As environmental knowledge and awareness grew in the 1990s, it was recognised that toxic blue-green algal blooms, loss of native fish and waterbird populations, rising salinity and other adverse environmental outcomes would become more prevalent in New South Wales unless water was shared in an equitable manner between extractive users and the environment. These problems were particularly apparent in regulated rivers.
Under the Water Management Act 2000, a regulated river is one where downstream flows are regulated by a major storage or dam to supply irrigation water. The NSW Government had introduced environmental flow rules in the regulated Gwydir, Namoi, Macquarie, Lachlan, Murrumbidgee, and Hunter River valleys, as well as the Barwon-Darling River by 1997. Environmental rules were generally designed to provide water for the environment across a range of flow events, from floods to very low flows. These environmental flow rules now form the basis of environmental water provisions within statutory water sharing plans, prepared under the Water Management Act 2000. Ecological benefits of these flow rules include reduced algal blooms, increased wetland biodiversity, more abundant native fish and more natural ecosystem processes.
The Integrated Monitoring of Environmental Flows (IMEF) program was established in 1997 and is managed by the NSW Office of Water. The IMEF is a systematic scientific program assessing the ecological benefits of the environmental flow rules. The program uses around 180 targeted sites on inland and coastal rivers to gather information and data.
The objectives of the IMEF program are:
- to investigate relationships between water regimes, biodiversity and ecosystem processes in the major regulated river systems, and the Barwon-Darling River
- to assess responses in hydrology, habitats, biota and ecological processes associated with specific flow events targeted by environmental flow rules
- to use the resulting knowledge to estimate likely long-term effects of environmental flow rules and provide information to assist in future adjustment of rules.
IMEF provides the scientific information needed to review and inform water sharing plans. The program also contributes to our broader knowledge and understanding of the biodiversity and ecological processes in all New South Wales rivers and wetlands. Managers of water resources gain reliable information that assists them to balance the many competing demands for river water, including environmental, recreational, domestic, agricultural and industrial uses. All members of the NSW community who use rivers and river water will benefit from more natural ecology in catchments and improved water quality in rivers.
- Assessing translucent environmental water release in the Murrumbidgee River below Burrinjuck Dam 1999-2002. Report 1 – Background. Regulated and unregulated rivers of the Murrumbidgee catchment and the effect of translucent releases – an Integrated Monitoring of Environmental Flows background report (PDF 352 KB). This project was designed to monitor the effects of 'translucent' releases linked to tributary inflows between autumn and spring. This first report of a series of five, provides the policy background to the study.
- Assessing translucent environmental water releases in the Murrumbidgee River below Burrinjuck Dam 1999-2002. Report 2 – Water quality. Regulated and unregulated rivers of the Murrumbidgee catchment and the effect of translucent releases – an Integrated Monitoring of Environmental Flows Report (PDF 785 KB): This report typifies the water quality of the regulated rivers impacted by translucency and transparency rules and their unregulated tributaries.
- Assessing translucent environmental water releases in the Murrumbidgee River below Burrinjuck Dam, 1999-2002. Report 3 - Effect of translucent releases on biofilms and periphyton in the Murrumbidgee River (PDF 2.5 MB). This report documents the outcome of monitoring the regulated Murrumbidgee and Tumut rivers impacted by translucency and transparency rules, and their unregulated tributaries, the Goodradigbee and Goobarragandra rivers.
- Ecology of the Murrumbidgee River (PDF 26 KB): This project assesses the ecological benefits of protecting natural low flows, and protecting or restoring a portion of the natural peak flows from Burrinjuck Dam to the Murrumbidgee River.
- Hunter Estuary Freshwater Inflow Assessment: This IMEF assessment project is investigating freshwater inflow influences on Hunter River estuary functioning. The project has developed an estuary inflow model to predict movement and changes in the Hunter estuary salt wedge that may result from implementation of environmental flow rules associated with the combined Hunter valley water sharing plans.
Details of the current modelling work are explained in the modelling report prepared by BMT WBM Pty Ltd Assessment of Salinity Response to River Flow Modification in the Hunter River Estuary (PDF 5.2 MB). Results from 2005- 2007 studies are contained in Integrated Monitoring of Environmental Flows: IMEF Hypothesis 11 Environmental Flow Rules and Hunter Estuary Productivity Study (PDF 1.2 MB).
- Integrated Monitoring of Environmental Flows: Glennies Creek environmental contingency allowance scouring flow study (PDF 2 MB). The construction of Glennies Creek Dam has resulted in substantial changes in the flow pattern of Glennies Creek. The study was designed to assess the impacts of changes in flow regime on stream biofilm and macroinvertebrate communities present at sites in the Glennies Creek catchment.
- Integrated Monitoring of Environmental Flows: Hunter River low flow phytoplankton study (PDF 292 KB). The IMEF phytoplankton studies undertaken in the Hunter River system were designed to provide a broader understanding of the Hunter River's phytoplankton ecology. Results from these studies have been used to advance the understanding of the specific Hunter River phytoplankton growth, temperature and flow relationships.
- Monitoring of Murrumbidgee translucent releases – Hydraulic modelling from Downstream Burrinjuck Dam to Gundagai using HEC-RAS (PDF 2 MB). This IMEF report documents hydrologic and hydraulic modelling performed to relate river flows to wetted perimeter. The results can be used to measure wetted perimeter created by translucent and other flows on rocky riffles downstream of Burrinjuck Dam and river banks to Gundagai.
- Peel Valley Regulated, Unregulated, Alluvium and Fractured Rock Water Sharing Plan 2010-2011 progress report: Assessment of environmental flow rules developed for the Regulated Peel River (PDF 209 KB). This study aims to provide ongoing baseline information for planning of environmental flow allocations that meet the requirements of the Water Sharing Plan for the Peel Valley Regulated, Unregulated, Alluvium and Fractured Rock Water Sources.
- Replenishing the wetlands of the Lachlan River (PDF 26 KB). The benefits of environmental flows for wetland habitat and biodiversity are being investigated in the Lachlan and Namoi Rivers and in the Macquarie Marshes and Gwydir/Gingham wetlands.
- Suppressing algal blooms and fish kills (PDF 26 KB). Stratification of temperature and dissolved oxygen within the weir pools of the lower Darling River is being monitored to investigate the use of environmental flows to avoid conditions that encourage excessive growth of blue-green algae, and kill fish by oxygen starvation.
- Survival of fish hatchlings (PDF 89 KB). This project is investigating the use of environmental flows released from dams to maintain the abundance of fish hatchlings when their survival is threatened by drought and unnatural patterns of water flow in regulated rivers.
- Tenterfield Creek water source report - fish survey (PDF 147 KB). This preliminary study was commissioned in the Tenterfield Creek water source (DIPNR, 2003) to determine the presence or absence of fish species.
- Wetting terrestrial organic matter (PDF 510 KB). This project is examining how environmental flows can improve the ecology of NSW rivers by increasing the supply of dissolved organic carbon to nourish the aquatic food chain in the Phase 1, 1998-2005 Report.