Australia ―7 Snowy River below Lake Jindabyne Map of River 3 Australia ―7 Table of Basic Data Name(s): Snowy River below Lake Jindabyne Serial No. : Australia-7 Location: Southeastern Australia N 36° 27' ~ 37° 50' E 148° ~ 149° 30' Area: 11,720 km2 below Lake Jindabyne Length of main stream: 350 km Origin: Lake Jindabyne Highest point: Mt Cobberas, 1,833 m Outlet: Tasman Sea Lowest point: River mouth at sea level Main geological features: Low grade metamorphic and granitic rocks Main tributaries: Maclaughlin, Delegate, Deddick and Buchan rivers Main lakes: None Main reservoirs: Jindabyne Dam (most upstream point of the catchment) Mean annual precipitation: 500 mm in the coastal region to 3,800 mm in the upper central region Mean annual runoff: 43.1 m3/s post Jindabyne Dam construction Population: approx 12,000 (2001) Main cities: Orbost Land use: Grazing, National Park, forestry, intensive cropping in lower reaches 1. General Description The Snowy River catchment extends from Kiandra in the Snowy Mountains to the river mouth at Marlo where it flows into the Tasman Sea. The total catchment area is 13,570 km2 with the area below Lake Jindabyne being 11,720 km2. The annual precipitation ranges from 500 mm to 3,800 mm with the highest precipitation occurring on the mountain peaks in the form of winter snow. Precipitation in the upper Snowy catchment is highest during late autumn and lowest during summer and is increased by orographic effects. The central portion of the catchment (below Lake Jindabyne) is in a rainshadow and experiences mean annual rainfall of about 500 mm. The mean annual precipitation then increases moving south to the coast where it is about 800 mm. Construction of the Snowy Mountains Hydro-electric Scheme has reduced annual average natural flows in the Snowy River immediately below Jindabyne Dam by 99 percent. Two tributaries below the dam, Mowamba River and Cobbin Creek are substantially diverted into the dam. The Delegate River is the first substantial river to contribute to the Snowy below Lake Jindabyne. Flow releases from Jindabyne Dam range from a ‘visible’ flow to 50 ML/d to satisfy riparian users. Under natural conditions the Snowy River exhibited a strong seasonal pattern characterized by low summer flows and high persistent spring flows due to snowmelt. The elimination of the high spring flows is evident even at the river mouth. Moving downstream from Jindabyne Dam, tributary inflows substantially increase the flow of the Snowy River. The Delegate River contributes approximately 30% of the post-Scheme mean annual flow of the Snowy River. At Jarrahmond the Snowy flows are approximately 53 percent of pre-Scheme flows. The catchment from the Buchan River and below generates low summer flows with the highest flows occurring in autumn. The lower reaches of the Snowy (below the Buchan River) change from riverine to estuarine. Under natural conditions the Snowy River experienced a number of floods each year that could occur at any time but particularly in spring when rainfall coincided with snowmelt. Under existing conditions there are no floods immediately downstream of Jindabyne. Even at the coast, the frequency and magnitude of floods have been reduced. 