Water management in the Anthony–Pieman hydropower scheme
Pieman Sustainability Review June 2015 FACT SHEET
Background The Anthony–Pieman hydropower scheme provides a highly valued and reliable source of electricity. The total water storage of the hydropower scheme is 512 gigalitres and the average annual generation is 2367 gigawatt hours. Construction of the Anthony–Pieman hydropower scheme has resulted in creation of water storages (lakes) and alterations to the natural flow of existing rivers and streams. The Pieman Sustainability Review is a review of operational, social and environmental aspects of the Anthony–Pieman hydropower scheme that are influenced by Hydro Tasmania. This fact sheet elaborates on water management issues presented in the summary report, available at http://www.hydro.com.au/pieman-sustainability-review
Water storage levels in the Anthony–Pieman Water levels have been monitored at these storages since hydropower scheme their creation in stages between 1981 and 1991. The Anthony–Pieman hydropower scheme includes eight Headwater storages: Lake Mackintosh and Lake water storages, classified as headwater storages (Lakes Murchison Mackintosh and Murchison), diversion storages (Lakes Lakes Mackintosh and Murchison are the main headwater Henty and Newton and White Spur Pond) and run-of-river storages for the Anthony–Pieman hydropower scheme. storages (Lakes Rosebery, Plimsoll and Pieman). Lakes The water level fluctuates over the entire operating range Murchison, Henty and Newton and White Spur Pond do not from Normal Minimum Operating Level (NMOL) to Full release water directly to a power station; rather they are Supply Level (FSL) (Figures 1, 2). used to transfer water to other storages within the scheme.
Lake Mackintosh
231.00 230.50 230.00 229.50 FSL 229.00 228.50 228.00 227.50 227.00 226.50 226.00 225.50 225.00 224.50 224.00 223.50 223.00 222.50 222.00
Lake Level (mASL) 221.50 221.00 220.50 220.00 219.50 219.00 NMOL 218.50 218.00 217.50 217.00 216.50 216.00 215.50 215.00 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Figure 1: Lake Mackintosh daily water level since inundation (1981–2014). Spill events are indicated by peaks over FSL Lake Murchison FACT SHEET FACT 245.00 244.00 243.00 242.00 241.00 FSL 240.00 239.00 238.00 237.00 236.00 235.00 234.00 233.00 232.00 231.00 230.00 229.00 228.00
Lake Level (mASL) 227.00 226.00 225.00 224.00 223.00 222.00 221.00 220.00 219.00 NMOL 218.00 217.00 216.00 215.00 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Figure 2: Lake Murchison daily water level since inundation (1982–2014). Spill events have been more frequent at Lake Murchison than at Lake Mackintosh Mean monthly water levels are typically high in spring and summer, drawn down over late summer/autumn and re-filled over late winter and early spring (Figures 3, 4).
Lake Mackintosh Lake Murchison 231 Max 250 FSL 229 245 Max 227 240 FSL 225 235 223 230 221 Min Lake Level (mASL) Lake Level (mASL) 225 219 NMOL Min 220 217 NMOL 215 215
Figure 3: Lake Mackintosh mean (squares), maximum and Figure 4: Lake Murchison mean (squares), maximum and minimum (bars) monthlyA: Lake lake Henty levels (Nov -basedApril) on daily water minimum (bars) monthly lakeWhite levels Spur Pond based on daily water level 524 532 level data from 1981 to 2014. Mean monthly lake Maxlevels are data from 1982 to 2014 530 Max useful for523 visualising the average or typical water levelsFSL within FSL 528 each lake.522 The minimum and maximum values for each month 526 were obtained521 by taking the highest and lowest single values for each month over the entire period of record. A maximum 524 520 Lake Level (mASL) value above FSL indicates that the lake is spilling Lake Level (mASL) 522 Min NMOL 519 Min 520 Western Tasmania typically receives most rain, NMOLand hence storages receive the highest inflows, in winter and early 518 518 spring. Consequently Lakes Mackintosh and Murchison spill more frequently between May and October than between November and April (Figures 5, 6).
