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Yarra Watch 2017–18 Summer Highlights Report

Yarra River in Melbourne Yarra River in Melbourne. Source: Melbourne Water

 

The Yarra River is widely used for recreational activities such as boating and swimming throughout summer.*

Environment Protection Authority Victoria (EPA), in partnership with Melbourne Water, runs the Yarra Watch program, which forecasts and monitors recreational water quality at four sites along the Yarra River – Kew, Warrandyte, Healesville and Launching Place. Water quality is determined by the levels of bacteria in the water, which can pose an increased risk of disease for people coming into contact with the water.

The summer season ran from 1 December 2017 until 12 March 2018.

* Please note that it is illegal to swim in the Yarra downstream of Gipps Street, Abbotsford. Kew at Chandler Highway Bridge is the only Yarra Watch site in the Lower Yarra where it is legal to swim.

Fast Facts for 2017-18

  • Of the total water forecasts issued over the summer, 42 per cent were Good, 31 per cent Fair and 27 per cent Poor (in 2016-17 summer, 52 per cent were Good, 30 per cent Fair and 18 per cent Poor).
  • During the summer, there were six water quality alerts issued for the Yarra River and its catchment.
  • The most water quality alerts were issued for the Yarra River, especially in the lower reaches.  Some tributaries to the Yarra River, such as Scotchmans and Darebin Creeks were also issued with alerts.
  • Forecasts were provided to over 6,500 followers on Twitter.

How did swimming spots along the Yarra perform?

Table 1: Results of water quality monitoring at Yarra River swimming spots.

Location

Objective

Launching Place

Healesville

Warrandyte

Kew

 

Half the Yarra River swimming spots met the water quality objective for swimming this summer (Table 1).

Warrandyte comfortably met our water quality objective for swimming and had the best overall water quality of all Yarra swimming spots this season.

The two Yarra sites that did not meet the objective were Launching Place and Kew. This does not mean these sites were unsafe for swimming the whole season, but they did experience a higher number of days with poorer water quality, which can increase the risk of swimmers being exposed to disease-causing bacteria. Bacterial levels were variable over the summer for Launching Place and Kew. Most days of poorer water quality occurred after recent rain and stormwater runoff. Poorer water quality during dry weather was less frequent. Poor water quality may be due to a range of pollution sources such as leaking septic tanks and animal faeces (e.g. agricultural livestock and birds).

All sites meet objectives for secondary contact recreation (i.e., boating, rowing, canoeing).

Yarra water quality has been variable in recent summers 

Table 2: Water quality trends for swimming at Yarra River sites.

Swimming objectives met?

2013–14 2014–15 2015–16 2016–17  2017–18 Water quality trend
Launching Place ✗  No change
Healesville ✓  Variable
Warrandyte ✓  No change
Kew  ✗ Variable

 

Water quality in the Yarra River has varied over the last five years. Stormwater pollution after rain has been the most common factor determining whether a Yarra River site meets the objective for swimming (Table 2). 

Warrandyte has been consistently the best location for swimming in the Yarra River in terms of water quality for recreation.

Healesville and Kew vary between summers, while Launching Place has continually not met overall season objectives. This means bacterial levels in water at these sites have, from time to time, posed an increased risk to swimmers. Bacterial pollution was most often due to stormwater runoff entering the river. We note that our monitoring results may pick up more bacteria if the scheduled sampling happened directly following a rain event. However, bacteria may also be present during dry weather as a result of faecal contamination from a range of animal and human sources in the Yarra’s rural and upper catchment (see ‘Water quality and health for swimmers’ section for more information on faecal sources). EPA Victoria will be working with Melbourne Water to better understand and track pollution sources in the mid to upper Yarra River (e.g. Launching Place and Healesville) where dry-weather pollution is known to occur.

What information do we gather and report about the Yarra River?

The information we report on this website and through Twitter includes the following:

  • Water quality forecasts: 
    • These are reported twice daily during the summer season.
    • Forecasts of Good, Fair or Poor are given for each location to inform decisions about recreational use.
    • They are based on weather forecasts, observations and warnings, water quality history, and weekly water sampling results.
  • Weekly water quality monitoring:
    • Samples are analysed for the presence of E. coli bacteria, which indicates that water may not be safe for recreational use due to an increased risk of exposure to disease-causing bacteria and other pathogens.
    • If it’s not considered safe to swim, the public are notified on the Yarra and Bay website and Twitter.
    • EPA works with local councils and water authorities to investigate the source of water pollution.
    • These samples are used to assess whether the site has met the end-of-season water quality objectives for swimming.
  • Alerts about pollution incidents, fish deaths and algal blooms:
    • Water quality alerts are given all year round.
    • Alerts are based on reports from the community, businesses and government, and EPA or other responding agency.

Pollution can be reported at any time to EPA on 1300 EPA VIC (1300 372 842).

How accurate were Yarra Watch water quality forecasts?

The accuracy of Yarra Watch forecasts was measured by comparing weekly bacterial water quality sampling results at beaches to the corresponding morning forecasts (10am) on the same day.  

This summer:

  • 79 per cent of forecasts provided appropriate advice about whether it was safe to swim. That is, when actual water quality was Good EPA issued either Good or Fair forecasts. When water quality was Poor EPA issued either Poor or Fair forecasts.
  • 69 per cent of forecasts correctly predicted the actual water quality, so the forecast matched water sample quality of Good or Poor.
  • Missed alarms were issued for three out of 56 forecasts issued on Wednesdays over summer, or 5 per cent of total forecasts issued. Of the eight Poor water quality sample results on Wednesdays, we issued Good forecasts for three of them. However, these three missed alarms related to only one or two sites at a time; the remaining 2-3 sites on those days were provided with appropriate advice.
  • Forecasting can provide false alarms. Of the Good water quality samples over the summer, 16 per cent were issued with Poor forecasts.

