The BOREAS Information System
1.1 Data Set Identification
Stream Discharge Rates Measured Hourly.
1.2 Data Set Introduction
1.3 Objective/Purpose
This project will seek to identify, through field measurements and computer modeling, the space-time distribution of meltwater supply to the soil during the spring melt period, and the evolution of soil moisture, evaporation, and runoff from the end of the snowmelt period through freeze up. The snow modeling activity will consist of two components: The first will make use of existing "off the-shelf" models, to forecast the onset and spatial extent of snowmelt and meltwater supply to the soil column prior to the 1994 IFCs. The second phase will extend, implement, and verify a physically based energy balance snowmelt model of the two sites and will evaluate approaches to aggregating detailed snowmelt predictions and measurements based on the model to larger scales, up to the size of a rectangle of several hundred km containing the northern and southern sites. The soil moisture modeling is based on a grouped response unit method which will allow characterization of soil moisture, evaporation, and runoff for the entire northern and southern sites.
1.4 Summary of Parameters
The following phenomena and their parameters are being
reported in this data set:
Discharge Rate of Streams
1.5 Discussion
The locations for 12 tipping bucket measuring devices, 10 belfort gauges and 5 stream sites were selected within the two BOREAS study sites (NSA and SSA). These instruments were installed during the FFC-T (Focused Field Campaign-Thaw) 1994 in the last week of April 1994. They were in operation until October 1994 when they were removed from service. The gauges were reinstalled and collected data from April 1995 to October 1995. The tipping buckets and belfort gauges provided an approximate measure of the precipitation in the study areas. The discharge rates of streams provide a measurement of water leaving the study area. When used together these two sets of data provide a balance of the water cycle.
1.6 Related Data Sets
Precipitation data measured with belfort gauges and tipping buckets are also available.
2.1 Investigator(s) Name and Title
Prof. Ric Soulis University of Waterloo Department of Civil Engineering Waterloo, Ontario N2L 3G1 Canada Phone: (519) 885-1211 x2175 FAX: (519) 888-6197 E-Mail: ric@sunburn.uwaterloo.ca
2.2 Title of Investigation
From Micro-Scale to Meso-Scale Snowmelt, Soil Moisture and Evapotranspiration from Distributed Hydrologic Models
2.3 Contact Information
Contact 1 --------- Dr. Nicholas Kouwen Univ. of Waterloo Dept. of Civil Engineering Waterloo, Ontario N2L 3G1 Tel: (519) 885-1211 x3309 FAX: (519) 888-6197 Email: kouwen@sunburn.uwaterloo.ca Contact 2 --------- Dr. Ric Soulis Univ. of Waterloo Dept. of Civil Engineering Waterloo, Ontario N2L 3G1 Tel: (519) 885-1211 x2175 FAX: (519) 888-6197 Email: ric@sunburn.uwaterloo.ca
To continuously measure the discharge rate of a stream as a function of depth it is first necessary to construct a stage-discharge rating curve. To find the discharge rate at a specific stage, the cross section of the stream must be divided into subsections. No one sub-section should account for more than ten percent of the total stream flow. In the center of each subsection a current meter is lowered into the water at various depths to measure velocity. Two types of current meters were used in this study, a propeller meter, and an electromagnetic meter. A propeller meter measures the rate of flow by relating it to the rotation of its propeller while an electromagnetic meter measures the voltage produced when water passes through a magnetic field produced by the meter. Two different types of meters were used to reduce the error associated with each individual device.
When the velocities have been determined the total discharge of the stream can be calculated. This, along with the level of the stream at that time, can be used to compare the rate of flow at that time with other times. The discharge rate must be found at several different stream levels so that a relationship can be established between the height of the stream and its discharge. This relationship is represented graphically as a rating curve.
Once a rating curve is established the discharge can be found at any time if the height of the stream is known. To constantly monitor the stream height a float tube and a data logger were used. The stream height was manually checked at periodic times using a staff gauge. From this a detailed description of the stream's water level over several months was possible.
4.1 Sensor/Instrument Description
Propeller Meter
The Swoffer 2100 STDX current velocity meter consists of a propeller that rotates about an axis parallel to the flow of the stream. An onboard computer calculates the speed and displays it in the desired units. The computer averages the velocity over a given time (ie. 90 sec). The propeller meter was used to determine the rating curve for the stream.
Electromagnetic Meter
The MMI model 2000 flo-mate portable water flowmeter measures the velocity of a liquid using an electromagnetic method. When a fluid, which has conductive properties, passes through a magnetic field at a right angle, the magnetic field induces an electromotive force in the fluid at right angles to both the magnetic field and the velocity of the fluid. The voltage produced by the movement of the water through the meter is measured by electrodes and is proportional to the average velocity of the fluid. A built in computer uses this information to calculate and display the velocity. The electromagnetic meter was used to determine the rating curve for the stream.
