Case study 11 - Thresholds application to unregulated surface water planning in New South Wales
- Case study 11 - Thresholds application to unregulated surface water planning in New South Wales (PDF -92 KB)
The macro planning approach to coastal unregulated water sources (river sub-catchments) and their highly connected groundwater is designed to direct resources into higher risk sub-catchments as a priority.
Unregulated water sources are rivers that do not have dams that control releases for extraction, mainly for irrigation. Their highly connected groundwater is in the upriver alluvial deposits. Higher risk parts of the catchment are identified through a risk management approach that uses thresholds to guide the level of attention given to that area.
- To identify areas with higher levels of risk to enable limited resources to be targeted to those areas
- To put a higher level of management in an area based on a threshold level of acceptable risk
- To establish and change the level of water management rules based on risk thresholds.
Application of a risk-based approach to management
There are two factors that express risk in unregulated river and highly connected groundwater water management:
- instream value (default for consequence)
- hydrological stress (default for likelihood).
In this approach, the consequence can be considered to be equivalent to the value of the environmental asset under threat. The consequence of losing a high-value asset is more than that of losing a low-value one. The likelihood of impact is related to the level of hydrological stress. If a greater percentage of flow is extracted the likelihood of damage is greater.
Risk to instream value = instream value x hydrological stress
For each water source, these factors are placed within a risk matrix, which guides the rules in the water sharing plan in the level of management applied.
Prior to this approach, there was one set of rules whether there were one or 1000 users and irrespective of the health of the water source. This approach allows for managing areas differently depending on the circumstance but within an accountable framework – in other words, more stringent rules are phased in over time or differential rules are applied to different areas of risk within the same water source.
Information requirements to achieve objectives
The impacts of extraction do not necessarily occur in just the water source where extraction takes place, but they can accumulate downstream. The hydrological stress of lower catchment water sources must therefore consider extraction in all of upstream tributaries, as well as extraction from within the water source.
There are two main information requirements:
- Estimating hydrological stress
This is normally calculated as the ratio of extraction demand (based on peak daily demand) to supply during limited flows (based on a low flow index, generally the 80th percentile).
Daily flow rules – cease-to-pump rules – are developed for each water source based on all current water licence entitlements accessing either surface water or groundwater (in the case of the highly connected upriver alluvial aquifers). The rules are based on there being full development of all access licences (generally greater than the actual volume of water being currently extracted) to cater for potential total extraction. Extraction demand is based on surveyed crop types and an estimate of water use.
Where flow information is not available or where extraction is affecting another indicator (such as depth of water in a lagoon or the change in salinity in an estuary), then alternative estimates of hydrological stress are made.
- Determine instream values
Coastal water sharing plans can influence management relating only to water extraction – only values considered vulnerable to water extraction are considered.
Three different types of values contributing to instream value are considered:
- ecological (intrinsic)
- economic (non-extractive use)
- cultural (place)
Instream values also include an assessment of declared special environmental areas (for example, critical habitat as identified in the State Environmental Planning Policy (SEPP) 14 wetlands1 )), threatened and endangered species, ecological communities and populations. Indigenous values, part of place values (not measurable) is not included in the technical assessment and is normally considered through Aboriginal consultation meetings. All water related attributes are scored to determine relative instream value.
Approach taken in dealing with uncertainty
Uncertainty over information is addressed by an adaptive management approach where a future decision is bounded by upper and lower limits (bounds of change).
Removing levels of uncertainty is achieved by undertaking further studies during the life of a water sharing plan). For example, in the Lower North Coast Unregulated and Alluvial Water Sources Water Sharing Plan in the Upper Manning Water Source, a bounds of change rule was put in place in recognition of:
- the lack of locally appropriate data available on the optimum cease-to-pump level
- lack of understanding of the effect of changes in management rules on environmental gains versus potential social and economic loss.
The cease-to-pump level will be based on the findings of the study, with the intention that it is completed by year five of the water sharing plan. The final cease-to-pump level will be somewhere between the 99th percentile flow (near pre-plan extraction) and the 95th percentile flow (default state policy level). This is the bounds of change. If the study is not completed by year six, the cease-to-pump level will default to the 98th percentile flow. This will not be introduced until the study is completed, which must be within the life of the water sharing plan (10 years). The 98th percentile is considered an improvement on current arrangements.
As a result of the approaches outlined above, stakeholders (irrigators) are able to work in a known operating environment based upon the guaranteed cease-to-pump figures with a definite 10-year life span.
Another example within this water sharing plan is the Upper Gloucester Water Source. On the value matrix, this water source was assessed as having high instream values and high hydrologic risk. On further investigations, the attributes that drove the high instream rating were all located in the upper end of the catchment where there were low levels of extraction. As a result, the water source was regraded on the risk matrix as being at 'medium' risk. This upper portion was made into a management zone and was quarantined by establishing rules allowing trading out but no trading in, in recognition of the environmental values and the value of water use further down the catchment.
Approach taken in consulting with stakeholders
A regional panel guides the development of the rules. The panel is comprised of state agency representatives. It agreed to amend rules to provide for further studies to determine the environmental requirements of the river and assess this against social and economic needs of water users.
A major river system with large numbers of extractors and high environmental values will generate more debate on the range of the bounds. Managing this risk is achieved through the agreement of further studies. In the meantime, a wider bounds of change is proposed to manage the complexity and to gain more agreement. Further studies with consultation narrows the boundary range over time.
Targeted consultation with key stakeholders was implemented to outline the potential issues, options and solutions around the application of thresholds to water resources in New South Wales. After extensive community consultation, a public exhibition of the draft water management rules was put on display for the wider public comments.
Monitoring and reporting
Water sharing plans include a number of performance indicators. Some of these are monitored over their ten-year life. An 'evaluation reporting framework' is currently being developed to determine the appropriateness, efficiency and effectiveness of plans. The framework is being developed in collaboration with key stakeholders and will be consistent with requirements of the New South Wales Natural Resource Commission and the National Water Commission. The intention is that the framework can be applied to existing water sharing plans.
It is not practicable to monitor all issues in all water sources. The performance indicators identify that monitoring will be undertaken for specific issues in key priority water sources. A risk assessment approach will be used to identify specific issues and high-risk water sources where detailed monitoring and reporting need to occur.
Each plan indicated the relevant mandatory conditions for extraction, including that all licences measure water use. This will be developed via a measurement-of-use strategy that meets the objective of the New South Wales Water Extraction Monitoring Policy.
Both monitoring strategies will assist in defining threshold applications to water planning in the next round of water sharing plans.
More infomation, please visit: National Water Initiative
1SEPP – State based list of important wetlands.