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Indicator: IW-23 Mapping of water temperature depression due to dam releases

Data

Structures in NSW likely to cause severe cold water pollution

Rank	Name	Height (m)	Capacity (ML)	Mean Depth (m)	Intake Depth (m)	Discharge (ML day –1)	Estimated length of river (km) subject to severe (>5°C peak depression) CWP
1	Blowering	112	1 628 000	36.5	74	8 200	60
2	Hume	51	3 038 000	15	29	20 000	300
3	Copeton	113	1 364 000	32	69	3 600	300
4	Burrinjuck	93	1 026 000	18.7	42	5 200	400
5	Burrendong	76	1 190 000	16.5	37	4 000	400
6	Wyangala	85	1 220 000	23	50	1 700	400
7	Keepit	55	423 000	9.6	24	2 000	300
7	Khancoban	18	21 500	4.6	12	4 000	120
9	Pindari	85	312 000	29.7	11	1 000

Source: Preece, R 2004, Cold water pollution below dams in New South Wales, Department of Infrastructure, Planning and Natural Resources, Sydney, viewed 14 Oct 2005, http://www.dlwc.nsw.gov.au/care/water/cold_water_pollution.html.

Experiments demonstrated that some native fish were affected by cold water pollution in the areas of growth, survival, distribution and activity. Consequences include reduced recruitment to adult populations, forced re-distribution of fish populations to less favourable habitats and general declines in fish populations because of decreased survival.

Source: Astles, K, Winstanley, R, Harris, J and Gehrke, P 2003, Regulated Rivers and Fisheries Restoration Project - Experimental study of the effects of cold water pollution on native fish, NSW Fisheries, Cronulla, NSW, viewed N/A, http://www.fisheries.nsw.gov.au/science/scientific_outputs/aqua-eco/317_experimental.

What the data mean

Cold water pollution occurs below large dams when cold water is released from the bottom of the dam into the river downstream, cooling the river water to 10 - 12°C; below its natural range. The size and scale of disturbance vary considerably between dams.

The effects of cold water pollution on organisms vary, depending on the species affected.

Data Limitations

National data are not available for this indicator. Long term trend data for dams where temperatures are routinely measured are also unavailable.

Issues for which this is an indicator and why

Inland Waters - Habitat scale influences - Water Quality (for surface and groundwater) - Thermal pollution 

Mapping of water temperature is a direct measure of this pressure.

Further Information

• Cold Water Pollution (DF95) - September 2001 
• Cold Water Pollution Below Dams in NSW 
• Experimental study of the effects of cold water pollution on native fish (Astles et al. 2003)