at
specific water levels. Additional station information is available on the following Internet
link:
http://www.cosmoshydro.org/stations/UKogoRvr/
Figure 13. Site picture of the Upper Kogoluktuk River Station, taken on the east bank, and
looking slightly upstream (8/18/10, M. Lilly).
3.8 UPPER KOGOLUKTUK FALLS WINTER SUPPLEMENTAL
STATION
The Upper Kogoluktuk Falls Winter Supplemental Station is located in the upper portion
of the Kogoluktuk River watershed, at an approximate elevation of 339 feet above sea
level. This station was established in October 2011 to help collect data for winter flow
conditions on the Kogoluktuk River. The bedrock-controlled channel concentrates the
winter under-ice flow into a single channel. The station is located on the east bank (left-
hand bank) of the river. The station is also located downstream of the Upper Kogoluktuk
River Station and is the upstream end of the Kogoluktuk Falls reach. Both banks are
24
high, with bedrock exposures, swept clean during spring breakup flooding when the
channel is packed with ice jams. There is thick brushy vegetation along both banks with
scattered birch, spruce and black spruce trees. The station is located east of Asbestos
Mountain and Northeast of Kobuk. The survey control points are located on the east
bank near the station and upstream of the station location. Some survey control points
are located down the steep eastern bank. The discharge measuring locations are near
the station or upstream and may vary in location based on flow conditions at specific
water levels. Additional station information is available on the following Internet link:
http://cosmoshydro.org/stations/KogoFalls
Figure 14. Site picture of the Upper Kogoluktuk Falls Repeater Station (9/30/11, M. Lilly).
25
3.9 LOWER KOGOLUKTUK RIVER STATION
The Lower Kogoluktuk River Station is located on the west bank (right-hand bank), just
downstream of the upper falls area (Figure 15). The location was chosen on an outside
bank so that there would be a greater chance of the sensor being under ice and not
frozen in during winter months. The general river conditions are well mixed so the
temperature data should be representative of the general river reach. There are large
bedrock exposures on both sides of the river. The riverbed in this reach is likely a mix of
bedrock, boulders and gravel. Data collection at this station is with a Hobo stream
temperature sensor and manual river observations. There is no real-time reporting from
this station.
Figure 15. Site picture of the Lower Kogoluktuk River Station, looking downstream from
the west bank (8/18/10, M. Lilly).
26
4.0SELECTED RESULTS AND DISCUSSION
This section provides a summary of data collected during the 2010-2011 reporting
period. The primary goal of this project is to develop rating curves for gauging stations
installed on the four streams selected for hydropower evaluations. Improved rating
curves and more detailed interpretations will be possible after completion of the 2012
field season. Additional data is available on the project website
(www.cosmoshydro.org), and appendices following the text of this report provide a
summary of manual measurements collected during the field program.
4.1 DISCHARGE MEASUREMENTS
The following section summarizes results for discharge measurements performed using
conventional current meter and acoustic Doppler measurement methods. Salt dilution
methods were also attempted on Dahl and Cosmos Creeks, but better precision was
obtained using current meter methods (see below). Flow conditions were adequate for
current meter measurements on each of the small creeks, and during low-flow
conditions (October 2010) on the Kogoluktuk River.
The August 2010 and October 2010 discharge measurements on the Kogoluktuk River
were performed at the location shown on Figure 16. Due to the presence of shore ice in
the vicinity of the gauge, the October 2010 stage measurements on Cosmos Creek and
the Kogoluktuk River could have been ice-affected and were not used. High-flow ADCP
measurements on May 23 and May 25, 2011 could not be used due to excessive signal
loss, subsequent ADCP measurements on May 28 and May 30 yielded acceptable
precision values (2.0 to 2.9 percent).
A summary of discharge measurements is shown in Table 2, indicating that the average
precision of current meter measurements was 1.7 percent, and the average precision of
ADCP measurements was 3.0 percent. All of the current meter measurements satisfied
the USGS criterion of no more than 10 percent of the total discharge within any partial
vertical section.
27
Figure 16. 2010 Discharge measurement locations, Kogoluktuk River.
Comparison of ADCP discharge values based on bottom-track vs. GPS positioning
indicate that moving bed conditions occurred only during spring breakup on the
Kogoluktuk River. Correction of bottom-track discharge measurements using the loop
moving bed test (Mueller and Wagner 2009) yielded reasonable moving bed velocities
(0.15-0.2 ft/s) and acceptable precision values (< 2.9 percent).
