Hydrologic Reference Stations
Analytical Methodology
The Extended Hydrological Prediction Section of the Bureau of Meteorology (the Bureau) hosted a workshop on streamflow trend analysis in December 2011. Technical experts from the Water Information Branch of the Bureau, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) , The University of Melbourne and Sinclair Knight Merz, were invited to:
- Explore the merits of the available fit-for-purpose scientific methods for trend analysis on long-term streamflow datasets.
- Develop the trend analysis methodology and identify the time frame for the delivery of products.
The outcomes of the trend analysis workshop identified the key streamflow variables and trend tests (as described in Chiew et al., 2005) that have been applied in the time-series analysis of streamflow data at each station. The key streamflow variables and statistical tests for the detection and identification of change are given in the table below.
| Analysis Component or Purpose | Variable |
|---|---|
| Streamflow Variables |
|
| Test for independence (randomness) |
|
| Trend Test |
|
| Test for step change in mean |
|
| Test for difference in median in data periods |
|
| Test for variability in daily flow duration between different decades |
|
The missing streamflow data was filled using the GR4J model (Perrin et al, 2003) which is a daily, lumped, four parameter, soil moisture accounting rainfall-runoff model. The baseflow was separated from the daily streamflow using a digital filter based on the theory developed by Lyne and Hollick (1979) and applied by Nathan and McMahon (1990).
It is important to note that the scope of the Hydrologic Reference Stations (HRS) project includes only the identification and attribution of decadal variability and change in long-term streamflow. Other variables such as rainfall, temperature and radiation are not included. Please see the Bureau of Meteorology web portal for high quality climate reference stations for further information on the long term trends in climate variables.
The Australian Hydrological Geospatial Fabric (Geofabric) was utilised from the initiation of the HRS project, with potential hydrological reference stations created as ghost nodes on network streams within the Geofabric. Hydrological Reference Stations are now included in Geofabric V2.1 as ghost node monitoring points within the Surface Network product. HRS catchments derived from the Geofabric was used for land use/forest cover change analysis and modelling. The station facts were also derived from Geofabric data.
