Beverly Clayton
19/7/06
Has the Government taken any steps to clean up water under Sydney?
Improving the quality of groundwater in the shallow sand dune sediments at multiple sites in the Botany Basin is well under way (mostly by the polluters under the direction of DEC). The risks associated with this groundwater are too high to be considered for potable use. The deeper groundwater across the metropolitan area is saline and generally not suitable for use.
If not, why not?
Groundwater remediation is long term and can take many years (and in many cases there are limits to the available technology to remediate groundwater
Why has mine residual water not been considered?
Mine water is being considered as part of the SCA’s groundwater investigation program – investigation results are unlikely to be available until early 2007. Substantial testing and proving the suitability of supplies is likely to be required
Kerrie Eyding
14/7/06
Will pumping from cracks result in ground subsidence?
Ground subsidence is highly unlikely. Groundwater is derived from both the sandstone rock and the fractures within the sandstone. The sandstone rock mass is competent enough to stand up without the water in the matrix (the many road and rail crossings across the Sydney Basin are good examples).
Given that this will be a 'buffer' measure, what are the plans for getting water to Sydney when the aquifers are exhausted, i.e. in 2 or 3 years time?
The rate of extraction proposed would not dewater or exhaust the aquifers to the point where there is no water left - it is anticipated that around 10% of the storage volume would be available for use over a pumping period of 2 to 3 years. If drought conditions still prevail after 2 or 3 years, and water levels are such that the borefield should be turned off to recover, then construction of a desalination plant may be triggered.
Karen Guymer
19/7/06
Acronyms Used
GIR = Groundwater Investigations Report
TOR = Technical Overview Report
CRG = Upper Nepean Groundwater Community Reference Group
DEC = Department of Environment and Conservation
EEC = Endangered Ecological Community
DNR = Department of Natural Resources
1. The modelling in the TOR shows 0m drawdown from a 2-year pumping cycle at Wingecarribee Swamp, however there are potential inaccuracies in the model used. There are monitoring bores in the swamp. Will the SCA integrate the monitoring that is occurring in the swamp with the Kangaloon Aquifer monitoring to prove the accuracy of the model? Is the data available already to assess the impacts of the pilot testing on the swamp or would further groundwater pumping tests be necessary?
The numerical model is a regional impact assessment model based on the best available information (including available Wingecarribee Swamp data). Drawdowns during the 7 to 40 day pilot testing pumping tests were not long enough to create drawdowns over more than a few hundred metres and would not extend to the swamp area. Large extended pumping tests would need to be carried out over very long periods to assess any impacts (even if the swamp is connected to the sandstone aquifers) as the model predicts there are no drawdowns at the swamp even after 2 years.
2. The GIR (pp 17 & 19) suggests that south flowing rivers such as the Kangaroo River may be supplied by the Kangaloon Aquifer. Will the Kangaroo River and Macquarie Rivulet be impacted by the extraction of groundwater?
I see no reference to the south flowing rivers being linked to the Upper Nepean (Kangaloon) sandstone area. The cross sections on pages 18 and 21 are quite specific in indicating the respective groundwater flow directions.
3. Where is the meteorological station that has been used for climate data for the recharge and sustainable yield modelling?
All the long-term Bureau of Meteorology stations in the area have been used for recharge calculations – there is in fact a gradation across the proposed borefield area based on location and rock type. CRG members are referred to the Groundwater Modelling report for an appreciation of rainfall recharge calculations used for model calibration.
4. Predicted reductions in rainfall will effect the ability of the aquifer to recharge, and will lead to the eventual draining of the aquifer, if severe and more prolonged droughts occur more frequently. If long-term rainfall records have been used in the hydrogeological model, can the CRG be supplied with an alternative model based on recent rainfall and projected rainfall data based on predicted reductions in rainfall from global warming?
There is no evidence to suggest that lesser rain (but possibly more severe events) will diminish the volume of groundwater recharge. There is not a direct relationship between the two, even though rainfall recharge is required for the aquifer system to remain sustainable. Also the aquifer will never be drained, the total volumes expected to be extracted over a 2-3 year period are around 10% of the available storage (assuming no recharge).