28
Table 2. Summary of discharge measurements.
Station Date, Time
Water Surface
Elevation Method Q, cfs Precision (%)
Upper Dahl
Creek
8/11/10 14:15 91.08
Current meter
37.6
8/11/10 15:15 91.09 39.4
8/11/10 16:00 91.14 52.7
10/13/10 16:40 90.75 16.4
5/29/11 13:55 91.61 103 1.5
5/30/11 17:15 91.49 87.9 2.8
8/11/11 12:37 91.17 46.7 0.7
9/20/11 15:35 91.12 43.4 1.2
Upper
Wesley Creek
8/13/10 16:45 91.49
Current meter
27.1 1.6
10/14/10 15:40 91.30 9.5 2.7
5/20/11 13:30 91.53 36.5
5/20/11 14:20 91.54 40.4
5/24/11 12:30 91.70 65.5
5/24/11 14:00 91.78 78.7
5/29/11 16:25 91.72 65.3
5/29/11 17:15 91.73 64.9
8/10/11 18:15 91.57 34.1
9/20/11 12:40 91.50 24.5 3.2
Upper
Cosmos
Creek
8/13/10 11:30 97.05
Current meter
41.3 1.4
10/14/10 13:35 96.59 13.2 0.4
5/27/11 13:30 97.50 124
5/27/11 14:20 97.53 131
5/30/11 13:45 97.24 82.4 2.3
8/10/11 12:30 97.16 64.1 0.5
9/23/11 11:50 96.89 31.7
Upper
Kogoluktuk
River
8/14/10 17:15 85.15 ADCP 1,623 4.8
10/15/10 13:00 86.00 Current meter 335
5/28/11 13:03 86.67 ADCP 5,614 2.9
5/28/11 14:12 86.62 ADCP 5,232 2.0
5/30/11 10:03 86.08 ADCP 3,789 2.7
8/9/11 15:09 85.07 ADCP 1,588 0.8
9/19/11 17:37 84.62 ADCP 921 4.7
4.2 STREAMFLOW COMPUTATIONS
Computation of daily streamflows was accomplished using corrected stage data and
preliminary rating curves developed for each station. The following sections describe
the correction of pressure transducer data, rating curve development, and computation
of daily streamflows.
29
4.2.1 CORRECTION OF PRESSURE TRANSDUCER DATA
Pressure transducer readings are converted to stream stage by adding an “offset” so
that the sum of the transducer reading and the offset equals the surveyed water surface
elevation. If the pressure transducer is moved, the offset is changed so that the
calculated stage equals the surveyed water surface elevation. Similarly, the effect of
transducer “drift” can be removed by changing the offset values so that the calculated
stage equals the surveyed water surface elevation. These corrections were performed
using the Aquarius Workstation, a commercial software package designed for
streamflow computations. Aquarius data files for each gauging station are archived with
project records. These files contain a record of all of the corrections performed on each
data set. The following sections summarize corrections performed on transducer data
from each gauging station.
30
Upper Dahl Creek Station. Figure 17 shows the raw and corrected stage data for the
Upper Dahl Creek Station. The corrected data is initially based on pressure transducer
no. 1 (PT1), but switches to PT2 on October 17, 2010. The PT2 record is fairly “clean”,
requiring only a minor drift correction during the summer of 2010. Several pressure
spikes were removed during the winter months, which are assumed to reflect ice
formation on the transducers.
Figure 17. Raw and corrected stage data for the Upper Dahl Creek Station.
31
Upper Wesley Creek Station. Figure 18 shows the raw and corrected stage data for
the Upper Wesley Creek Station. The corrected data is based on records from PT2,
with minor drift corrections after October 2010. A few pressure spikes were removed
during the winter months, which are assumed to reflect ice formation on the
transducers.
Figure 18. Raw and corrected stage data for the Upper Wesley Creek Station.
32
Upper Cosmos Creek Station.Camera images, transducer records, and field visits
indicate that the Cosmos Creek gauge height was ice-affected from about October 1,
2010 until May 2011. In addition, the gauging section was struck by an avalanche on
February 23, 2011, resulting in temporary damming until a flow conduit melted through
the avalanche debris. Upon the first field visit in May 2011, overflow channels were
melted in the avalanche debris, indicating that breakup gauge heights were affected by
snow damming.