Float Tube
A float tube consists of a hollow perforated plastic tube mounted perpendicular to the water's surface near the stream bank where it is accessible to observers. A float inside the tube reacts to different water heights that the data logger electronically records every 15 minutes. It is used to monitor the height of water over small intervals of time (ie. 15 minutes) for long periods of time.
Data Logger
The chart pac CP-X data logger was connected to the float tube so that it could record stream levels every 15 minutes. The data was stored in the logger's memory until it was retrieved.
4.1.1 Collection Environment
4.1.2 Source/Platform
Propeller Meter - mounted on a pole that was lowered manually into a stream.
Electromagnetic Meter - mounted on a pole that was lowered manually into a stream.
Float Tube - mounted in a stream near the bank where observers can reach it easily.
Data Logger - mounted inside the float tube
4.1.3 Source/Platform Mission Objectives
A measurement of the stream discharge rate was necessary so that a precise estimate of the total amount of water leaving the watershed due to surface and subsurface flows could be made. The data logger stored the information until it was retrieved.
4.1.4 Key Variables
Propeller Meter - Water Velocity
Electromagnetic Meter - Water Velocity
Float Tube - Stream Height
Data Logger - Voltage
4.1.5 Principles of Operation
A propeller meter and an electromagnetic meter are manually operated devices that measure the velocity of water. The propeller meter counts the number of propeller revolutions over a given time period. The computer compares this to a calibration coefficient and then displays the resulting velocity. The electromagnetic meter measures the voltage prvduced by water moving through a magnetic field, which is proportional the water's velocity. The float tube and the data logger are self-contained devices that automatically record the height of water every hour over an indefinite time period.
4.1.6 Sensor/Instrument Measurement Geometry
The propeller meter and the electromagnetic meter are mounted on a pole and lowered to various depths in a stream. The tester must repeat this for each subsection of the stream so that the average velocity can be calculated.
The float tube is mounted near the stream bank so that the tube is perpendicular to the surface of the water. The tube must be in an area that is accessible for data retrieval and can measure high and low water levels. The data logger is attached to the float tube.
4.1.7 Manufacturer of Sensor/Instrument
Propeller Meter - Swoffer Instruments Inc. 1048 Industry Drive Seattle, Washington 98188 U.S.A. (206) 575-0160 Fax (206) 575-1329 Electromagnetic Meter - Marsh-McBirney Inc. 4539 Metropolitan Court Frederick, Maryland 21701, U.S.A. (301) 874-5599 Fax (301) 874-2172 Float Tube - Lakewood Systems 9258-34A Avenue Edmonton, Alberta, Canada T6E 5P4 Data Logger - Lakewood Systems Edmonton, Alberta, Canada
4.2 Calibration
The propeller meter and the electromagnetic meter were calibrated by dragging them through a still body of water (a long tank, or a lake) at a known velocity and then adjusting the instrument as needed.
The float tube was calibrated by measuring the height of the water directly with a staff gauge and comparing that to the reading that the float gauge had determined.
4.2.1 Specifications
Propeller Meter
temperature range: -10 degrees Celsius to 49 degrees Celsius
Electromagnetic Meter
analog display: 0.1v per 1 m/sec
material: polyurethane shell
temperature range: 0 degree Celsius to 50 degrees Celsius
Float Tube
range: 0 to 4.6m (0 to 15 feet)
accuracy: +/- 1cm. (0.4 inches)
operating temperatures: -66 degrees Fahrenheit to 140 degrees Fahrenheit
4.2.1.1 Tolerance
The propeller meter can measure velocities from 0.1 to 25 feet per second.
The electromagnetic meter can measure velocities from - 0.5 to 19.99 ft/sec (-0.15 to 6 m/sec). The meter measures the velocity to within 2% of the reading +/- 0.05 ft/sec.
The float tube can measure a stream heights from 0 to 4.6 meters.
The data logger can record voltage from 0 to 2.5 volts D.C. It can store 64 thousand samples with an accuracy of 1/4095.
4.2.2 Frequency of Calibration
The propeller meter and the electromagnetic meter were calibrated once before the readings were made and then once afterwards.
The float tube was calibrated during the beginning of the study period. The staff gauge readings were compared to that of the float tubes.
4.2.3 Other Calibration Information
6.1 Data Notes
6.2 Field Notes
Several computer programs are required to develop the rating curves and the stream discharge rates.
