3.5.3 Economic assets

Table 34 Water source areas and extraction points in the zone of potential hydrological change

^aOf the 3950 elements in the zone of potential hydrological change (Table 33), 3911 relate to water access licences and basic water rights.

Data: Bioregional Assessment Programme (Dataset 15)

Of the 3950 elements in the zone of potential hydrological change (Table 33), 3911 relate to bores and surface water extraction points. The following clarifications and conclusions can be made about extraction points within potentially impacted water sources:

Of the 1450 groundwater bores identified in Table 33 as in the zone of potential hydrological change, 780 bores are within the groundwater zone of potential hydrological change and 670 bores are solely within the surface water zone of potential hydrological change. Of the 670 bores selected due to intersection with the surface water zone of potential hydrological change, only those bores used to extract water from an alluvial aquifer could potentially be impacted. This is because alluvial aquifers tend to be highly connected to the streams that intersect them, such that changes in baseflow due to additional coal resource development could affect water levels at bores within the alluvium, even outside the area of greater than 0.2 m of drawdown. In NSW, these highly connected water sources are managed conjunctively. Analysis of the bore dataset revealed that 62 of these bores are in fractured rock aquifers (Sydney Basin – North Coast) and can be ruled out. Another 415 were clearly identified as in alluvial aquifers and therefore potentially impacted. Of the remaining 193, drill depth data were used to determine likelihood of potential impact, with bores lacking drill depth data being retained as potentially impacted. In the Hunter subregion, depths of alluvium have been reported as ranging from 3 to 17 m (Australian Groundwater Consultants Pty Ltd, 1984) and up to 20 m (Wilford et al., 2015). In companion product 1.5 for the Hunter subregion (Zhang et al., 2016), a depth of 20 m was adopted to distinguish bores that (i) had no screen depth data and (ii) coincided with mapped Hunter River alluvium into alluvial and fractured rock bores. The same threshold is used here to differentiate alluvial bores, which are potentially impacted, from deeper, fractured rock bores that are unlikely to be impacted due to additional coal resource development. Table 35 summarises the breakdown, with 590 of these bores retained as potentially impacted and 80 ruled out as unlikely to be impacted.

Table 35 Drill depths and purpose of potentially impacted bores solely in surface water zone of potential hydrological change

Data: Bioregional Assessment Programme (Dataset 15)

In summary, 19 surface water sources and 5 groundwater sources are potentially impacted by hydrological changes due to additional coal resource development. Figure 71 summarises the steps for deeming bores and surface water extraction points in the zone ‘potentially impacted’. Of 3911 bores and surface water extraction points within the zone, 3831 are potentially affected due to additional coal resource development.

Figure 71 Determining 'potentially impacted' extraction points in the Hunter zone of potential hydrological change

Data: Bioregional Assessment Programme (Dataset 15)

Whether the modelled hydrological changes due to additional coal resource development are likely to impact water rights holders can be assessed through quantifying changes in water availability and reliability of flows in the potentially impacted unregulated and alluvial water source areas and determining whether the modelled drawdowns could interfere with licensed bore water users access to groundwater. These three indicators of impact are considered in the following sections.

3.5.3.2 Impact on water availability (surface water)

The change in average annual flow is used here as an indicator of change in water availability due to additional coal resource development.

Twenty-four water source areas intersect the Hunter zone of potential hydrological change. Five were identified as having minimal intersection with the zone and unlikely to be impacted, with results at model nodes on Baerami Creek and Black Creek confirming no significant hydrological change for two of these water sources. Modelling results at model nodes on Wybong Creek and Dart Brook also indicate no significant change in average annual flows. Surface water modelling was not undertaken for Dora Creek, South Lake Macquarie, Ourimbah Creek, Jilliby Jilliby Creek and Tuggerah Lakes water sources, and changes in average annual flows cannot be quantified. Results of changes in average annual flows are presented for 11 water sources, noting that changes in the Luskintyre water source (not reported) are encapsulated in the changes reported for zone 2B of the Hunter Regulated River.

