ACT State of the Environment 2007

Indicator: Surface water quality

Summary

Reduced availability of water across the ACT and in the western catchments of the ACT as a result of the drought combined with the effects of the 2003 bushfire have led to poor surface water quality for the reporting period. The full extent of the water quality problem however, is relatively unknown. In the many ACT catchments, there is insufficient water quality data to reveal the full extent of the state of the Territory's surface water quality.

What the results tell us about the ACT

Surface water quality is a function of the solid and solute loads transported by rivers and streams. In addition to natural loads generated by the catchment, surface water quality is affected by discharges from premises and runoff from agricultural, industrial and urban areas. Within the ACT there is a mix of agricultural, urban and industrial land uses with some 53% of the ACT being managed as conservation reserves. This mix of land use and reserves leads to a wide variation in catchments across the ACT from native forested mountain catchments in near pristine condition to a catchment of low relief with a high level of run-off from agricultural, industrial and urban activities.

During the reporting period, poor water quality has been exacerbated by uncontrollable influences. Most notably, the low flow conditions as a result of the prolonged drought and, in the Territory's western catchments, the landscape response to the 2003 bushfire has seriously degraded the capacity of some catchments to yield normal flow conditions and acceptable water quality.

The availability and quality of surface water quality data is a problem. The bulk of the data recorded during the reporting period only provides a snapshot of water quality as at some sites fewer than 10 samples were collected per year for key water quality parameters. From this, the data collected, can only indicate a water quality trend and not present the full story. For several catchments, the available data indicates the quality of water in the ACT, for the most part, meets Environmental Protection Authority guidelines. Catchments with areas of intense land use (such as developing urban areas) are a cause for concern as the water quality guideline is frequently exceeded.

The overall trend of available water quality data is improving. Water quality monitoring is indicating that as land use practices improve or the urban expansion in certain areas approaches its limits, water quality improves.

When upstream data is compared to data from the Territory's most downstream site at Halls Crossing on the Murrumbidgee River (Site 204), the evidence indicates that the ACT is having an appreciable impact on water quality with guideline limits regularly exceeded. The available data since 1992 reflects this trend.

Murrumbidgee River

The available water quality data indicate that the quality of several water parameters leaving the ACT (Murrumbidgee at Halls Crossing – Site 204; 185 kB pdf) frequently fail the acceptable water quality limits. This is in contrast to water entering the ACT at Angle Crossing on the Murrumbidgee River (Site 213; 154 kB pdf), where the quality of water is of a better standard with minimal failures across the measured water quality parameters. This has been consistent throughout the reporting period.

During the reporting period, other upstream monitoring sites, for example, on the Molonglo and Queanbeyan Rivers, showed that a few water quality results exceeded the standards. Downstream sites recorded slightly worse results. However, these results were mostly within acceptable water quality guideline parameters. While these results offer some optimism, it must be acknowledged that they are based on a limited number of samples. Accordingly, they should be interpreted cautiously and further data collected to allow an accurate assessment.

The expected and observed impact of the 2003 bushfire has not been fully identified at the above water quality sites. This is suspected to be an artifact of the water quality sampling strategy. Other sites, such as those in the Cotter River monitored by ActewAGL, and the results of the Community Assessment Monitoring Program for Fire Impacted River Ecology (Campfire) monitoring program, reveal to a greater extent the impact of the 2003 bushfire on surface water quality.

Campfire found changes consistent with catchments affected by fire, that is, increased turbidity following rainfall events, at several of their monitoring sites. In addition there has been a change to the surface water quality through an increase in dissolved salt concentrations measured at the Upper Tidbinbilla River site.

Canberra's catchments

The Cotter River catchment is a major supplier of Canberra's water supply. It is divided into three sub catchments – the Corin, Bendora and Cotter dams. Following the 2003 bushfire, the Corin and Bendora dam sub catchments infrequently recorded high levels of turbidity and associated parameters for 2003 (White et al. 2006). Following this period, water quality returned to normal levels. However, in the Cotter Dam catchment, the long history of landscape disturbance, the 2003 bushfire and the pine plantation salvage operations of 2003–05 led to poor water quality in the Cotter Dam and associated water quality monitoring sites throughout the reporting period (White et al. 2006).