4 Australia ―7 2. Geographical Information 2.1 Landform and Geological Map 5 Australia ―7 2.2 Land Use Map 2.3 Characteristics of River and Main Tributaries Length [km] Highest peak [m] Cities No. Name of river Catchment area 1) Lowest point [m] Population (2001) Land use [km2] Snowy 350 1,833 Orbost 1 (below L Jindabyne) 11,720 0 Approx. 3,000 (Main river) Maclaughlin 57 1,018 2 A (Tributary) 459 528 G Delegate 79 1,308 N 3 (Tributary) 2,687 515 Buchan 81 1,566 4 (Tributary) 1,214 30 1) A: Agricultural G: Stock grazing N: National Park 6 Australia ―7 2.4 Longitudinal Profiles 3. Climatological Information 3.1 Annual Isohyetal Map and Observation Stations Based on thin plate spline analysis of all available rainfall stations. 7 Australia ―7 3.2 List of Meteorological Observation Stations1) Mean annual Mean annual Elevation Observation Observation No. Station Location precipitation2) evaporation [m] period items3) [mm] [mm] S 36° 54' 41" 070005 Bombala PO 705 1912 - 2003 646 P, T E 149°14' 16" Nimmitabel S 36° 30' 44" 070067 1,075 1911 - 2003 695 P, T PO E 149° 17' 06" Tombong S 36° 55' 57" 070084 800 1908 - 2003 593 P (Hilcrest) E 148° 56' 21" S 36° 50" 42" 070106 Cathcart 803 1899 - 2003 801 P E 149° 23' 18" Cooma S 36° 13' 54" 070278 778 1973 - 2003 537 P, T (Visitor Centre) E 149° 07' 27" Dalgety S 36° 43' 30" 070337 790 1993 - 2003 643 P (Jimenbuen) E 148° 51' 17" Dalgety S 36° 30' 15" 071005 765 1896 - 2003 481 P (Hamilton St) E 148° 50' 02" Jindabyne S 36° 29' 14" 071021 1,030 1906 - 2002 623 P (Lynwood) E 148° 34' 56" Guthega S 36° 21' 06" 071034 1,340 1952 - 1994 1,780 P Power Station E 148° 24' 45" Ingebyra S 36° 36' 08" 071042 1,240 1971 - 2003 857 P, TB (Grosses Plains) E 148° 28' 04" Berridale S 36° 16' 27 071043 (Eucumbene 1,050 1973 - 2002 627 P E 148° 43' 06" Trout Farm) Khancoban S 36° 13' 31" 072060 337 1961 - 2003 981 1,193 P, T, W, E SMHEA E 148° 08' 35" S 37° 07' 07" 084000 Bendoc Park 790 1887 - 2003 696 P E 148° 57' 48" S 37° 10' 23" 084002 Bonang 675 1887 - 2003 916 P E 148° 43' 16" S 37° 29' 55" 084005 Buchan 90 1883 - 2003 817 P, TB E 148° 10' 23" Butchers S 37° 16' 52" 084007 670 1933 - 2003 970 P Ridge E 148° 15' 14" Cabbage Tree S 37° 42' 36" 084008 51 1946 - 2003 1,084 P Creek E 148° 42' 29" S 37° 41' 30" 084030 Orbost 41 1883 - 2003 850 1,073 P, TB, T, E E 148° 27' 32" Black S 37° 00' 31" 084044 915 1920 - 2003 726 P Mountain E 148° 15' 52" S 37° 24' 59" 084085 Combienbar 213 1967 - 2003 987 P, TB E 149° 00' 44" Orbost S 37° 42' 54" 084093 20 1968 - 2003 845 P (Bete Bolong) E 148° 23' 38" 8 Australia ―7 Mean annual Mean annual Elevation Observation Observation No. Station Location precipitation2) evaporation [m] period items3) [mm] [mm] S 37° 05' 03" 084107 Wulgulmerang 914 1970 - 2003 699 989 P, E E 148° 16' 40" S 37° 20' 28" 084134 Goongerah 235 1980 - 2003 961 - P E 148° 42' 38" 1) Only a representative sub-set of stations available in the basin are presented. 