WATER COMPLIANCE REPORT

2018 - 2019 Water Year

Water Report 2018 - 2019 1 ABOUT THIS REPORT COMPLYING WITH

Since the Snowy Scheme’s completion in 1974, Limited has carefully managed the water that flows through the Scheme’s , tunnels, aqueducts and power stations in accordance with our OUR LICENCE water licence. This report outlines how we are managing the water that flows through the Scheme. Snowy Hydro complied with all of the requirements imposed upon the company under the Snowy Hydro operates a complex hydro-electric scheme utilising the water captured by the Scheme Snowy Water Licence during the 2018 - 19 water year, including each water release target to generate energy to meet the market’s needs, while also moving water from east to west to support relating to: irrigation districts. ● The Required Annual Release to the Murray catchment. Each year, we have to reach certain targets for downstream and environmental water releases. Snowy ● The Required Annual Release to the catchment. Hydro has operational flexibility day-to-day to strategically manage our generation and water releases while at the same time giving long-term security to the downstream users around annual water releases. ● Environmental releases into the from Jindabyne . In the Snowy Scheme, water releases and electricity generation are inseparably linked. ● Environmental releases into the Murrumbidgee River from Tantangara Dam. ● Environmental releases into the from Goodradigbee Aqueduct. Snowy Hydro is operated under the Snowy Water Licence, issued to us by the NSW Government. The licence has many legally-binding and enforceable obligations on the company. ● Environmental releases into the from Middle Creek and Strzelecki Creek Aqueducts. ● Environmental releases into the Snowy River from Falls Creek, Bar Ridge and Diggers Snowy Hydro is obligated under the Snowy Water Licence to: Creek Aqueducts. Target water releases to the River Murray and Murrumbidgee River catchments, the annual volumes of which are determined according to highly-prescriptive formulae set out in the Snowy Water Licence; Target water releases from into the Snowy River for environmental purposes (Snowy River Increased Flows); and

Facilitate additional natural flows to nominated for environmental purposes (Snowy Montane

Rivers Increased Flows).

This report is an important channel to educate and inform our stakeholders about the water operations of the Scheme. While we generate energy from the water that moves through the Scheme, we don’t own a drop of it; nor do we sell the water or charge people to access it.

Snowy Hydro must operate the Snowy Scheme to first meet its water release obligations and then to maximise electricity market opportunities within the constraints imposed by the Snowy Water Licence.

The Snowy Water Licence recognises the difficulties inherent in achieving precise release volumes at each release point, so any shortfall or excess is accounted and generally dealt with by an ‘unders’ and ‘overs’ approach, whereby the shortfall or excess is added or subtracted to the following year’s target – i.e. there is no way that Snowy Hydro can consistently ‘under-deliver’ water to any aspect of the release program.

For more information about the Snowy Water Licence we encourage people to visit the NSW Department of Primary Industries Water at water.nsw.gov.au

Water Report 2018 - 2019 2 WESTERN RIVER RELEASES RIVER MURRAY CATCHMENT MURRUMBIDGEE RIVER CATCHMENT

Snowy Hydro complied with its obligation to target the Required Annual Release (RAR) from the Snowy Hydro complied with its obligation to target the Required Annual Release from the Snowy-Murray Development to the River Murray catchment during the 2018 - 19 water year. Snowy-Tumut Development to the Murrumbidgee River catchment during the 2018–19 water year.

The total accounted release volume was 914GL (Note 1GL rounding error). This was made up of: The total accounted release volume was 793GL. This was made up of: 763 GL being the 2018–19 Required Annual Release calculated under the Snowy Water Licence; less 730 GL being the agreed 2018–19 Required Annual Release calculated under the Snowy Water 47 GL of Net DISV Increase; plus Licence; plus 199 GL of pre-release of the 2019–20 Required Annual Release; plus 63 GL of pre-release of the 2019–20 Required Annual Release; plus 0 GL of Discretionary Above Target Water Releases (water not required for RAR releases that Snowy 0 GL of Discretionary Above Target Water release (water not required for RAR releases that Snowy Hydro is able to release at its discretion) Hydro is able to release at its discretion). This total accounted release volume includes 18 GL of Montane environmental flow releases provided This total accounted release volume includes 10 GL of Montane environmental flow releases provided to the Geehi and Swampy Plains River which did not flow through Scheme power stations. to the Murrumbidgee and Goodradigbee Rivers which did not flow through Scheme power stations.