Table 36 summarises changes in annual flows for the Hunter Regulated River water source by management zone. Management zones along the Hunter River number from 1A immediately below Glenbawn Dam to 2B at the downstream end of the regulated river, a few kilometres north of Maitland; zone 3A corresponds to the regulated reach between Glennies Creek Dam and the junction with the Hunter River. In absolute terms, the biggest reduction in annual flows occurs in zone 2B, and reflects the cumulative impact of all the modelled developments upstream of this point. Between 2013 and 2042, this is modelled to be up to 12 GL/year (95th percentile) or 1.6% of the baseline mean annual flow for the same period. By the 2073 to 2102 period, this impact is modelled to have lessened to 6 GL/year. Reductions in mean annual flows range between 2 and 5 GL/year along zones 1B and 2A, the length of river between the Goulburn and Hunter rivers junction and the Wollombi Brook and Hunter River junction.

Table 36 Change in water availability due to the additional coal resource development for management zones within the Hunter Regulated River water source. The average annual baseline flow for the short-term period (2013–2042, 95th percentile) is provided as context

Data: Bioregional Assessment Programme (Dataset 17)

Table 37 summarises changes in annual flows for Hunter unregulated and alluvial water sources. Generally, the most downstream node for the water source has been used to assess the change in water availability, however for the Singleton, Jerrys and Muswellbrook water sources, which overlap the Hunter Regulated River water source, the sum of changes in annual flows at nodes on small tributary streams within the water source area has been used to give an indication of the change in water availability for these water sources. They are likely to underestimate the change due to additional coal resource development because the effect of baseflow reductions downstream of these nodes is not captured in the reported numbers at this scale. However, the changes in the management zones along the Hunter Regulated River water source (Table 36) include those baseflow reductions: for the Muswellbrook water source, zone 1A is relevant; zone 1B reflects changes in Jerrys water source; and zone 2 captures changes in tributary flows within the Singleton water source.

The biggest reductions in annual flows occur in the Singleton water source (95th percentile of ~6.3 GL/year), followed by Jerrys (~3.5 GL/year) and Muswellbrook (~2.85 GL/year) water sources between 2013 and 2042. In the Wyong River, decreases in the mean annual flow are modelled to peak between 2043 and 2072 (95th percentile of ~5.7 GL/year), with the effect persisting through the 2073 to 2102 period. Changes to water availability in the Goulburn River water sources – Lower Goulburn River, Upper Goulburn River, and Bylong and Wollar Creek – are comparatively small, with the largest decrease in mean annual flow of 0.9 GL/year (95th percentile) occurring in the Wollar Creek water source between 2013 and 2042, and increasing reductions in the Bylong water source from 0.24 to 0.4 to 0.48 GL/year over the three 30-year periods.

Table 37 Change in water availability due to the additional coal resource development for Hunter unregulated and alluvial water sources in the zone of potential hydrological change. The average annual baseline flow for the short-term period (2013–2042, 95th percentile) is provided as context

^aWater sources with no suitable downstream node – values represent the sum of changes at multiple nodes within the water source area.

Data: Bioregional Assessment Programme (Dataset 17)

3.5.3.3 Impact on reliability (surface water)

3.5.3.3.1 Regulated river

The Hunter Regulated River – between Glenbawn Dam and Glennies Creek Dam and the tidal limit of the Hunter River – has a prescribed long-term average annual extraction limit and is a fully allocated water source. No new water access licences are available from the state, so access to water is permitted only through an existing licence or purchase of an entitlement or an allocation through the water market. Licensed entitlement holders in regulated rivers are able to place orders for water from Glenbawn and Glennies Creek dams to meet their water needs. How much they are permitted to extract in any given year depends on water availability in these storages. Available water determinations (AWDs) are made at the commencement of the water year based on the volume of stored water and the assumption that inflows to the dams in the ensuing year will be the lowest on record. In years when the starting AWD is less than 100% of entitlement, the AWD can be updated throughout the water year in response to changing conditions.

The environment is also a recognised ‘user’ of water in the regulated river. The Water Sharing Plan for the Hunter Regulated River Water Source makes provision for environmental water through not only setting a limit on long-term annual extractions of 217,000 ML/year, which ensures about 80% of the long-term annual flow is left in the river, but also through specifying environmental water requirements (EWRs) at the Liddell and Greta gauging stations (nodes 31 and 1, respectively). EWRs are managed through imposing limits on extractions when the dam spills or when high flows from unregulated tributaries enter the system to ensure sufficient volumes for flooding of wetland areas; imposing limits on extractions when inflows from the unregulated tributaries to the regulated river are low to ensure sufficient water is retained in the river; and through releases of water from Glenbawn and Glennies Creek dams.

