WATER COMPLIANCE REPORT

2016-2017 Water Year

Water Report 2016-2017 1 SH1083B ABOUT THIS REPORT COMPLYING WITH

Since the Snowy Scheme’s completion in 1974, Snowy Hydro Limited has carefully managed water that flows through the Scheme’s dams, tunnels, aqueducts and power stations in accordance with our water OUR LICENCE 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 operate a complex hydro-electric scheme utilising the water captured by the scheme Snowy Water Licence during the 2016 – 17 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 Dam In the Snowy Scheme, water releases and electricity generation are inseparably linked. ● Environmental releases into the Murrumbidgee River from

Snowy Hydro is operated under the Snowy Water Licence, issued to us by the NSW Government. ● Environmental releases into the Goodradigbee River from Goodradigbee Aqueduct 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 Bar Ridge and Diggers Creek Aqueducts Snowy Hydro is obligated under the Snowy Water Licence to: 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 Jindabyne Dam 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, own 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 years 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 2016-2017 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- Snowy-Murray Development to the River Murray catchment during the 2016 – 17 water year. Development to the Murrumbidgee River catchment during the 2016 – 17 water year.

The total accounted release volume was 1477 GL. This was made up of: The total accounted release volume was 1074 GL (Note: 1 GL rounding error). This was made up of: 926 GL being the 2016 – 17 Required Annual Release calculated under the Snowy Water Licence; ● 900 GL being the 2016 – 17 Required Annual Release calculated under the Snowy Water Licence; plus plus ● 0 GL of Net DISV Increase; plus ● 175 GL of pre-release of the 2017 – 18 Required Annual Release; plus ● 529 GL of pre-release of the 2017 – 18 Required Annual Release; plus ● 0 GL of Discretionary Above Target Water release (water not required for RAR releases that Snowy ● 22 GL of Discretionary Above Target Water Releases (water not required for RAR releases that Hydro is able to release at its discretion). Snowy Hydro is able to release at its discretion) This total accounted release volume includes 16 GL of montane environmental flow releases provided This total accounted release volume includes 36 GL of Montane environmental flow releases provided to the Murrumbidgee and Goodradigbee Rivers which did not flow through Scheme power stations. to the Geehi and Swampy Plains River which did not flow through Scheme power stations.

Inflows and Releases to the River Murray Catchment during 2016 - 17 Inflows and Releases to the Murrumbidgee Catchment during 2016 - 17

1700 1600 1600 1500 1400 1400 1300 1200 1200 1100 1000 1000 900 800

Gigalitres 800 Gigalitres 700 600 600 500 400 400 300 200 200 100 0 0 Long Term Average Inflows 2016 - 17 Actual Inflows 2016 - 17 Actual Release Long Term Average Inflows 2016 - 17 Actual Inflows 2016 - 17 Actual Release (Upper Tumut) (Upper Tumut)

Water Report 2016-2017 3 Snowy River Increased Flows (SRIF) and Jindabyne Base Passing Flow (BPF) ENVIRONMENTAL RELEASES Release and Daily Limits 2016 - 2017 Water Year | Period under review: 1 May 2016 to 30 April 2017 SNOWY RIVER INCREASED FLOWS 8000 Number of days when SRIF releases Snowy Hydro complied with its obligation to target releases from Jindabyne Dam for environmental were outside daily limits = 2 7000 purposes during the 2016 – 17 water year. 6000 The volume of Snowy River Increased Flows (SRIF) released from Jindabyne Dam during the 2016 5000 – 17 water year was 124.7 GL, which was 2.5 GL above the target volume of 122.2 GL. That excess is well within the +/–10% annual tolerance around the target volumes allowed under the Snowy Water 4000

Licence. The 2017 – 18 target has been adjusted down to account for this release surplus. 3000

In addition to the environmental releases, 8.5 GL Base Passing Flow (BPF) was also released from (ML/day) Release Daily 2000

Jindabyne Dam and 0.5 GL riparian flow was released from the Mowamba Weir. 1000

All monthly releases were within the +/–20% monthly tolerance around the target volumes tolerance 0 allowed under the Snowy Water Licence. There were two days following the Flushing Flow in October 2 Apr 2 Apr 17 8 Jan 8 Jan 17 2 Oct 16 5 Mar 17 5 Mar 5 Feb 17 5 Feb 10 Jul 16 10 Jul 1 May 16 1 May 4 Sep 16 7 Aug 7 Aug 16 24 Jul 16 24 Jul 22 Jan 22 Jan 17 16 Apr 16 Apr 17