During the previous reporting period, the Territory's highest water quality was associated with forested catchments of Namadgi National Park. The water quality problems experienced during 2003 indicate the bushfire has greatly affected catchments within the borders of the ACT. Additionally, intensive land use associated with pine forest salvage operations and other human activities in the catchment has exacerbated the impact of the bushfire on water quality in the Cotter Dam catchment and nearby tributaries of the Murrumbidgee River. The bushfire affected tributaries of the Murrumbidgee River including the Cotter and Paddys River that have yielded large volumes of sediment to the Murrumbidgee despite impoundments such as the Cotter Dam acting as a sediment trap for the Cotter River. A study commissioned by ActewAGL found some 70,000 tons of sediment from the Lower Cotter catchment was deposited in the Cotter Dam following the 2003 bushfire (Ecowise 2006). While little is known about the source of the sediment, scientific theory suggests that a large percentage of the material was derived from areas under pine plantations with some material derived from conservation areas, as observed in the Corin and Bendora catchments.

During the reporting period the ACT Government embarked on an ambitious restoration plan to replant the former pine plantation in the Lower Cotter Catchment with native plants. A key objective was to improve water quality. The plan included closure of many roads and installation of soil control measures. While implementation of the plan is well under way, the extensive restoration work needed throughout the catchment (road closures and rehabilitation, planting native vegetation, weed control and soil conservation programs) will take many years to complete. Issues remain with the use of heavy machinery in site preparation for planting and achieving a balance between the objectives of the restoration program with, for example, the objectives of Bushfire Operation Plans.

The Paddys River catchment has a mix of conservation, agricultural and forestry land uses. The 2003 bushfire burnt much of this catchment, leaving many areas of bare soil vulnerable to erosion and the potential for degrading downstream water quality during rainfall. In addition, the fires necessitated salvage operations in the pine plantations.

While these pressures, combined with the drought, would have predicted poor water quality conditions for this catchment during 2003, the results of the measured water quality parameters at Paddys River at Riverlea (Site 842; 136 kB pdf), a site upstream of forestry operations, recorded results that fall within the water quality guidelines for this site. There are no water quality monitoring sites below the pine plantations.

The Gudgenby River catchment (Site 901; 136 kB pdf) reveals, for the most part, that the catchment was in good condition during the reporting period. The 2003 bushfire affected a large percentage of this catchment that is dominated by native species and is protected as a reserve with a limited amount of agriculture. The response to the fire was seen with frequent turbidity measurements exceeding the guidelines during the reporting period.

The Molonglo River catchment is subject to high pressures from its urban and industrial uses, including those in Queanbeyan and other New South Wales towns such as Captains Flat. Within the ACT, the Molonglo River, which includes Lake Burley Griffin, is sampled at two sites above Lake Burley Griffin – Dairy Flat (Site 601; 137 kB pdf) and Yass Road (Site 608; 140 kB pdf).

Upstream of Lake Burley Griffin, various water quality parameters indicate that the Molonglo River catchment generally yields a high standard of water. The longer-term trend indicates a stable or slightly improving water quality for the measured parameters. Nevertheless, infrequent occurrences of lower water quality do occur as rainfall events transport solutes and soils to streams, particularly as the lake is downstream is of the Queanbeyan sewerage treatment plant.

The Ginninderra Creek catchment is sampled for water quality at Parkwood (Site 301) on Ginninderra Creek below the confluence with Gooromon Ponds Creek. The main trunk of the Ginninderra Creek runs though a highly modified landscape subject to urban and agricultural land uses. Notably, Lake Ginninderra is located approximately in the centre of the catchment.

Water quality during the reporting period saw several infrequent water quality exceedences of the turbidity, dissolved oxygen, faecal coliform, and chlorophyll 'a' limits.

The Queanbeyan River catchment is sampled at the ACT border before the river reaches the Molonglo River. Water flowing from the Queanbeyan River catchment (Site 769; 136 kB pdf) has acceptable results for water quality. Although low dissolved oxygen levels during low flow suggests impacts from urban runoff.

Canberra's lakes

Canberra's lakes encompass a range of notable values from mainly ornamental to limited recreation. While the lakes have obvious consequences for downstream water availability, they are also critical in terms of downstream surface water quality. The lakes are a final barrier to pollution from rural, urban and industrial areas of the ACT and the waters of the Murrumbidgee River.

The water quality in Canberra's lakes is managed by preventing the surface water pollution from entering the lakes. To this end, small dams in rural areas and gross pollution traps in urban areas have been constructed. These structures capture solid waste, and with regular maintenance, increase the quality of water entering Canberra's lakes. There is no data available on the overall adequacy of the urban gross pollutant traps or the adequacy of their maintenance. Given the importance of these structures in controlling pollution from surface water it seems timely for an investigation into their adequacy and maintenance.