A potential economic impact of coal resource development is upon security of supply to consumptive users. If reductions in baseflow and catchment runoff lead to a greater frequency of flow rates below the minimum EWR at Liddell and Greta, then water in the Glenbawn and Glennies Creek storages that might otherwise have been part of the consumptive pool may be needed to meet the EWR. This could potentially reduce the security of supply to users of the consumptive pool, reflected in a decrease in the percentage of years that they can expect to receive an AWD of 100% at the start of the water year. This potential impact has not been modelled as part of the BA for the Hunter subregion, but is identified as a risk. The NSW Department of Primary Industries Water IQQM of the Hunter Regulated River is the appropriate modelling platform for exploring the implications of potential flow reductions on environmental water and the consumptive pool.

3.5.3.3.2 Unregulated river and alluvial water sources

One way flows in unregulated rivers can be protected is through controls on extraction. Cease-to-pump rules in water sharing plans specify the river level below which extractions are not permitted. Some plans specify how much water is permitted to be extracted for different flow ranges. Cease-to-pump rules are developed for each water source based on all current water licence entitlements accessing either surface water or groundwater (in highly connected alluvial aquifers) – that is, rules assume full development rather than actual take. For water sources covered by the Water Sharing Plan for the Hunter Unregulated and Alluvial Water Sources that have cease-to-pump rules, the general requirement is for pumping from the river to cease when there is no visible flow in the water source at the location where water is proposed to be taken or, where water is taken from a pool, there is no visible flow into or out of the pool. Some water sources are split into a number of management zones (e.g. Dart Brook has five; Jerrys has two), some of which may have a groundwater trigger, rather than a streamflow trigger, to define when extractions are and are not permitted. Not all water sources in the Hunter subregion have had the groundwater trigger, reference point and cease-to-pump rules specified for them. Table 38 lists the water sources within the zone of potential hydrological change that surface water modelling found to have an above-threshold change in the number of zero-flow days (ZFD) or low-flow days (LFD) due to additional coal resource development, details the cease-to-pump rules for each water source and specifies the flow threshold used to quantify the impact on cease-to-pump days due to additional coal resource development. Where cease to pump is triggered by ‘no visible flow’, the change in the average number of zero-flow days in each 30-year period has been used to quantify the change. Where cease to pump is based on the flow rate falling below a specified flow rate at a reference location, then the change is assessed using the specified threshold. Where the cease-to-pump trigger has not been specified for a water source, the assessment has been based on the change in the average number of zero-flow days.

Table 38 Cease-to-pump rules for water sources in the surface water zone of potential hydrological change that surface water modelling found to have a change in zero-flow or low-flow days due to additional coal resource development greater than the defined thresholds

Source: Water Sharing Plan for the Hunter Unregulated and Alluvial Water Sources 2009; Water Sharing Plan for the Central Coast Unregulated Water Sources 2009

Table 39 summarises the increase in the number of cease-to-pump days from the additional coal resource development at model nodes where there was at least a 5% chance of an increase in ZFD or LFD of at least 3 days/year. Baseline cease-to-pump days for 2013 to 2042 are provided for context. Under the baseline, cease-to-pump days are relatively unlikely in Black Creek, Wollombi Brook, Glennies Creek and Foy Brook, whereas in Doctors Creek, Redbank Creek and an unnamed creek in Jerrys water source (node 29), reliability of flow is low as reflected in the high number of cease-to-pump (zero-flow) days even at the 5th percentile. In Doctors Creek, additional coal resource development is predicted to increase the number of cease-to-pump days by a median 34 days, but with some simulations estimating as many as 102 more cease-to-pump days. Redbank Creek, Wollombi Brook, Glennies Creek, Foy Brook, Bayswater Creek, Saltwater Creek, Goulburn River and Dart Brook are unlikely to experience significant change in the reliability of flows due to additional coal resource development.

