Gwydir Operations Plan. August 2018

Transcription

1 ` Gwydir Operations Plan August

2 Contents 1. Highlights Dam storage Copeton Dam storage Supplementary access Commentary Explanation Water availability /2019 water availability for Gwydir as of 31 July Resource assessment Significance of this resource assessment Resource assessment process Rainfall month rainfall month rainfall Inflows Copeton Dam inflows Operational loss Operational losses to date Storage forecast Copeton Storage forecast Next 3 months scenario from the BOM forecast Outage planning Prognosis

3 1. Highlights Under a minimum inflow sequence the delivery loss account is expected to be drawn down to empty by end December Essential supplies account will then be utilised to deliver remaining account volumes, becoming relatively stable from Feb 2019 to May 2020 before improving at the end of sequence. WaterNSW recommends adopting efficiency measures, including block releases for delivery of relatively low remaining account volumes of general security irrigation throughout 2018/19. The block releases strategy will consist of up to 3 defined blocks of water being delivered to effluent streams (Moomin, Carole/Gil Gil and Mehi) throughout spring and summer 2018/19. The first block is currently planned to arrive at extraction sites October 15 and have a duration of 14 days. 80GL of environmental water (ECA +general security) and roughly 40 GL of general security irrigation water plus approximately 14GL of high security water is planned to be delivered this season. 3

4 2. Dam storage 2.1 Copeton Dam storage Copeton Dam storage 80% 2013/ / / / /18 70% 60% 50% 40% 30% 20% 10% 0% Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun From the above figure it can be seen that Copeton Dam was at 50.4% at the start of the last water year and it is now close to 26.6% of active capacity. The storage was drawn down by releases for deliveries, and it did not rise as there were no significant inflows. In comparison to , last water year was very dry. 3. Supplementary access 3.1 Commentary There have not been any supplementary events in the Gwydir since the start of the 2017/18 water year. 3.2 Explanation No supplementary access was available since the start of the 2017/18 water year due to lack of high flow runoff events entering the system. 4

5 4. Water availability /2019 water availability for Gwydir as of 31 July 2018 Licence Category Sum of Share Component Sum of Carryove r In Sum of AWD Volume Sum of Trade In Sum of Trade Out Sum of Usage Sum of Accoun t Balance DOMESTIC AND 2, , ,466 STOCK DOMESTIC AND STOCK [DOMESTIC] DOMESTIC AND STOCK [STOCK] E C A 45,000 66, ,430 LOCAL WATER 3, , ,836 UTILITY REGULATED RIVER 509, , ,605 2, ,249 (GENERAL SECURITY) REGULATED RIVER 20, , , ,439 (HIGH SECURITY) REGULATED RIVER (HIGH SECURITY) [RESEARCH] REPLENISHMENT 4, SUPPLEMENTARY 181, ,748 3,121 3, ,748 WATER GRAND TOTAL 764, , ,844 13,726 13, ,544 River valley Allocation Licence category Date of allocation (ML/Share, %) Gwydir 0.0 / 0% General security 1 July / 100% High security 1 July / 100% Domestic and stock 1 July / 100% Local water utilities 1 July 2018 * Carry-over water can also be available. General Security water users in the Gwydir have access to unused water in their account carried over from the previous year. Towns, domestic and stock, and high security licence categories cannot carryover. In this current water year, 0% Available Water Determination (AWD) has been announced on 1 July 2018 for General Security (GS). For other water users (e.g. High Security and Town Water Supply), the AWD is 100%. No additional AWD has been announced since 1 July Further general security AWD s are possible throughout the year. The sum of account balance refers the amount of water available to the account of the users after trades and usage. 5

6 4.2 Resource assessment Copeton Dam - storage breakdown (GL) July GL 25.4% Storage Loss Storage Loss shortfall Essential Supplies Essential Supplies shortfall Delivery Loss Delivery Loss shortfall ECA General Security Irrigation General Security environmental Total shortfall ,600 1,400 Gwydir water balance July ,200 1,000 Available Airspace General Security environmental General Security Irrigation 800 1,001 ECA Delivery Loss 600 Essential Supplies Storage Loss Dead Storage 6

7 4.2.1 Significance of this resource assessment The current resource assessment at 1 August 2018 indicates that there is no general security AWD announcement in this month. It also shows that GL of inflow is required to make up for the shortfall before any future AWD announcements Resource assessment process The Resource Assessment is the process of calculating how much water is available based on the rules of the Water Sharing Plan (WSP). This is done at the end of the month and when any significant inflow event happens. The above resource assessment table is for the planning horizon from 1 July 2018 to 30 June Rainfall month rainfall 7

8 From the above figures the last 6-month total rainfall lies is in the range of 150 to 250mm, which is below average to very much below average (average 6-month total rainfall is between 350 and 450 mm) month rainfall 8

