Sustainability reviews

Pieman Sustainability Review (2018)

We worked with key stakeholders and the broader west coast community over a four year period to identify and resolve key concerns within the Anthony-Pieman hydro catchment area.

You can read more in our outcomes and commitments report (PDF 1 MB)

Mersey-Forth sustainability review (2011)

Derwent sustainability review (2001)

Technical studies

+Shannon Lagoon habitat improvement assessment

Technical study brief

Following on from previous studies reviewing options for improving water quality in Shannon Lagoon, this study aimed to assess threatened native species and their habitat to give some indication of local distribution and habitat preference, and how any proposed changes to the present management system might affect these species.

Outcome

A desktop study on the impacts of turbidity on biota, and an investigation into options to reduce turbidity was completed. A number of management options were investigated including water level and pumping management, automated gates, etc. It was concluded that there are no practical solutions to improve the clarity of water in Shannon Lagoon.

In a memorandum of understanding (MoU) on water level management, established between Hydro Tasmania and Inland Fisheries Service in 2008, we agreed to endeavour to maintain a water level at Shannon Lagoon of 1017.50 metres above sea level (mASL) through to 1017.60 mASL during the fishing season (1 August to 30 May); and between 1017.30 mASL to 1017.55 mASL during the off-season (1 June to 31 July).

+Recreational management and planning assessment

Technical study brief

The level of recreational use of Hydro Tasmania's waterways in the Derwent Catchment has resulted in a number of land management and access issues.

Anglers concerned about the environmental conditions at some storages (in particular Penstock Lagoon) have also questioned boating use and have suggested potential alternatives for managing access.

This study reviewed the level of concern across the catchment with the aim of identifying or developing options for managing these issues at key waterways. Where applicable, this work was undertaken in parallel and close consultation with the Inland Fisheries Service.

Outcome

Issues and options associated with recreational management at Penstock Lagoon were assessed and various management options proposed.

A recreational management steering committee was established to ensure integrated recreational management and assessment of the lake systems.

+Derwent above Meadowbank riparian, flood study and frog survey

Technical study brief

This study involved surveys of the upper basin of the lake and the Derwent River upstream of Meadowbank riparian to determine the scale and extent of willow infestation and riverbank erosion; undertake a geomorphic assessment of the river and an identification of the hydraulic processes that are causing erosion in particular areas; and an assessment of the impact willows may have had on water levels during flood flows in the Derwent and lower Ouse rivers.

This was conducted in close consultation and cooperation with all riparian landholders and other stakeholders as appropriate, with the aim to develop a management regime for this area that is holistic and strategic.

In conjunction with this, surveys for the endangered Green and Gold Frog were undertaken to determine the presence or absence of the frog in the area, its distribution and habitat preferences within the lake, and the implications lake level management and willow infestation may have had on frog populations in the lake. The findings of this study may have had a bearing on any possible management measures that were identified to control willow infestation around the northern shores of the lake.

Outcome

An analysis of technical aspects of hydromorphic condition and river behaviour and an assessment of the nature and extent of our operational impact (in terms of hydrology and geomorphology) on river health in the research was undertaken.

The Lake Meadowbank management action plan was developed in collaboration with Greening Australia, Derwent NRM and landowners to address re-vegetation, willow removal and erosion.

A survey of the Green and Gold Frog population was undertaken. No Green and Gold Frog were found.

+Derwent below Meadowbank instream processes study

Technical study brief

Studies of the Derwent River and estuary below Meadowbank Dam have identified gaps in knowledge of the environment in this area, particularly to geomorphic processes and instream habitat.

This study reviewed knowledge of the environmental conditions of this section of the river with the aim of designing and implementing a program to gather data that would address some of these knowledge gaps. The study included a review of water use and other stakeholder issues, so that public discussions were balanced with respect to environmental and water use issues.

Outcome

We joined the Derwent Estuary Program to collaborate on studies and actions to improve environmental conditions in the lower Derwent River.

+Ouse River environmental and water use assessment

Technical study brief

Flow in this river is highly modified by hydro-electric generation activities and water extraction for agriculture is a major reason for water releases to this river from Shannon Lagoon and Lagoon of Islands.

Environmental health appeared to be considerably compromised and water quality deterioration recurrent. The focus of this study was to establish community accepted environmental and waterway values and determine specific objectives that would guide the development of environmental management options for the river.

This study involved substantial liaison and communication with the local community, along with investigative studies to shed light on issues related to the riverine environment and water use in the catchment.