The current modelling is steady state using Decile 10 rainfall. Additional transient model runs (rather than steady state) are proposed later in 2006 or early 2007 based on hydrographic data from the observation bore network and additional data from long-term pumping tests. When run in transient mode, the numerical model can be matched against any period of rainfall record, however it is premature to undertake additional model runs at this time.
5. a) Is there any risk of saline g/w intrusion from overlying Wianamatta Shale, either through vertical or lateral flow, from either the construction or operational phases of the proposed borefield?
b) If yes, what precautions will be made to ensure that the aquifer is not contaminated by salty water?
a) the risk of intrusion of saline water from the overlying shale is negligible during construction. During operation, the risk is also considered negligible. Migration is unlikely based on several orders of magnitude differences in permeability between the shale (very low) and sandstone (moderate), and the rainfall recharge is direct to the sandstone outcrop areas and not via the shale areas.
b) there is negligible risk but if shale is present near surface in any test or production bore it is always cased and cemented off to prevent saline seepage behind the casing into the borehole.
6. What input is DEC having in this pilot testing and monitoring process? There are endangered species and EEC’s and wetlands of national significance in the vicinity of the borefield. What is DEC doing to fulfil its obligations under the Threatened Species Legislation Amendment Act (2004)?
DEC is a member of an informal groundwater technical review group that has met several times over the last 12 months to exchange information about the investigation program and probability of borefield extraction. DEC also assisted with the siting of monitoring bores at Butlers Swamp as part of the pilot testing program. Further advice from DEC will be sought during the borefield planning approval process.
7. There has been no mention of an environmental allocation. The TOR (p40) states that 15GL p.a. for 2 years is possible, so why is 3 years being suggested as an option? Has an environmental allocation been calculated into the annual extraction limit of 15 GL and is this the sustainable yield of the aquifer? What method has been used to determine the sustainable yield? Has a 30% environmental use allocation been used as a basis for determining the sustainable yield or will the allocation be determined once the report on groundwater dependent ecosystems has been finalised?
The modelling report says that 15GL p.a. is available for two years because that was the modelling brief. Additional water will be available in Year 3 if pumping was extended (but probably not to the same volume of 15GL). The concept of environmental allocations within the context of sustainable yield of an aquifer system is a management concept that is being applied to regional aquifer systems by the Department of Natural Resources (DNR) when determining the volumes to be allocated from particular groundwater sources. The Upper Nepean borefield area is located within the Nepean Sandstones groundwater source area and will be managed under the Porous Rocks Macro Water Sharing Plan which is being developed and implemented by DNR.
Environmental allocations are not determined on a case-by-case or borefield basis – it is a predetermined percentage and volume set aside before allocations for consumptive uses are made for each water source. DNR will assess this borefield development on the basis of the Nepean Sandstone volumes and all the available hydrogeological and ecological data for this Kangaloon area, and will set appropriate regulatory limits (such as allocation, extraction regime and monitoring requirements). This assessment occurs during the formal planning approval process.
8. The TOR (p14) states “recharge comes from rainfall, runoff and streams”, not just direct rainfall penetration on sandstone as suggested at the inaugural meeting of the CRG. The assumption that the shale is completely impermeable is difficult to accept given that there must be fractured rock and fissures similar to the “complex” sandstone formation. Will there be an impact on surface springs, soaks and wetlands in the basalt formation due to a lowering of the zone of saturation in the sandstone, and the fact that less water will travel further because it will be pulled into the dryer sandstone rather than running off into a creek?
The p14 reference is a generic statement of groundwater systems with rainfall and perhaps sideslope runoff being dominant for the Upper Nepean. There is no evidence of connection between basalt and sandstone rock strata and associated groundwater systems in the Upper Nepean catchment (based on water table elevation data and limited water quality data). With the confining shale layer (and its low permeability) it is not possible to drain the basalt groundwater because of the permeability contrast even if there is some water level decline in the underlying sandstone. Also shale weathers to clay, sandstone to sand, so if there are cracks in the shale with some water in them they are most likely weathering to clay which makes flow through this rock type extremely slow and limited.
The predictive modelling suggests most drawdown in the sandstone aquifer occurs within 2km of the borefield and negligible drawdown occurs in those areas where basalt outcrops. While there is some predicted impact on creek/river baseflows within the influence of the borefield after 2 years pumping, the impacts are small and are unlikely to drain creeks with permanent flow.