Inflows and Releases to the River Murray Catchment during 2018 - 19 Inflows and Releases to the Murrumbidgee Catchment during 2018 - 19

1300 1400 1200

1100 1200

1000 1000 900

800 800 700

600 600 Gigalitres Gigalitres 500

400 400 300

200 200

100 0 0 Long Term Average Inflows 2018 - 19 Actual Inflows 2018 - 19 Actual Release Long Term Average Inflows 2018 - 19 Actual Inflows 2018 - 19 Actual Release (Upper Tumut) (Upper Tumut)

Water Report 2018 - 2019 3 Snowy River Increased Flows (SRIF) and Jindabyne Base Passing Flow (BPF) ENVIRONMENTAL RELEASES Releases and Daily Limits 2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019 SNOWY RIVER INCREASED FLOWS 6000 Number of days when SRIF releases Snowy Hydro complied with its obligation to target releases from Jindabyne Dam for environmental were outside daily limits = 5 purposes during the 2018 – 19 water year. 5000

The volume of Snowy River Increased Flows (SRIF) released from Jindabyne Dam during the 2018 – 19 4000 water year was 129.4GL, which was 0.8 GL above the target volume of 128.6GL. That deficit is well within the +/–10% annual tolerance around the target volumes allowed under the Snowy Water Licence. 3000 The 2019–20 target has been adjusted up to account for this release deficit. 2000

In addition to the environmental releases, 8.5GL Base Passing Flow (BPF) was also released from (ML/day) Release Daily 1000 Jindabyne Dam and 0.5GL riparian flow was released from the Mowamba Weir.

All monthly releases were within the +/–20% monthly tolerance around the target volumes tolerance 0 allowed under the Snowy Water Licence. There were five days where the daily releases were outside 2 Apr 2 Apr 19 8 Jan 8 Jan 19 2 Oct 18 5 Mar 19 5 Mar 5 Feb 19 5 Feb 10 Jul 18 10 Jul 1 May 18 1 May 4 Sep 18 7 Aug 7 Aug 18 24 Jul 18 24 Jul 12 Jun 12 Jun 18 22 Jan 22 Jan 19 16 Apr 16 Apr 19 16 Oct 18 30 Apr 30 Apr 19 the daily target by more than 20%. These were reported to NSW DoI Water. All other releases were 11 Dec 18 26 Jun 26 Jun 18 19 Mar 19 19 Mar 19 Feb 19 19 Feb 30 Oct 18 13 Nov 18 13 Nov 21 Aug 21 Aug 18 18 Sep 15 May 18 15 May 27 Nov 18 27 Nov 25 Dec 18 29 May 18 29 May within the +/–20% daily tolerance allowed under the Snowy Water Licence. SRIF Jind BPF SRIF Low Limit SRIF High Limit As allocations for the 2018–19 water year once again exceeded 100GL, a flushing flow was Scheduled for the Snowy River as set out on page 5. Due to persistent dry inflows, the level required to Snowy River Increased Flows (SRIF) and Jindabyne Base Passing Flow deliver the flushing flow could not be achieved. Snowy Hydro worked closely with NSW DoI Water to (BPF) Releases including Mowamba Riparian Releases deliver a flow with a lower peak and longer duration. 2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019

The comparison of the annual, monthly and daily release targets for the Snowy River Increased Flow 80 240 Actual SRIF releases Actual BPF releases releases against the actual releases is shown in the following charts. 70 SRIF monthly target +20% 200 SRIF monthly target -20% 60 Target progressive SRIF releases Actual progressive SRIF releases 160 50 SRIF annual target +10% SRIF annual target -10% 40 120

30 80 Monthly Release (GL) Release Monthly

20 (GL) Releases Progressive 40 10

0 0 May 18 Jun 18 Jul 18 Aug 18 Sep 18 Oct 18 Nov 18 Dec 18 Jan 19 Feb 19 Mar 19 Apr 19