9 GL From the above figures the last 24-month total rainfall lies in the range of 1000 to 1700mm, which is below average (average 24-month total rainfall is between 1200 and 2000 mm). 6. Inflows 6.1 Copeton Dam inflows Copeton Past 6 months cumulative inflow/statistical inflows Actual inflow 20%ile 50%ile 80%ile minimum Feb-18 Mar-18 Apr-18 May-18 Jun-18 Jul-18 Inflows are consistent with rainfall over the past 6 months period. Actual inflows for last 6 months were only around 10 GL which is slightly worst than minimum observed/historic flow. 9

10 Aug-16 Sep-16 Oct-16 Nov-16 Dec-16 Jan-17 Feb-17 Mar-17 Apr-17 May-17 Jun-17 Jul-17 Aug-17 Sep-17 Oct-17 Nov-17 Dec-17 Jan-18 Feb-18 Mar-18 Apr-18 May-18 Jun-18 Jul-18 GL Copeton Past 24 months cumulative inflow/statistical inflows Actual inflow minimum 80%ile 50%ile 20%ile Inflows are consistent with rainfall over the past 24 months period. Due to dry conditions in the last 24 months only around 450 GL of inflows were recorded which is slightly above to 50th percentile inflow condition, with most of this inflow in spring Operational loss 7.1 Operational losses to date Operational loss is water above that which could reasonably be expected to pass the last delivery point on any given stream (dam releases and controlled tributary inflows not supplementary flows). Gywdir cumulative totals Sales + environmental delivery Operational surplus Actual Target July 2, % 5% July-Aug 13, % 5% July-Sep 22, % 5% July-Oct 43, % 5% July-Nov 80,305 2,932 4% 5% July-Dec 157,228 7,002 4% 5% July-Jan 261,828 9,424 4% 5% July-Feb 286,390 11,919 4% 5% July-Mar 286,390 11,919 4% 5% July-Apr 292,722 11,919 4% 5% July-May 299,857 11,919 4% 5% July-Jun 299,857 11,919 4% 5% 10

11 Jul-17 Aug-17 Oct-17 Nov-17 Dec-17 Jan-18 Feb-18 Mar-18 Apr-18 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-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20 Apr-20 May-20 Jun-20 Gigalitres (GL) Operational Surplus / Sales (%) 6% 5% 4% Gwydir River - water delivery operational surplus vs sales cumulative % (regulated licenced is included in sales) Target below 5% 3% 2% 1% 0% 8. Storage forecast 8.1 Copeton Storage forecast 1400 Copeton - forecast storage volume - chance of exceedance Actual Minimum 99% COE DRY 80% COE Median 50% COE WET 20% COE Assessment done end of July 2018 The above figure demonstrates the behavior of Copeton Dam under different inflow conditions 11

12 through to June For example, with 20th percentile inflow the dam may reach full storage before the end of February COE in the figure refers to the Chance Of Exceeding these conditions in the time frame. For example, Wet 20% COE indicate that there is 20% of chance that the dam volume will be better than the projected volume, and there is 80% chance that the dam volume will be less than the projected volume Next 3 months scenario from the BOM forecast 9. Outage planning Item Time Description Copeton Dam N/A None Boolooroo Weir N/A None Combadello Weir N/A None Tareelaroi Weir N/A None Tyreel Weir N/A None Carole Creek Regulator N/A None Gundare Bridge and Regulator N/A None Mallowa Creek Regulator N/A None Mongyer Lagoon Block Dam and Regulator N/A None Tareelaroi Regulator N/A None Tyreel Regulator N/A None 12

13 10. Prognosis Current Conditions River valley Allocation Licence category Date of allocation Gwydir Valley* 0% General security 1 July % High security 1 July 2018 * Carry-over water is also available 100% Domestic and stock 1 July % Local water utilities 1 July 2018 The chances of improved General Security Allocation, based on different inflow scenarios are as follows: Gwydir Valley 3-month forecast to 31-Oct month forecast to 31-Jan - 19 Extremely Dry Average Wet dry Minimum inflows 80th percentile inflows 50th percentile inflows 20th percentile inflows 0.0% 0.0% 4.6% 17.8% 0.0% 4.0% 20.2% 55.8% If the dry condition continues with minimum inflow, then there will be no AWD announcement in this water year ( ). If the dry condition continues with 80th percentile inflow, then there may be an increased AWD announcement by January 2019 to 4.0%. If the flow condition improves to 50 th percentile inflow, then an increased AWD announcement by the end of October 2018 to 4.6% and to January 2019 to 20.2%. With high inflow conditions (i.e. 20 th percentile inflow), the AWD can be increased by the end of October 2018 to 17.8% and even further to 55.8% by January Reviewed by Vladimir Stojnic on 24 August