A: Lake Mackintosh (Nov-April) B: Lake Mackintosh (May-Oct) 231 231 229 FSL 229 FSL 227 227 225 225 223 223 221 221 Lake Level (mASL) Lake Level (mASL) 219 NMOL 219 NMOL 217 217 215 215 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 % of time exceeded % of time exceeded
Figure 5: Lake Mackintosh lake level duration curves based on daily water level data from 1981 to 2014 for November to April (A) and May to October (B). The lake spilled (exceeded FSL) 4% of the time in November–April, and 7% of the time in May–October during the wetter winter months. Lake water level duration curves were derived by calculating percentiles of daily time series. Lake level duration curves show the percentage of time a specific level is exceeded over the recording period. The y-axis shows the range of lake levels (expressed as elevation in metres above sea level (m ASL)) and the x-axis shows the percentage of time a particular lake level is exceeded. Normal Minimum Operating Level (NMOL) and full supply level (FSL) are also marked on the plot
Pieman Sustainability Review Water Management in the Anthony–Pieman hydropower scheme 2 A: Lake Murchison (Nov-April) B: Lake Murchison (May-Oct)
245 245 SHEET FACT
FSL FSL 240 240
235 235
230 230
225 225 Lake Level (mASL) Lake Level (mASL)
220 220 NMOL NMOL
215 215 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 % of time exceeded % of time exceeded
Figure 6: Lake Murchison lake level duration curves based on daily water level data from 1982 to 2014 for November to April (A) and May to October (B). The lake spilled (exceeded FSL) < 1% of the time in summer (November–April) and 5% of the time in winter (May–October)
Diversion storages: Lake Henty, Lake Newton and White Spur Pond Lake Henty, Lake Newton and White Spur Pond are small diversion storages in the Anthony-Pieman hydropower scheme that experience rapid changes in water levels. Water levels in Lake Henty and White Spur Pond tend to fluctuate over the entire operating range due to rainfall events in the local catchment (Figures 7, 8). This effect is enhanced in Lake Henty due to the inter-basin transfer from the Halls Creek Rivulet diversion. In comparison Lake Newton is maintained at lower levels more often due to the rules governing the operation of the Newton pumps (Figure 9).
Lake Henty 524.00
523.50
523.00 FSL
522.50
522.00
521.50
521.00
520.50 Lake Level (mASL)
520.00
519.50
519.00
518.50 NMOL
518.00 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Figure 7: Lake Henty daily water level since inundation (1991–2014)
White Spur Pond
531.00 530.50 530.00 FSL 529.50 529.00 528.50 528.00 527.50 527.00 526.50 526.00 525.50 525.00 524.50 524.00 Lake Level (mASL) 523.50 523.00 522.50 522.00 NMOL 521.50 521.00 520.50 520.00 519.50 519.00 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Figure 8: White Spur Pond daily water level since inundation (1991–2014)
Pieman Sustainability Review Water Management in the Anthony–Pieman hydropower scheme 3 Lake Newton FACT SHEET FACT 481.00 480.50 480.00 FSL 479.50 479.00 478.50 478.00 477.50 477.00 476.50 Lake Level (mASL) 476.00 475.50 475.00 NMOL Lake Murchison Lake474.50 Mackintosh 250 231 Max 474.00 FSL 229 245 Max 473.50 227 240 FSL 473.00 225 235 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 223 230 221
Min Lake Level (mASL) 225 Lake Level (mASL) 219 Figure 9: Lake NewtonNMOL daily water level since inundation (1991–2014) Min 220 217 NMOL Mean water215 levels in Lake Henty and White Spur Pond are highest over215 winter (Figures 10, 11) whereas seasonal differences in lake levels are less pronounced in Lake Newton (Figure 12).
A: Lake Henty (Nov-April) White Spur Pond 524 532
Max 530 Max 523 FSL FSL 528 522 526 521 524 520
Lake Level (mASL) Min Lake Level (mASL) 522 NMOL 519 Min 520 NMOL 518 518
Figure 10: Lake Henty mean (squares), maximum and Figure 11: White Spur Pond mean (squares), maximum and minimum (bars) monthly lake levels based on daily water minimum (bars) monthly lake levels based on daily water level data from 1991 to 2014 level data from 1983 to 2014
Lake Newton 481 Max 480 FSL 479
478
477
476 Lake Level (mASL) 475 NMOL 474 MIN 473
Figure 12: Lake Newton mean (squares), maximum and minimum (bars) monthly lake levels based on daily water level data from 1991 to 2014
Pieman Sustainability Review Water Management in the Anthony–Pieman hydropower scheme 4 Lakes Henty and Newton spill infrequently from November to April (approximately 1% of the time) and approximately 4% and 3% of the time, respectively, from May to October (Figures 13, 14). In contrast, White Spur Pond spills < 1% of SHEET FACT the time all year round (Figure 15).