Water Report 2018 - 2019 4 DELIVERING ‘FLUSHING FLOWS’ OUT OF JINDABYNE DAM INTO THE TEMPERATURE OF RELEASES FROM LAKE JINDABYNE THE SNOWY RIVER The Snowy Water Licence requires the outlet works at Jindabyne Dam to be capable of releasing In any year when allocations exceed 100GL, Snowy Hydro can be instructed by NSW Office of Water to water from above any thermocline in the reservoir. The thermocline is a thin, but distinct, layer in a deliver a flushing flow to the Snowy River. A flushing flow is defined as a day when the release target large body of water in which water temperature changes more rapidly with depth than it does in the exceeds the 5GL capacity of the other release infrastructure at Jindabyne Dam, meaning that the layers above or below. Typically, as the summer progresses, the surface waters warm and the deeper spillway gates must be opened to achieve the flow target. waters remain cold. This causes a lack of mixing between the upper and lower layers, which can result in the lower layer having reduced oxygen levels. For these reasons the deeper waters within The intent of the flushing flows is to mimic the effect of the spring snow melt in the Snowy River. These are generally viewed as having undesirable water quality characteristics for releases, hence the high flows are intended to scour the bed of the channel and remove fine sediment to improve the requirement for the outlet works to be able to draw from above the thermocline. habitat of the river for fish and macro invertebrates. The intake works at Jindabyne are located at the end of a channel excavated into the bank of Lake A flushing flow had been scheduled for October 2018, but the ongoing drought meant that despite Jindabyne. In addition to the variable level shutters in the intake tower, the level of the base of the prudent management of storage levels in Jindabyne Dam, the level was not sufficient to make a channel means that the deeper waters of the reservoir are inaccessible. This means that the thermocline release from the spillway infrastructure. Snowy Hydro worked closely with the NSW Office of Water to is only likely to be above the levels of the intake channel when the lake is at much higher levels. develop an alternative release schedule. The release pattern was set by the NSW Office of Water, with releases peaking at 3.8 GL per day and was discharged through the cone valves. Snowy Hydro undertakes temperature monitoring at the intake tower to detect the presence of a thermocline and adjusts shutter height as necessary. As can be seen in the chart opposite, all releases The NSW Office of Water, working with representatives across local, state and Commonwealth were made from above the thermocline. Government agencies, was responsible for the advice to downstream landholders and other stakeholders that would be impacted by the increased Snowy River levels. Jindabyne Dam Intake Water Temperatures and Level

908

906

904

902

900

Dam Level Dam 898

896

894

892

890

888 5 10 15 20 25

Temperature (Deg C) Water Report 2018 - 2019 5 SNOWY MONTANE RIVERS INCREASED FLOWS Snowy Montane Rivers Increased Flows (SMRIF) from Tantangara Dam and Daily Limits Snowy Hydro complied with its obligation to target Snowy Montane Rivers releases for Environmental 2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019 purposes during the 2018 – 19 water year. 300 Number of days when Montane releases During the 2018 – 19 water year, Snowy Hydro was directed to make Snowy Montane Rivers Increased were outside daily limits = 0 250 Flows (SMRIF) from the following locations:

Tantangara Dam to the Murrumbidgee River, 200 Goodradigbee Aqueduct to the Goodradigbee River (a tributary of the Murrumbidgee River), 150 Middle Creek Aqueduct to Middle Creek and Strzelecki Creek Intake on the Geehi River Aqueduct to

Strzelecki Creek (tributaries of the Geehi River), and 100 Daily Release (ML/day) Release Daily Bar Ridge and Diggers Creek Aqueducts to Tolbar Creek and Diggers Creek respectively (tributaries 50 of the Snowy River).

Falls Creek to the Snowy River below 0 The target volume for Snowy Montane Rivers Increased Flows totalled 62.1GL, with 5.1GL from 2 Oct 17 2 Apr 2 Apr 18 8 Jan 8 Jan 18 10 Jul 17 10 Jul 5 Mar 18 5 Mar 1 May 17 1 May 5 Feb 18 5 Feb 4 Sep 17 7 Aug 7 Aug 17 24 Jul 17 24 Jul 12 Jun 12 Jun 17 16 Oct 17 22 Jan 22 Jan 18 16 Apr 16 Apr 18 11 Dec 17 26 Jun 26 Jun 17 30 Oct 17 30 Apr 30 Apr 18 13 Nov 17 13 Nov 21 Aug 21 Aug 17 19 Mar 18 19 Mar 19 Feb 18 19 Feb 18 Sep 17 15 May 17 15 May 27 Nov 17 27 Nov Tantangara Dam, 12GL from Goodradigbee Aqueduct, 22.7GL from Middle Creek/Strzelecki Ck, 18.9GL 25 Dec 17 29 May 17 29 May from Bar Ridge and Diggers Creek Aqueducts and 3.4GL from Falls Creek, all to be targeted over the Actual SMRIF SMRIF SMRIF whole water year. Releases Low Limit High Limit