The stage hydrographs for Dahl and Wesley Creeks both exhibit smooth recession
curves from September 2010 through May 2011 (Figures 16 and 17). Although the
stage record for Cosmos Creek was affected by ice cover and avalanches, it is
reasonable to assume that the flow hydrograph should show a similar recession. As a
tool to estimate winter flows, a synthetic winter stage hydrograph was drawn mimicking
those for Dahl and Wesley Creeks (Figure 19). The synthetic winter stage record has
no physical significance other than as a tool to estimate winter flows.
Figure 19. Raw and corrected stage data for the Upper Cosmos Creek Station.
33
No attempt was made to estimate the breakup stage hydrograph for Cosmos Creek.
Due to its larger basin area, breakup flows were probably higher than those for Wesley
and Dahl Creeks. However, there is no way to eliminate the effect of snow damming
caused by avalanche debris on the breakup stage record.
The corrected stage data for Cosmos Creek is based on records from PT1, which was
replaced by PT2 after the 2011 breakup. Aside from the synthetic winter hydrograph
and the missing breakup hydrograph, only minor drift corrections were applied to the
2011 stage record.
Upper Kogoluktuk River Station. Camera images, transducer records, and field visits
indicate that the Kogoluktuk River gauge height was ice-affected from about October 1,
2010 until late May 2011. During the first field visit on May 23, 2011, stranded ice
blocks indicated that the breakup stage hydrograph was probably affected by ice
jamming.
Like the stage hydrographs for Dahl and Wesley Creeks, the mean daily discharge
hydrograph for the Kobuk River near Kiana (USGS Station No. 15744500) shows a
smooth recession curve from October through May of the following year. Although the
stage record for the Kogoluktuk River was affected by ice, it is reasonable to assume
that the flow hydrograph exhibits a similar recession. As a tool to estimate winter flows,
a synthetic winter stage hydrograph was drawn mimicking those for Dahl and Wesley
Creeks (Figure 20).
34
Figure 20. Raw and corrected stage data for the Upper Kogoluktuk River Station.
No attempt was made to estimate the breakup stage hydrograph for the Kogoluktuk
River. Without flow measurements, there is no way to eliminate the effect of ice jams on
the stage record during breakup.
The corrected stage data for the Kogoluktuk River is based on records from PT1, which
was replaced after the 2011 breakup. In addition to the synthetic winter hydrograph and
the missing breakup hydrograph, several offset and drift corrections were applied to the
2011 stage record.
35
4.2.2 PRELIMINARY RATING CURVE DEVELOPMENT
Rating curves were developed for each station to allow computation of discharge from
corrected stage records. Assuming steady and uniform flow, the rating equation can be
developed from Manning’s equation for open-channel flow:
Q=C(G-e)
where:
Q = discharge,
C = a coefficient mainly controlled by channel width and bed roughness,
G = gauge height,
e = an offset that relates gauge height to hydraulic head, and
= an exponent mainly controlled by channel geometry.
With field measurements of Q and G, the rating equation contains three unknowns,
which require solution by numerical optimization. Without constraints on the realistic
ranges of C, e, and , an equally-good fit of Q and G can be obtained for a wide variety
of parameter values. Within the range of measurement, inaccurate parameter values
may have only a minor effect on the overall goodness-of-fit. However, when the rating
equation is extrapolated to high and low flows, unrealistic parameter values can result in
significant computation errors. Although no low flow measurements have been
performed, low flow estimates are needed to prioritize further field work. These
estimates were developed by rating curve extrapolation, using care to ensure that
parameter values were within reasonable limits.
With choice of the correct gauge offset (e), measurements of flow vs. (G - e) should plot
as a straight line in bilogarithmic space. The gauge offset is further constrained by the
elevation of zero flow, which should approach the lowest gauge offset. If there is a
breakpoint in the rating, the gauge offset should be larger at higher flows.
The exponent varies between about 1.3 and 3.0, depending on the shape and
length of the control. The exponent is typically lower for rectangular than for v-shaped
36
channels, and should increase with channel complexity. Higher exponents can also
result from failure to conform to the steady, uniform flow assumption.
The coefficient C carries information regarding the slope, roughness, and channel
complexity. V-shaped channels should have larger coefficients than rectangular
channels. With realistic values for a and e, C can be determined by curve-fitting.