7.1 Spatial Characteristics
The five stream sites were located so that they would give an overall view of water movement throughout the basin. In the large study areas (NSA and SSA), smaller basins were chosen so that a more detailed study could be performed. Two basins were chosen in the NSA and one in the SSA. In each basin the stream sites were chosen so that the flow contributions from a number of land cover types could be determined.
The stream sites were also chosen for other characteristics. They must be accessible during all water levels. The location must be suitable to measure the water height at high and low water levels. The river bed must be uniform in shape and of a material that resists erosion so that the rating curve will not change significantly over the period of observation. Areas that didn't overflow their banks and were away from human traffic were also desired.
The stream gauge at SW1 was chosen by HYD-9 Canada before the BOREAS project. During the project, the Environment Canada Water Survey operated the NW1 gauge.
7.1.1 Spatial Coverage
The five stream gauges measure the discharges throughout the 2 areas. The NSA basins were both 27 km^2 while the SSA basin was 574 km^2. Two additional stream gauges SW1 and NW1 were operated by the water survey.
The stream gauges were located at the following coordinates: SITE_ID LONGITUDE LATITUDE -------------------- ---------- ---------- NSA-NW1-HYD09-STGAN1 -98.49168 55.90877 NSA-NW2-HYD09-STGAN2 -98.52746 55.91528 NSA-NW3-HYD09-STGAN3 -98.37563 55.91683 SSA-SW1-HYD09-STGAS1 -104.61986 53.86453 SSA-SW2-HYD09-STGAS2 -104.68167 53.895 SSA-SW3-HYD09-STGAS3 -104.79116 55.92669 SSA-SW4-HYD09-STGAS4 -104.82028 53.92639
7.1.2 Spatial Coverage Map
7.1.3 Spatial Resolution
The stream discharge rates reported in this data set represent the discharge rate at a point in the stream in which they were located.
The collected data is designed to provide a reasonable estimate of the total surface and subsurface runoff from the White Gull Creek and Sapochi River watersheds during the study period.
7.1.4 Projection
7.1.5 Grid Description
7.2 Temporal Characteristics
7.2.1 Temporal Coverage
The data was collected from the end of April until October in 1994, 1995 and 1996. Gauges SW1 and NW1 were operated all year.
7.2.2 Temporal Coverage Map
7.2.3 Temporal Resolution
The data was collected at fifteen minute intervals over the study period. The data was then converted to hourly flow during the processing phase.
7.3 Data Characteristics
7.3.1 Parameter/Variable
7.3.2 Variable Description/Definition
7.3.3 Unit of Measurement
7.3.4 Data Source
7.3.5 Data Range
Observation Date: The date and time (GMT) when the measurement was made.
Discharge Rate: The discharge rate that the gauge measured. (cubic meters per
7.4 Sample Data Record
DATA_UNIT_ID OBS_DATE DISCHARGE_RATE GAUGE CRTFCN_ REVISION_ ------------------------------------------------------------------------------- HYD09_STGA_NW002_26APR94 26-APR-94 .162 NW002 CPI 23-MAY-95 TIMEC PARM_VALUE_FLAGS ---------------------------- 15:15
8.1 Data Granularity
[BORIS and ORNL DAAC to fill in]
8.2 Data Format(s)
The CD-ROM data format consists of a text field to identify the data followed by several numeric fields to store the data for that day.
9.1 Formulae
To find the average velocity in a subsection:
Velocity = the average of the velocity measured at 0.8 of the depth and at 0.2 of the depth:
u = (u(0.8D)+u(0.2D))/2
To find the flow in a subsection:
Flow = Average velocity in subsection * area of subsection
Q = u * A
To find total discharge from velocity readings:
Flow = the sum of the flows in all of the subsections
Q = (sum from i=1 to i=N) of (u to the ith power) * A
To find the flow at a particular stream height:
Q = a2(volts-a1) + a3(volts-a1)^2 + a4(volts-a1)^3 + a5(volts-a1)^4 + a6(volts-a1)^5
where q = flow
a1 to a6 = coefficients of the rating
curve volts = the voltage recorded by the float tube for a specific height
To find the height of the stream from the data logger information:
height of stream = voltage output * calibration coefficient
9.1.1 Derivation Techniques and Algorithms
At frequent intervals during the monitoring period the flow of the stream (using the propeller and electromagnetic metering devices), the voltage produced by the float tube, and the true height of the stream measured from a staff gauge were recorded. This data showed a relationship between the level of the stream (staff and voltage gauges) and the rate of flow. The voltage produced by the float tube was converted to stream height using a calibration coefficient.
The information was entered into a computer program called 'Fitflow' that calculated the coefficients for the rating curve of a stream (a1 to a6). After this was done it was a simple matter to find the rate of flow using the equation.
