Lower Darling Operations Plan. September 2018

Transcription

1 Lower Darling Operations Plan September 218

2 Contents 1. Introduction Operational objective Operational rules Water Sharing Plan (WSP) Murray-Darling basin agreement Customers Domestic and stock Local water utility Broken Hill, Pooncarie Regulated river (high security) Regulated river (general security) Drought management measures Reduce water sharing plan minimum flow requirements Pumping to Copi Hollow (maximum storage volume 12GL) Pumping lake Tandure to lake Wetherell Reverse osmosis (Broken Hill) Lower Darling river block banks Temporary bore field for Broken Hill and Menindee Resource analysis /18 water year /19 water year forecast Water allocations Current situation winter rainfall Operations strategy Drought strategy Dry scenario (8 th percentile inflows) Medium/wet scenario (5 th percentile) Water quality Key operational decisions and dates Key messages regarding drought measures

3 1. Introduction WaterNSW has developed the Lower Darling Operations Plan to ensure water supplies for Broken Hill and surrounding communities and reliable water supply to the customers along the Lower Darling can be maintained through a repeat of the worst drought of record. The Operations Plan is a living document and will be updated regularly based on changing conditions. Water is stored in Menindee Lakes to meet water needs including provision for water losses (seepage and evaporation), maintaining the Lower Darling environment supply for essential requirements (e.g. town water supply, domestic and stock and basic land holder rights) and General Security Licenses in the Lower Darling and lower Murray systems. The Operations Plan looks to optimise water delivery through maximising releases from the lower storages (Menindee and Cawndilla) and retaining water in the more efficient Upper Lakes (Wetherell and Pamamaroo) until demands and outlet capacity constraints of the lower storages necessitates releases. WaterNSW has analysed the lowest inflow sequences and maximum evaporation data for the region to ensure operations of the lakes are optimised for supply through a repeat of the drought of record and drier scenarios. 3

4 2. Operational objective The aim of the plan is to maximise the use of the resource to meet customer demands within the Lower Darling water source and to meet NSW and Victoria s contribution to the Murray while ensuring that essential water needs can be met through a repeat of the worst drought on record. The plan also identifies the key actions required to extend supplies if inflows are lower than previous droughts. The plan therefore has been developed to ensure that critical water needs can be met and the environmental needs of the Lower Darling River are maintained. Key operational objectives: Maintain supply to meet Broken Hill s demands; Maintain a continual flow of water along the Lower Darling (maintain flow at Burtundy) through a repeat of the lowest inflows on record; and Maximise use of water in the lower Lakes to meet customer demands first. The operations plan has considered 3 inflow scenarios that will guide operational decisions. They provide assessment of a range of conditions that may occur in the coming months. Scenario 1 Sahara no inflow occurs at Wilcannia through to resource being exhausted; Scenario 2 Drought - Statistical worst inflow sequence on record - applied from Sep 218 with resources managed to the next significant inflow; and Scenario 3 Dry scenario - 8th percentile inflow sequences applied from Sep 218 to represent the likely no inflow scenario. The dry scenario considers an inflow sequence that could be expected to be exceeded 8 years out of 1 based on historical records. WaterNSW will continue to review the system operations forecast with the aim to implement drought measures as the volume of water in the lakes reduce. As there is no guarantee that the next drought will not be more severe than the last, the design scenario is considered to be scenario 1, it is the worst case scenario. Scenario 2 provides for a repeat of the worst inflow sequence, this scenario considers the measures required to manage the systems water resources through a repeat of these conditions to provide the best outcome possible. Scenario 3 provides scope of the potential system operations in the event of some inflows, but overall the system remains relatively dry, and what this would mean for river flows and town water supplies. Overall it is unlikely that the conditions presented in these scenarios will be repeated. Rather they will be used to help inform customers and community about potential system operations over the next months and guide operational decisions as time progresses. Ultimately the decisions made will be in response to the conditions that do occur. 3. Operational rules 3.1 Water Sharing Plan (WSP) The WSP provides a framework for sharing of water resources within the Lower Darling, aiming to provide a balance between environmental, economic and social objectives. The plan establishes a bulk access regime for the extraction of water under access licences providing for environmental water rules or planned environmental water, water for basic landholder rights and extraction under a number of access licence categories. 4