2016 where the daily releases exceeded the daily target by more than 20%. All other releases were 12 Jun 16 30 Apr 30 Apr 17 16 Oct 19 Mar 17 19 Mar 19 Feb 17 19 Feb 11 Dec 16 26 Jun 26 Jun 16 30 Oct 16 13 Nov 16 13 Nov 21 Aug 21 Aug 16 18 Sep 16 15 May 16 15 May 27 Nov 16 27 Nov 25 Dec 16 29 May 16 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 2016 – 17 water year once again exceeded 100 GL, a flushing flow was delivered to the Snowy River as set out on the next page. Snowy River Increased Flows (SRIF) and Jindabyne Base Passing Flow (BPF) Releases including Mowamba Riparian Releases The comparison of the annual, monthly and daily release targets for the Snowy River Increased Flow releases against the actual releases is shown in the following charts. 2016 - 2017 Water Year | Period under review: 1 May 2016 to 30 April 2017

60 240 Actual SRIF releases Number of months when SRIF releases Actual BPF releases were outside monthly limits = 0 50 200 SRIF monthly target +20% SRIF monthly target -20% Target progressive SRIF releases 40 160 Actual progressive SRIF releases SRIF annual target +10% SRIF annual target -10% 30 120

20 80 Monthly Release (GL) Release Monthly Progressive Releases (GL) Releases Progressive

10 40

0 0 May 16 Jun 16 Jul 16 Aug 16 Sep 16 Oct 16 Nov 16 Dec 16 Jan 17 Feb 17 Mar 17 Apr 17

Water Report 2016-2017 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 100 GL, Snowy Hydro can be instructed by NSW Office of Water water from above any thermocline in the reservoir. The thermocline is a thin but distinct layer in a large to deliver a flushing flow to the Snowy River. A flushing flow is defined as a day when the release target body of water in which water temperature changes more rapidly with depth than it does in the layers exceeds the 5 GL capacity of the other release infrastructure at Jindabyne Dam meaning that the above or below. Typically, as the summer progresses, the surface waters warm and the deeper waters spillway gates must be opened to achieve the flow target. 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 reservoirs The intent of the flushing flows is to mimic the effect of the Spring snow melt in the Snowy River. are generally viewed as having undesirable water quality characteristics for releases, hence the These high flows are intended to scour the bed of the channel and remove fine sediment to improve requirement for the outlet works to be able to draw from above the thermocline. the habitat of the river for fish and macroinvertebrates. The intake works at Jindabyne are located at the end of a channel excavated into the bank of Lake In October 2016 Snowy Hydro delivered another flushing flow, as has been done each year since the Jindabyne. In addition to the variable level shutters in the intake tower, the level of the base of the first in October 2011. The release pattern was set by the NSW Office of Water with releases peaking at channel means that the deeper waters of the reservoir are inaccessible. This means that the thermocline 5.3 GL per day and was discharged through the large spillway gates as well as the cone valves. is only likely to be above the levels of the intake channel when the lake is at much higher levels. The NSW Office of Water, working with representatives across local, state and Commonwealth Snowy Hydro undertakes temperature monitoring at the intake tower to detect the presence of a Government agencies, was responsible for the advice to downstream landholders and other thermocline and adjusts shutter height as necessary. As can be seen in the chart opposite, all releases stakeholders that would be impacted by the increased Snowy River levels. were made from above the thermocline.