2) For period of observation. 3) P: Precipitation. TB: Tipping bucket with recording chart or logger. T: Temperature E: Evaporation W: Wind 3.3 Monthly Climate Data Observing station: 072060 Khancoban Observation Period for Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual item the mean Temperature 21.2 21.4 18.4 14.1 9.9 6.7 6.2 7.8 10.3 13.5 16.3 19.1 13.7 1962 - 1994 [°C] Precipitation 63.0 47.8 57.9 63.6 87.5 84.7 101.7 114.4 99.4 101.5 80.6 73.8 981.0 1961 - 2003 [mm] Number of 767912 14 16 16 14 13 11 9 134 1961 - 2003 rain days Evaporation 205.1 171.0 135.9 70.7 36.3 20.7 22.4 35.9 65.4 106.3 144.4 187.3 1,193.0 1966 - 2003 [mm] Duration of 9.9 9.5 8.3 7.0 4.7 3.3 3.5 4.4 5.8 7.5 8.7 8.7 6.7 1962 - 1994 sunshine [hr] Observing station: 084030 Orbost Observation Period for Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual item the mean Temperature 19.2 19.4 17.9 15.0 12.4 10.2 9.5 10.4 12.0 14.0 15.8 17.6 14.5 1938 - 2003 [°C] Precipitation 68.1 58.2 67.5 74.8 70.9 85.0 67.1 58.9 71.4 78.0 71.7 78.2 849.5 1883 - 2003 [mm] Number of 878910 11 11 11 12 12 10 9 117 1883 - 2003 rain days Evaporation 152.7 135.4 107.5 66.7 49.0 36.6 40.3 61.4 81.6 103.9 120.0 136.4 1,073.0 1994 - 2003 [mm] Observing station: 084107 Wulgulmerang Observation Period for Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual item the mean Precipitation 57.9 60.2 63.3 47.2 45.6 53.5 44.3 47.5 60.7 68.9 86.2 64.1 699.4 1970 - 2003 [mm] Number of 989910 10 10 11 11 12 12 9 121 1970 - 2003 rain days Evaporation 156.6 123.5 99.5 64.9 44.5 30.3 36.6 52.7 72.6 92.7 107.7 157.8 988.6 1972 - 1982 [mm] 9 Australia ―7 3.4 Long-term Variation of Monthly Precipitation 4. Hydrological Information 4.1 Map of Hydrological Observation Stations 10 Australia ―7 4.2 List of Hydrological Observation Stations Catchment Observation Observation No. Station Location area (A) period items1) [km2] The Falls S 36° 55' 00" 222009 559 1951 - 2003 H, Q (Bombala River) E 149° 12' 36" Buchan S 37° 30' 00" 222206 822 1926 - 2003 H, Q, W Q (Buchan River) E 148° 10' 30" Deddick (Caseys) S 37° 05' 30" 222210 857 1964 - 2003 H, Q, WQ (Deddick River) E 148° 25' 30" Quidong S 36° 54' 24" 222008 1,127 1951 - 2003 H, Q (Delegate River) E 149° 02' 00" The Hut S 36° 39' 18" 222017 313 1978 - 2003 H, Q (Maclaughlin River) E 149° 06' 06" Suggan Buggan S 36° 57' 12" 222213 357 1957 - 2003 H, Q, WQ (Suggan Buggan River) E 148° 19' 30" Jindabyne S 36° 25' 24" 222501 1,850 1902 - 1957 H, Q (Snowy River) E 148° 38' 00" Dalgety S 36° 30' 00" 222006 3,040 1949 - 1997 H, Q (Snowy River) E 148° 50' 00" Burnt Hut Crossing S 36° 50' 30" 222013 7,081 1975 - 2003 H, Q (Snowy River) E 148° 55' 54" D/S of Basin Creek S 37° 30' 00" 222219 11,964 1978 - 2003 H, Q, WQ (Snowy River) E 148° 16' 12" Jarrahmond S 37° 39' 42" 222200 13,421 1937 - 2003 H, Q, WQ (Snowy River) E 148° 21' 30" Orbost S 37° 43' 00" 222201 13,570 1907 - 2003 H, WQ (Snowy River) E 148° 27' 30" Marlo Jetty S 37° 47' 54" 222203 NA 1934 - 1998 H (Snowy River) E 148° 31' 42" －2) 3) － 4) － 5) － Q Qmax Qmax Qmin Q/A Qmax/A Period of No.