Outcome

A desktop assessment was undertaken to describe the catchment and set the foundation for the Ouse River technical study.

A study was done to recommend water management solutions for the Ouse-Shannon-Lagoon of Islands and Ripple Canal water management systems and develop a cost-benefit analysis for each of these options.

An Ouse River environmental health study, to define the hydrological and environmental condition of the Ouse River with particular emphasis on the impact from our infrastructure on the ecological assets along the Ouse River, was completed.

The Ouse Shannon Clyde Project was initiated to address environmental flows, water use and water allocation along the Ouse River.

Investigation into the establishment of an environmental flow for the Ouse and Shannon rivers is underway.

+Pest fish management study

Technical study brief

A number of pest fish (Redfin Perch, Tench and Carp) are known to occur throughout the Derwent Catchment, and the potential for inadvertent translocation of these fish has been recognised as an issue.

The threat from pest fish invasion (in particular Redfin Perch) is of particular concern at Little Pine, Shannon Lagoon and Penstock Lagoon (where there are threatened native fish) as well as in the Shannon River.

This study focused on the development and implementation of a strategic action plan for managing pest fish dispersal within the hydro-electric generation system. The study reviewed data and information from past work, field surveys were undertaken to produce a map that identifies 'hot spots' for potential translocation and barriers to translocations, and identified specific migration options for implementation.

Outcome

Pest fish migration barriers were identified.

A pest fish management strategy forms part of our river program.

+Water level communication process review

Technical study brief

During the community consultation stage of the Derwent water management review (WRM), a number of respondents raised concerns about the lack of communication from Hydro Tasmania regarding changes in water levels in the vicinity of Lake Meadowbank and the problems this created for irrigation extraction or flooding.

This study reviewed these concerns and focused on establishing a new protocol for stakeholder communication.

Outcome

Water and river level plot information is now available via our lake levels page.

+Fish migration and mitigation study

Technical study brief

This study reviewed the existing impediments to fish passage in the Catchment, the types of fish involved and their life-cycle needs.

This led to a consideration of specific actions that might be undertaken in close cooperation with the Inland Fisheries Service, who is the main stakeholder.

Outcome

Inland Fisheries Service operates a fish trap downstream of Meadowbank Dam. An elver restock agreement, between Hydro Tasmania and Inland Fisheries Service, was established to facilitate the transfer of lampreys and elvers.

+Lake management for multiple use assessment

Technical study brief

Although a number of historical lake level agreements are in place for various water bodies in the Catchment, the effectiveness of these in achieving their objectives needed to be reviewed.

We are formalising some of these agreements through memorandums of understanding (MoUs) with the Inland Fisheries Service, however as a number of survey respondents have concern about current water level management and access issues at a variety of water bodies, the pattern of operations at key storages, and the system whereby we notify stakeholders of unusual drawdown events.

The study examined the use of signage at specific locations and various communication strategies that might assist with increasing public understanding of level management by us.

Outcome

Hydro Tasmania and the Inland Fisheries Service water level arrangements in the form of a MoU have been developed and implemented for seven lakes.

+Lake St Clair environmental review

Technical study brief
This study reviewed the existing management of water level in Lake St Clair and St Clair Lagoon. At present, we manage water in the lake to minimise shoreline erosion within the World Heritage Area and potential erosion in the Derwent River downstream, the former being done in consideration of the views of the National Parks and Wildlife Advisory Council.

The study involved liaison with Parks and Wildlife Service (PWS), surveys of the lake shore to assess erosion, a review of water management and infrastructure operations, and discussion with angling interest groups on perceived requirements for fishing in St Clair Lagoon.

Outcome
Assessment was completed to determine whether implementation of the lake level agreement at Lake St Clair and St Clair Lagoon had the required result of moderating lake-shore erosion. It was determined that the existing lake level management regime was effective.

Discussions were held with the Inland Fisheries Service regarding maintaining water level in St Clair Lagoon to promote additional fishing activities. It was established that it is not feasible to maintain the water level in St Clair Lagoon.

Rehabilitation works were undertaken at Narcissus in collaboration with PWS.

+Lagoon of Islands study

Technical study brief
We have had long involvement at the Lagoon of Islands following construction of the Ripple Canal in 1984, which appeared to have resulted in continual ecosystem imbalance and poor water quality.

Investigation of these issues through a PhD study aimed at identifying viable long-term management solutions for the lagoon.