Jindabyne Dam Intake Water Temperatures and Level

910 May - 16 Temp Jun - 16 Temp 908 Jul - 16 Temp Aug - 16 Temp 906 Sep - 16 Temp Oct - 16 Temp Nov - 16 Temp 904 Dec - 16 Temp Jan - 17 Temp 902 Feb - 17 Temp Mar - 17 Temp 900 Apr - 17 Temp May - 16 Dam Level Level 898 Jun - 16 Dam Level Jul - 16 Dam Level 896 Aug - 16 Dam Level Sep - 16 Dam Level Oct - 16 Dam Level 894 Nov - 16 Dam Level Dec - 16 Dam Level 892 Jan - 17 Dam Level Feb - 17 Dam Level 890 Mar - 17Dam Level Apr - 17 Dam Level 888 Shutter Position 5 10 15 20 Temperature (Deg C) Water Report 2016-2017 5 SNOWY MONTANE RIVERS INCREASED FLOWS Snowy Montane Rivers Increased Flows (SMRIF) and Riparian Releases from Tantangara Dam Snowy Hydro complied with its obligation to target Snowy Montane Rivers releases for Environmental 2016 - 2017 Water Year | Period under review: 1 May 2016 to 30 April 2017 purposes during the 2016 – 17 water year. 8 40 Actual SMRIF Releases Number of months when Tant Montane During the 2016 – 17 water year, Snowy Hydro was directed to make Snowy Montane Rivers Increased Actual Riparian Releases releases were outside monthly limits = 0 7 35 SMRIF monthly target -20% Flows (SMRIF) from the following locations: SMRIF monthly target +20% 6 30 Actual Progressive SMRIF Release ● Tantangara Dam to the Murrumbidgee River, Target Progressive SMRIF Release 5 25 ● Goodradigbee Aqueduct to the Goodradigbee River (a tributary of the Murrumbidgee River), SMRIF annual target -10% SMRIF annual target +10% ● Middle Creek Aqueduct to Middle Creek and Strzelecki Creek Intake on the Geehi River Aqueduct 4 20

to Strzelecki Creek (tributaries of the Geehi River), and (GL) Releases 3 15 ● Bar Ridge and Diggers Creek Aqueducts to Tolbar Creek and Diggers Creek respectively

2 10 (GL) Releases Progressive (tributaries of the Snowy River). 1 5 The target volume for Snowy Montane Rivers Increased Flows totalled 58.6 GL, with 10.0 GL from 0 0 Tantangara Dam, 7 GL from Goodradigbee Aqueduct, 22.7 GL from Middle Creek/Strzelecki Creek, May 16 Jun 16 Jul 16 Aug 16 Sep 16 Oct 16 Nov 16 Dec 16 Jan 17 Feb 17 Mar 17 Apr 17 and 18.9 GL from Bar Ridge and Diggers Creek Aqueducts, all to be targeted over the whole water year.

The total actual montane release volume was 76.9 GL. This was made up of 9.9 GL from Tantangara Snowy Montane Rivers Increased Flows (SMRIF) from Tantangara Dam Dam, 6.1 GL from Goodradigbee Aqueduct, 36.2 GL from Middle Creek Aqueduct and Strzelecki Creek and Daily Limits combined and 24.7 GL from Bar Ridge and Diggers Creek Aqueducts combined, released over the 2016 - 2017 Water Year | Period under review: 1 May 2016 to 30 April 2017 whole water year. 450 Number of days when Montane releases The comparison of the annual, monthly and daily release targets for the Snowy Montane Rivers 400 were outside daily limits = 0

Increased Flows against the actual from Tantangara Dam is set out in the graphs on the next page. 350

All daily, monthly and annual release targets were within the compliance limits. 300

Monthly releases from Goodradigbee, Middle Creek, Strzelecki Creek, Bar Ridge and Diggers Creek are 250 also provided in the graphs on subsequent pages. As these releases are made from small catchments 200 Daily Release (ML/day) Release Daily and the inflows (and therefore releases) cannot be predicted or controlled, there are no annual 150 compliance targets for these releases. The above/below target delivery of water in these catchments 100 in 2016 - 2017 reflects the inflows received in these locations. In years when inflows are above average, 50 above average volumes of water will be delivered to these catchments and vice versa. 0 2 Apr 2 Apr 17 8 Jan 8 Jan 17 2 Oct 16 5 Mar 17 5 Mar 5 Feb 17 5 Feb 10 Jul 16 10 Jul 1 May 16 1 May 4 Sep 16 7 Aug 7 Aug 16 24 Jul 16 24 Jul 22 Jan 22 Jan 17 16 Apr 16 Apr 17 12 Jun 12 Jun 16 30 Apr 30 Apr 17 16 Oct 19 Mar 17 19 Mar 19 Feb 17 19 Feb 11 Dec 16 26 Jun 26 Jun 16 30 Oct 16 13 Nov 16 13 Nov 21 Aug 21 Aug 16 18 Sep 16 15 May 16 15 May 27 Nov 16 27 Nov 25 Dec 16 29 May 16 29 May

