2019 - 2020 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 – WHAT WATER water licence. This report outlines how we are managing the water that flows through the Scheme. Snowy Hydro operates a complex hydro-electric scheme utilising the water captured by the Scheme WENT OUT to generate energy to meet the market’s needs, while also moving water from east to west to support Snowy Hydro complied with all of the requirements imposed upon the company under the Snowy irrigation districts. Water Licence during the 2019–20 water year, including each water release target relating to: Each year, we have to reach certain targets for downstream and environmental water releases. Snowy Hydro has operational flexibility day-to-day to strategically manage our generation and water releases, ● The Required Annual Release to the Murray catchment. while at the same time providing long-term security to the downstream users around annual water ● The Required Annual Release to the catchment. releases. In the Snowy Scheme, water releases and electricity generation are inseparably linked. ● Environmental releases into the from Jindabyne . Snowy Hydro operates under the Snowy Water Licence, issued by the NSW Government. The licence has ● Environmental releases into the Murrumbidgee River from . many legally-binding and enforceable obligations on the company. ● Environmental releases into the from Goodradigbee Aqueduct.

Snowy Hydro is obligated under the Snowy Water Licence to: ● Environmental releases into the from Middle Creek and Strzelecki Creek Aqueducts. Target water releases to the River Murray and Murrumbidgee River catchments, the annual volumes of ● Environmental releases into the Snowy River from Bar Ridge, Diggers Ck and Falls Ck Aqueducts 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 for 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 Planning, Industry and Environment at industry.nsw.gov.au/water/basins-catchments/snowy-river

Water Report 20192018 - 20202019 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 (RAR) from the Snowy-Murray Development to the River Murray catchment during the 2019–20 water year. Snowy- Development to the Murrumbidgee River catchment during the 2019–20 water year.

The total accounted release volume was 654 GL. This was made up of: The total accounted release volume was 997 GL. This was made up of: 880 GL being the 2019–20 RAR calculated under the Snowy Water Licence; plus 781 GL being the 2019–20 RAR calculated under the Snowy Water Licence; less 117 GL of pre-release of the 2019–20 RAR; plus 254 GL of Net Dry Inflow Sequence Volume (DISV) Increase; plus 0 GL of Discretionary Above Target Water release (water not required for RAR releases that Snowy 127 GL of pre-release of the 2020–21 RAR; plus Hydro is able to release at its discretion). 0 GL of Discretionary Above Target Water Releases (water not required for RAR releases that Snowy This total accounted release volume includes 8 GL of montane environmental flow releases provided Hydro is able to release at its discretion) to the Murrumbidgee and Goodradigbee Rivers which did not flow through the Scheme’s power This total accounted release volume includes 20 GL of montane environmental flow releases provided stations. to the Geehi and Swampy Plains River which did not flow through the Scheme’s power stations.

Inflows and Releases to the River Murray Catchment during 2019 - 20 Inflows and Releases to the Murrumbidgee Catchment during 2019 - 20

1300 1400 1200

1100 1200 1000

900 1000 800

700 800

600 Gigalitres 600 500 Gigalitres

400 400 300

200 200 100

0 0 Long Term Average Inflows 2019 - 20 Actual Inflows 2019 - 20 Actual Release Long Term Average Inflows 2019 - 20 Actual Inflows 2019 - 20 Actual Release (Upper Tumut) (Upper Tumut)

Water Report 2019 - 2020 3 Snowy River Increased Flows (SRIF) and Jindabyne Base Passing Flow (BPF) ENVIRONMENTAL RELEASES Releases and Daily Limits SNOWY RIVER INCREASED FLOWS 2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020 4,500 Number of days when SRIF releases Snowy Hydro complied with its obligation to target releases from Jindabyne Dam for environmental 4,000 were outside daily limits = 1

purposes during the 2019–20 water year. ) 3,500

The volume of Snowy River Increased Flows (SRIF) released from Jindabyne Dam during the 2019–20 3,000 water year was 109.3 GL, which was 0.0 GL below the target volume of 109.4 GL (note 0.1 GL rounding 2,500

error). That deficit is well within the +/–10% annual tolerance around the target volumes allowed under Release (ML/day 2,000 the Snowy Water Licence. The 2020–21 target has been adjusted up to account for this release deficit. Daily 1,500