For more information on how we generate forecasts and the accuracy of our forecasting go to Generating forecasts for Beach Report and Yarra Watch.

Water quality and health for swimmers

Increased risk of illness primarily occurs when water is contaminated with human or animal faeces. Yarra Watch monitors E. coli in the River, which is a bacteria that is an indicator of faecal pollution. Faeces may carry any number of disease-causing organisms (pathogens), with gastroenteris being the most common illness experienced by swimmers.

The level of human faecal sources in stormwater or other pollution can vary according to the duration and intensity of rain, and depends on land use or activities in the Yarra’s large catchment. Human faecal contamination was found during wet and dry weather in a 2005 EPA study at 38 different tributaries and drains entering the Yarra. Overall around 27% of total samples returned high amounts of human faecal contamination. Human faecal contamination in the River still occurs today with dry weather sewer spills and sewage overflows during storms (e.g. late December 2016) entering the Yarra. The extent of human faecal contamination in the Yarra is comparable to studies in other parts of the world. For example, human faecal contamination was present in between 21-44% of samples from a study in Ochlockonee and St Lucie River in Florida, and 25-69% for Dungeness River catchment in the state of Washington (United States).

High bacterial levels in stormwater run-off to the river can be caused by sewerage and septic tank leakages, cross-connections between sewerage and drainage systems, or litter and animal faecal waste (for example, bird and dog droppings) entering drains. Additionally, when there have been heavy rain events, such as in late December 2016, sewage overflows from emergency relief structures can also increase bacterial levels in the River.

In dry weather, potential sources of faecal contamination in the River include:

  • leaking sewer infrastructure (particularly where it is above the stormwater drainage system)
  • cross-connections between sewerage or septic tanks with stormwater drainage systems
  • poorly-operating septic tanks and onsite sewage treatment plants
  • animal faeces from:
    • birds
    • agricultural livestock accessing the River or its tributaries, or runoff of livestock faeces during periods of irrigation
  • Sediment that contains bacteria resuspended during environmental-flow releases.

Increased bacterial levels can be expected as a result of these inputs, however, they are usually short-lived.

What influenced water quality and forecasts this summer?

Yarra River at Warrandyte

Yarra River at Warrandyte. Source: Melbourne Water

During rain events, pollutants wash down stormwater channels and into the Yarra River, which increases the risk of swimming at nearby swimming spots.

When rain occurred this season, Yarra Watch informed the public by issuing a water quality forecast of Poor, advising people to avoid swimming near stormwater outlets after rain.

Extended periods of Poor forecasts were mainly issued during periods of heavy rain; these occurred around early December 2017 and late January 2018.

Swim advisories and other water quality alerts issued over summer

Swim advisories are issued if there are high bacterial levels found during dry weather, when people are more likely to use the River for swimming. This summer, there were no swim advisories issued for the Yarra based on the weekly sampling at the four swimming spots.

There were two high bacterial results from Yarra Watch weekly testing that were posted as alerts online. On 4 January 2018 an alert was issued for Kew following high sampling results, however water quality returned to low levels in the resample the next day. A desktop investigation could not find an obvious pollution source, however 1mm of rain in the day prior to sampling may have increased stormwater flows. On 8 February 2018 an alert was issued for Launching Place following high bacterial results. The alert was removed when bacterial results in resamples returned low levels. A desktop investigation could not find an obvious pollution source, however may have been related to a flushing of water from the Upper Yarra Reservoir and Maroondah Reservoir.

There were six water quality alerts issued for the Yarra River based on reports to EPA from the public and businesses. Four of these were in the lower Yarra where it is illegal to swim:

  • A pollution alert was issued on 1 December 2017 for an oil film on the water near the end of Collins Street. The alert was removed once the film had dispersed.
  • A second pollution alert was issued on 1 December 2017 following forecasts of high rainfall. Discharges from emergency relief structures can occur during large rainfall events, when heavy rain enters sewerage systems and increase flows in sewer pipes beyond the capacity of the sewer. If this occurs, the excess flow (a mix of stormwater and sewage) is discharged directly into the stormwater system. The alert was removed when rain was no longer forecast.
  • A pollution alert was issued on 17 January 2018 due to a hydrocarbon spill. Although the source was stopped, the alert remained active as there was a waxy film visible between Abbotsford and Collingwood. The alert was removed once the film had broken down.
  • A pollution alert was issued on 23 February 2018 for the Yarra near Fairview Park, following a sewage spill. The alert was removed once bacterial levels were acceptable.
  • A pollution alert was issued on 27 February 2018 for the Yarra, as well as Victoria Harbour and Moonee Ponds Creek, following a diesel spill in West Melbourne. The alert was removed when investigation confirmed diesel did not make it into the waterways from the stormwater system.
  • A pollution alert was issued on 5 March 2018 for discoloured water flowing in to the Yarra from a drain in Abbotsford. The alert was removed when the discharge ceased and pollution dispersed.

Alerts were removed after the pollution could not be detected or was no longer visible. Pollution of rivers and creeks can be difficult to investigate as EPA relies on timely public reports of pollution and for the pollution to still be occurring when EPA officers arrive at the scene. Pollution should be reported to the EPA hotline on 1300 EPA VIC (1300 372 842).

Future directions

EPA Victoria will continue to work with Melbourne Water to better understand and track pollution sources that cause water quality to be unsafe for swimming. The focus of this work will be on the mid to upper Yarra River (e.g. Launching Place and Healesville) where dry-weather pollution is known to occur.

For more information on how we generate forecasts and the accuracy of our forecasting go to Generating forecasts for Beach Report and Yarra Watch.

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