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Surface water science

Monitoring changes in surface water environments

Sentinel 2 imagery from May 2021 with the Normalised Difference Water Index (NDWI).
Figure 1: The surface water science team is using satellite imagery to monitor surface water across the state. This image shows Sentinel 2 imagery from May 2021 with the Normalised Difference Water Index (NDWI) applied to show surface water in blue.

Our surface water science team uses monitoring and targeted research projects to identify changes to the hydrology, geomorphology, water quality and ecology of surface water environments. This allows us to better understand the impact of water management decisions. It also allows us to track if changes in water management protect or improve surface water environments. We also use research projects to improve our understanding of potential impacts from climate change.

Understanding these relationships improves science-based decision making. It also improves the evaluation of legislation and policies. This gives us an opportunity to adjust the way we manage surface water environments so environmental impacts are minimised.

Some of the themes we monitor include:

  • how our surface water environments are responding to water that is set aside for the environment
  • how different patterns of water flow affect the way our rivers function (i.e. flow-ecology)
  • the river's physical form, its fringing vegetation and what sort of fish and insects live there.

Our monitoring and research projects evaluate and report changes in surface water environments. We use this information to gauge the health of our surface water environments. With increased scientific understanding of these environments we can better manage water for the environment and other users.

Why do we monitor changes?

The sustainable management of our surface water environments is our priority and a key principle of the Water Management Act 2000 (NSW). The Act enables the sharing of water for different purposes through water sharing plans developed for each catchment.

Water sharing plans define the rules for sharing water between the needs of the environment and all other water users. The needs of the environment include the water-dependent ecosystems, the plants and animals that rely on surface water environments. Water users include town water supplies, stock and domestic, industry, and agricultural users.

Water sharing plans contain a set of environmental, economic, social, cultural and heritage objectives. The overarching environmental aim is to protect and contribute to the enhancement of surface water environments. We assess water sharing plans to determine whether the plans are successful in maintaining or improving the health of our surface water environments.

Our monitoring and research projects aim to improve the management of water for the plants and animals dependent on surface water environments. This includes monitoring the performance of water sharing plans and other legislation within the Water Management Act 2000 (NSW).

How do we evaluate and report changes?

We evaluate and report changes in the following ways.

Water sharing plans

To determine how well a water sharing plan is meeting its objectives, we need monitoring and research.

We use environmental monitoring and research to assess the response of water-dependent ecosystems to water management practices. We also look at how different patterns of water flow affect the way rivers function.

We work with partner agencies to monitor the river's physical form, the water quality, its fringing and floodplain vegetation and the organisms (e.g. frogs, fish, insects) that live in the river environments. This information gauges the health of our surface water environments. We can then assess the effectiveness of water sharing plan strategies that aim to protect or enhance the environment.

Monitoring and research projects enable us to identify new innovative methods for managing surface water. They allow us to develop and test relationships. For example, our research shows that species of insects living in flowing river environments need different rates of river flow. We can apply this information to any river with similar habitat and similar insects to show what flows are needed to protect it.

Risk assessments

Risk assessments allow us to identify and prioritise where surface water environments are at greatest risk. That is, where we should focus our monitoring and research.

A risk assessment is a key step in preparing water resource plans and water sharing plans. It looks at risks to the condition and continued availability of water resources.

The risk assessment framework adopts a cause/threat/impact model. The model describes the risk pathway of impacts to a receptor. The risk level of an impact is a function of likelihood and consequence. The likelihood of a cause and threat occurring, and the consequence of the impact on the receptor. We use the following definitions for risk assessments:

  • Likelihood: the probability that a cause will result in a threat. It is not a sign of the size of the threat, but rather conveys the probability that the threat will be significant.
  • Consequence: the loss of value for an impacted receptor.

We assess the risk level using current strategies and rules as provided by the Water Management Act 2000 (NSW) and the relevant water sharing plan/s. The risk assessment outlines the management actions and mechanisms to address risks.

The figure below combines the cause/threat/impact model and likelihood/consequence. As an example, it shows risks arising from river regulation and licensed surface water extraction.

Cause, threat and impact model

Medium and high-risk results identified in risk assessments undergo review. This determines whether these risks are adequately addressed by existing strategies. If not, they may need modifications or new strategies. In NSW, a medium or high risk does not always imply that existing rules or strategies are inadequate. The risk assessment is a 'red flag' process to provide guidance during the life of a plan. It identifies areas that may need further investigation.

Risk-based management assists water managers to prioritise and plan. This allows managers to direct resources to the factors that pose the highest risks. They can target strategies to the appropriate part of the water system.

Tools we use to monitor changes

NSW River Condition Index

A consistent riverine condition assessment method.

River Condition Index Impact Assessment Tool

Predicting the impact of aquifer interference activities on river health.

River styles in NSW

A consistent method to characterise the types of rivers.

Environmental value of NSW rivers: HEVAE

Identifying surface and groundwater systems with high conservation values.