The total actual montane release volume was 43.0GL. This was made up of 5.4GL from Tantangara Dam, Snowy Montane Rivers Increased Flows (SMRIF) and Riparian Releases 4.9GL from Goodradigbee Aqueduct, 18.4GL from Middle Creek Aqueduct and Strzelecki Ck combined from Tantangara Dam ,11.8GL from Bar Ridge and Diggers Creek Aqueducts combined and 2.5 GL from Falls Creek, released 2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019 15 40 over the whole water year. The Bar Ridge montane release was delivered via in the Actual Riparian Releases 14 Actual SMRIF Release 2018 - 19 Water Year 13 35 SMRIF monthly target - 20% 12 The comparison of the annual, monthly and daily release targets for the Snowy Montane Rivers SMRIF monthly target + 20% 30 11 Actual Progressive SMRIF Release Increased Flows against the actual from Tantangara Dam is set out in the graphs opposite. All daily, 10 Target Progressive SMRIF Release 25 monthly and annual release targets were within the compliance limits. 9 SMRIF annual target - 10% 8 SMRIF annual target + 10% 20 Monthly releases from Goodradigbee, Middle Creek, Strzelecki Creek, Bar Ridge and Diggers Creek 7

Release (GL) Release 6 are also provided in the graphs on the following two pages. As these releases are made from small 15

5 (GL) Releases Progressive catchments and the inflows (and therefore releases) cannot be predicted or controlled, there are 4 10 no annual compliance targets for these releases. The above/below target delivery of water in these 3 catchments in 2018-2019 reflects the inflows received in these locations. In years when inflows are above 2 5 1 average, above average volumes of water will be delivered to these catchments and vice versa. 0 0 May 18 Jun 18 Jul 18 Aug 18 Sep 18 Oct 18 Nov 18 Dec 18 Jan 19 Feb 19 Mar 19 Apr 19

Water Report 2018 - 2019 6 Snowy Montane Rivers Increased Flows (SMRIF) Snowy Montane Rivers Increased Flows (SMRIF) from Goodradigbee Weir from Strzelecki Creek Aqueduct

2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019 2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019

2.0 15 2.0 10 Note: There are no monthly or annual compliance 1.9 Actual Releases (GL) Note: There are no monthly or annual compliance Estimated Releases (GL) Actual Progressive Releases (GL) targets for Goodradigbee 14 targets for Strzelecki Creek 1.8 1.8 9 Water Year Target (GL) 1.7 13 Estimated Progressive Releases (GL) 1.6 12 1.6 8 1.5 11 Water Year Target (GL) 1.4 1.4 7 1.3 10 1.2 9 1.2 6 1.1 8 1.0 1.0 5 0.9 7 0.8 6 0.8 4 Releases (GL) Releases 0.7

5 (GL) Releases 0.6 0.6 3 4 Progressive Releases (GL) Releases Progressive 0.5 (GL) Releases Progressive 0.4 3 0.4 2 0.3 2 0.2 0.2 1 0.1 1 0.0 0 0.0 0 May 18 Jun 18 Jul 18 Aug 18 Sep 18 Oct 18 Nov 18 Dec 18 Jan 19 Feb 19 Mar 19 Apr 19 May 18 Jun 18 Jul 18 Aug 18 Sep 18 Oct 18 Nov 18 Dec 18 Jan 19 Feb 19 Mar 19 Apr 19

Snowy Montane Rivers Increased Flows (SMRIF) Snowy Montane Rivers Increased Flows (SMRIF) from Middle Creek Aqueduct from Falls Creek Aqueduct

2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019 2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019

1.0 5 11 30 Estimated Releases (GL) Note: There are no monthly or annual Actual Releases (GL) 28 Note: There are no monthly or annual compliance Estimated Progressive Releases (GL) compliance targets for Falls Creek 10 targets for Middle Creek Actual Progressive Releases (GL) 26 Water Year Target (GL) 9 24 0.8 4 Water Year Target (GL) 8 22 20 7 18 0.6 3 6 16 5 14