Extra SCA monitoring bores, and nominated private bores and springs, and possible creek locations will assist proving this disconnection and assist in monitoring flows.
9. The CRG needs a briefing from DNR Hydrogeology Unit or an independent hydrogeologist to allow discussion regarding:
a) Update on data and mapping on groundwater vulnerability and availability for the Southern Highlands area and the greater Wollondilly-Nepean Groundwater Management Plan Area.
b) Their opinion regarding the proposition by SCA that the Kangaloon Aquifer is a separate source of water to the Hawkesbury Sandstone Aquifer.
c) An update on A Review of the Status of the Groundwater Resources in the Southern Highlands NSW (DIPNR, 2004).
These queries will be directed to DNR for a formal response. SCA will arrange DNR to present at a future meeting.
10. Will endangered flora be marked and protected during the monitoring and operational phases of this development?
Ecosystems that are likely to have some groundwater dependence will be monitored. At this preliminary stage this is likely to include some upland swamps, selected monitoring bores (for aquifer species) and some terrestrial vegetation. A suggested monitoring strategy is being proposed in the detailed ecosystem report that is due from SMEC in early August. Any threatened species will be afforded a high level of protection.
11. How can SCA ensure that impacts on aquatic and terrestrial fauna (from lowering of the water table, reduction in drought flows and run-of-river transfers) will be minimal? Can the DNR license contain a clause to allow a cease to pump or revocation if an impact on local and migratory fauna is shown to be occurring?
Comprehensive monitoring programs will be in place to monitor ecosystems. Aquatic ecosystems are likely to be the least affected by the borefield development proposal. Water that is discharged at selected river locations will be compatible to the receiving river quality. Only discharge locations with permanent flows are being considered for run-of-river discharges.
DNR manages regional aquifer systems on the basis of the available data, and it is expected that all the monitoring data collected during borefield operation will be available periodically for DNR and others to review and assess trends against the expected aquifer behaviour. There will be discussions between SCA and DNR if pumping needs to be reduced or the borefield operated in a different manner. The Minister for Natural Resources has the final say in regard to water licensing matters.
12. How can the license conditions between DNR and SCA ensure that the base flows in the rivers and smaller streams are not affected by the borefield and that a suitable environmental provision is allowed under the license?
The SCA studies suggest there will be some affect on baseflow but only in the vicinity of the borefield when it is fully operational. Monitoring data for a borefield will be available periodically for DNR and others to review and assess trends against the expected aquifer behaviour. There will be discussions between SCA and DNR if pumping needs to be reduced or the borefield operated in a different manner. The Minister for Natural Resources has the final say in regard to water licensing matters.
13. Which parishes were embargoed in December 2005 by DNR? Are further embargoes planned by DNR to protect this supply of potable water?
All the parishes in the Upper Nepean Catchment have been embargoed by DNR (in 2005) but those in the Upper Wingecarribee catchment have not been included ie. Yarrawa and Burrawang are not embargoed but Yarrunga is embargoed.
Those parishes embargoed by DNR in the Southern Highlands are:
21 May 2004 – Parishes of Berrima, Mittagong, Bong Bong, Yarrunga, and Sutton Forest
16 December 2005 – Parishes of Belanglo, Murrimba, Bundanoon, Wingello, Kangaloon, Burke and Wongawilli
DNR have advised that a further review of embargo areas is under way for this and other developing groundwater areas in the Sydney – South Coast area.
The following comments and questions are from a community member who has read the reports:
1. The “supply” of water in the aquifer might be renewable, over up to seven years (Pp 33, & 40), but as water is integral to the environment, and as a number of ecosystems are acknowledged as being ground-water dependent, it is surely not “sustainable” to draw down water from the root zone of plants, for up to ten years (a 3 year pumping cycle, plus up to 7 years recovery to pre-pumping levels). This would surely threaten the survival of plants and, consequently other fauna types, within large portions of the study area.
The higher rate of extraction is only for a 2-3 year period of severe drought. When extractions are averaged over a longer period of a decade, the extraction rates are in keeping with the expected groundwater recharge rates. Hence the substantial groundwater storage can be used in a sustainable manner (NOTE that sustainability is always assessed on a long term basis (generally decades) and not year-to-year).