It was planned to complete this study by 2006, at which time the cost-effectiveness of potential options would be assessed within Stage 4 of the Derwent water management review.

Outcome
The PhD study investigating the nutrient cycling in the Lagoon of Islands was completed. Information gathered from the research informed the Lagoon of Islands nutrient management strategy.

Investigations into rehabilitation options for Ripple Canal and Lagoon of Islands were completed and a rehabilitation strategy has been developed and is being implemented.

We made the decision to return the Lagoon of Islands to its wetland state. Removal of the dam was completed in 2013.

Ripple Creek Canal was decommissioned in May 2010, allowing four tributaries to revert back to their natural course. Find out more >

 

South Esk / Great Lake (1999)

Technical reports

+Brumbys and Westons Weirs pump maintenance

Issue
The main issue of concern was the flooding along Westons Rivulet when pumps in Western Weir have insufficient capacity or fail to pump all the water diverted from Upper Brumbys Creek and Westerns Rivulet into yingina / Great Lake.

Our commitment

We commit to ensure reliability of the pumps at Westerns Weir through a scheduled program of maintenance, and will review procedures accordingly.

Outcome
We have installed remote monitoring of the pumps which enable operational issues to be identified sooner. The pumps are part of our scheduled maintenance program.

+Spills at Trevallyn Dam

Issue
The main issue of concern was access by irrigators in the South Esk and Macquarie Catchments to floodwaters for the purpose of filling on-farm storages, rather than see this water spill over Trevallyn Dam.

We undertook extensive hydrological analyses and identified the flow conditions that can be used as triggers to allow the Department of Primary Industries, Parks, Water and Environment (DPIPWE) to grant temporary licences to extract water during periods of high flow.

Our commitment
We commit to make timely and appropriate hydrological data available to DPIPWE in order to enable them to issue temporary water licences when the Trevallyn Dam is spilling.

Outcome
We provide data to DPIPWE which is updated at least twice a day.


+Arthurs Lake

Issue
The key issues focused on in the investigations were threatened native fish populations and fishing amenity, as this is by far the most popular recreational trout fishery in the State. Native fish studies undertaken during this study found that fish populations in Arthurs Lake are currently healthy and are not threatened by the present lake level management regime.

Our commitment
We will endeavour to maintain Arthurs Lake levels above a minimum of 949 metres above sea level (mASL) particularly during the fishing season, subject to yingina / Great Lake being above 1029.8 mASL. At all other times the system will be operated to avoid, where possible, the lake going below this level.

Outcome
Since 2001 lake levels in yingina / Great Lake have been below 1029.8 mASL. It was acknowledged that the lake level in yingina / Great Lake rarely will exceed 1029.8 mASL which makes the commitment inefficient in protecting fish populations and fishing amenity. To better accommodate the multiple demands on water from Arthurs Lake, including electricity generation, fishing, irrigation, and ecosystem health, new operating rules and an updated memorandum of understanding (MoU) between Hydro Tasmania and Inland Fisheries Service have superseded this commitment.

The new commitment is that we will make reasonable endeavours to operate Arthurs Lake so that the lake level is at, or above, 950.00 mASL on 1 November each year and at, or above, 949.00 mASL on 1 June each year, subject to the water level in yingina / Great Lake being above 1023.00 mASL and the Midlands Irrigation Scheme being in operation.

If yingina / Great Lake is below 1023.00 mASL, or if the Midlands Irrigation Scheme is not operating, then we will make reasonable endeavours to operate Arthurs Lake so that the water level is at, or above, 949.00 mASL on 1 November each year and at, or above, 948.00 mASL on 1 June each year.

This will ensure that Arthurs Lake is at, or above, 949.00 mASL during general Brown Trout angling season (1 August to 30 April in the following year).

Environmental and social risk bands have been developed for this lake.


+Woods Lake

Issue
The key issues focused on wind-generated sediment re-suspension causing poor water quality, native galaxiid fish species, recreational angling and downstream irrigators.

Aim to avoid the lake level being drawn down to depths where turbidity levels have been shown to increase.

Our commitment
We commit to maintain the minimum operating level for Woods Lake at 735.4 metres above sea level (mASL).

We will also support further research into native fish species through the provision of data and field assistance.

We, as part of this commitment, will review its alarm systems for the lake to ensure that the system operators are aware when lake levels are approaching this minimum and adjust system operation accordingly.

