ISSUE 1, 2020 WATER LINES Waterways and Ecology Diana Seneque It goes without saying that it has been a challenging start to the year for all of us. The COVID-19 response has impacted everyone here at Water Technology, and many of us were directly affected by the earlier fires. In amongst the ongoing impact of COVID-19 and responses to contain it, it is easy to forget the devastating impact of the earlier fires on massive areas and the communities that are (and will continue) to recover. We are acutely aware of the challenges our colleagues, families, friends, clients and communities as well as the environment – natural and built – are facing and fortunately continue to be well placed to deliver for our clients; while supporting staff working remotely. As the immediate fire emergency of last year has passed, in our professional capacities, we are now witnessing the unfolding impacts on our landscapes and in particular our waterways and our drinking water supplies. These impacts will play out over different time scales ranging from the immediate impacts as we are currently witnessing, to much longer-term effects on catchment yields. STEVE CLARK Managing Director Welcome to our latest issue of Waterlines This edition of Waterlines presents a small portion of the work Water Technology staff are currently undertaking within waterways across the country. • Rehabilitating urban waterways • Removing fish migration barriers • Coastal management planning in NSW • A Climate Change Champion recognised @Binikins 2 : WATER LINES : ISSUE 1, 2020Waterways, fire and management challenges The recent bushfire crisis along much of the east coast of Australia and the storms which followed them highlight the difficulties of waterway management. The environmental impacts associated with widespread, intense burning on waterway health have been observed before, although perhaps not to this extreme. Not least on the list of impacts is an increase in sediment loads to waterways which results from intense burning and the removal of ground cover followed by sheet erosion from intense rainfall runoff. Following the 2009 Black Saturday fires in Victoria, vast quantities of sediment were delivered to waterways, and we are now seeing the same in catchments such as the Herbert River. This can have multiple impacts, not only on the waterway itself but also in the receiving waters. These effects can include decreases in dissolved oxygen and influxes of nutrients associated with soil and ash (potentially leading to the growth of cyanobacteria). From a physical perspective, the intense burning of catchments also has dramatic effects on waterway health. The loss of ground cover and forest canopy makes the landscape far more vulnerable to the effect of rainfall runoff, leading to dramatically increased hillslope erosion. This then leads to the stripping of valuable soil and increased sediment delivery to waterways. Such large and localised increases in sediment delivery to waterways can lead to significant short-term increases in turbidity and reduced water quality. There are also physical implications such as the development of “sand slugs” (large deposits of sand and gravel) which are far less easily transported (generally episodically during floods) and which can take decades to move downstream. These “sand slugs” have various detrimental effects on waterway health, aquatic habitat and stream stability. Importantly, there are few ways of mitigating or managing “sand slugs” once they have entered a waterway. Control measures can be undertaken at the source, however there is generally a very long lag time before this has any effect, as the slug is only transported downstream during floods. Whereas the impacts of bushfires described above are intense, it should be noted that these impacts can also result from land clearing. The removal of vegetation on hillslopes and floodplains leads to an increased rate of sediment transport to the waterway. With the conversation in the media turning to catchwords such as “resilience”, a word that has been used in the industry for some time, it is important to take stock and consider what a resilient landscape looks like. A resilient landscape is not a cleared landscape. With increased extreme weather due to climate change and the necessity for the protection of people and infrastructure, it is unlikely that a resilient landscape can consist of unmaintained dense vegetation either. The conversation is turning to management and hazard reduction, but to maintain a resilient landscape that can’t be achieved by land clearing. To effectively increase landscape resilience to drought, flood and fires - a delicate balance needs to be struck. That balance is likely to be widescale reforestation and management of these areas through traditional aboriginal burning practices, capable of reducing fuel load whilst maintaining soil and ecological health. Such reforestation would have the added benefit of assisting in the mitigation of climate change. For more information +61 7 3105 1460 Michael Cheetham ( michael.cheetham@watertech.com.au ) +61 3 5721 2650 Julian Martin ( julian.martin@watertech.com.au ) WATER LINES : ISSUE 1, 2020 : 3returning big outcomes In the past 200 years, there have been big changes to Australia’s water catchments. Land development and capturing water have provided