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New South Wales summary from water balances
For New South Wales, water balances were prepared for eight water management areas, the Sydney water supply area, the regulated and unregulated areas of the Richmond River, and the regulated areas of the following rivers: Gwydir, Hunter, Lachlan, Macquarie, Murrumbidgee, and Namoi. Water balances were also prepared for three interjurisdictional areas, the Snowy River (NSW and Vic), Cooper Creek (NSW, Qld, SA) and Border Rivers (Qld and NSW) catchments.
Key points
- While rainfall conditions across most of these catchments were close to long term average values (exceptions being the Lachlan which had 88% and Gwydir and Namoi which both received about 120% of the long term average annual rainfall), streamflows generally remained well below long term average values. In addition, while the annual average rainfalls across the state were about average for the year, the rainfall in each month was generally below average (particularly during the January – May period), apart from December and June where many parts of New South Wales received high monthly rainfall totals.
- The Gwydir River – Regulated, Murrumbidgee River – Regulated and Richmond River WMAs all experienced increases in surface water storage levels over 2004-05. Across the state, major surface water reservoir volumes remained significantly below capacity during 2004-05. As such, a range of urban water restrictions were in place across many areas of the State, including Sydney and irrigation water allocations were low across most of the State.
- The information contained within the water cycle reports was collated and provided by DNR (November, 2006). The data have various sources, predominantly, DNR databases, the State Water database ‘CAIRO’ and the models held by DNR (including IQQM and regional groundwater models). Reliable information is available for many items of the water balance in all catchments, with a few items such as the volume of groundwater storage being a lower quality estimate. Overall, there were very few items in the New South Wales water balances for which the required data were not held in databases or models or where an estimate could not be provided for this project.
- IQQM models have been developed for the regulated area for most catchments in New South Wales, enabling estimates of seepage losses to groundwater, flows to floodplain and evaporation to be calculated. In addition, regional groundwater models are available for most regulated areas in the state and have enabled estimates of baseflow, recharge (from rainfall and irrigation), lateral and vertical aquifer flows to be made for most of the water balances. Groundwater usage is generally un-metered, particularly in unincorporated groundwater management units. Reasonable estimates have been possible for most groundwater extractions, however data for stock and domestic bores is poor and estimates of extractions for them have been given a quality ‘D’ rating.
- The water balances were completed for regulated areas of New South Wales only (with the exception of the Sydney water supply area, Snowy River and Richmond River). For regulated areas, a large amount of data was available, including detailed modelling of both surface and groundwater resources for most areas. Hence the data quality for the water balances is relatively high. However, these balances may be misleading without considering the entire hydrological catchment (i.e. the combined regulated and unregulated areas) in each case. This is a major opportunity for improvement in future assessments of water balances in New South Wales.
- The error terms in all of the New South Wales water balances (apart from the Sydney water supply area) is 0%. This is because the errors are allocated in other items of the water balance as appropriate in order for the water balance to balance. For surface water the term ‘Other losses’ was used and for groundwater the unaccounted flows were included with the closing storage volume. As most surface water data was from detailed models, the ‘Other losses’ term was considered to be reasonably accurate.
Further discussion of the water balances for New South Wales is provided in the Water Availability National Perspective report, and the Regional Water Balances report, which are both available on the
Publications page.
For individual results of water balance assessments go to
Regional Water Resources Assessments
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