Actual SMRIF SMRIF SMRIF Releases Low Limit High Limit

Water Report 2016-2017 6 Snowy Montane Rivers Increased Flows (SMRIF) from Goodradigbee Weir Snowy Montane Rivers Increased Flows (SMRIF) from Strzelecki Creek Aqueduct 2016 - 2017 Water Year | Period under review: 1 May 2016 to 30 April 2017 2016 - 2017 Water Year | Period under review: 1 May 2016 to 30 April 2017 2.0 15 Note: There are no monthly or annual Actual Releases (GL) compliance targets for Goodradigbee 14 2.0 10 1.8 Note: There are no monthly or annual compliance Estimated Releases (GL) Actual Progressive Releases (GL) 13 targets for Strzelecki Creek Water Year Target (GL) 1.8 9 1.6 12 Estimated Progressive Releases (GL) 11 Water Year Target (GL) 1.4 1.6 8 10 7 1.2 9 1.4 8 1.0 1.2 6 7 5 0.8 6 1.0 Releases (GL) Releases 5 4 0.6 0.8 4 Progressive Releases (GL) Releases Progressive Releases (GL) Releases 0.4 3 0.6 3 Progressive Releases (GL) Releases Progressive 2 0.2 0.4 2 1 0.2 0.0 0 1 May 16 Jun 16 Jul 16 Aug 16 Sep 16 Oct 16 Nov 16 Dec 16 Jan 17 Feb 17 Mar 17 Apr 17 0.0 0 May 16 Jun 16 Jul 16 Aug 16 Sep 16 Oct 16 Nov 16 Dec 16 Jan 17 Feb 17 Mar 17 Apr 17

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

2016 - 2017 Water Year | Period under review: 1 May 2016 to 30 April 2017 2016 - 2017 Water Year | Period under review: 1 May 2016 to 30 April 2017

11 30 3.0 20 Estimated Releases (ML) Actual Releases (GL) 28 2.8 Note: There are no monthly or annual 10 Estimated Progressive Releases (GL) compliance targets for Bar Ridge 18 Actual Progressive Releases (GL) 26 2.6 Water Year Target (GL) 9 Water Year Target (GL) Note: There are no monthly or annual 24 2.4 16 compliance targets for Middle Creek 8 22 2.2 14 20 2.0 7 18 1.8 12 6 16 1.6 10 5 14 1.4 12 1.2

Releases (GL) Releases 8 4 (GL) Releases 10 1.0 3 6

8 (GL) Releases Progressive 0.8 Progressive Releases (GL) Releases Progressive 2 6 0.6 4 4 0.4 1 2 2 0.2 0 0 0.0 0 May 16 Jun 16 Jul 16 Aug 16 Sep 16 Oct 16 Nov 16 Dec 16 Jan 17 Feb 17 Mar 17 Apr 17 May 16 Jun 16 Jul 16 Aug 16 Sep 16 Oct 16 Nov 16 Dec 16 Jan 17 Feb 17 Mar 17 Apr 17

Water Report 2016-2017 7 Snowy Montane Rivers Increased Flows (SMRIF) from Diggers Creek Aqueduct THE TEMPERATURE OF RELEASES FROM TANTANGARA

2016 - 2017 Water Year | Period under review: 1 May 2016 to 30 April 2017 RESERVOIR

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

0.8 (GL) Releases Progressive 0.6 4 The new intake works at Tantangara Dam are located on the upstream face of the dam wall. They 0.4 2 comprise a series of ‘telescoping’ shutters to create a variable level off-take. 0.2 0.0 0 Snowy Hydro undertakes temperature monitoring at the intake tower to detect the presence of a May 16 Jun 16 Jul 16 Aug 16 Sep 16 Oct 16 Nov 16 Dec 16 Jan 17 Feb 17 Mar 17 Apr 17 thermocline and adjusts the shutter height as necessary. As can be seen in the chart opposite, a persistent thermocline was not present during the 2015 - 16 water year.

Tantangara Dam Intake Water Temperatures and Level May - 16 Temp Jun - 16 Temp 1224 Jul - 16 Temp Aug - 16 Temp Sep - 16 Temp Oct - 16 Temp Nov - 16 Temp Dec - 16 Temp 1219 Jan - 17 Temp Feb - 17 Temp Mar - 17 Temp Apr - 17 Temp May - 16 Dam Level 1214 Jun - 16 Dam Level Level Jul - 16 Dam Level Aug - 16 Dam Level Sep - 16 Dam Level Oct - 16 Dam Level Nov - 16 Dam Level 1209 Dec - 16 Dam Level Jan - 17 Dam Level Feb - 17 Dam Level Mar - 17Dam Level Apr - 17 Dam Level 1204 Shutter Position 0 5 10 15 20 25 Temperature (Deg C)

Water Report 2016-2017 8 Water Report 2016-2017 9