Lake Burley Griffin

At a capacity of 33 GL, Lake Burley Griffin impounds a great deal of water. It receives waters of poor quality from the Molonglo River catchment and some of the Territory's other catchments, including Sullivan's and Jerrabomberra Creek. Land use in the Lake Burley Griffin catchment is a mix of agricultural, urban, industrial and reserve areas. Significant measures throughout the history of the lake have been implemented to protect the quality of the water flowing into the lake. These measures include gross pollution traps in urban areas, which collect a great deal of the solid waste found in our waterways. Regular maintenance of these measures is required to protect water quality.

The National Capital Authority, on behalf of the Commonwealth, is responsible for overall management of Lake Burley Griffin. The lake is generally regarded as a major recreational water body in the ACT. Sustainable use of the lake for recreational activities is promoted along with protecting and enhancing its water quality.

Under the National Capital Authority's water quality management program the lake's water quality is routinely tested at a number of sites. Since 1981 the results from the lake have shown a trend toward improved water quality. This trend has continued through the reporting period with few water quality records exceeding the guidelines.

Swimming or primary contact recreational activities are generally encouraged in the western sections of the lake. Lake Burley Griffin has four specified swimming areas – Black Mountain Swimming Area, Weston Park (west) Swimming Area, Weston Park (east) Swimming Area, and Yarralumla Swimming Area. Weekly samples, obtained at these sites, are tested and reported in accordance with the approved Australian Water Quality Guidelines.

Lake Burley Griffin bacterial conditions

During the reporting period, overall bacterial quality of the water was assessed as generally high under the Australian Water Quality Guidelines. A few swimming sites with limited water circulation in Lake Burley Griffin were found to be affected intermittently with bacterial levels exceeding the guideline values. The exceedance of bacterial levels generally occurred after storm events that brought debris and therefore altered the water quality conditions. Other exceedances occurred during high variations in day and night temperatures that tend to occur during February–March.

Generally no bacterial problems were recorded during the winter to mid summer months.

Lake Burley Griffin algae conditions

Algae are naturally common in freshwater systems. Under certain conditions, including high water nutrient loads and high water temperatures, the algae populations may increase to levels where a threat may exist to other life. For this reason, lakes in the ACT are monitored for algae levels.

There were specific algae alert events in the lake during the reporting period. Generally minor incidences of algae levels reaching to a low alert level occurred at varying times (March 2003, late March 2005, June 2005) but were cleared within a few days and did not require lake closure.

Algae levels reaching a medium alert level were recorded in East Basin in late January 2004 during which time primary contact recreation was restricted.

In October 2003, the presence of the cool-season strain of blue-green algae Tychonema was detected. This algal strain is known to be highly toxic to animals. This matter came to the National Capital Authority's attention following an incident in which two dogs became ill after drinking and playing in shallow waters at Yarralumla beach. Following this incident, the Chief Health Officer (ACT Health), advised the prohibition of all activities on or in Lake Burley Griffin and Lakes Tuggeranong and Ginninderra, as well as other minor water bodies, pending further testing. Following confirmation by additional tests (20–28 October 2003) showing no presence of Tychonema, the National Capital Authority lifted the warning on primary contact recreation on 30 October 2003. An extended testing program was continued for the next two weeks and no adverse effects of algae condition was noted.

In June and August 2004, blue-green algae alerts were issued in East Basin, Central Basin and West Basin. The blue-green alga identified was Phormidium, a potentially hazardous type of blue-green algae. A few large clumps of Phormidium were noted in these sites. This particular species of blue-green algae is more common during winter and appears as brown clumps of varying sizes on the water surface.

On a few occasions (in November and December 2005), observers noted the presence of visible green algae in some parts of the lake; samples taken identified it as predominantly Botryococcus, a non-toxic strain. The affected sites were cleared within a few days.

In November 2006, a low-level algae alert was issued in areas near Yarramundi Reach–Scrivener Dam. This was cleared to normal level within one week. Around the same period, certain western sections of the lake were reported to have green scum on the surface of the water. Samples taken identified it as predominantly the non-toxic Botryococcus; the affected sites were cleared within a few days.

Also in late February and March 2007, low to medium algae alert levels were issued for the lake mostly in the eastern sections of the lake.

Lake Ginninderra

Lake Ginninderra is monitored at two sites, one near the inflow of Ginninderra Creek in the eastern reach (Site 321) and the second near the dam wall (Site 318). The results for Lake Ginninderra indicate high water quality for the reporting period. Nevertheless, during infrequent storm events, water quality guidelines were exceeded because of runoff from urban and developing areas.

Lake Tuggeranong

Two sites are monitored in Lake Tuggeranong. One is located at the Kambah Wetland (Site 248), which is near the northern inflow to the lake and the other is at the dam wall (Site 249). Since 1992 the data measured at these sites has shown an improving trend across the measured parameters as the expansion of urban area in the catchment has slowed. During the warmer months there were high levels of chlorophyll 'a', consistent with algae outbreaks (following nutrient rich runoff from urban areas). Lake closures in the summer months coincided with algal outbreaks.