The following sections discuss the rating curves obtained for each gauging station.
Upper Dahl Creek Station. A preliminary rating for the Upper Dahl Creek Station is
illustrated in Figure 21, based on eight flow measurements ranging from 16.4 to 103 cfs.
One flow measurement on August 12, 2010 was not honored, possibly due to unsteady
flow conditions resulting from heavy rain. A gauge offset of 89.81 feet results in a linear
plot in bilogarithmic space, and is consistent with the elevation of the downstream
control. The rating exponent (2.824) is also consistent with a laterally confined, bouldery
control. Extrapolation of the rating curve to the highest and lowest gauge heights results
in maximum and minimum instantaneous flows of 290 and 2.1 cfs, respectively. The
maximum and minimum mean daily flows are 209 and 2.2 cfs, respectively, which show
reasonable agreement with the maximum and minimum mean daily flows for the Lower
Dahl Creek Station (224 and 2.5 cfs; USGS No. 15743850). Except for some short
pressure spikes, the 2011 winter gauge record at the Upper Dahl Creek Station does
not require correction for ice effects, as is necessary at the Lower Dahl Creek station
(USGS No. 15743850). This is probably due to the relatively confined cross section at
the upper Dahl Creek gauge pool (Figure 22).
37
Figure 21. Preliminary rating for the Upper Dahl Creek Station.
38
Figure 22. Surveyed cross section at the Upper Dahl Creek Station.
Upper Wesley Creek Station. A preliminary rating for the Upper Wesley Creek Station
is illustrated in Figure 23, based on ten flow measurements ranging from 9.5 to 79 cfs. A
gauge offset of 90.97 feet results in a linear plot in bilogarithmic space, but yields
unrealistically low flows (< 0.1 cfs) at the lowest observed gauge height (90.95 feet on
May 12, 2011). Camera images suggest flows on the order of 1-2 cfs during this
timeframe, which is consistent with the ratio of annual minimum to October 15th flows on
nearby measured streams (Figure 24). As a result, a breakpoint was added and a
smaller exponent was used to obtain higher minimum flows.
39
Figure 23. Preliminary rating for the Upper Wesley Creek Station.
Figure 24. Ratios of annual minimums to flows on the previous October 15.
40
Although no data supports the lower rating curve segment, the gauge offset (90.97 feet)
and the rating exponent (2.485) for the upper segment are consistent with the control
geometry (Figure 25). Extrapolation of the rating curve to the highest and lowest gauge
heights results in maximum and minimum instantaneous flows of 590 and 1.4 cfs,
respectively, and a maximum mean daily flow of 237 cfs. Although the maximum
instantaneous flow is higher than that for upper Dahl Creek (290 cfs), the mean annual
flow for upper Wesley Creek is 70 percent of that for upper Dahl Creek. This compares
favorably with the ratio of basin areas (67 percent). The lower peak flow for upper Dahl
Creek may be related to the elongated shape of the Dahl Creek watershed as
compared with the Wesley Creek drainage basin.
Figure 25. Surveyed cross section at the Upper Wesley Creek Station.
41
Upper Cosmos Creek Station. A preliminary rating for the Upper Cosmos Creek
Station is illustrated in Figure 26, based on seven flow measurements ranging from 31.7
to 131 cfs. One flow measurement on October 14, 2010 was not honored due to ice
effects. A gauge offset of 90.97 feet results in a linear plot in bilogarithmic space, but
yields unrealistically high flows at low gauge heights, even when October 2010 ice
effects are removed (Figure 19). As a result, a breakpoint was added and a smaller
offset applied to gauge heights below 96.8 feet.
Figure 26. Preliminary rating for the Upper Cosmos Creek Station.
42
Figure 27. Surveyed cross section at the Upper Cosmos Creek Station.
Although no data supports the lower rating curve segment, the gauge offset (96.14 feet)
and the rating exponent (2.296) for the upper segment are consistent with the control
geometry (Figure 27). Extrapolation of the rating curve to the lowest synthetic gauge
height results in flows consistent with the ratio of annual minimum to October 15 flows
on nearby measured streams (Figure 24). The rating curve was not extrapolated to the
highest gauge heights due to snow damming caused by avalanche debris.