economic opportunities but have also had an impact on our rivers and streams. In the Eastern Mount Lofty Ranges, near Adelaide, South Australia, there are over 8,000 dams that provide on-farm water. With so many dams in place, surrounding streams aren’t receiving the water they need, when it is needed. As a result, catchment health and water quality are declining. Returning small flows in a more natural flow pattern allows catchment ecosystems to receive water at critical times. These low flows help maintain water quality by flushing salt and pollutants that accumulate during dry periods and supports more sustainable stream ecosystems. The Flows for the Future Program by the Australian and South Australian governments provides funding for landholders in the Eastern Mount Lofty Ranges to improve catchment health by passing low flows of water from their dams and watercourse diversions into downstream waterways. Gravity low flow devices installed at selected dams and diversions are an efficient way to deliver small flows back into downstream waterways to return the duration of flows through streams to more natural levels. These devices promote improvements in ecosystem health, while maximising the water available for sustainable use. Site assessments, design advice and testing of low flow devices were undertaken by Water Technology, and a design for a Gravity Low Flow Device completed; now the most common device used within the Program. Small flows 4 : WATER LINES : ISSUE 1, 2020The Gravity Low Flow Device consists of an in-stream offtake weir near the dam inlet. Low flows in the stream are diverted and piped to the natural watercourse downstream of the dam. Water Technology worked closely with Department for Environment and Water (DEW) staff to improve constructability of the device and to verify that the performance of installed devices meets requirements. Through many site inspections, Water Technology has developed innovative approaches to adapt the device to suit local conditions at difficult sites, where more expensive options would have been required. The design can be constructed by landholders using commonly available parts, and uses natural flows for self- cleaning, and native vegetation and mesh screening to prevent blockage. This ensures the device continues to pass adequate flows downstream with minimal maintenance. Returning low flows assists in achieving and maintaining healthy waterways, which helps provide sustainable water resources for generations to come. For further information about the program visit www.naturalresources. sa.gov.au/samurraydarlingbasin/ water/flows-for-future For more information +61 8 8378 8000 Michael Di Matteo (michael.dimatteo@watertech.com.au) Melinda Lutton (melinda.lutton@watertech.com.au) What are low flows? Low flows are naturally occurring, small events which originate from rainfall or groundwater discharge. The low flows (coloured blue in the graph above) are a small proportion of total flows but are part of the flow pattern most impacted by farm dams and diversions. Under current conditions, these flows are delayed until dams fill and overflow later in the season. Why are low flows important to catchments? Low flows play a key role in determining the health of aquatic habitats. Although small in volume, low flows provide a continuous or intermittent flow over the bottom of channels, providing connectivity between aquatic refuges, and refreshing in-channel pools during drier seasons. Low flows help maintain water quality by flushing nutrients and pollutants that would otherwise accumulate. They provide and maintain aquatic refuges during dry periods and support the life cycle of water-dependent plants and animals. Low flows help to maintain vegetation alongside river banks, which then protects them from erosion under high flow conditions. Changes to flow patterns impact the whole river system, including terminal wetlands and estuaries. WATER LINES : ISSUE 1, 2020 : 5Mt. Cole Creek, like many waterways in the upper Wimmera Catchment, has experienced a decline in condition and is experiencing flow stress as a result of reduced rainfall combined with land-use change and historic land management practices. Several strategies have been adopted in the Wimmera region to try and understand, maintain and improve waterway health in the upper catchment. Under current operations, it has been identified that there is potential to protect the aquatic habitat of the creek through the supply of additional fresh water inflows. MT. COLE CREEK For more information +61 3 8526 0800 Ben Hughes ( ben.hughes@watertech.com.au ) +61 3 5721 2650 Julian Martin ( julian.martin@watertech.com.au ) The Wimmera CMA is exploring the opportunity to supply Mt. Cole Creek with small volumes of water from the nearby Mt. Cole Reservoir. Mt. Cole Reservoir is situated on Spring Creek, a tributary of Mt. Cole Creek. It is a relatively reliable storage during years of low rainfall - which should enable the supply of water to Mt. Cole Creek during drought years. Water Technology’s investigations involved the community, two rapid electrofishing surveys (working with Ecology Australia) and hydraulic modelling to determine the volume of water required to achieve a range of outcomes along the waterway. Electrofishing revealed an abundance of Southern Pygmy Perch, Flat- headed Gudgeon and Obscure Galaxias with no invasive species, which was an outstanding finding. Several critically endangered Western Swamp Crayfish were also identified, Flow Investigation demonstrating the ecologic value of Mt Cole Creek to the upper Wimmera River system. The community has been actively looking for the best sections of Mt Cole Creek to support protection and enhancement activities. This project provides the potential basis for environmental flows along Mt. Cole Creek to be reviewed, and a future plan developed. 