12 (GL) Releases 0.4 2 Releases (GL) Releases 4 10

3 (GL) Releases Progressive

8 (GL) Releases Progressive 0.2 1 2 6 4 1 2 0 0 0.0 0 May 18 Jun 18 Jul 18 Aug 18 Sep 18 Oct 18 Nov 18 Dec 18 Jan 19 Feb 19 Mar 19 Apr 19 May 18 Jun 18 Jul 18 Aug 18 Sep 18 Oct 18 Nov 18 Dec 18 Jan 19 Feb 19 Mar 19 Apr 19

Water Report 2018 - 2019 7 Snowy Montane Rivers Increased Flows (SMRIF) THE TEMPERATURE OF RELEASES FROM TANTANGARA from Bar Ridge Aqueduct RESERVOIR

2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019 The Snowy Water Licence requires the outlet works at Tantangara Dam to be capable of releasing water from above any thermocline in the reservoir. The thermocline is a thin, but distinct, layer in a large body 3.0 20 Estimated Releases (GL) Note: There are no monthly or annual 2.8 of water in which temperature changes more rapidly with depth than it does in the layers above or below. Estimated Progressive Releases (GL) compliance targets for Bar Ridge 18 2.6 Water Year Target (GL) Typically, as the summer progresses, the surface waters warm and the deeper waters remain cold. This 2.4 16 2.2 causes a lack of mixing between the upper and lower layers, which often results in the lower layer having 14 2.0 reduced oxygen levels. For these reasons the deeper waters within reservoirs are generally viewed as 1.8 12 having undesirable water quality characteristics for releases, hence the requirement for the outlet works 1.6 10 1.4 to be able to draw from above the thermocline. 1.2 8 Releases (GL) Releases 1.0 The new intake works at Tantangara Dam are located on the upstream face of the dam wall. They 6

0.8 (GL) Releases Progressive comprise a series of ‘telescoping’ shutters to create a variable level off-take. 0.6 4 0.4 2 Snowy Hydro undertakes temperature monitoring at the intake tower to detect the presence of a 0.2 0.0 0 thermocline and adjusts the shutter height as necessary. As can be seen in the chart below, a persistent May 18 Jun 18 Jul 18 Aug 18 Sep 18 Oct 18 Nov 18 Dec 18 Jan 19 Feb 19 Mar 19 Apr 19 thermocline was not present during the 2018 - 19 water year.

Tantangara Dam Intake Water Temperatures and Level

May-18 Temp 1222 Snowy Montane Rivers Increased Flows (SMRIF) Jun-18 Temp from Diggers Creek Aqueduct Jul-18 Temp 1220 Aug-18 Temp Sep-18 Temp 2018 - 2019 Water Year | Period under review: 1 May 2018 to 30 April 2019 Oct-18 Temp 1218 Nov-18 Temp 3.0 20 Dec-18 Temp Estimated Releases (GL) Note: There are no monthly or annual 2.8 1216 Jan-19 Temp Estimated Progressive Releases (GL) compliance targets for Diggers Creek 18 Feb-19 Temp 2.6 Water Year Target (GL) Mar-19 Temp 2.4 16 1214 Apr-19 Temp 2.2 May 18 Dam level

14 (m) Level 2.0 Jun-18 Dam Level 1212 1.8 12 Jul-18 Dam Level 1.6 Aug-18 Dam Level 10 1210 Sep-18 Dam Level 1.4 Oct-18 Dam Level 1.2 8 Nov-18 Dam Level Releases (GL) Releases 1.0 1208 Dec-18 Dam Level 6 Jan-19 Dam Level 0.8 (GL) Releases Progressive 0.6 4 1206 Feb-19 Dam Level Mar-19 Dam Level 0.4 2 Apr-19 Dam Level 0.2 1204 Shutter Position 0.0 0 3 8 13 18 23 May 18 Jun 18 Jul 18 Aug 18 Sep 18 Oct 18 Nov 18 Dec 18 Jan 19 Feb 19 Mar 19 Apr 19 Temperature (Deg C) Water Report 2018 - 2019 8