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DWE Home > Home > Water Management > Water for the environment > Environmental monitoring in unregulated rivers

Water for the environment

Environmental monitoring in unregulated rivers

The term “unregulated river” applies to rivers without major storages, or, at least, to rivers where the storages do not release water downstream (in these cases, water is piped to where it is needed, such as metropolitan centres). The start of the following twenty water sharing plans in unregulated rivers means that these rivers need to be monitored to determine whether the environmental flow rules in the plans are benefiting the environment. Monitoring will be extended to the other river systems as the water sharing plans come on–line.

Unregulated rivers with water sharing plans in NSW

Adelong Creek	Apsley River
Castlereagh River above Binnaway	Commissioners Waters
Coopers Creek	Dorrigo River
Jilliby Jilliby Creek	Kangaroo River
Karuah River	Mandagery Creek
Ourimbah Creek	Phillips Creek, Mooki River , Quirindi Creek, Warrah Creek
Rocky Creek, Cobbadah, Upper Horton, Lower Horton	Tarcutta Creek
Tenterfield Creek	Toorumbee Creek
Upper Billabong	Upper Brunswick River
Wandella Creek	Wybong Creek

Project aims

The purpose of ecological monitoring in the unregulated rivers is to determine whether the environmental objectives of the water sharing plans are being achieved. The objectives of the plans are diverse, but most intend to maintain or improve the ecological condition of the river.

The second aim is to demonstrate how achievement (or non-achievement) of these objectives is related to plan strategies. For example, it is conceivable that other factors – climate change, land use – may affect the condition of a river, and any monitoring program needs to be able to discriminate between the plan and non-plan related impacts.

Design challenges in monitoring unregulated rivers

Frog eggs (Litoria sp.) indicated by the black dots.
Source: Simon Williams, DNR

The environmental water provisions in the unregulated river water sharing plans are different to those in the regulated rivers. Generally, in unregulated rivers the environmental flow rules consist mainly of annual extraction limits and cease to pump levels which prevent pumping when the river falls below a specified daily low flow level.

The protection of low flows is important to the survival of many aquatic species. For example the photo above shows frog eggs in a shallow pool of water.

While the measures to protect low flows are an effective way of protecting instream habitats, they are more limited in their immediate impact than the more obvious environmental flow rules such as release of water from a dam to support a bird breeding in the wetland.

As our understanding of hydrology and water extraction is also limited in unregulated streams, the predictive modelling approach employed by the environmental monitoring programs in the regulated rivers is not applicable. Instead the approach adopted for the unregulated rivers is to compare randomly chosen sites on the river affected by water extraction with physically matched reference sites on rivers unaffected by extraction (known as ‘positive’ reference sites). Monitoring at ‘negative’ reference sites may also occur – these are sites of diminished environmental health. The use of reference sites enables changes due to plan implementation to be distinguished from natural changes and changes due to other human influences. Figure 1 shows how this reference information can aid interpretation of a measured trend in a selected attribute.

Figure 1: An example of interpretation of a measured trend in an ecological attribute by comparison with trend of a positive reference (expected attribute status with little or no extraction) and a negative reference (expected attribute status with major extraction).

In this hypothetical example, the measured trend in the attribute is identical in both the left–hand and right–hand panes. However, in the left–hand pane, both the positive and negative reference values of the attribute are declining, for example, because of a climatic shift to drier conditions. The measured values are trending towards the positive reference, indicating a decrease in the impact of extraction. In the right–hand pane, both the positive and negative reference values of the attribute are increasing, for example, because of a climatic shift to wetter conditions. The measured values are trending towards the negative reference, indicating an increase in the impact of extraction. Without such complementary information from reference sites, it would be easy to misinterpret the impacts of environmental flows.

Selection of attributes for monitoring

Measuring trends in attributes with respect to reference conditions is the main way in which the benefits of the environmental rules will be monitored. But a great many attributes could potentially be measured, so it is vital that the right ones are selected. To refine the selection process, conceptual models have been developed that link water extraction to ecosystem response in various environments, and under various flow scenarios. One such conceptual model is shown below, illustrating how an attribute such as tadpoles can be logically selected by following the linkages through the ecosystem.

Figure 2: Conceptual model: Ecosystem responses to upstream water extraction in rivers under medium–flow and high-flow conditions (freshes and floods). Responses will vary with natural discharge patterns and the timing, frequency and magnitude of extraction.

In addition to the conceptual models, the process of selecting attributes is to be filtered by the following criteria:

1. Relevance. Attributes must be relevant to the various types of environment, flow classes and ecosystem properties included in the objectives of the plans.
2. Sensitivity. Attributes must potentially be responsive to plan strategies. Specifically, they must be sensitive to the extraction of water and hence to controls on extraction.
3. Practicality. Attributes must be measurable in a repeatable and representative manner with the resources that are likely to be available.
4. Interpretability. It must be feasible to distinguish the response of the attributes to water extraction, and ideally to plan strategies, from their responses to other factors.

Infra–red aerial photograph of the Bega River showing “wetted area”.
Source Simon Williams.

For example, the “wetted area” of a river is highly responsive to water extraction, and when such data is collected using remote sensing techniques is sensitive and easily interpretable. The photo at top taken with infra–red photography is an aerial view of the Bega River showing standing water (blue), wet streambed (brown) and dry sand (white).

But high costs of remote sensing may make such methods impractical for a long–term environmental monitoring program. Conversely, measurement of water temperature is practical and interpretable, but may not be sensitive to the environmental flow rules. The attributes listed in the table below, along with many others, will be assessed by each of these criteria in the development of the monitoring program for the unregulated rivers.

Examples of ecosystem attributes for monitoring and reporting.

Ecosystem property	Measurable attribute	Possible measurement methods
Flow	Continuous discharge	Continuous stage recording plus discharge rating
Flow	Instantaneous discharge	Spot gauging
Hydraulics	Water velocity	Hydrographic current meter Acoustic doppler velocimeter 1D and 2D hydraulic modelling
Hydraulics	Wetted area	Ground survey (e.g. theodolite; range finder) Photo point monitoring Remote sensing (e.g. infra red or radar imagery) 1D and 2D hydraulic modelling
Habitat quality	Concentrations of nutrients e.g. nitrogen and phosphorus	Automatic and manual samples
Habitat quality	Diurnal maximum and minimum temperature	Continuous temperature recorder (e.g. max–min thermometer; tidbit)
Species / ecosystems	Aquatic plant abundance and composition	Transect and quadrat surveys
Species / ecosystems	Frog abundance and composition	Night-time census

In the latter half of 2006, a final list of attributes and monitoring sites across the unregulated rivers of NSW will be selected. It is anticipated that data collection will be begin in late 2006. Small research projects will also be developed to enhance our understanding of these systems.

For more details on the framework and design of the monitoring program, see Program framework for ecological monitoring and reporting of water sharing plans for unregulated rivers – scoping paper.

Simon Williams
Senior Scientist
Science and Information Division
Department of Water and Energy
PO Box 53
Wollongong, NSW, 2500, Australia