5 The WSP was originally gazetted in 23 and as such the framework has been established based on inflow sequences prior to this time. Since gazette of the plan, the minimum inflow sequence prior to 23 has been exceeded on at least 2 occasions. The WSP provides for licenced entitlements of: Domestic & Stock Local Water Utility Regulated River (High Security) Regulated River (General Security) Supplementary although all supplementary entitlement is now held by government and has essentially be retired from extractive use The WSP provides that minimum releases be delivered at Weir 32 for the suppression of algae, noting the seasonal variability, the minimum release requirements are as follows: Jan - Mar 35 ML/d Apr 3 ML/d May - Oct 2 ML/d Nov - Dec 3 ML/d These releases total 95.6 GL/year. 3.2 Murray-Darling basin agreement The Commonwealth Water Act 27 provides the Murray-Darling Basin Agreement within Schedule 1 of the Act. Clause 95 of Schedule 1 provides the New South Wales entitlement to water from Menindee Lakes. Clause 95 provides that: Whenever water in the Menindee Lakes storage falls below 48 GL, New South Wales may use stored water as it requires until the volume next exceeds 64 GL. Whenever sub clause 1 does not apply, the resources within the storage are shared in accordance with Clause 94 (c), meaning that inflows to the storage are shared 5:5 between Victoria and New South Wales. The agreement provides that the Murray-Darling Basin Authority, acting on behalf of the signatories to the agreement, shall manage the access and delivery of resources held within the Menindee Lakes storage in accordance with system operating requirements. 4. Customers 4.1 Domestic and stock Domestic & Stock 115 licences share component 1,37 ML. Domestic & Stock use in the Lower Darling generally exceeds 4 ML/year. Average annual use has been impacted by periods of no access in the Lower Darling in recent years. Figure 1 shows the annual historical use for domestic and stock from 212/13.Domestic & stock water is required 5

6 Usage (ML) Lower Darling Operations Plan September 218 all year round and requires a continual flow along the Lower Darling between Weir 32 and Burtundy Weir. 8 Domestic & stock /13 213/14 214/15 215/16 216/17 217/18 Average Figure 1: Historical Use - Domestic & Stock 4.2 Local water utility Broken Hill, Pooncarie LWU - 2 licences share component - Broken Hill 9,975 ML; Pooncarie 16 ML. Broken Hill demand varies from 15 ML/d over winter to 35 ML/d over summer. Historical use shown in figure 2 indicates that use is usually over 3,5 ML/year, and regularly exceeds 5, ML/year. Water quality can be a big issue for town water supplies with salinity content above 1, EC resulting in taste concerns and above 1,5 EC resulting in corrosive issues on residential, commercial and industrial equipment. Once water quality exceeds these levels additional levels of treatment is required to ensure the water can be used for town supply. 6

7 Usage (ML) Usage (ML) Lower Darling Operations Plan September Local water utility /13 213/14 214/15 215/16 216/17 217/18 Average Figure 2: Historical Use Local Water Utility 4.3 Regulated river (high security) High security 69 licences share component 7,771 ML Consumptive 4,196 ML E-water 3,575 ML Historical use shows that use is in most years over 3,5 ML/year, and regularly exceeds 4, ML/year (refer to figure 3). The exceptions being years in which use restrictions have been in place for drought management. 5 High security /13 213/14 214/15 215/16 216/17 217/18 Average Figure 3: Historical Use - high security 7

8 Usage (ML) Lower Darling Operations Plan September Regulated river (general security) General security 92 licences share component 79,57 shares Consumptive 1,143 shares E-water 69,364 shares The history of general security use has been highly variable. Recent years has been boosted by significant allocation assignments into the Lower Darling system by both consumptive users and the environmental water managers. While the average use is calculated as 91,1 ML/year, that annual use ranges from 9 ML in 215/16 to 185, ML in , where e-water holders used 183, ML. Figure 4 shows the historical general security uses since 212/13. 2 General security /13 213/14 214/15 215/16 216/17 217/18 Average Figure 4: Historical Use - General Security 5. Drought management measures 5.1 Reduce water sharing plan minimum flow requirements The WSP provides 95.6 GL of water for release over Weir 32, in a seasonal pattern for improved water quality in the lower Darling. Meeting the WSP requirement is a significant draw on the available resources, once the system reaches 48 GL and access to resources transfers solely to NSW. WaterNSW has allocated a budget of 63 GL per year for releases downstream of Weir 32, once the 48 GL trigger is achieved when no significant inflows are in transit upstream of the storage. 8