Point Hut Pond (Site 270)

Since the construction of the Point Hut Pond, this site has been regarded as one of the poorer water quality sites found in the ACT. During this reporting period however, the water quality results were improving as the intensive residential development in the catchment concludes.

Gungahlin Pond

Water quality measured at the Gungahlin Pond site (Site 346; 145 kB pdf) suggests that for most of the period the water quality was within acceptable limits. Nevertheless, intensive residential development in the Gungahlin Pond catchment remained a significant limit to achieving acceptable water quality results throughout the entire reporting period. Runoff from bare ground is associated with long-term average turbidity values higher than the regulation limits.

Surface water dependent ecosystems

Surface water supports a wide range of biological systems including ecosystems of the riparian zone, wetlands and those restricted to the aquatic environment. Environmental threats to these systems include loss of water, pollution and introduced species. For example, the amount of dissolved oxygen in a water body is frequently the key determinant of the extent and kinds of organic life in that water body. Low levels of dissolved oxygen lead to reduced fish populations.

The extent of ecosystems dependency on surface water is evident throughout the state of the environment report. For example, the indicators for riparian condition, native species and ecological communities provide some measure of the state of surface water dependent ecosystems. Additionally, the biannual assessment of macroinvertebrate community composition undertaken by community and research groups provides some indication of aquatic ecosystem function.

Macroinvertebrate assessment during the reporting period found some reference sites were degraded following the 2003 bushfire. The low flow conditions due to the drought have also affected these sites. The macroinvertebrate communities in urban water bodies remain under considerable stress from habitat degradation, altered flow regimes, pollutants and pest species.

Data sources and references

In this indicator, the surface water quality of the Territory's major catchments is measured using available water quality indicators. The indicators used are not the full suite of water quality parameters that could be measured, but they do provide some indication of catchment stress. This information is placed in the context of land use information, water quality trends and responses to significant uncontrollable external influences such as flood, drought and bushfire.

The ACT Department of Territory and Municipal Services (TAMS) manages a water monitoring and assessment program for the ACT that includes water quality, stream flow and biological monitoring. The program is part of maintaining up-to-date information on the water resources of the ACT, a statutory requirement under the Water Resource Act 1998. This information is also used to help determine whether management strategies being used to achieve or maintain the aquatic values set for ACT waters are appropriate.

Community data is derived from the ACT Waterwatch program, which is managed by Environment and Recreation (TAMS) with funding from the Australian Government. The aim of the program is to encourage and support the community to take responsibility for improving the quality of water in the catchment. The program also has an environmental education and awareness focus, aiming to encourage and support the community to play a role in improving the quality of water in the Upper Murrumbidgee catchment.

The references to limited data in this chapter reflect the few water samples taken at any one site. While this varies across the Territory, for example, sites in the water supply catchments are well monitored with systems in place to measure water quality at minute intervals, other catchments in the ACT receive as few as 10 measurements per year. In a dynamic system such as the Territory's waterways, 10 measurements per year fail to reveal the detail of a single event. In other cases, a shift in trends might not be revealed for many years.

To fully understand the Territory's water resources, adequate monitoring systems are required to measure the detail. This will allow the community to better understand the resource and to identify and respond to issues within a reasonable time.

ACT Government 2004, ACT Water Report 2003–2004 Canberra, available at <http://www.tams.act.gov.au/live/environment/water/act_water_reports/2004-2004#act_water_report_2003-2004>

ACT Government 2005, ACT Water Report 2004-2005 Canberra, available at   <http://www.tams.act.gov.au/live/environment/water/act_water_reports/2004-2005>

ACT Government 2006, ACT Water Report 2005-2006, Canberra, available at   <http://www.tams.act.gov.au/live/environment/water/act_water_reports/2005-2006>

ACT Government 2007, ACT Water Report 2006-2007, Canberra, available at   <http://www.tams.act.gov.au/live/environment/water/act_water_reports/2006-2007>

Ecowise 2006, GIS Analysis of the Cotter Dam Reservoir Bathymetry, Report to ACTEW Corporation.

White I, Wade A, Worthy M, Mueller N, Daniell TM and Wasson R 2006, The vulnerability of water supply catchments to bushfires: impacts of the January 2003 wildfires on the Australian Capital Territory online, Australian Journal of Water Resources, vol. 10, no. 2:179-194, available at <http://search.informit.com.au/documentSummary;dn=203285123640127;res=IELENG>

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