Murrumbidgee Valley 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 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 conservatively assumes extremely dry inflow conditions (99th percentile) for the remainder of the current (2016-17) water year. It then looks at various inflow scenarios extending into 2017-18.
- The Murrumbidgee Valley has experienced very wet conditions this water year, with higher flows experienced in only 18 out of 100 years (18th percentile inflows). However, in the last two months conditions have been drier with inflows falling below the monthly long-term average.
- 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. With the arrival of wet conditions late last year and full allocations, carryover is estimated to be close to the maximum allowable 30 per cent of entitlement, namely around 650,000 megalitres (ML).
- Access to inter-valley trade in 2017-18 is dependent on the balance of the IVT account. The 30 June balance will carry forward to 1 July and be made available for delivery in 2017-18.
- According to the Bureau of Meteorology, the overall conditions between April and June are likely to be hotter and drier than average for the Murrumbidgee Valley, with particularly high 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
- Full allocation can be expected for all towns, as well as domestic and stock access licences.
- Private carryover will be fully deliverable. At this early stage, it is estimated that the averagecarryover across the valley will be close to the maximum 30 per cent of entitlement.
- Murrumbidgee High Security access licences will receive an initial allocation of 95 per cent of entitlement, consistent with the Murrumbidgee regulated river water sharing plan.
- Under ‘extreme dry’ inflow conditions (99th percentile) through to the end of this (2016-17) water year, there will be 9 per cent commencing general security allocation on 1 July. Should conditions through to the end of this year be closer to ‘dry’ inflow conditions (75th percentile), then general security opening allocation on 1 July is estimated to be 12 per cent.
- A 9 per cent allocation under ‘extreme dry’ conditions, together with 30 per cent carryover, means an average general security water availability on 1 July of 39 per cent of entitlement.
- Water will be allocated to conveyance licences, commensurate with the opening general security allocation.
- Supplementary access licence holders will receive a full allocation; however, as usual, diversion is only allowed during periods of announced supplementary access.
- Water in Environmental Water Allowances (EWA) accounts will be available in accordance with the rules of the water sharing plan.
- In the Murrumbidgee water source, general security and conveyance licences can carry over water up to a maximum of 30 per cent of entitlement, and the account limit (allocation plus carryover) is 100 per cent of entitlement.
- Murrumbidgee inter and intra valley trade will operate in accordance with existing procedures and protocols, particularly in relation to the inter-valley trade (IVT) account limits.
- Releases from headwater storages will be managed to maximise water availability and deliverability including equalising their risk of spill.
- Chances of improvement
The chances of improved general security allocation based on different inflow conditions into 2017- 18 are as follows:
- Read the outlook here