9 The WSP minimum flow requirements have been set based on what is assumed necessary to maintain ecological function and minimise risk of Blue Green Algal outbreaks. Reducing below the minimum required flows during Summer will create an increased risk of algal outbreak, that is unlikely to be mitigated through increased flow. The option of maintaining minimum flow requirements at Weir 32 will reduce the duration of time that flow through the system can be maintained if no further inflows occur. That is, the resources will be depleted sooner, and as such, without inflow, cease to flow at weir 32 will occur sooner. In this plan greater value has been placed on maintaining a reliable supply to the Lower Darling water users, extending the duration of stock, domestic and town water supplies. However, if higher rates of release are supported by community and customers for management of water quality, these would be considered. 5.2 Pumping to Copi Hollow (maximum storage volume 12GL) Additional storage in Copi Hollow requires the installation of a block bank across the interconnecting channel between Copi Hollow and Lake Pamamaroo. Pumping from Lake Pamamaroo to Copi Hollow needs to commence before the water level and water quality in Pamamaroo drops too low, commencing when Pamamaroo reaches 18GL, and can only be achieved to a volume of 72 GL. Pumping to Copi Hollow extends the period of time that supply can be made to Broken Hill without the need for reverse osmosis. 5.3 Pumping lake Tandure to lake Wetherell Lake Tandure is a small flat storage lake that is usually connected to Lake Wetherell. Naturally the two lake bodies separate when the storage reaches 57.8 m or approximately 9.4 GL. However, efficiency in system storage can be achieved by installing a bank and isolating Lake Tandure when the Lake Wetherell total storage reaches around 53 GL, and pumping the volume held in Lake Tandure to Lake Wetherell. This reduces the surface area of the stored volume and provides efficiency through reduced evaporation. Pumping from Lake Tandure can extend the period that supply can be made to Broken Hill. 5.4 Reverse osmosis (Broken Hill) Water quality in Lake Wetherell decreases as the water evaporates and leaves the salt behind. The electrical conductivity (measurement of salinity) increases to a point where it becomes unsuitable for domestic supply (above 1,5 E.C.). Essential Water has capacity to install a reverse osmosis treatment plant for use when water supplies from the Menindee scheme exceed 1,5EC. This requires some work by Broken Hill to re-instate the facility. Essential Water have a primary extraction point for supply from upstream of Weir 32. The Weir 32 weir pool has continuous monitoring of E.C. at the WaterNSW hydrometric gauging station. Essential Water may also source water from Copi Hollow for drought supplies. Monthly monitoring of Lake water quality is the normal regime, however, this would be increased during drought 9

10 management periods or algal outbreaks. Essential water is also likely to complete a rigorous water quality monitoring program of all supplies. 5.5 Lower Darling river block banks When the water supply is insufficient to secure both Broken Hill and maintain continuous flows in the Lower Darling, block banks are constructed as temporary weirs in the Lower Darling. The water behind these block banks would then extend the supply of stock and domestic and high security supplies in these locations. However, they supply only a limited number of customers and do not address the need of all customers along the lower Darling. 5.6 Temporary bore field for Broken Hill and Menindee Bores have been installed in the Menindee Lake and Tallyawalka aquifers. The water quality in these aquifers is suitable for supply to Broken Hill and Menindee township, although the Menindee bore-field would still require reverse osmosis treatment due to salinity marginally above the 1,5EC threshold. Commissioning of these bore-fields would require; power, pumps and substantial pipelines that would take about six months to construct. This action has been strongly opposed by the Broken Hill community in past years. 6. Resource analysis /18 water year Inflows to Menindee Lakes System have been very low during 217/18 water year. Storage volume peaked at 1,585 GL on 17 December 216 and since then decreasing due to evaporation and releases to meet downstream demands. As shown in figure 5, the storage volume was 768 GL at the start of 217/18 water year which has depleted to 29 GL at the end of water year by 3 June 218. The storage volume is 179 GL as of 29 August 218. The 217/18 total flow at Willcannia was 52 GL and inflows to the lake system was 21 GL. Most of the inflows arrived during July to Dec 217 and a small inflow arrived at the end of the water year from Northern Connectivity Event i.e. when Environmental water was released from Gwydir and Border River Catchments and s324 order was in place to protect the water. Around 2 GL inflow was recorded since the start of 218/19 water year and that was mostly from Northern Connectivity Event. Figure 6 shows the recorded flows along the Barwon Darling River system since July