Also water is NOT being drawn from the root zone of plants – the average depth to water table is around 15m and is in the sandstone bedrock well below the rooting depth of most species.
16. The “depth to water table” column in Table 5.1 (P. 29) at sites # 2, #3, #4, #5, #8, #9 Stockyard Swamp and site #12 (East Kangaloon) all report water table depths of less than 20 metres. That puts the pre-pumping water table at all those sites within the reported range of Eucalyptus roots (Scoping Study, 5.2.3 p 24). Consequently, to commence pumping, and hence to knowingly draw-down water levels, in any of those areas, would threaten the survival of the key species within this environment. Many of these areas support Endangered Ecological Communities, protected under NSW and Federal legislation. To draw-down the water table in any of these areas, with a time frame of up to 10 years, would be unconscionable.
The Scoping Study was not an assertion that Eucalypts in this area have tap roots to 20m in solid sandstone. The scoping study suggested that this was a possibility (based on rooting depths in unconsolidated formations elsewhere) and that this should be looked at. It is generally agreed that these species are principally sustained by rainfall and the groundwater component is much less important. Further information will be available in the upcoming SMEC study.
Mim Merrick
14/7/06
1. An issue I wish to raise relates to findings contained in A Review of the Status of the Groundwater Resources in the Southern Highlands NSW (DIPNR, 2004). It is stated in the report that a critical stage of groundwater development had been reached in parishes abutting the Upper Nepean Catchment Kangaloon Aquifer area. Three of the seven parishes the report studied have groundwater entitlements exceeding the calculated unsustainable yields and two were approaching their extraction limit. The community is naturally concerned that with groundwater already being in a parlous state that more water should be extracted to meet the Sydney supply needs. The SCA advises that the aquifer systems are separate. Could scientific evidence of the hydrogeological features underlying this separation be made available to allay the anxiety of concerned community members?
The separation of the Upper Nepean (Kangaloon) aquifer from the more developed sandstone aquifers to the south and west is articulated in the Hydrochemistry and Environmental Isotope report and the Groundwater Modelling report. Summary information is provided in the Technical Overview Report.
Reflecting the concern of the community to the Government’s proposal to develop groundwater sources for drought relief, David Tranter has raised the following key questions re groundwater characteristics for the SCA response:
1. Movements:
How long does it take for rainfall recharge to percolate through the (sandstone) aquifer?
Water chemistry and age dating suggests that most groundwater in the sandstone strata in the vicinity of the borefield is “modern” and generally less than 50 years old. Age increases with depth and along the flow path to the north.
2. When aquifers are full, what happens to the “excess”?
When aquifers are full, the rainfall that may have become groundwater recharge does not infiltrate (or infiltrates to a shallow depth) and discharges as increased runoff or as increased baseflow to nearby streams.
3. Do “recent” aquifer recharges displace “older” ones”?
Generally yes. Groundwater is naturally migrating through the rock mass from recharge areas to discharge areas – the rate of flow is determined by the permeability of the formation and the hydraulic gradient. As a general rule, younger water is found in recharge areas and older water in discharge areas.
4. Do recent recharges mix withholder ones? How? – by convective overturn?
There is mixing of waters in the fractured sandstone aquifer (not a physical displacement of a body of water). Hence open fracture zones have the youngest water but this may be present beside older water that is moving more slowly or is trapped in the rock matrix.
5. How long does it take aquifer water to reach rivers feeding into the catchment?
The flow paths and residence times are highly variable depending on which area, groundwater at which depth, and which river receptor is under consideration. Typical velocities are tens of metres per year to perhaps 100-200 metres per year. Most groundwater travel times from recharge to discharge zones are expected to be in the range of several decades to many centuries.
6. Does the temperature of groundwater very with depth?
Temperatures are generally around 16-17ºC in the sandstone strata. Geophysical logging suggests there is a slight increase in temperature with depth. There are also seasonal variations with slight increases noted in 2006 from autumn to winter.
7. Does groundwater salinity vary with depth?
Within the Hawkesbury Sandstone, in the areas tested, there is very little difference in water quality with depth (it is all low salinity) except where there is overlying or nearby shale. In these instances, there is a general improvement in water quality with depth (ie. water becomes less saline).
