About Waterinfo data
The NSW Government WaterInfo website contains a range of provisional data from a range of State Government agencies concerning NSW rivers and water bodies. This data is generally used for the management of our rivers, storages and the surrounding environment.
Some of the data, since it is measured in the field, is close to real-time. This includes water levels, flow and continuous electrical conductivity (used to assess salinity levels).
Other water quality information is determined by sampling, and is updated nightly when laboratory analyses are complete. Water quality is measured for a variety of projects, each producing purpose-built datasets.
An appropriate level of care needs to be taken when using information from this site. Consideration of the purpose for which the data was collected is required. Time constraints have also meant that rigorous quality control checks have not been undertaken on some of the datasets.
The NSW Strategic water information and monitoring plan will assist NSW and the Commonwealth meet the requirements of the Improving Water Information program coordinated by the Australian Bureau of Meteorology.
How the continuous data is collected and validated
River operations is the activity of managing and manipulating river flows. It is a task performed by departmental staff located in offices in the river catchments. At each of these offices, a telemetry system polls instruments at sites within the catchment and stores the information on a local database, where it is used for daily operation of the river system. Additional data from non-telemetered sites is entered manually. All this information is termed 'provisional data'.
In the river operation process, errors in data may occur due to instrument faults, changes to stream profiles that affect correlations between gauge height and flow, electronic errors during transmission and errors during manual data entry. The most obvious errors are identified when the data is visually examined and first used by river operations staff.
This provisional data differs from the government's historical data. Historical data undergoes more rigorous quality checking and more accurate height to flow conversion processes. These additional quality assurance processes can delay data availability by up to six months.
How discrete sample data is collected and validated
Most water quality determinands cannot be measured by on-site instruments. Normally, water samples are collected by scientists for laboratory analysis. Some determinands (such as temperature) are measured in the field using hand-held instruments. Electrical conductivity, for example, is measured both in the field and the laboratory depending on individual project requirements.
Each water quality project manager is required to verify that protocols for undertaking an investigation are fully documented and that appropriate quality codes are added to the dataset. These codes indicate the suitability of results for the purpose for which they were originally collected. All departmental water laboratories are regularly audited by NATA to ensure that standard laboratory procedures are followed.
Basic checks to apply when using this data.
Errors may be identified by applying the following data checks:
- A level, flow or volume value changes while dependent data is unchanged, e.g. a gauge height value changes but the corresponding flow does not.
- A daily value is identical to a number of its previous values, when variation would normally be expected.
- There is a large, unexpected change from one value to the next.
- A value, especially a level, drops to zero.
- A value is negative.
- A value does not perform as expected, e.g. gauge heights and flows should recede following a high flow.