9.2 Data Processing Sequence
9.2.1 Processing Steps
9.2.2 Processing Changes
9.3 Calculations
9.3.1 Special Corrections/Adjustments
9.3.2 Calculated Variables
9.4 Graphs and Plots
10.1 Sources of Error
Most error will occur in the actual measuring of the initial data. Turbulent water flow will effect the velocity readings by causing the meter to measure a larger or smaller velocity than actual. The stream site must be of uniform shape where the velocity measurements are taken to reduce variations in flow. If an instrument is allowed to get dirty it may become clogged and produce faulty readings. The propeller meter suffers from rotational friction that becomes more apparent at low velocities. Careful cleaning and calibration will prevent this though. As the temperature of water changes, its volume will also change.
Some of the gauges experienced shifting during the observation period. This movement made the development of rating curves more difficult.
10.2 Quality Assessment
10.2.1 Data Validation by Source
The electronic readings of the float gauge were routinely checked with the staff gauge readings taken directly from the stream. To account for the movement of the float tube, shifting of the streambed or the growth of vegetation, the rating curves were broken up into different time periods. For example there were different rating curves for the spring thaw than for the fall freezing period.
After the information had been collected it was run through an algorithm to detect any data that was abnormal, when compared to the rest of the data.
10.2.2 Confidence Level/Accuracy Judgement
The confidence level of the data varies with the particular stream and the level of the stream at the time of measurement.
10.2.3 Measurement Error for Parameters
10.2.4 Additional Quality Assessments
10.2.5 Data Verification by Data Center
[For BORIS and ORNL DAAC Use]
11.1 Limitations of the Data
11.2 Known Problems with the Data
For short periods of time some of the monitoring stations were inoperative. The data lost during this time made the final results less accurate.
11.3 Usage Guidance
The float tubes and data loggers were switched to double precision in May 1994. This effected the resolution of the reported data.
11.4 Other Relevant Information
14.1 Software Description
14.2 Software Access
15.1 Contact Information
Primary contact:
Ms. Beth McCowan BOREAS Information System Bldg. 22, Room G87 Code 923 NASA Goddard Space Flight Center Greenbelt, Maryland 20771 (301) 286-4005 (301) 286-0239 beth@ltpmail.gsfc.nasa.gov
15.2 Data Center Identification
BOREAS Project Office Code 935, Goddard Space Center Greenbelt, Maryland 20771
15.3 Procedures for Obtaining Data
Anyone wanting information may place requests by letter, telephone, FAX, electronic mail, or in person.
15.4 Data Center Status/Plans
As the BOREAS data are processed and sufficiently quality checked, they will be available from the EOSDIS ORNL DAAC (Earth Observing System Data and Information System) (Oak Ridge National Laboratory) (Distributed Active Archive Center). The BOREAS contact at ORNL is:
Merilyn Gentry, User Services/Data Coordinator Oak Ridge National Laboratory DAAC P.O. Box 2008 Bldg. 1507, MS-6407 Oak Ridge, TN 37830-6407 (615) 241-5926 (615) 574-4665 mjg@walden.rmt.utk.edu
16.1 Tape Products
Contact BORIS Staff
16.2 Film Products
Contact BORIS Staff
16.3 Other Products
Contact BORIS Staff
17.1 Platform/Sensor/Instrument/Data Processing Documentation
Hoskin Scientific Limited. 1992. Chart pac Cp-X (price and specification sheet).
Lakewood Systems Ltd.: float sensor fs-15: data sheet
Marsh-McBirney, Inc. Flo-Mate Model 2000 Portable Water Flowmeter Instruction Manual. 1990.
Swoffer Model 2100 Indicator Operation Manual
17.2 Journal Articles and Study Reports
17.3 Archive/DBMS Usage Documentation
AES - Atmospheric Environment Service of Canada BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System CD-ROM - Compact Disk (optical), Read-Only Memory DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System FFC-T - Focused Field Campaign - Thaw GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center IFC - Intense Field Campaign NASA - National Aeronautics and Space Administration NSA - Northern Study Area ORNL - Oak Ridge National Laboratory SSA - Southern Study Area URL - Uniform Resource Locator
20.1 Document Revision Date
20-NOV-1996
20.2 Document Review Date(s)
BORIS Review:
Science Review:
20.3 Document ID
[For BORIS and ORNL DAAC Use]
20.4 Citation
Ric Soulis, University of Waterloo
Nick Kouwen, University of Waterloo
20.5 Document Curator
[For BORIS and ORNL DAAC Use]
20.6 Document URL
[For BORIS and ORNL DAAC Use]
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