Outcome
We have maintained our commitment to a minimum operating level of 735.4 mASL, although incursions below this occurred in 2007 during the prolonged dry period when water was required to meet irrigation requirements along the Lake River.

In a memorandum of understanding (MoU), on water level management, established between Hydro Tasmania and Inland Fisheries Services, we agreed to make reasonable endeavours to maintain a water level in Woods Lake at, or above, 736.20 mASL.

In addition, we have reviewed the alarm system for the lake, to ensure that system operations are aware when lake levels are approaching this minimum and adjust system operations accordingly. Environmental and social risk bands have been developed for this lake.

We have funded research, completed in 2004, on the distribution, reproductive and dietary habits of the Saddled Galaxias (galaxias tanycphalus) in Woods Lake.


+Downstream Poatina Power Station re-regulation pond

Issue
Key issues of concern were the impacts of normal power station operations on water levels at Brumbys Creek and the lower Macquarie River - specifically the impacts on riparian land use and water extraction, erosion of riverbanks, and poor water quality and power station flood rules.

The majority of these issues were investigated in depth as part of studies for the Basslink Integration Impact Assessment Statement. Basslink was shown to be likely to exacerbate many of the concerns downstream of Poatina, and a re-regulation storage was identified as the best option to mitigate these issues.

Our commitment
We are committed to construction of a re-regulation storage downstream of Poatina Power Station.

Outcome
We completed the development of a re-regulation storage downstream of Poatina Power Station in 2006. A ramp rule is also in place which means flows do not fluctuate as frequently and at a much reduced magnitude.


+yingina / Great Lake

Issue
The key issue raised was movement of algal beds in response to water level fluctuations. These beds are habitat to a number of endemic fauna species listed under the Tasmanian Threatened Species Protection Act 1995, and the concern was that the beds are unable to migrate up and down at a sufficient rate to ensure habitat protection.

Investigations showed not only lake levels variations, but other factors such as water clarity (affected by turbidity due to long-shore erosion and wind-induced sediment suspension) had an influence on algal bed movement, and these factors were not well enough understood at this state to define management responses. Faunal relationships also needed further understanding.

Our commitment
We committed support a further five years of research into the yingina / Great Lake algal beds and associated faunal relationships.

Outcome
We conducted five years of research into the yingina / Great Lake algal beds. The research showed that there is a high degree of variability in the charophyte beds themselves and the interactions with the threatened species. The charophyte flora of yingina / Great Lake has been found to be a diverse and inherently resilient to changes based on a high species richness and widespread seed bank of oospores in sediment.


+Lake Augusta

Issue
The key issue for the investigations was dune erosion in relation to lake level fluctuations. The study was unfortunately inconclusive due to an absence of long-term data.

Our commitment
We will install instrumentation at Lake Augusta to monitor groundwater movement in relation to lake levels for a three year period, and commits to supporting further investigation of the dune system.

Outcome
Monitoring equipment was installed for groundwater movement in relation to lake levels and a Masters study was completed on the erosion of the dune system.


+Environmental flow at Cataract Gorge

Issue
Key issues in Cataract Gorge were whether the existing environmental flow was sufficient to meet ecological requirements of aquatic fauna, water quality deterioration during the summer months, and implications of summer minimum flows for public use, amenity and aesthetics.

Our commitment
We commit to a year-round environmental flow of 1.5 m3/sec and seasonal monitoring of effectiveness at three sites in the river for five years.

Outcome
The flow was increased from 0.43 m3/sec to 1.5m3/sec. Monitoring and a number of scientific studies have been conducted in the Gorge. The flow was reviewed five years after implementation.

The outcome of this review was to increase the flow to 2.5 m3/sec. You can read more details here >


+Eel passage at Trevallyn Power Scheme

Issue

The main issue of concern is that Trevallyn Dam blocks upstream migration of juvenile eels (elvers) from the sea, and adult eels enter the power station on their downstream migration toward the sea to breed.

The investigation looked at a wide range of options, but were unable in the time frame of these investigations to finalise a preferred option to facilitate eel migration.

Our commitment

We committed to further research into eel movements, fate and options at the Trevallyn Power Scheme, to the feasibility of eel deterrent at the Trevallyn Power Station intake, and to continue work towards facilitating eel migration at Trevallyn Dam.

Outcome

We installed an elver ladder in the dam wall - find out more.

The effectiveness of the ladder is being monitored each year during the elver migration season.

Deterrent options are currently being investigated to prevent mature eels going into the power station.


 

© Hydro-Electric Corporation 2019