Unregulated Diversions Water Outlook for Melbourne Water Licence Holders

Size: px

Start display at page:

Download "Unregulated Diversions Water Outlook for Melbourne Water Licence Holders"

Muriel Poole
5 years ago
Views:

We manage Melbourne s water supply catchments, remove and treat most of Melbourne s

1 Unregulated Diversions Water Outlook for Melbourne Water Licence Holders November 2017 Melbourne Water is owned by the Victorian Government. We manage Melbourne s water supply catchments, remove and treat most of Melbourne s sewage, and manage rivers and creeks and major drainage systems throughout the Port Phillip and Westernport region.

Table of contents 1. Executive Summary... 3 2. Introduction... 3 3. Season to date & current streamflow... 4 4. Climate Outlook... 6 4.1 Average rainfall and warmer season ahead... 6 4.2 Seasonal Streamflow Forecasts October December 2017.

2 Table of contents 1. Executive Summary Introduction Season to date & current streamflow Climate Outlook Average rainfall and warmer season ahead Seasonal Streamflow Forecasts October December Forward outlook for 2017/18 summer season Other factors affecting entitlement holders and the environment Further information

3 1. Executive Summary Prevailing dry to average conditions through winter and spring this year has led to the early introduction of bans and restrictions within major catchments in the Yarra basin. The seasonal rainfall and temperature outlooks suggest Melbourne Water s unregulated stream customers should anticipate high levels of bans and restriction commencing in early December and likely to extend to the end of the peak irrigation period in March / April Recovery of streamflows is likely to be slow without an influx of above average rainfall over several months. The outlook does favour chance of wetter than average rainfall but this is coupled with higher chances of warmer than average temperatures which will increase water demand. 2. Introduction The Minister for Water has delegated Melbourne Water with the responsibility for managing surface water licensing within the waterways and major drainage systems of the Yarra River, the lower Maribyrnong River, Stony, Kororoit, Laverton and Skeleton Creek catchments. Within these catchments we currently manage approximately 1300 licenses from waterways and administer approximately 500 farm dam registrations and licences relating to catchment dams. The total allocation issued under these licences is approximately 44,000 Megalitres (ML). The majority of allocation (41,700ML) is issued on catchments in the Yarra River basin, while the Maribyrnong and western catchments account for approximately 1,600ML and southeast catchments approximately 800ML. Water use is primarily for agricultural, industrial, commercial, sporting grounds and domestic and stock purposes. All licences managed by Melbourne Water are on unregulated systems except for a small number of licences in the lower Maribyrnong which are semi-regulated. The Water Act 1989 requires Melbourne Water to protect the environment and consider the needs of water users. Management of the water resource is achieved through a number of different mechanisms that include a Drought Response Plan (DRP), Stream Flow Management Plans (SFMPs) and Local Management Rule (LMRs). During drought or low flow conditions, licenced diverters access to water may be restricted or banned to protect the environment. Our Drought Response Plan is active at all times, and specifies how water is shared when there is not enough to meet all users needs. It states river flow levels which trigger restrictions or bans, and how these are applied to different licence types. These trigger points have been developed together with stakeholders in formulating stream flow management plans or local management rules. The status of restrictions and bans for individual catchments is posted on Melbourne Water s website at and is also available by calling Melbourne Water on at any time. Individual catchment status is also available via an automated SMS services to subscribed customers. In addition the website will provide catchment specific stream-flow data including daily and 7-day average stream flow conditions. For additional licensing information and data please visit the website 3

3. Season to date & current streamflow 2017 rainfall across the Yarra Valley, where the majority of licensed users are located, has been well below average in most months.