11 1-Jul Jul-17 3-Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun-18 Flow (ML/day) Storage volume (ML) Lower Darling Operations Plan September 218 3,5 Darling river flows and Menindee storage volume 9, 3, Menindee storage volume 8, 7, 2,5 2, Weir 32 release Evaporation (3 day moving average) 6, 5, 1,5 4, 1, 3, 2, 5 1, Figure 5: Menindee Lakes Total Volume, Storage release and Evaporation 217/18 WaterNSW HYPLOT V133 Output 5/9/218 Period 15 Month 1/7/217 to 1/1/ BARWON MUNGINDI 141. Discharge (ML/d) CP 4221 DANGAR BDGE141. Discharge (ML/d) CP 4253 DARLING@BOURKE TOWN 141. Discharge (ML/d) CP DARLING@WILC. MAIN C 141. Discharge (ML/d) CP Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Figure 6: 217/18 Recorded system Inflows 11

12 /19 water year forecast Water allocations Water allocation for the Lower Darling were announced in early July with 1% allocation provided to High Security customers and no allocations for General Security customers. Average carryover was 15%. Customer group Account volume (ML) LWU 1,135 Domestic and Stock 1,37 High Security 7,77 General Security AWD General Security Carryover 12,213 General Security Environmental 9,528 Table 1: Available Water as at 1 July Current situation As of 29 August 218, the storages were at 179 GL. More water was held in the Upper Lakes (152.5 GL) than the Lower Lakes (26.5 GL). Due to low rainfall events, Barwon Darling River system was mostly disconnected during the second half of 217/18 water year. Wilcannia was at cease to flow condition for 97 days starting from 27 January 218. Flow arrived at Wilcannia during 1 st week of May from rainfall events of Moonie and Culgoa in Queensland then continues with Northern Connectivity Event. Barwon Darling River is not currently flowing, and flows has now ceased at the end of Northern Connectivity Event. The Menindee Lakes system has received around 1.5 GL of inflow over the winter months. Currently, with the total storage is below the trigger volume of 48 GL a number of drought mitigation measures are in place: a) Installation of block bank between Lake Tandure and Lake Wetherell was completed on 15/3/218. Water was pumped from Lake Tandure into Lake Wetherell to reduce the evaporation loss from the former. About 7,2 ML was pumped into Lake Wetherell between 26/3/218 and 17/5/218 b) Reduced flow targets at Weir32 to target minimal flows at Burtundy c) Installation of block banks in the Lower Darling River to provide a reliable supply to water users in the Lower Darling River. a. Jamesville Bank: Located near Pooncarrie the bank was constructed on 4 July 218 and filling has commenced with reduced supply to Lower Darling River. By mid- September the bank was about 2.613m full. 12