In addition to the environmental releases, 8.5GL Base Passing Flow (BPF) was also released from 1,000

Jindabyne Dam and 0.5GL riparian flow was released from the Mowamba Weir. 500

0 All monthly releases except March 2020 were within the +/–20% monthly tolerance allowed under the Snowy Water Licence. There was one day where the daily releases was outside the daily target by 1 May 19 7 Aug 19 4 Sep 19 2 Oct 19 8 Jan 20 5 Feb 20 4 Mar 20 1 Apr 20 more than 20%. This was reported to NSW DPIE Water. All other releases were within the +/–20% daily 15 May 19 29 May 19 12 Jun 19 26 Jun 19 10 Jul 19 24 Jul 2019 21 Aug 19 18 Sep 19 16 Oct 19 30 Oct 19 13 Nov 19 27 Nov 19 11 Nov 19 25 Nov 19 22 Jan 20 19 Feb 20 18 Mar 20 15 Apr 20 29 Apr 20 tolerance allowed under the Snowy Water Licence. SRIF Jind BPF SRIF Low Limit SRIF High Limit

As allocations for the 2019–20 water year once again exceeded 100GL, a flushing flow was scheduled for the Snowy River, as set out on page 5. Snowy River Increased Flows (SRIF) and Jindabyne Base Passing Flow The comparison of the annual, monthly and daily release targets for the Snowy River Increased Flow (BPF) Releases including Mowamba Riparian Releases releases against the actual releases is shown in the following charts. 2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020

80 240 Actual Riparian Releases Number of months when SRIF releases were Actual SRIF Release outside monthly limits = 1 70 SRIF monthly target - 20% 200 SRIF monthly target + 20% 60 Actual Progressive SRIF Release Target Progressive SRIF Release SRIF annual target - 10% 160 (GL) 50 SRIF annual target + 10% (GL) 40 120 e Releases

Release 30 y 80

20 Progressiv Monthl 40 10

0 0 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20

Water Report 2019 - 2020 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 DPIE Water to water from above any thermocline in the . 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 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 water 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 In October 2019 Snowy Hydro delivered a flushing flow, following the release pattern set by the NSW Jindabyne. In addition to the variable level shutters in the intake tower, the level of the base of DPIE Water, with releases peaking at 5.0 GL per day and discharged through the spillway gates, as well the channel means that the deeper waters of the reservoir are inaccessible. This means that the as the cone valves. thermocline is only likely to be above the levels of the intake channel when the lake is at much higher The NSW DPIE Water, working with representatives across local, state and Commonwealth levels. Government agencies, was responsible for the advice to downstream landholders and other Snowy Hydro undertakes temperature monitoring at the intake tower to detect the presence of a stakeholders that would be impacted by the increased Snowy River levels. thermocline and adjusts shutter height as necessary. As can be seen in the chart below, all releases were made from above the thermocline.

Jindabyne Dam Intake Water Temperatures and Level

910 May-19 Temp Jun-19 Temp 908 Jul-19 Temp Aug-19 Temp

906 Sep-19 Temp Oct-19 Temp Nov-19 Temp 904 Dec-19 Temp Jan-20 Temp 902 Feb-20 Temp Mar-20 Temp 900 Apr-20 Temp May-19 Dam Level

898 Jun-19 Dam Level Jul-19 Dam Level Aug-19 Dam Level 896 Sep-19 Dam Level Oct-19 Dam Level 894 Nov-19 Dam Level Dec-19 Dam Level 892 Jan-20 Dam Level Feb-20 Dam Level 890 Mar-20 Dam Level Apr-20 Dam Level

888 Shutter Position 510152025

Water Report 2019 - 2020 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 2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020 purposes during the 2019–20 water year. 160 Number of days when montane releases During the 2019–20 water year, Snowy Hydro was directed to make Snowy Montane Rivers Increased were outside daily limits = 0 140 Flows (SMRIF) from the following locations: 120 Tantangara Dam to the Murrumbidgee River, y) Goodradigbee Aqueduct to the Goodradigbee River (a tributary of the Murrumbidgee River), 100 L/da