A: Lake Henty (Nov-April) B: Lake Henty (May-Oct) 524 524
523 FSL 523 FSL
522 522
521 521
520 520 Lake Level (mASL) Lake Level (mASL)
519 519 NMOL NMOL 518 518 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 % of time exceeded % of time exceeded
Figure 13: Lake Henty lake level duration curves based on daily water level data from 1991 to 2014 for November to April (A) and May to October (B)
A: Lake Newton (Nov-April) B: Lake Newton (May-Oct) 481 481 480 FSL 480 FSL 479 479 478 478 477 477 476 476 Lake Level (mASL) 475 Lake Level (mASL) NMOL 475 NMOL 474 474 473 473 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 % of time exceeded % of time exceeded
Figure 14: Lake Newton lake level duration curves based on daily water level data from 1991 to 2014 for November to April (A) and May to October (B)
A: White Spur Pond (Nov-April) B: White Spur Pond (May-Oct) 532 532
530 FSL 530 FSL
528 528
526 526
524 524 Lake Level (mASL) Lake Level (mASL) 522 522 NMOL NMOL 520 520
518 518 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 % of time exceeded % of time exceeded
Figure 15: White Spur Pond lake level duration curves based on daily water level data from 1983 to 2014 for November to April (A) and May to October (B)
Pieman Sustainability Review Water Management in the Anthony–Pieman hydropower scheme 5 Run-of-river storages: Lake Rosebery, Lake Pieman and Lake Plimsoll FACT SHEET FACT The water level in Lake Rosebery is normally kept within a one-metre operating range (Figure 16). The narrow operating range is close to FSL and results in little seasonal variation in storage level. In comparison, Lakes Pieman and Plimsoll are operated as run-of-river storages; they are drawn down over autumn and early winter to minimise spill when inflows are typically high (Figures 17, 18).
Lake Rosebery
162.00 161.50 161.00 160.50 160.00 159.50 FSL 159.00 158.50 158.00 157.50 157.00 156.50 156.00 155.50 155.00 Lake Level (mASL) 154.50 154.00 153.50 153.00 152.50 152.00 151.50 151.00 NMOL 150.50 150.00 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Figure 16: Lake Rosebery daily water level since inundation (1983-2014)
Lake Pieman
101.00 100.50 100.00 99.50 99.00 98.50 98.00 97.50 FSL 97.00 96.50 96.00 95.50 95.00 94.50 94.00 Lake Level (mASL) 93.50 93.00 92.50 NMOL 92.00 91.50 91.00 90.50 90.00 89.50 89.00 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Figure 17: Lake Pieman daily water level since inundation (1986-2014)
Lake Plimsoll
514.00 513.50 513.00 FSL 512.50 512.00 511.50 511.00 510.50 510.00 509.50 509.00 508.50 508.00
Lake Level (mASL) 507.50 507.00 506.50 506.00 505.50 NMOL 505.00 504.50 504.00 503.50 503.00 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Figure 18: Lake Plimsoll daily water level since inundation (1993-2014)
Pieman Sustainability Review Water Management in the Anthony–Pieman hydropower scheme 6 Water levels in Lakes Rosebery, Pieman and Plimsoll tend not to fluctuate greatly which is due to the ability to regulate inflows in the upstream storages (Figures 19, 20, 21). Lake Pieman is maintained closer to FSL over summer when SHEET FACT rainfall is typically lower (Figure 20).
Lake Rosebery 164
162 Max 160 FSL 158
156
Lake Level (mASL) 154 Min 152 NMOL 150
Figure 19: Lake Rosebery mean (squares), maximum and minimum (bars) monthly lake levels based on Lake Plimsoll 516daily water level data from 1983 to 2014 Max 514 FSL 512
510
508 Lake Pieman 102 Min Lake Level (mASL) 506 100 NMOL 504 Max 98 502 FSL 96
94 Lake Rosebery Min 164 NMOL
Lake Level (mASL) 92 162 90 Max 160 88 FSL 158
156
Lake Level (mASL) 154 Min Figure 20: Lake Pieman mean152 (squares), maximum and minimum (bars) monthly lake levels based on Lake Newton 481 NMOL 150daily water level data from 1986 to 2014Max 480 FSL 479
478 477
476 Lake Plimsoll 516 Lake Level (mASL) 475 NMOLMax 514 474 MinFSL 512 473 510
508 Min Lake Level (mASL) 506 NMOL 504
502
Figure 21: Lake Plimsoll mean (squares), maximum and minimum (bars) monthly lake levels based on daily water level data from 1993 to 2014
Pieman Sustainability Review Water Management in the Anthony–Pieman hydropower scheme 7 Lake Rosebery and Lake Pieman storages spill infrequently from November to April (approximately 1% of the time) but spill approximately 8% and 7% of the time, respectively, in the wetter winter months from May to October (Figures 22, SHEET FACT 23). Lake Plimsoll spills 3% of the time from November to April and 6% of the time from May to October (Figure 24).