13 b. Ashvale Bank: Located near Burtundy the bank was constructed on 3 August and filling has commenced with reduced supply to Lower Darling River. By mid- September the bank was about 2.126m full. c. In addition to the above, planning is underway to install two more banks at Karoola and at Court Nareen. d) Installation of a bank to isolate Copi Hollow from Lake Pamamaroo has been completed on 24 August as originally planned. Pumping has commence to fill Copi Hollow to about 12 GL with an aim to extend the supply to Broken Hill. With low storage volume and minimum inflows, demands for town water supply, stock and domestic and expected to be delivered during this spring/summer. Very limited supply will be available only for permanent plantings during the summer months. Any supply will be dependent upon future inflows and after ensuring enough water is available to meet critical environmental and human water needs. Demands for town water supply, stock and domestic, are expected to be met until June winter rainfall Rainfall over the winter months has been below to very much below average across NSW, with large areas especially in the north west receiving very much below average rainfall. Areas west of the Great Dividing Range has received less than 25-1mm of rain during winter. South West Queensland has experienced average to below average rainfalls with the Murray Darling basin catchment receiving less than with only 1-1mm of rain falling. This has result in low flow generating along the Barwon Darling during winter from rainfall but releases from Gwydir and Border catchments for Northern Connectivity Event, with s324 order in place, delivered more than 7.4 GL at Wilcannia with a peak of 5 ML/day. Flow ceased at Wilcannia by the end of August. 13

14 Figure 7: Last 3 months rainfall in the Murray Darling Basin 14

15 1/7/18 6/7/18 11/7/18 16/7/18 21/7/18 26/7/18 31/7/18 5/8/18 1/8/18 15/8/18 2/8/18 25/8/18 3/8/18 Flow (ML/day) Lower Darling Operations Plan September 218 Barwon Darling flows Barwon Mungindi Darling Bourke Darling Wilcannia Figure 8: Flows in the Barwon Darling since 1 July Operations strategy WaterNSW will operate the storages to ensure that key objectives can be met based on the worstcase scenario (repeat of the drought of record) inflow sequence. However, the plan also looks at a less conservative strategy (8 th percentile) to show the variability of water to allow for broader planning. WaterNSW has engaged with customers to understand demands for the next year and has developed a release strategy that addresses the system key objectives including ensuring a continuous flow along the Lower Darling and supply to Broken Hill. The main drivers for customer demands in 218/19 will be supply to: Water Sharing Plan requirements for the Lower Darling; Broken Hill water supply (1GL) High security customer in the lower Darling (8GL) Environmental license holder (9GL); As outlined in the Operational Objective (Section 2) WaterNSW has consider a number of scenarios within the operational strategy. All strategies assume that there will be no inflows between the end 15

16 Jun-16 Aug-16 Oct-16 Dec-16 Feb-17 Apr-17 Jun-17 Aug-17 Oct-17 Dec-17 Feb-18 Apr-18 Jun-18 Aug-18 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-19 Feb-2 Apr-2 Jun-2 Aug-2 Storage volume (ML) Lower Darling Operations Plan September 218 of the recession. Figure 9 shows the Menindee lakes storage volume forecasts for three different scenarios Actual Menindee lakes volume (ML) Forecast Zero inflow sequence Drought inflow sequence Dry 8th percentile inflow sequence Figure 9. Menindee Lakes volume based on the three inflow scenarios 7.1 Drought strategy To ensure that customer demands and operational objectives are met a number of drought management measures will be needed as the drought sequence intensifies. These drought management measures include reducing the minimum environmental releases along the Lower Darling and implementing drought storages (Copi Hollow) and treatment options (Broken Hill Reverse Osmosis). Timeframes for implementing these measures have been identified in the Operational Plan based on storage triggers. 16

17 Jul-16 Aug-16 Oct-16 Dec-16 Feb-17 Apr-17 Jun-17 Aug-17 Oct-17 Dec-17 Feb-18 Apr-18 Jun-18 Aug-18 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-19 Feb-2 Apr-2 Jun-2 Aug-2 Storage (ML) Lower Darling Operations Plan September 218 6, Lake storage under drough inflow scenario Actual Forecast 5, 4, Wetherell (total) Pamamaroo (total) Menindee Cawndilla 3, 2, 1, Figure 1. Individual lakes total volume (drought inflow scenario) Inflows during the ending quarter Zero Inflow Minimum statistical Flow 8th percentile Flow End of quarter storage Zero inflow Minimum statistical flow 8th percentile flow Quarter Dec-Feb 18 6,917 6,917 6, , , ,654 Mar-May ,31 216,31 216,31 Jun-Aug 18 1,455 1,455 1, , , ,491 Sep-Nov 18 5,16 93,223 93,225 96,74 Dec-Feb 19 66,9 32,138 32,146 78,81 Mar-May ,3 18,458 18, ,249 Jun-Aug 19 3,64 151,74 13,654 17, ,875 Sep-Nov 19 13,2 82,77 7,95 23,15 196,957 Dec-Feb 2 43,992 17,24 3,846 32,79 231,37 Mar-May 2 266,1 2,325 19, ,363 Jun-Aug 2 3,64 74,98 1,491 19,748 39,55 Table 2: Total Lake Inflow Scenarios WaterNSW has adopted the drought scenario recommencing in Sep 218 (24-months of minimum inflows based on historical records), as the basis for its drought preparedness. The tables below outline the likely inflows, releases and evaporation from the storages to enable the development of a drought management plan to be prepared for the system. 17

