Data FAQs

Here you'll find frequently asked questions regarding our data.

Stage data

The stage of the river is the height of the water surface above an established datum plane. A diver is submerged in the water to assess the height of the water. The datum plane used during the measurements was at the top of the diver instrument.

Stage data is used to calculate discharge of the river. Stage is used because direct measurements of river discharge are very difficult, whereas water surface elevations are easy in comparison.


Barometric Pressure Gauge

A barometric gauge (barodiver) is used to calculate atmospheric pressure. These readings are essential for the calibration and use of stage and flow data.

What does the diver zip file contain?

The data download zip file for a diver has the form SITE.zip, where SITE refers to the Diver location. It contains data for the diver, manual stage and flow data (for use in calibration the diver measurements) recorded using a tape measure and portable flow gauging equipment, and information on channel cross-section where the diver is located:
  1. Manual rating data (rating_SITE.txt)
  2. Manual measurements (manual_measurements_SITE.txt)
  3. Channel cross sectional survey (SITE_xsec.txt)
  4. Raw stage measurements (SITE_STARTDATE_ENDDATE_raw.txt)
  5. Raw stage measurement Quality Assurance notes; indicating quality issues with data periods, where applicable (SITE_STARTDATE_ENDDATE_raw_qa.txt)

What does the barometric gauge zip file contain?

The download zip file for a barometric gauge has the form SITE.zip, where SITE refers to the Barometric gauge location. It contains
  1. Raw pressure measurements (SITE_STARTDATE_ENDDATE_raw.txt)
  2. Raw pressure measurement Quality Assurance notes; indicating quality issues with data periods, where applicable (SITE_STARTDATE_ENDDATE_raw_qa.txt)

What is the format of the rating data?

The rating data files have 4 columns: (1) date; (2) time; (3) stage (m) and (4) discharge (m³/s). (The site and number of rating measurements are provided in the first two rows of the file.) The discharge was measured using current metering or, in the larger river channels, TDR (time domain reflectometry). Stage is the number indicating the water surface elevation relative to a local datum, and the local datum is the top of the lid on the tube that holds the Diver. This was measured manually in the field during the rating exercises.

What are manual stage measurements?

Manual stage measurements give the water surface elevation relative to a local datum, where the local datum is the top of the lid on the tube that holds the Diver. Manual measurements are recorded whenever a gauge is visited.

Each manual measurement has two rows, containing;

  1. Date, time, manual stage measurement (m)
  2. Date, time, raw Diver reading and temperature, raw Barometric gauge reading and temperature (these raw data are recorded so that the manual measurement can be compared directly against the automatic stage measurement; note that the method for converting from raw data to stage is described below under the following FAQS: "What are the raw stage measurements?" and "How do I convert the raw stage measurements to stage?).

Which Barometric gauges are associated with which divers?

The following Barometric gauge/Diver pairings are always to be used.

Baro_Footholme is used with the following
BRE_out; BRE_rhw; BRE_sap; BRE_grip; CRO_out; EAS_out; HAR_out; HOD_mid; LAN_mid; LAN_out; LOS_out
LOS_mid; LOS_stock; LOS_stock; WHI_out; WHI_mid; WHI_tree
Baro_Croasdale is used with the following
CRO_mid; CRO_sc1; CRO_sc2; CRO_sc3; CRO_sc4; CRO_sc5
Baro_Loud is used with the following
LOU_out

What is the coordinate system for the cross sectional survey data?

The cross sectional surveys consist of a set of (x,y) data pairs (m). The local coordinates (x,y) apply when facing downstream. Coordinate x is horizontal and increases from left to right, and y increases vertically upwards. The coordinate (0,0) refers to the top of the lid on the tube that holds the Diver.

What are raw stage measurements?

The raw stage measurements are raw readings from stage gauges (Divers) for water pressure (cm H²O) and temperature (°C).

How do I convert raw stage measurements to actual stage?

Compensation is required for atmospheric pressure, and this compensation uses data from a nearby barometric gauge (baro). See the FAQ: "Which Barometric gauges are associated with which divers?" The Final Science Report (Section 9.1) shows the details of how the diver and baro data are used to obtain stage, including how compensation is made for the temperature sensitivity of the instruments.

How do I convert stage to discharge?

The rating data can be used, but where there are too few rating data some form of rating curve extension will be needed. An extension method based on calibrating and extrapolating a velocity curve is described in the Final Science Report (section 9.3).


Rainfall

What instrument is used to measure precipitation?

A tipping bucket rain gauge (TBR) is used to measure the amount of precipitation over a set time period.

What does the TBR zip files contain?

The download zip file has the form SITE.zip, where SITE refers to the TBR location. It contains
  1. 5min rainfall totals (SITE_STARTDATE_ENDDATE_5min.txt)
  2. Quality Assurance notes; indicating quality issues with data periods, where applicable (SITE_STARTDATE_ENDDATE_5min_qa.txt)
Note, the Automatic Weather Station(AWS) also records rainfall.

Do I need to process the rainfall data?

The rainfall data do not require processing or corrections of any type. The data are 5min totals.


Automatic Weather Station (AWS)

This measures wind speed/direction, relative humidity, temperature, net radiation and rainfall at 15-minute intervals, for use in estimating potential evaporation.

What does the AWS zip file contain?

The download zip file has the form SITE.zip, where SITE refers to the AWS location. It contains wind speed / direction, temperature, net radiation and precipitation (SITE_STARTDAT_ENDDATE_raw.txt). Values are recorded at 15min intervals.

What is the date format in the AWS files?

The first four data columns in the data files provide (1) flag, (2) year, (3) day of year and (4) hour. The flag has no meaning. The day of year ranges from 1 to 365 (366 for leap years). For example, February 6th is 037.

How do I calculate potential evaporation using the AWS data?

The AWS records the necessary time series to calculate potential evaporation. In the Final Science Report (Section 9.2) details of the FAO Penman Monteith equation are provided, which gives an estimate for "a hypothetical crop with an assumed height of 0.12 m, with a surface resistance of 70 s m-1 and an albedo of 0.23, closely resembling the evaporation from an extensive surface of green grass of uniform height, actively growing and adequately watered" (www.fao.org/docrep/X0490E/X0490E00.html ).





Document last modified: Fri Feb 20 2015 11:12:34 GMT Standard Time