8. How was groundwater salinity measured?
In the field, the water salinity is measured by calibrated meters as electrical conductivity (EC) which has units of microsiemens per centimetre. In the laboratory, water quality is measured as both EC and Total Dissolved Solids (TDS) in milligrams per litre (or ppm). A general conversion is 100 EC = 65mg/L TDS.
9. Can “recent” (say post-1960) recharges of the Kangaloon aquifer (e.g.1960, 1974, and 1998) be individually aged?
Dating of individual rainfall events or years is difficult because of the mixing of waters in the different sandstone strata. Some additional research work is planned in this regard.
10. How was this done?
Dating is based on carbon-14 and tritium isotope analytical results – the reader is referred to the hydrochemistry and environmental isotope report.
11. Were radioactive “signals” from postwar atomic explosions at Bikini and Eniwetok used? (as they have been for the Great Artesian Basin?}
Yes the tritium measured in the groundwater and surface water is the result of atmospheric bomb testing over the last 50 years.
12. Sustainability
Since catchment dam levels have been falling year by year over the past 6 years, is this not clear evidence that the supply rate is unsustainable?
Dam levels are falling in response to severe drought and the lack of runoff. Groundwater baseflows that flow into the dam storages are reasonably constant and are determined by the permeability of the aquifer and the natural gradient. The dam inflows are not related to these groundwater baseflows which are a very small component compared to rainfall runoff. However it is the large groundwater volume in storage that is the key to using groundwater as a periodic drought supply. The groundwater storage is independent of the current storage levels in the dams
13. Why, then, adopt supply (dam level) as the “trigger” for groundwater use rather than absolute household need?
The trigger is based on comparing the amount of water remaining in our storages with the demand on the water supply system. This is an appropriate way of deciding when an additional drought relief supply such as groundwater is needed to supplement the existing water supply system.
14. Why propose to draw on groundwater at 2.5 times its recharge rate, adding one unsustainability problem to another?
The higher rate of extraction is only for a 2-3 year period of severe drought. When extractions are averaged over a longer period of a decade, the extraction rates are in keeping with the expected groundwater recharge rates. Hence the substantial groundwater storage can be used in a sustainable manner.
15. If groundwaters ultimately find their way into surface catchments as the investigations suggest, then why not conserve groundwater for future use when droughts are predicted to be even worse?
The answer here is borrowing groundwater from future decades when it would discharge to the storages so that we can use it now. This strategy will only be effective if a depleted storage is able to recharge relatively quickly during intervening non-drought periods when there is excess surface water. This is expected to be the case given the aquifer characteristics that have been identified.
16. Why promote the use of groundwater as a panacea for Sydney’s water supply when it cannot meet more than one month of Sydney’s “needs” at current usage rates?
Groundwater pumping would slow the rate at which storages decline and (at other sites apart from Upper Nepean) substitute for water that is delivered to Water filtration plants. This buffering effect allows the system water resources to be extended for longer periods in the expectation of returning to more normal rainfall patterns.
17. Isn’t the promotion of groundwater as a “drought solution” to Sydney’s “water problem” rather counter-productive, lulling Sydney users into complacency, rather than urging them on to even greater conservation measures?
Demand management measures and greater water conservation are a major part of the 2006 Metropolitan Water Plan with the aim of saving 145GL per year by 2015, but groundwater has a role to play in being an additional water source available in time of severe drought.
Ray Nolan
16/7/06
1. If your drawdown affects a nearby bore, will you pay for lowering of the pump and/or deepening of his bore? Such was required of the Bowral Country Club bore when their pumping for irrigation affected their neighbour's bore. If the locals had that guarantee, they may be more amenable to the proposal.
The NSW Government is committed to ensuring that existing users are not disadvantaged. The location and condition of existing springs and bores will be confirmed in advance of borefield operation. If there are identified impacts, the options include lowering pumps and deepening bores. This would not be at the user’s expense.