18 Total Lakes Quarter ending Inflows Release Evaporation End of quarter storage Weir 32 daily flow (ML/d) Dec-Feb 18 6,917 73,45 141,96 316, Mar-May 18 3,35 65,18 216, Jun-Aug 18 1,455 2,148 29,15 177, Sep-Nov 18 19,42 66,41 93, Dec-Feb 19 5,674 54,48 32, Mar-May ,63 18,466 9 Jun-Aug 19 3, ,54 17, Sep-Nov 19 13, ,83 23,15 26 Dec- Feb 2 43,992 2,93 15,4 32,79 23 Mar-May 2 8,681 5,71 19, Jun-Aug 2 3,64 1,945 3,99 19, Table 3: Total Lake Forecast Data (Drought Scenario) Upper Lakes (Wetherell and Pamamaroo) Quarter ending Inflows Release Evaporation End of quarter storage Weir 32 daily average flow (ML/d) Dec-Feb 18 6,917 73,45 69,1 238, Mar-May 18 3,35 38,21 179, Jun-Aug 18 1,455 2,148 18,35 151, Sep-Nov 18 19,42 46,72 86,4 269 Dec-Feb 19 5,674 47,16 32, Mar-May ,71 18,465 9 Jun-Aug 19 3, ,62 17, Sep-Nov 19 13, ,92 23,13 26 Dec-Feb 2 43,992 2,93 14,13 32,77 23 Mar-May 2 8,681 4,79 19, Jun-Aug 2 3,64 1,945 3,7 19, Table 4: Upper lakes (Wetherell and Pamamaroo) forecast data (Drought Scenario) L Cawndilla Quarter Release Evaporation End of quarter storage Dec-Feb 18 43,21 51,9 78,31 Mar-May 18 7,55 26,97 36,596 Jun-Aug 18 1,8 26,62 Sep-Nov 18 19,69 6,824 Dec-Feb 19 7,32 35 Mar-May Table 5: Lake Cawndilla forecast data 7.2 Dry scenario (8 th percentile inflows) The dry scenario considers the 8 th percentile inflow sequence to the lakes, inflows that would be exceed 8 years in 1. 18

19 Jun-16 Aug-16 Oct-16 Dec-16 Feb-17 Apr-17 Jun-17 Aug-17 Oct-17 Dec-17 Feb-18 Apr-18 Jun-18 Aug-18 Oct-18 Dec-18 Feb-19 Apr-19 Jun-19 Aug-19 Oct-19 Dec-19 Feb-2 Apr-2 Jun-2 Aug-2 Storage volume (ML) Lower Darling Operations Plan September 218 Under this scenario the volume of water held within the lakes would start to increase from Dec 218. Refer to figure 11 for Menindee lakes storage volume forecast for this scenario. No major drought management measures will be required. Under this scenario supply along to customers would continue. However, depending upon timing of the inflows it is high likelihood the total volume in the Lakes will remain below the 48GL and not increase above the 64GL over the two-year period. This means no water will be available for the MDBA to meet demands in the Murray over that period. 1,8, 1,6, 1,4, Menindee lakes volume (ML) Actual Forecast Dry 8th percentile inflow sequence 1,2, 1,, 8, 6, 4, 2, Figure 11: Lakes total volume under the 8 th percentile inflow sequence. 7.3 Medium/wet scenario (5 th percentile) Under either the 5 th percentile or wet scenario will result in the filling of the lakes with the volume of water held in the lakes exceeding the needs of all customers and WaterNSW will be able to meet all customer demands. 7.4 Water quality Based on current forecasts the salinity levels will reach 1, electrical conductivity (E.C.) in December 218 and 1,5 E.C. in April 219. Figure 12 shows the lake Wetherell salinity levels for drought inflow sequence. If raw water salinity levels increase above 1, E.C. it will begin to have an impact on the taste of the Broken Hill water supply and once salinity levels reach 1,5 E.C. the water quality will have a corrosive impact on water using appliance and equipment. 19