Middle Creek Aqueduct to Middle Creek and Strzelecki Creek Intake (on the Geehi River Aqueduct) (M 80 to Strzelecki Creek (tributaries of the Geehi River), and 60 Release Bar Ridge and Diggers Creek Aqueducts to Tolbar Creek and Diggers Creek, respectively (tributaries

of the Snowy River) Daily 40

Falls Creek to the Snowy River below . 20 The target volume for SRIF totalled 55.3 GL, with 3.3 GL from Tantangara Dam, 7.0 GL from Goodradigbee 0 19 19 20 20 20 19

Aqueduct, 22.7GL from Middle Creek and Strzelecki Ck, 18.9GL from Bar Ridge and Diggers Creek 20 Jan Feb Aug Mar Oct May Apr Oct 19 Jun 19 May 19 Apr 20 Jul 19 Dec 19 Nov 19 Jan 20 Jul 19 Oct 19 Sep 19 Mar 20 Feb 20 May 19 Apr 20 Nov 19 Jun 19 Aug 19 Dec 19 1 7 4 Sep 19 2 8 Aqueducts and 3.4GL from Falls Creek, all to be targeted over the whole water year. 5 4 1 15 29 12 26 10 24 21 18 16 30 13 27 11 25 22 15 29 19 18

The total actual montane release volume was 42.9GL. This was made up of 3.6 GL from Tantangara Dam, Actual SMRIF SMRIF SMRIF Releases Low Limit High Limit 4.5GL from Goodradigbee Aqueduct, 19.9 GL from Middle Creek Aqueduct and Strzelecki Ck combined, 12.2 GL from Bar Ridge and Diggers Creek Aqueducts combined and 2.7 GL from Falls Creek, released Snowy Montane Rivers Increased Flows (SMRIF) and Riparian Releases from Tantangara Dam over the whole water year. The Bar Ridge montane release was delivered via in the 2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020 2019 - 20 water year. 15 40 The comparison of the annual, monthly and daily release targets for the SMRIF against the actual release 14 Number of months when Tant montane releases Actual Riparian Releases were outside monthly limits = 0 13 35 from Tantangara Dam is set out in the graphs opposite. All daily, monthly and annual release targets were Actual SMRIF Release 12 SMRIF monthly target - 20% SMRIF monthly target + 20% within the compliance limits. 11 30 Actual Progressive SMRIF Release 10 Target Progressive SMRIF Release SMRIF annual target - 10% 25 Monthly releases from Goodradigbee, Middle Creek, Strzelecki Creek, Bar Ridge and Diggers Creek (GL) 9 SMRIF annual target + 10%

8 releases (GL) are also provided on the following pages. As these releases are made from small catchments and the 20 7 ve inflows (and therefore releases) cannot be predicted or controlled, there are no annual compliance Releases 6 15 5

targets for these releases. The above/below target delivery of water in these catchments in 2019-2020 Progressi 4 reflects the inflows received in these locations. In years when inflows are above average, above average 10 3 volumes of water will be delivered to these catchments, and vice versa. 2 5 1 0 0 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20

Water Report 2019 - 2020 6 Snowy Montane Rivers Increased Flows (SMRIF) Snowy Montane Rivers Increased Flows (SMRIF) from Goodradigbee Weir from Strzelecki Creek Aqueduct

2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020 2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020 2.0 15 2.0 10 1.9 Note: There are no monthly or annual 14 Note: There are no monthly or annual Actual Releases (GL) 1.8 Estimated Releases (GL) 9 1.8 Actual Progressive Releases (GL) compliance targets for Goodradigbee Estimated Progressive Releases (GL) compliance targets for Strzelecki Creek 1.7 Water Year Target (GL) 13 Water Year Target (GL) 1.6 12 1.6 8 1.5 11 1.4 1.4 7