2. What is the effect on the Standing Water Level if the pump is lowered, or raised, in the Bores?
The production bores are designed and constructed to tap all water bearing zones in the sandstone strata – generally slotted casing and screens are installed below depths of around 25 to 30m to the base of the sandstone. Hence the water level that is measured in each bore is a composite level of both shallow and deeper aquifers. Those shallow bores that were constructed to monitor the shallow water bearing zones suggest that the shallow zones generally have slightly higher water levels compared to the deeper zones (ie hence there is potential for water to migrate vertically in the profile). However the water level differences are small (generally just a few centimetres difference up to maximum of around 50cm) suggesting that upper and lower zones are hydraulically connected (this is also proven by the very similar water quality across all aquifers).
To answer the question regarding the effect on water levels by lowering or raising the pump in the production bores – the short answer there is no difference in the standing water level in a borehole where there are composite water levels across many zones and there is no difference in where the water is sourced from. When pumping, the bore will take water from all aquifer zones that are open. Water will be produced from all zones but the upper zones will be the first to dewater as water levels decline.
Pump intake levels are projected to be in the range 60 to 90m. This will ensure that the sandstone strata is not dewatered and that water remains in storage for basic rights and environmental uses.
3. If the pump is at a shallow depth, are the deeper aquifers also being drained?
Yes in a bore where all the aquifers are connected, all will produce water irrespective of the pump setting. The inflow volumes are proportional to the permeability of each zone – obviously a high permeability fracture zone will produce more that a smaller fracture zone or porous sandstone layer.
4. Relative to my queries, could John or another present data of at least one borefield with a graphic geology log, next to geophysical logs, with aquifers defined and with explanations of the behaviour of water levels during pumping tests in those bores? The overall picture is hard to assess from the many separate data sheets and I remain to be convinced of 700 day projections of 10 day pumping tests.
If time permits SCA will give a detailed response to this question via a graph in the presentation at CRG Meeting 2.
The modeling report, just been released, may also help to
clarify this.
Jenny Smith
14/7/06
1. The role of the CRG is ‘advisory’. In what form and at what time will this advice be given?
The CRG provides advice to the Minister for the Environment throughout the course of the consultation process. The CRG is also welcome to make submissions either individually or collectively through the chair. The SCA will report back to the NSW Government all issues and concerns raised by the CRG and the community through the submissions report.
2. How will this proposal fit with the groundwater macro planning and surface water planning processes being undertaken by DNR?
It is expected that all drought water supply borefields will be managed under the groundwater Macro Water Sharing Plan process. There is no overlap with the DNR’s surface water planning process. The Upper Nepean borefield area is located within the Nepean Sandstones groundwater source area and will be managed under the Porous Rocks Macro Water Sharing Plan
DNR will assess this borefield development on the basis of the Nepean Sandstone volumes and all the available hydrogeological and ecological data for this Kangaloon area, and will nominate appropriate regulatory limits (such as allocation, extraction regime and monitoring requirements). This assessment occurs during the formal planning approval process.
3. What are the assumptions that underpin the conceptual hydrogeological model? For example, it was stated at the meeting that the yield figures assume there will be no system losses.
The conceptual model refers to the water cycle components and the sandstone aquifer system as it occurs in the Upper Nepean Catchment – underlying assumptions are:
All groundwater recharge is derived from rainfall
All groundwater discharge is to downstream creeks, rivers and storages as baseflow
Stockyard Swamp is the only swamp linked to the regional water table in the sandstone aquifers There is always flow in the permanent rivers and creek systems
The reader is also referred to the modelling report for detail regarding the underlying numerical model assumptions. The volumes quoted in the groundwater reports are mostly bore and borefield volumes (not yields which have a different meaning).
4. How will the 10-20% loss of baseflows in local streams be calculated into the yield?
The five main perennial streams in the borefield area assume that water is always available from these streams. Each of these (Nepean R, Doudles Folly C, Burke R, Little R, and Dudewaugh C) is each treated as river cells (ie water can move into and out of these cells) – further downstream in the gorge country the rivers are treated as drain cells (ie. water can only move out of these cells).
Loss of baseflow to groundwater is calculated in the flow budgets for each of modelling scenarios that were run. The loss is part of the total borefield volumes that are pumped. The reader is referred to Tables 10 and 11 in the modelling report for the most likely flow budgets at the end of the modelled two-year pumping cycle. These predictions will be assessed against streamflow data once gauging stations are installed.
