Increased monitoring is key to managing blue-green algae

Managing over 20 storages in seven river basins, Goulburn-Murray Water (GMW) is the largest raw water provider on the continent, and is tasked with keeping track of algae blooms in waterways across a staggering 68,000 square kilometers – most of northern Victoria.

As part of Water Source’s algae management series, we spoke to Goulburn-Murray Water’s Water Quality Coordinator Bianca Atley about the unique challenges and strategies involved in monitoring blue-green algae within Australia’s largest water provision region.

“Goulburn-Murray Water manages around 70% of Victoria’s stored water resources. We do not supply treated water, but we do supply raw water to six drinking water corporations across our region,” Atley said.

“We also supply irrigation water via open channels in Australia’s largest irrigation delivery network. We supply stock and domestic water too, mostly via the delivery network but also through piped and gravity districts.

“As a raw water supplier, GMW must continue to operate its supply system for all water users, even if there are high levels of blue-green algae.”

Atley said that while GMW is not required to guarantee the quality of supply, it is required to inform stakeholders of risks and changes to water quality, which is particularly challenging when covering such a vast area.

Risk-based monitoring

Generally, increasing monitoring frequency and locations helps reduce the risk of unknowingly supplying water with high levels of blue-green algae, Atley said.

“GMW has a regular monitoring program for water quality, not just blue-green algae, at our major water storages. During scheduled sampling events, we also analyse for nutrients and water quality parameters, like electrical conductivity, pH and chlorophyll,” she said.

“The monitoring program helps inform our decision making around changing risks. If we see increasing nutrient levels, we can determine whether we should increase our sampling of a particular storage."

Taking a risk-based approach, Atley said GMW will conduct additional sampling for a variety of reasons.

“Taking a sample is relatively easy for us to do, so if we have any level of concern we will undertake additional sampling. If there is evidence of blue-green algal scums or discoloured water, we will sample,” she said.

“If there is a major recreational event planned in one of our storages, we may take some samples ahead of that event. Or if we had high levels of algae within a certain storage, like our Waranga Basin, we will take samples in the irrigation supply channels that come off that Basin.

Managing risk of blue-green algae

With such a large remit of storages and channels, GMW’s management strategy is different to typical utilities with smaller catchments and focuses on isolating problematic algal blooms to ensure the issues doesn’t become more widespread.

“If a warning for blue-green algae is issued, we don’t have the option of trucking in water from alternate sources due to the large quantities of water we supply. That’s often the go-to for an urban water supplier, but we simply can’t truck a lake to another lake,” Atley said.

“We can’t treat the water, either. Our storages are natural habitats and are popular locations for water-based recreational activities, so we can’t apply chemicals. One of our storages holds six times the amount of water in Sydney Harbour. Can you imagine the amount of chemicals we would need, even if we could?

“Instead, we try to isolate the high levels of blue-green algae in our storage when we can. If possible, we lower the level at which water is released from the dam, so we don’t cause a bigger problem. Algae tends to accumulate at the surface, so taking water from a lower level reduces the chance of us sending algae downstream.”

Atley said GMW’s Waranga Basin is an example of how difficult the task of isolation can be, given the size of the waterbody and its associated channel system.

“Waranga is a large, shallow basin, and water is diverted down irrigation channels from the surface. When we have a warning in that waterbody, we have no ability to stop the algae going down those channels with the water. We have to supply the water.

“The channel distribution system is thousands of kilometres in length and in the ends of the channels the water slows down, which increases the risk of blue-green algae problems. Smaller spur channels are higher risk, especially if there are areas where the water is sitting stagnant in those channels.”

Communication is key to managing algae

In situations where blue-green algae cannot be isolated, the challenge then becomes about communicating the risk to stakeholders, Atley said.

“In a lot of cases, management is about communication. We notify our customers directly, via letter and SMS. But our stakeholders are not isolated to customers, the wider community that uses our storages for recreational use are also our stakeholders,” she said.

“Our catchments are open and recreational use is permitted at most of our storages. Lake Eildon has over 700 houseboats on it. It’s a very popular lake and has high tourism value. It has over 550 km of foreshore, and closing the lake would be extremely hard to police.”

GMW issued a blue-green algae warning for Lake Eildon on 7 July 2020 and that warning is still current, Atley said.

“We have to make sure we have tried our best to warn the public that high levels of blue-green algae are present, and that they have access to information that explains what may happen to them if they use that water anyway,” she said.

“We have this information on our blue-green algae website, and we inform the public via our hotline and media releases. We put up signs on site too, but it is such a large area that not everyone who visits will see the signs. We have found that social media is a great way of raising awareness.

“Our aim is to try and spread the word before people arrive at the lake, so that they are not disappointed when the water is unsuitable for use.”