Upper Kogoluktuk River Station. A preliminary rating for the Upper Kogoluktuk River
Station is illustrated in Figure 28, based on six flow measurements ranging from 921 to
5,614 cfs. One flow measurement on October 15, 2010 was not honored due to ice
effects. A gauge offset of 82.60 feet results in a linear plot in bilogarithmic space, and
43
both the gauge offset and the rating exponent (2.568) are consistent with the complex
channel cross-section (Figure 29). To obtain annual minimum flows consistent with
Figure 24, a breakpoint was added and a smaller offset applied to gauge heights below
84.54 feet. Parameter values for the lower segment have little meaning because stage
hydrograph is synthetic below the assumed breakpoint.
Extrapolation of the rating curve to the lowest synthetic gauge height results in flows
consistent with the ratio of annual minimum to October 15th flows on nearby measured
streams (Figure 24). The rating curve was not extrapolated to the highest gauge heights
because they probably reflect ice jams during spring breakup.
Figure 28. Preliminary rating for the Upper Kogoluktuk River Station.
44
Figure 29. Surveyed cross section at the Upper Kogoluktuk River Station.
4.2.3 MEAN DAILY FLOW COMPUTATIONS
Mean daily flows were computed with the Aquarius Workstation using the rating curves
and corrected stage records described above. Mean daily flows are tabulated in
Appendix L, and the corresponding hydrographs are shown in Figure 30.
4.2.4 STREAMFLOW MEASUREMENT DISCUSSION
In contrast with the U.S. Geological Survey’s Lower Dahl Creek Station (no. 15743850),
winter stage hydrographs at the upper Dahl and upper Wesley Creek stations exhibited
only brief pressure spikes during periods of extreme cold. Upon return to more
moderate winter temperatures, both stage hydrographs reverted to a gradual recession
curve (Figure 30). This behavior is interpreted as pressurized flow beneath ice cover
45
during cold snaps, followed by open-water conditions beneath ice cover as the stream
stage continues to decline. Based on the stage hydrographs, it appears that the wetted
perimeter beneath ice cover was largely ice-free, allowing extrapolation of the rating
curves to winter low-flow conditions.
Although 2011 winter flows for the Kobuk River at Kiana (USGS Station no. 15744500)
are estimated at a constant 1,500 cfs from February 10 to May 7, the 31-year mean flow
shows a smooth recession curve matching those for Dahl and Wesley Creeks (Figure
30). This suggests a regional relationship that may be applicable to other streams.
Although no winter flow measurements are available to confirm them, winter flows for
Cosmos Creek and the Kogoluktuk River were estimated by mimicking the recession
curves for Dahl Creek, Wesley Creek, and the 31-year record on the Kobuk River.
Specifically, annual minimum flows for Cosmos Creek and the Kogoluktuk River were
estimated at 14 percent of flow on the preceding October 15th, which represents the
average value for the Kobuk River record. Inspection of the resulting hydrographs
suggests that the Kogoluktuk’s actual minimum flow might be higher than the resulting
50 cfs, perhaps due to unusually low flows on October 15, 2010.
Additional high-flow measurements will be needed to confirm the estimated peak flow
for Wesley Creek (590 cfs), provided that the Upper Wesley Creek Station rating
remains stable. The estimated peak flow for upper Dahl Creek (290 cfs) agrees with
daily flows for the Lower Dahl Creek USGS station (no. 15743850). Estimated peak
flows were not obtained for Cosmos Creek and the Kogoluktuk River, where the stage
records were affected by ice jams and avalanche debris.
Although the upper Cosmos and upper Dahl Creek stations have been
decommissioned, winter low-flow measurements are needed to confirm the rating curve
on Wesley Creek, and the recession curve for the Kogoluktuk River. If ice cover
prevents open-water discharge measurements, salt dilution could be used on Wesley
Creek, and dye dilution could be used at the Upper Kogoluktuk Supplemental Station.
46
Both techniques require thorough mixing, which would be possible at the Upper
Kogoluktuk Falls and in the rapid above the Upper Wesley Creek Station.
If peak flow measurements are needed for the Kogoluktuk River, these will require
direct ADCP measurements using GPS positioning. With ADCP measurements on both
limbs of the breakup hydrograph, it should be possible to estimate the peak flow if ice
prevents direct measurement.
Figure 30. Mean Daily Hydrographs.
4.3 WATER TEMPERATURE MEASUREMENTS
Understanding baseline water temperature conditions is important for evaluating any
type of hydropower development.