1.3 10 (GL) 1.2 9 1.2 6 (GL) (GL) 1.1 8 1.0 1.0 5 releases (GL) 0.9 7 e releases ve 0.8 6 0.8 4 Releases Releases 0.7 5 0.6 0.6 3 Progressiv 0.5 4 Progressi 0.4 3 0.4 2 0.3 2 0.2 0.2 1 0.1 1 0.0 0 0.0 0 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20

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

2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020 2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020 11 30 1.0 5 Note: There are no monthly or annual 28 Note: There are no monthly or annual 10 Actual Releases (GL) Estimated Releases (GL) compliance targets for Middle Creek compliance targets for Falls Creek Actual Progressive Releases (GL) 26 Estimated Progressive Releases (GL) Water Year Target (GL) Water Year Target (GL) 9 24 0.8 4 8 22 20 7 (GL) 18 0.6 3 (GL) 6 16 (GL) releases (GL)

5 14 e releases ve 12 0.4 2 Releases 4 Releases 10 Progressi 3 8 Progressiv

2 6 0.2 1 4 1 2 0 0 0.0 0 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20

Water Report 2019 - 2020 7 Snowy Montane Rivers Increased Flows (SMRIF) THE TEMPERATURE OF RELEASES FROM TANTANGARA from Bar Ridge Aqueduct RESERVOIR

2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020 The Snowy Water Licence requires the outlet works at Tantangara Dam to be capable of releasing water 3.0 20

2.8 Estimated Release (ML) Note: There are no monthly or annual from above any thermocline in the reservoir. The thermocline is a thin, but distinct, layer in a large body Estimated Releases (GL) 18 2.6 Estimated Progressive Releases (GL) compliance targets for Bar Ridge Water Year Target (GL) of water in which temperature changes more rapidly with depth than it does in the layers above or below. 2.4 16 2.2 Typically, as the summer progresses, the surface waters warm and the deeper waters remain cold. This 14 2.0 (GL) causes a lack of mixing between the upper and lower layers, which often results in the lower layer having 1.8 12

(GL) 1.6 reduced oxygen levels. For these reasons, the deeper waters within reservoirs are generally viewed as 10

1.4 e releases having undesirable water quality characteristics for releases, hence the requirement for the outlet works 1.2 8 Releases to be able to draw water from above the thermocline. 1.0 6

0.8 Progressiv The new intake works at Tantangara Dam are located on the upstream face of the dam wall. They 0.6 4 0.4 comprise a series of ‘telescoping’ shutters to create a variable level off-take. 2 0.2 0.0 0 Snowy Hydro undertakes temperature monitoring at the intake tower to detect the presence of a May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20 thermocline and adjusts the shutter height as necessary. As can be seen in the chart below, a persistent thermocline was not present during the 2019-20 water year.

Tantangara Dam Intake Water Temperatures and Level

Snowy Montane Rivers Increased Flows (SMRIF) 1218 May-19 Temp from Diggers Creek Aqueduct Jun-19 Temp Jul-19 Temp Aug-19 Temp 2019 - 2020 Water Year | Period under review: 1 May 2019 to 30 April 2020 1216 3.0 20 Sep-19 Temp Oct-19 Temp 2.8 Estimated Releases (GL) Note: There are no monthly or annual compliance targets for Diggers Creek 18 Nov-19 Temp 2.6 Estimated Progressive Releases (GL) Water Year Target (GL) 1214 Dec-19 Temp 2.4 16 Jan-20 Temp 2.2 Feb-20 Temp 14 Mar-20 Temp 2.0 1212 (GL) Apr-20 Temp 1.8 12 ) May-19 Dam Level (GL) 1.6 Jun-19 Dam Level

10 Level (m 1210 Jul-19 Dam Level

1.4 e releases Aug-19 Dam Level 1.2 8 Releases Sep-19 Dam Level 1.0 6 1208 Oct-19 Dam Level

0.8 Progressiv Nov-19 Dam Level 0.6 4 Dec-19 Dam Level Jan-20 Dam Level 0.4 1206 2 Feb-20 Dam Level 0.2 Mar-20 Dam Level 0.0 0 Apr-20 Dam Level May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20 1204 Shutter Position 3813 18 23

o Temperature ( C)