NSW Murray and Lower Darling Preliminary water availability outlook for 2017-18 – update
18 April 2017
18 April 2017
This additional update between the scheduled mid-March and mid-May water availability outlooks is provided at the request of some water users. Despite very dry conditions in recent weeks there has been little change in the forecasts.
The outlooks for next year are intended to assist water users with their late season decisions about cropping, trading and carryover. Actual allocations are not guaranteed to conform to forecasts.
Water users are reminded to check with WaterNSW about dates for end of year trade closures.
- This updated outlook for the likely 1 July 2017 water allocation is now based on very dry, 90th percentile inflow conditions for the remainder of the current (2016-17) water year. This is consistent with recent observations and drier than the earlier 75th percentile conditions that were assumed would prevail for the remainder of the year.
- The River Murray system has experienced very wet conditions this (2016-17) water year, with higher flows experienced in only 11 out of 100 years (11th percentile inflows). This was due primarily to flooding in spring, because recent months have been much drier.
- It allowed full allocations for to be announced in November 2016 and contributed to Hume and Dartmouth Dams holding combined 2,490,000 megalitres (ML) more than this time last year.
- It is difficult to reliably predict end-of-year carryover, as it is highly dependent on weather conditions over the next few months and individual decisions by water users.
- Conditions this year are still indicating potentially much higher carryover volumes in the NSW Murray than in recent years. Indications are that private carryover could average up to 45 per cent of entitlement or some 750,000 ML. Maximum carryover in the valley is 50 per cent.
- According to the Bureau of Meteorology, the overall conditions between April and June are likely to be hotter and drier than average for the Murray, with higher chances of hotter and drier conditions in the western portion of the catchment.
- Although the El Niño–Southern Oscillation (ENSO) indicator remains neutral, climate models suggest El Niño conditions are likely to develop during winter. The Bureau notes caution should be exercised as models have lower accuracy at this time of year in forecasting El Niño. El Niño is often associated with a drier than average winter–spring and warmer daytime temperatures in the region.
- Once the commencing allocations are announced on 1 July 2017, regular assessments will be undertaken and allocation announcements made fortnightly on the 1st and 15th of each month, or next working day following, as required for the remainder of the water year.
- An update to this preliminary forecast of water availability for 2017-18 will be made on 15 May 2017.
Indicative allocations on 1 July 2017 – Lower Darling
- With the Menindee Lakes System (MLS) currently holding about 830,000 ML (48 per cent capacity), there is sufficient resource to assure full allocation for all Lower Darling licence categories for the 2017-18 water year from 1 July.
- This means water security for towns, domestic and stock users, and permanent plantings.
- It also means full access to water for irrigation under high security and general security
entitlements, as well as access to carryover water.
- Lower Darling inter and intra valley trade will remain open while the system remains above 480,000 ML. Also above this threshold the system will continue to be managed as a shared resource in accordance with the Murray Darling Basin Agreement.
Indicative allocations on 1 July 2017 – NSW Murray
- Security of water for towns, as well as domestic and stock access licences, is assured.
Full allocations will be made for supplementary access licence holders. However, use of this
entitlement is only available subject to announced periods of supplementary flow.
Full access to carryover water in private accounts will be available on 1 July. As noted, carryover is estimated to be much higher than in previous years.
Preliminary estimates indicate that 65 per cent of water users1 may have at least 45 per cent carryover, with 75 per cent of water users having at least 25 per cent of carryover.
Water will be set aside for environmental requirements in accordance with the rules of the NSW Murray and Lower Darling regulated rivers water sharing plan.
NSW Murray high security access licences will receive an allocation of 97 per cent of entitlement in accordance with the water sharing plan.
General security allocation is expected to commence with at least 4 per cent of entitlement under both ‘dry’ and ‘very dry’ conditions for the remainder of this 2016-17 water year. This means that, when added to carryover, water availability for general security users could be on average close to 50 per cent of entitlement.
Sufficient water will be available to make opening allocations for conveyance water, commensurate with the expected opening allocations above.
Under the water sharing plan, the NSW share of the Barmah-Millewa Forest environmental water allowance may be borrowed for allocations when general security is less than 30 per cent. This assessment and outlook is therefore based on a full borrowing of the Barmah-Millewa account balance at the start of the 2017-18 water year.
In the NSW Murray only general security access licence entitlements can carryover water, up to a maximum of 50 per cent of entitlement, and the account limit (allocation plus carryover) is 110 per cent of entitlement.
NSW Murray inter and intra valley trade will be in accordance with existing procedures and protocols, including no net trade downstream of the Barmah choke.
1 These statistics exclude zero share water access licences.
Chances of improvement
The chances of improved general security allocation in the NSW Murray, based on different inflow conditions from 1 July 2017, are provided in the following tables.