4.3.1 WATER TEMPERATURE RESULTS
We measured water temperature at the primary gauging sites and locations
downstream in each of the three creeks and the Kogoluktuk River. The locations are at
the approximate discharge points for early designs of the hydropower infrastructure.
47
Examples of stream temperature data for the lower stations (Figure 31), upper stations
(Figure 32), and the Upper Kogoluktuk River Station (Figure 33) follow.
The Kogoluktuk River temperatures are warmer than the three creeks until the onset of
winter. In early winter, the temperature relationship is changed and the Kogoluktuk
River water temperatures are colder at the downstream station. This change in
temperature relationship is likely due to the differences in groundwater inflow to the
streams, versus the upstream surface-water exposure to atmospheric warming. The
drop in the temperature below freezing at the Lower Kogoluktuk River Station in
October may be related to short-term freezing of the sensor in river ice. The data also
shows the sensitivity of the surface-water systems to diurnal temperature warming. The
summer temperatures are more similar between Cosmos Creek and Wesley Creek, with
Dahl Creek generally having colder temperature conditions.
48
Figure 31. Water-temperature data from the time of installation to the September 2011
field trip for the series of downstream stations.
49
Figure 32. Water-temperature data (15 minute averages) from the time of installation to
February 2012, for the series of upstream stations.
50
Figure 33. Water-temperature data from the time of installation to February 2012, for the
Upper Kogoluktuk River Station.
4.4 SPRING SNOW MEASUREMENTS AND FIELD OBSERVATIONS
The general snow conditions were fairly uniform at sites measured during the March
2011 field trip, Figure 34. In the lower slopes of the Cosmos Hills and the North-South
transect up Wesley Creek and Ruby Creek, the snow conditions were fairly uniform.
The snow conditions at the upper ridges were noted to be more wind packed and have
thinner snow cover. The average density at seven snow-course sites (Table 3) during
the March field trip ranged from 0.22 – 0.26 g/cm
3, which indicate very homogenous
snowpack conditions. Due to this consistency in density, as well as traveling and
sampling time constraints, at three sites (Kogoluktuk River-Forest, Wesley Creek-SC1,
and Wesley Creek-SC5) only snow-depth measurements were collected in order to
ensure adequate time to collect a greater spatial coverage of snow depth. SWE was
51
calculated for the three sites where density was not collected by taking the average
density from nearby representative (in terms of general landscape and vegetation type)
snow-course sites. The SWE ranged from 6.4 inches H 2 O (16.2 cm) to 12.8 inches H 2 O
(32.6 cm) with an area average of 10.1 inches H 2 O (25.7 cm). The average snow depth
for the study area was 43.0 inches (109.2 cm). The average density for all sites
sampled was 0.23 g/cm3. Discussions with local residents and teachers of Kobuk
indicated this was a relatively high snow year, compared to at least the last ten years.
Figure 34. Snow survey site locations during March 2011 field trip.
52
Table 3. Snow Survey Summary, March 24 to 27, 2011.
Snow-Course Site Name and Date Sampled
Wesley Cr Data Shown South to North
Cosmos
Lower
(3/25)
Dahl
Airstrip
(3/24)
Dahl
Station
(3/26)
Kogo
Forest
(3/26)
Kogo
Sandbar
(3/26)
Wesley
SC1
(3/24)
Wesley
SC2
(3/24)
Wesley
SC3
(3/27)
Wesley
SC4
(3/27)
Wesley
SC5
(3/27)
Average snow
depth (cm) = 85.4 73.9 127.8 115.5 91.7 141.8 121.5 117.4 123.8 93.2
Maximum snow
depth (cm) = 105.0 90.0 155.0 143.0 96.0 165.0 175.0 135.0 140.0 120.0
Minimum snow
depth (cm) = 63.0 61.0 85.0 101.0 86.0 100.0 65.0 100.0 110.0 70.0
Standard deviation
(cm) = 9.7 7.5 14.4 7.3 2.4 17.1 23.5 8.5 8.1 11.9
Average snow
depth (in) = 33.6 29.1 50.3 45.5 36.1 55.8 47.8 46.2 48.7 36.7
Maximum snow
depth (in) = 41.3 35.4 61.0 56.3 37.8 65.0 68.9 53.1 55.1 47.2
Minimum snow
depth (in) = 24.8 24.0 33.5 39.8 33.9 39.4 25.6 39.4 43.3 27.6
Standard deviation
(in) = 3.8 3.0 5.7 2.9 1.0 6.7 9.2 3.3 3.2 4.7
Average Density
(gr/cm3)=0.22 0.22 0.23 0.24 0.25 0.23 0.26 0.24 0.22 0.24
Average SWE
(cm H2O) = 19.2 16.2 29.1 27.7 23.0 32.6 31.9 27.9 27.4 21.9