6 : WATER LINES : ISSUE 1, 2020For more information +61 3 8526 0800 Ben Hughes (ben.hughes@watertech.com.au) +61 3 5721 2650 Julian Martin (julian.martin@watertech.com.au) The Glenelg River flows west from the Grampians National Park to the Rocklands Reservoir, where water is stored and used for supply purposes. Rocklands Reservoir is managed to provide environmental flow to the Glenelg River to help offset the impacts of regulation. Historically, there have been numerous fish barriers along the Glenelg River caused by agricultural crossings, instream weirs and streamflow gauges. The majority of barriers have been eliminated through the direct removal of the structure or various remediation works to allow fish passage. One significant fish migration barrier remains, a private crossing between the Glenelg River Estuary and Rocklands Reservoir. Key fish species which require long-distance fish passage along the Glenelg River include Estuary Perch, Tupong, Shortfinned Eels and Catadromous Galaxiids. Water Technology was engaged to design a fishway that would remove the fish migration barrier. A complex hydraulic modelling, options analysis, concept and detailed design process was undertaken to optimise the fishway design to ensure its stability during high flows and to optimise the range of flow rates the fishway is capable of operating under. The rock ridge fishway, constructed in January 2020 by Downryte Excavations, enables these species to travel along the Glenelg River through a full range of flows, including during environmental flow releases. Designing the Warrock Fishway Removing fish migration barriers Before After WATER LINES : ISSUE 1, 2020 : 7The Adelaide Park Lands were designed by Colonel William Light as part of his overall vision for Adelaide, with the design reflecting strong linkages to the colonial settlement of Adelaide. The Park Lands are located in Tarntanya land and hold significant cultural importance to the Kaurna people. Rehabilitating an urban parkland waterway Park Lands Creek is a highly modified urban watercourse. It is part of the broader Brownhill Creek/Keswick Creek system which has been subject to extensive investigations due to the potential for widespread damaging flooding across parts of metropolitan Adelaide. Park Lands Creek was a high energy incised channel with minimal vegetation and posed a substantial safety risk to pedestrians due to the high, near-vertical, banks, some exceeding 2 m in height. Park Lands Creek also weaves through a series of significant trees with numerous Red Gums which may pre-date European settlement. Water Technology was tasked with creating a rehabilitation design which achieved waterway and public safety goals and at the same time recognised the colonial settlement of Adelaide and the indigenous significance of the Park Lands. The initial stages of the project involved determining the main drivers of watercourse degradation and completion of a comprehensive site characterisation assessment. The Adelaide Park Lands also have a long history of mixed- use with some key heritage features (including numerous significant trees) identified. It was also recognised that there are numerous informal dumpsites spread through the Park Lands. 8 : WATER LINES : ISSUE 1, 2020For more information +61 8 8378 8000 Ben Taylor ( ben.taylor@watertech.com.au ) Development of the detailed masterplan was guided by the City of Adelaide’s project objectives and landscape principles relating to performance, public safety, environment and serviceability. The design philosophy for developing the rehabilitation options included (but was not limited to): • Seeking opportunities to manage flow better and stabilise banks; • Avoid disturbance to significant trees; • Avoid areas of contaminated soil and disturbance to heritage features; • Seeking opportunities which maximise/maintain water for existing vegetation; and • Explore opportunities to reuse excavated soil. Water Technology developed a design approach which: • Protected key heritage features. • Maintained all existing significant trees through the construction of ‘leaky’ culverts. • Minimised earthworks. • Provided of a series of ‘leaky’ weirs with stepping stones and pools which created diversity in the riparian zone and enhanced public connection to the watercourse. • Included revegetation with a specific focus on species endemic to the Adelaide Plains and with cultural values to the Kaurna people. Water Technology and the project team worked in a collaborative partnership with the City of Adelaide right through the process from site investigation to construction supervision in order to provide a highly effective outcome that has delivered a valuable green/blue asset for the City of Adelaide for the enjoyment of generations to come. WATER LINES : ISSUE 1, 2020 : 9Next >