4 3. Season to date & current streamflow 2017 rainfall across the Yarra Valley, where the majority of licensed users are located, has been well below average in most months. Annual rainfall total to the end of November has been 615.0mm at Coldstream against a mean total of 674.2mm. The May-July period through winter proved particularly dry and translated to lower winter streamflows than expected. In ephemeral systems such as the Steels Creek and Dixons Creek catchments around Yarra Glen, this resulted in bans being in place across the entire winter-fill period for all but 5 days. Winter-fill licences in other catchments fared slightly better, particularly with a return to average rainfall conditions in the August to November period. Current flow conditions (as at 29 November) across all major catchments are tabled in the information below. On the back of the dry winter and average spring rainfall conditions, a number of the usually more reliable systems such as the Hoddles Creek, Stringybark Creek and Wandin Yallock Creek have already gone onto early bans and the Woori Yallock, Yarra River Upper and Yarra River Lower catchments are restricted. Catchment Access to water Flow (ML/d) 7 Day Rolling Average (ML/d) No. Bans / Restriction days 1/7/16 20/11/16 No. Bans / Restriction days - 1/7/17-20/11/17 Arundel Creek Available Cockatoo and Shepherd Creek Restricted Darebin Creek Available Diamond Creek Available Dixons Creek Banned

5 Don River Banned Gardiners Creek Available Hoddles Creek Banned Kororoit Creek Available Little Yarra River Restricted Maribyrnong River (all year) Maribyrnong River (winter-fill) Available Licence Ban McCrae Creek Restricted Merri Creek Available Moonee Ponds Creek Available Mullum Mullum Creek Available Olinda Creek (Lower) Available Olinda Creek (Upper) Available Pauls Creek Banned Plenty River Available Steels Creek Banned Stringybark Creek (Lower) Stringybark Creek (Upper) Banned Available Wandin Yallock Creek Available Watsons Creek Available Watts River Available Woori Yallock Creek Restricted

6 Yarra River Lower Restricted Yarra River Upper Restricted Restrictions and bans Climate Outlook 4.1 Above average rainfall combine with warmer season ahead The Bureau of Meteorology seasonal climate outlook for the next three months shows no strong swing towards wetter or drier conditions for most of Australia. However, coastal regions of southeast Australia including Victoria are likely to have a wetter than average summer. There is a slightly wetter and warmer climate outlook across Melbourne & the water supply catchments for December February The Bureau's ENSO Outlook is at La Niña alert, as the tropical Pacific approaches La Niña thresholds. Most international models maintain a weak La Niña until early autumn. Typically when the tropical Pacific cools towards La Niña levels, the western Pacific and seas around northern Australia warm significantly, but models suggest this is not likely to occur this summer. Likewise, La Niña periods typically see warmer than average waters develop in the eastern Indian Ocean. This season, near average to cooler waters are forecast to remain in this area, while warmer waters remain off Africa. The combination of ocean patterns, and the likely weak La Niña itself, is why Australia does not have significant and widespread increased chances of a wetter and cooler summer. Temperature and rainfall influence water use, especially during summer periods. At the same time, rainfall and temperature also influence catchment soil moisture levels and inflows to Melbourne s unregulated waterways. Melbourne Water continually monitors flow conditions and the Bureau s seasonal climate outlooks which are updated monthly. Rainfall outlook The Australian Bureau of Meteorology outlook for rainfall (issued on 30 November 2017) for the period from December 2017 to February 2018 indicates December is likely to be wetter than average for Victoria with weakening chances moving into January. The map below provides Chance of above median rainfall for the December to February period: 6

likely to be warmer than average across Victoria.

7 Temperature outlook The Australian Bureau of Meteorology outlook for rainfall (issued on 30 November 2017) for the period from December 2017 to February 2018 indicates that both the daytime and overnight temperatures are likely to be warmer than average across Victoria. The map below provides Chance of above median maximum temperature for the December to February period: Source: Australian Bureau of Meteorology - 7

8 4.2 Seasonal Streamflow Forecasts November 2017 January 2018 Predicting Melbourne s future streamflow levels is complex and uncertain. This is primarily because it is not possible to accurately forecast the timing and extent of rainfall events and consequently the catchments runoff response to them up to one year ahead. Nevertheless the Bureau of Meteorology produces seasonal streamflow forecasts based on its climate data and flow conditions at 180 monitoring sites across Australia. This information is available at: Their broad forecast summary for the October to December period is: Low and near-median streamflows likely to dominate for November to January Low and near-median flows observed at 76% of locations in October El Niño Southern Oscillation and Indian Ocean Dipole remain neutral 8

