The
following definitions are important to understand how to get the most
out of the warehouse
Site
Elevation and Elevation History
Multiple
Site File Format – Extract Data from Warehouse Link
Computation
of Average Flow Information
Site
A
site is a location where one of more measurements may be taken.
Sites are classified by their type and the warehouse contains the
following types of sites
·
Surfacewater
·
Groundwater
·
Marine
·
Wetland
·
Lake
Every
site in the warehouse is identified by a unique site code, a site name
and optionally one of more site aliases.
Each site also has the capability to store its latitude and
longitude.
Sites
can also be classified as being Active or Inactive or Decommissioned.
Every
active site will have a data collection contractor assigned.
This contractor is responsible for collecting and uploading data
to the warehouse and can be a source of additional information relating
to the site.
Site
Alias
Each
site can have one of more site aliases to provide alternative mechanisms
to search for information. As
an example, the stream flow site 405209 has site aliases of 405209A and
405209B, which indicates that the Hydrographic contractors have used two
station numbers to identify the same logical site.
The
groundwater bore with a Site Code of B100 and Site Name of BORE 100 has
the site alias codes and alias name of B100 and RWCO respectively as
well as alias code and alias names of 3294900228 and DITR.
Contractor
Each
site has one or more contractors responsible for the collection, quality
assurance and uploading of information to the warehouse in a timely
manner.
Measurement
Definition
Every
site is capable of storing different types of measurements.
These measurement types are referred to in the warehouse as
measure definitions. For
example, Salinity is defined in the warehouse as a measure definition.
Specific sites are then assigned a measure definition and this
allows time series of measurements to be stored for any site.
Each
measure definition is assigned the following characteristics
·
Measure
definition Code
·
Description
·
Contractor
(the same measure definition will have a different measure definition
identifier if more than one contractor is assigned the measure
definition)
·
Type
of Measure (Typically Quantity or Quality)
·
Analysis
Method
·
Location
of Measurement (Field or Laboratory)
·
Unit
of Measure
·
Data
Format
·
Upper
and Lower Limits
·
Error
Tolerance and Detection limits
Measurements
Every
measurement stored in the warehouse is referenced against a site and
measure definition identifier. The
warehouse stores nearly 100 million measurements in both raw and
processed form. For example
average daily flows are computed from the raw instantaneous flow
measurements and stored against the Average Daily Flow (Computed)
Measurement definition.
Rating
Curves
Rating
curves are used to compute the flow at a stream flow site from water
level measurements. Rating
tables are established by Hydrographers on the basis of number gauging
measurements taken at different flow rates.
These ratings can change over time and the warehouse stores the
complete history of ratings recorded for a site, although only the
current rating table is accessible via the warehouse’s WEB interface.
Historic
Rating Tables for any site can be obtained by completing a
comments/requests or the Hydrographic contractors.
Site
Elevation and Elevation History
This
records the height of a known datum at the site.
This is often but not necessarily the gauge zero and the top of
the bore casing for stream flow and groundwater sites respectively.
Site
Location History
This
facility provides a mechanism to record how a site may have changed
location over time.
Extracted
Data – Single Site File Format
The
zip files downloaded from the warehouse using the Measurement Data link
on the Individual Site Information page are formatted as comma delimiter
text files with the following columns
|
Column
Heading |
Column
Description |
|
The
field contains the site code |
|
The
field contains the site name |
|
The
field contains the internal data warehouse identifier for the
measure definition |
|
The
field contains the measure definition description |
|
This
field contains the data and time the measurement was taken |
|
This
field contains the measurement value |
|
This
field indicates the magnitude of the know error associated with
the measurement |
|
The
field indicates the assigned quality and has legal values of A for high quality, B for good quality, C for low quality, E for extraordinary, N for no data, O
for OK and Z for approved lost data. |
|
This
field contains the collection method associated with the measure |
|
This
field contains the name of the contractor that provided the
measurement |
These
files need to be “unzipped” with the winzip utility. Note that the
file contains one row per measurement record.
Multiple
Site File Format – Extract Data from Warehouse Link
The
Extract Data From Warehouse link enables the user to extract
measurements for one or more sites.
The selection criteria provide considerable flexibility in what
can be extracted and also enables aggregated quantities to be extracted.
The results from the Extract Data process are displayed in the
browser and can also be downloaded in a file with the following
variables
|
Column
Heading |
Column
Description |
|
Basin
name where the site is located |
|
Date
of measure |
|
Name
of the measure definition |
|
Define
the units of measure |
|
Contains
the mean value of the specified data set |
|
Contains
the sum of the values of the specified data set |
|
Contains
the maximum value of the specified data set. |
|
Contains
the median value of the specified data set |
|
Contains
the minimum value of the specified data set |
Computation
of Average Flow Information
The
warehouse uses the measure definition Instantaneous Flow to compute and
store the following measure definitions
- Average
Daily Flow (Computed)
- Average
Monthly Flow
- Average
Season Flow (Summer, Autumn, Winter, Spring)
- Average
Annual Flow
Note
that the measure definition Average Daily Flow (Historic) has been
determined externally and generally represents information that has been
digitised from analogue recorders.
The
method for determining average quantities is to determine the volume
defined by the straight-line interpolation of the plot of Instantaneous
flow, over the specified averaging period.
The
following example shows how single daily measurements collected at 8:00
am are used to compute the average daily flow – this is a simplified
example as the warehouse stores many more points to represent this flow
hydrograph at the selected site (of the order of 280)
The
8:000 am raw values are tabulated
|
05-Jul-2002 |
703 |
|
06-Jul-2002 |
2139 |
|
07-Jul-2002 |
3055 |
|
08-Jul-2002 |
2578 |
|
09-Jul-2002 |
2035 |
|
10-Jul-2002 |
1837 |
|
11-Jul-2002 |
1586 |
|
12-Jul-2002 |
1444 |
The
volume for each day is marked on the graph and since it is common to
express flow in units of ML/Day, the volumes for each day represent the
average daily flow in units of ML/day.
For
most of the sites in the data warehouse the hydrograph shown in the
diagram would be represented by a greater density of points, but the
underlying principle for computation of average quantities is the same.
It
should be noted that the there a 6 values of average daily flow computed
from the 8 daily observations. It
is obviously not possible to compute averages for the “edges” ‘of
the data record and this principle applies when computing average daily,
monthly, seasonal and annual quantities.
In instances where there are “gaps” in the data record,
average quantities are still computed, but the records are marked with
an “E” (extraordinary) to draw attention to this fact.
Further work is currently underway to improve the processing of
gaps and the flagging of gaps to end users.