(in H2O)= 7.5 6.4 11.5 10.9 9.1 12.8 12.6 11.0 10.8 8.6
(ft H2O)= 0.6 0.5 1.0 0.9 0.8 1.1 1.0 0.9 0.9 0.7
Note: bold italics indicates averaged value for average density
53
5.0SUMMARY
A surface-water data collection network was established in the Cosmos Hills region in
August 2010 for the purpose of evaluating the hydropower potential for Cosmos Creek,
Wesley Creek, Dahl Creek and the Kogoluktuk River. The primary purpose of the
network and resulting field data collection efforts is to establish stage-discharge rating
curves for each of the surface water systems of interest. Secondary objectives include
the collection of surface-water temperature data at the main gauging stations and
downstream stations located near potential hydropower outlets. Summer precipitation
and spring snowpack measurements are also measured, along with air temperature and
relative humidity. Surveying, manual water quality measurements and other general
field hydrology observations were also recorded for the data stations and surface-water
systems. The data station network includes repeater sites to help provide telemetry
communications back to a base station located at Kobuk School. Selected data is
reported on a project website.
Additional surface-water discharge measurements were made in October 2010 to help
establish discharge observations at low water conditions. Cosmos Creek and the
Kogoluktuk River October discharge measurements were ice affected and are likely not
applicable to the rating curve development, but still useful for understanding the early
winter flow conditions at the respective stations. During severe winter storms in
February 2011, three of the repeater station radios were impacted by potential
atmospheric static conditions. These radios were repaired during the spring 2011 field
efforts.
Snow surveys and station visits were made near the end of March 2011. Warm
conditions and deep snowpack resulted in field crews not being able to access the
Upper Cosmos Creek Station and the Upper Kogoluktuk River Station. Upper Wesley
Creek and upper Dahl Creek stations were visited and station operations were normal
and data collection systems were working well. Snowpack conditions are high for spring
2011. Depending on spring weather conditions, this should result in relatively high
snowmelt discharge conditions. An evaluation of the hydropower potential allowed the
54
evaluation of the four main stations and it was determined that Wesley Creek and the
Kogoluktuk River hydrology data collection efforts should continue. A winter
supplemental gauging station was established on the Kogoluktuk River to help provide
winter flow information and establish a location to conduct winter flow measurement. All
of the project objectives were met during the period of August 2010 through December
2011, with the exception of the impacts of the February storm event on the telemetry
reporting system.
6.0REFERENCES
Benson, C. S. and Sturm, M. 1993. Structure and wind transport of seasonal snow on
the Arctic Slope of Alaska. Annals of Glaciology, 18, 261-267.
Derry, J., Lilly, M., Schultz, G., Cherry, J., 2009. Snow Data Collection Methods Related
to Tundra Travel, North Slope, Alaska. December 2009, Geo-Watersheds
Scientific, Report GWS.TR.09.05, Fairbanks, Alaska, 12 pp (plus appendices).
Kennedy, E. J. 1990. Levels at Streamflow Gaging Stations. Techniques of Water-
Resources Investigations of the United States Geological Survey, Book 3
“Applications of Hydraulics”, Chapter A-19.
Lilly, M.R., Derry, J. 2010. A workplan for Cosmos Hills hydro-electric hydrologic
network project: station installation and stream gauging, August 2010. August. 16
pp (plus appendices).
Mueller, D.S., and Wagner, C.R. 2009. Measuring discharge with acoustic Doppler
current profilers from a moving boat: U.S. Geological Survey Techniques and
Methods 3A-22, 72 p.
Rantz, S.E. and others. 1982. Measurement and computation of streamflow: Volume I.
Measurement of stage and discharge. U.S. Geological Survey Water-Supply
Paper 2175, 2 v., 631 p.
55
Rovansek, R.J., D.L. Kane and Hinzman, L.D. 1993. Improving estimates of snowpack
water equivalent using double sampling. Proceedings of the 61st Western Snow
Conference, 157-163.