20 1-Jul-17 3-Aug Oct Dec Feb Apr Jun Aug Oct Dec Feb Apr Jun-19 2-Aug Oct Dec Feb-2 16-Apr-2 15-Jun-2 14-Aug-2 Lake salinity (EC µm/cm) Lower Darling Operations Plan September 218 Water quality in Lake Wetherell will be key to the time of alternating supply from Weir 32 to Copi Hollow for supply to Broken Hill. Future of Broken Hill water supply will depend on the completion of Wentworth to Broken Hill pipe line project. 25 Actual Lake Wetherhell salinity Forecast Figure 12: Salinity levels in lake Wetherell (drought inflow sequence) 7.5 Key operational decisions and dates The follow table outlines dates for key operational changes required to ensure operational objectives are met. The model optimises the use of Lake Wetherell first drawing water from the flood plain then transferring releases to Pamamaroo. The model has also used the worst recorded evaporation data. Assumptions Base case Drought scenario Dry scenario Inflow No inflow beyond recession of current inflow Statistical worst inflow sequence on record - Applied from Sep 218 8th % Inflow sequence -Applied from Sep 218 Broken Hill reserve Planned 5 GL of active storage - but due to switch to Copi Hollow when Weir 32 EC forecast to exceed 1,5 EC. MDBA Delivery Ceased since second week of December 217 MDBA Delivery 15-Dec Dec Dec-17 Cease - 48 trigger Volume in Wetherell + 48GL 37 GL 37 GL 37 GL 2

21 Volume in Cawndilla 172 GL 172 GL 172 GL + 48 GL trigger Results Zero inflow Drought scenario Dry scenario Weir 32 Flows - NSW control - post 48 GL Sept to Dec 2 Flow ceased on Jan 219 Sept to Dec 2 Flow ceased on Jan 219 Per Water Sharing Plan MDBA volume accessible Tandure pumping Pumping to Copi Hollow Lower Darling Cease to Flow Switch Supply to Copi Hollow (depending upon EC level in Wetherell) Not available Not available Not available First phase completed 25 Mar to 17 May 218. First phase completed 25 Mar to 17 May 218. Sep 218 Sep 218 Sep 218 First phase completed 25 Mar to 17 May 218. End Dec 219 End Dec 219 No supply issue forecast Dec 218 Dec 218 Dec 218 Broken Hill Supply switch back to lake Wetherell Broken Hill Supply fail April 219* On hold pending W2BHill pipeline Sept 219 On hold pending W2BHill pipeline * Salinity is likely to be high Table 5: Key Operational changes required April 219* On hold pending W2BHill pipeline Secure end of forecast period 31 Aug 22 Feb 219 Secure end of forecast period 31 Aug Key messages regarding drought measures Drought measures are in place since Dec 217. WaterNSW is continuously monitoring the situations and implemented various measures to manage the resources during drought. Following are the highlights regarding key drought management measures WaterNSW has numerous works in place to secure Broken Hill until the pipeline is available, and to extend Lower Darling supplies to S&D and High Security. Block Bank in place between Wetherell and Tandure isolating lake Tandure providing efficiency through reduced evaporation. Block Bank between Copi Hollow and Lake Pamamaroo is in place to continue supply to Broken Hill without the need for reverse osmosis. Two temporary block banks downstream of Pooncarie (Ashville and Jamesville) have already been installed to maintain continuous flows with limited supply to number of customers. 21

22 Two additional temporary block banks upstream of Pooncarie are being planned at Karoola and at Court Nareen to secure S&D supply Increased frequency of lake water quality monitoring of all water supplies. Broken Hill Pipeline project is expected to provide assistance supplying the Broken Hill community after December 218 Reviewed by Partha Saha on 19 September