A: Lake Rosebery (Nov-April) B: Lake Rosebery (May-Oct) 162 162
160 FSL 160 FSL
158 158
156 156
154 154 Lake Level (mASL) Lake Level (mASL)
152 152 NMOL NMOL 150 150 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 % of time exceeded % of time exceeded
Figure 22: Lake Rosebery lake level duration curves based on daily water level data from 1983 to 2014 for November to April (A) and May to October (B)
A: Lake Pieman (Nov-April) B: Lake Pieman (May-Oct) 100 102
98 100 FSL 98 96 FSL 96 94 94 92 NMOL
Lake Level (mASL) NMOL Lake Level (mASL) 92
90 90
88 88 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 % of time exceeded % of time exceeded
Figure 23: Lake Pieman lake level duration curves based on daily water level data from 1986 to 2014 for November to April (A) and May to October (B)
A: Lake Plimsoll (Nov-April) B: Lake Plimsoll (May-Oct) 516 516
514 FSL 514 FSL
512 512
510 510
508 508 Lake Level (mASL) 506 Lake Level (mASL) 506 NMOL NMOL 504 504
502 502 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 % of time exceeded % of time exceeded
Figure 24: Lake Plimsoll lake level duration curves based on daily water level data from 1993 to 2014 for November to April (A) and May to October (B)
Pieman Sustainability Review Water Management in the Anthony–Pieman hydropower scheme 8 Flow regimes downstream of storages FACT SHEET FACT This section presents flow regimes for the Pieman River, the Anthony River and the Henty River and tributaries. There are no river reaches downstream of Lakes Mackintosh, Murchison and Rosebery because downstream storages reach the bases of their respective dams. The flow regime of the Pieman River downstream of Reece Dam reflects the operation of the Reece Power Station (Figure 25). The Pieman River now experiences periods of time without river flows, particularly in spring and summer (approximately 18% and 12% of the time respectively). However, compared to pre-development, median flows are now approximately 30 to 50% greater in all seasons and the magnitude of flood events (including rare and extreme events) are reduced, particularly in spring and summer. The occurrence of periods of time without river flows or very low flows, in addition to altered median and high flow events, is likely to have affected the natural fluvial geomorphological and ecological processes in the Pieman River.
Figure 25: Pre-inundation (blue line) and post-development (red line) flow in the Pieman River downstream of Reece Dam and Reece Power Station during spring, summer, autumn and winter. These flow duration curves show the frequency of occurrence of specific flows, in cumecs (cubic metres per second). The y-axis shows the range of discharges in cumecs (on a logarithmic scale) and the x-axis shows the percentage of time a particular discharge is exceeded. The difference between the red and blue lines indicates changes to the natural flow regime as a result of hydro-electric developments. The post-development curve is the sum of discharge and spill
There were even greater changes in the post-development flow regime of other rivers examined within the Anthony–Pieman hydropower scheme (Figures 26, 27). These changes are characterised by a substantial increase in the time period that the watercourses are de-watered (dry), which ranges from 92% of the time for the Henty River to 99% of the time for Newton Creek (Figure 26). The magnitude of flood events varied little in White Spur Creek and Henty River when compared with pre- development. However, the magnitude of large flood events (a flood that occurs ≤ 1% of the time) in the Newton and Anthony Rivers is reduced by 49% and 39% respectively. Large changes in the natural flow regimes of these watercourses since development is likely to have affected pre-development fluvial geomorphological and ecological processes, and aquatic and riparian habitats and communities.
Pieman Sustainability Review Water Management in the Anthony–Pieman hydropower scheme 9 FACT SHEET FACT
Figure 26: Natural (blue line) and post-development (red line) flow in the Henty River downstream of Anthony Dam, Newton Dam and White Spur Dam
Figure 27: Natural (blue line) and post-development (red line) flow in the Anthony River downstream of Lake Plimsoll and Anthony Dam
Pieman Sustainability Review Water Management in the Anthony–Pieman hydropower scheme 10