9 5. Forward outlook for 2017/18 summer season Based on the already below average rain conditions to date, low streamflows and forecast warmer temperatures in the coming summer months, licence holders can expect to face extended periods of bans and restriction in the coming summer irrigation period until the autumn break arrives. As highlighted under Section 3 above, a number of significant catchments such as the Hoddles Creek, Stringybark Creek, Wandin Yallock Creek and Yarra River are already on bans or restrictions. If predicted average rainfall conditions occur over the next three months this may delay the onset of bans in additional systems but if higher than average temperatures also occur, this will increase both water demand by users and system transpiration losses leading to reduced streamflows. Under average conditions unregulated licence holders around Melbourne are still likely to see an early introduction of bans / restrictions starting in December and likely to extend until at least March. This may be delayed somewhat if above average rainfall conditions occur as predicted. Under dry conditions, restrictions may start in November and continue through until May. Under worst on record conditions customers could see restriction starting immediately and not lifting until winter rainfalls occur in June. Access to water in unregulated systems in 2017/18 will remain highly dependant on weather conditions. The Melbourne Water region can be broken up into western and eastern areas when considering the impact of weather on streamflows, with the western region having a higher level of restrictions / bans in comparison to the eastern region (Table 5). This is due to significant differences in average rainfall totals across Melbourne as well as the eastern region catchments often benefitting from strong groundwater contribution. Region Worst on record weather conditions (5 th percentile) Dry weather conditions (25 th percentile) Average weather conditions (50th percentile) Western (Maribyrnong Basin) All streams on bans for extended period. All streams on bans Minor tributaries will be on bans. Eastern (Yarra Basin) All minor tributaries on bans for extended periods. Yarra River mainstem will be on restrictions and/or bans. All minor tributaries on bans for extended periods. Limited short term access in response to rain events. Yarra River mainstem will be on restrictions. All minor tributaries on bans. Limited access in response to rain events. Yarra River mainstem will be on restrictions Licence holders should continue to monitor restriction and ban status of their relevant catchment in accordance with their licence conditions by visiting the Melbourne Water website: Restrictions and bans - 9

10 6. Other factors affecting entitlement holders and the environment Melbourne Water, in partnership with the Victorian Environmental Water Holder (VEWH), may commence an environmental water release to the Yarra River during the coming summer period. Releases are normally considered in response to low flow conditions in the Yarra River which can result in available habitat for aquatic species being reduced. Releases over the summer have been successful in improving water quality in the lower part of the river. Potential water releases will benefit the river s many aquatic inhabitants, including the regionally significant River Blackfish, and Macquarie Perch. While not available for harvesting by water users, environmental water releases can help sustain flow levels in the river and make it more likely to come off bans or restrictions following subsequent rain events. 7. Further information While these water outlooks are produced only annually by Melbourne Water, information around rainfall and river levels is available on our website for over 200 monitoring sites across Melbourne. In addition our catchment ban and restriction status is updated daily on the website at 5am. Monitoring of both of these sources of information can provide useful insights to likely changes in catchment conditions. Other useful information around what the application of bans and restrictions means to your licence can be found in Melbourne Water s Drought Response Plan for Licensed Water Users: Climate and weather data including outlooks can be found on the Bureau of Meteorology website: 10

SEASONAL RAINFALL FORECAST FOR ZIMBABWE. 28 August 2017 THE ZIMBABWE NATIONAL CLIMATE OUTLOOK FORUM

2017-18 SEASONAL RAINFALL FORECAST FOR ZIMBABWE METEOROLOGICAL SERVICES DEPARTMENT 28 August 2017 THE ZIMBABWE NATIONAL CLIMATE OUTLOOK FORUM Introduction The Meteorological Services Department of Zimbabwe