Potentially significant changes in reliability of flow due to the additional coal resource development are possible for a number of creeks in the Singleton water source, in Saddlers Creek in Jerrys water source, in Dry Creek and an unnamed creek in the Muswellbrook water source, and in the Wyong River. In the Wyong River, the median change over the three 30-year periods is modelled to be between 6 and 8 days, but could be as much as 140 days (95th percentile, 2043 to 2072), noting that these predictions do not take into account the results of modelling using local-scale data from the Wallarah 2 Environmental Imapct Statement.

Table 39 Increase in cease-to-pump days due to additional coal resource development (ACRD)

Note that the baseline and additional coal resource development values are not additive.

Data: Bioregional Assessment Programme (Dataset 17)

3.5.3.4 Bores where ‘make good’ provisions might apply (groundwater)

Environmental provisions relating to extractions from aquifers are intended to protect the long-term storage component of the aquifer. Extractions are based on reserving a proportion of recharge for the environment. Cease-to-pump rules are used to restrict pumping when levels drop below some specified level or water quality is deteriorating. The NSW Aquifer Interference Policy (DPI Water, 2012), which was introduced in September 2012, is intended to protect groundwater resources from activities that potentially interfere with them. It requires that all water extracted from an aquifer must be accounted for, that the activity must address minimal impact considerations and planning must make provision for situations where actual impacts are greater than predicted.

Minimal impact thresholds are specified for highly productive and less productive groundwater sources and different aquifer types (alluvial, coastal sands, porous rock and fractured rock), but can generally be defined as less than 10% cumulative variation in watertable level, 40 m from any high-priority GDE or culturally significant site, with a maximum decline of 2 m at any water supply work. Where an activity is likely to result in the minimal impact threshold being exceeded, ‘make good’ provisions should apply, unless it can be demonstrated to the Minister’s satisfaction that the variation will not prevent the long-term viability of the GDE or culturally significant site. Here the ‘maximum decline of 2 m at any water supply work’ threshold is used as the basis for identifying bores where a potential economic impact may result due to the additional coal resource development. It is possible that ‘make good’ provisions could be required at bores where drawdowns are predicted to be less than the minimal impact threshold, but there is no basis for identifying these in a regional-scale assessment.

Table 40 lists the water sources that have bores within the zone of potential hydrological change with at least a 5% chance of drawdowns exceeding 2 m due to additional coal resource development. Of the 1450 bores in the zone, 170 bores have at least a 5% chance of drawdowns exceeding 2 m due to additional coal resource development; 50 of these are in the mine pit exclusion zone and might be, or have been, removed in the process of mine pit excavation. Using the 50% percentile to define the bores that are ‘more at risk of hydrological changes’, 51 bores outside the mine pit exclusion zone are considered to be more at risk. Of these, 44 are on exploration or mining leases and are likely to be held by mining companies, and 2 are on exploration leases held by the Secretary of the Department of Planning and Environment. There is at least a 5% chance that the drawdown due to the additional coal resource developments will exceed the minimal impact threshold at 11 bores that are not on mining or exploration leases, of which 5 are considered ‘more at risk of hydrological changes’. A summary graphic of potentially impacted bore numbers is provided in Figure 72. The 11 bores that are not on mining or exploration leases relate to extractions permitted under a water access licence, with 7 in the Sydney Basin – North Coast groundwater source, and the others in the unregulated and alluvial water sources of Jilliby Jilliby Creek (2), Tuggerah Lakes (1) and South Lake Macquarie (1). Bores that are ‘more at risk of hydrological changes’ are the three in the Jilliby Jilliby Creek and south Lake Macquarie water sources, and two in the Sydney Basin – North Coast groundwater source. The location of the 120 bores (95th percentile) are shown in Figure 73.

Table 40 Number of bores where additional drawdown is greater than 2 m for 5th, 50th and 95th percentiles

Additional drawdown is the maximum difference in drawdown (dmax) between the coal resource development pathway (CRDP) and baseline, due to additional coal resource development.

Data: Bioregional Assessment Programme (Dataset 15)

Figure 72 Summary of number of bores in the zone of potential hydrological change (95th percentile), and those with at least 5% and 50% chances that 'make good' provisions due to additional coal resource development could apply

Figure 73 Location of bores with at least a 5% chance of drawdown exceeding 2 m due to additional coal resource development (5th, 50th and 95th percentiles)

Data: Bioregional Assessment Programme (Dataset 8, Dataset 9, Dataset 18)