5. The report (p20) indicates that baseflow losses in local streams and swamps will be relatively small compared with creek flows under drought. Given that the pumping will occur during drought, won’t any stream losses have even more impact?
The rate of leakage from streams to groundwater is the same irrespective of whether average or drought conditions prevail. However it is true that baseflows from higher in the catchment will reduce with progression from drought to severe drought. The percentage of losses to groundwater will be slightly larger given the reduced baseflows but the losses are still considered small given the expected ongoing baseflows in each of the streams (to be monitored and assessed)
6. Have the major areas of discharge been identified and mapped, if not how can the impact be assessed?
The major areas of discharge are known – the modelling suggests that 23 ML/d of the total 37 ML/day inflows and outflows to the groundwater system discharges to incised rivers in the gorge country to the north. The exact location of these discharge areas is not known (and is not considered to be a major issue) as under borefield pumping, the modelling suggests these discharge volumes do not change. It would be impossible to map all discharge areas, however a representative area may be possible to identify and monitor.
7. There appears to be some discrepancy about impact on discharge areas. It was stated at the meeting that there will be no downstream effect on the rate or volume of discharge to the Nepean River below the water storages, yet it was stated that the groundwater mainly discharges into the gorge section of the Nepean River. The report states “pumping tests on the bores suggest negligible connection but the predictive modelling suggests a greater contribution over time once the borefield is operational.” Will system yields and system impacts be assessed on predictive modelling or short-term testing results?
The impact of borefield pumping is probably of the order of 200km2 – it does not extend to the storages and does not extend beyond the storages. The gorge section is beyond the area of influence, therefore there is no change to baseflows in this area. The quote from the report refers to the likely impact on baseflows within the area of influence of the borefield only. Groundwater impacts will be monitored to assess the difference between modelling and actual, and then the model will be rerun once more accurate time series data is available for verification purposes.
8. The flows in Nepean River downstream of the water storages are already critically depleted, yet it remains an important habitat for Macquarie Perch (an endangered species listed under the EPBC Act). As all major tributaries are dammed, any base flows in the Nepean are assumed to derive from groundwater discharge. Has the status of this habitat been taken into account in ecological impact assessments?
There will be no impact on groundwater baseflows downstream of the water storages due to pumping the proposed Upper Nepean borefield.
The Government has previously announced that improved environmental releases from Avon Dam will commence by the end of 2006 and from the other upper Nepean Dams in 2009.
9. Considering that the groundwater has been assessed as “mostly ‘modern’ (less than 50 years)” it will have been largely collected during a flood-dominated weather regime. Does the hydrological data that inform the model include the patterns of drought/flood dominated regimes as well as the effects of climate change
The groundwater model can be run in transient mode once more time series data is obtained. At this point of the investigations, the model has been calibrated using actual rainfall data from 2005 and run in steady state mode using even lower Decile 10 rainfall data for the area
10. Will the access regime be able to comply with the NSW Interim River Flow Objective 8 “to maintain groundwaters within natural levels, and variability, critical to surface flows or ecosystems”?
Monitoring programs will be designed to monitor water levels and stream flows. The predictive modelling suggest for the most likely base cases that the impacts to surface water are acceptable and manageable.
11. The environmental flow regime for the rehabilitation of the Nepean River which is to be implemented under the Water Plan, was designed on the very important assumption that the flows would be protected so that they would deliver the needed benefits to the river. The HNRMF discussion paper on this matter noted that: “This [protection] applies not only to environmental flow releases from the water supply dams, but also to other water sources within the system, including tributary flows, natural runoff and groundwater.” If groundwater contributions to the Nepean River are reduced, will further compensatory releases be added to the environmental flow release regime?
In this borefield proposal, groundwater baseflows will only reduce slightly in the immediate vicinity of the borefield. Further downstream, the flows will actually be greater than expected under the severe drought conditions because of the run-of-river transfer of groundwater using the major streams. These discharges will act as compensatory flows for those river sections between the borefield and the storages. There is no direct impact downstream of the storages.
If there is assessed to be any net impact on dam inflows this will be taken into account when making releases from the dam.
12. The transfer the water to the dams via creeks & the Nepean River will affect the hydrological and ecological balance of those streams. Why is this not mentioned in the environmental impacts?
Groundwater naturally discharges to the main streams (especially downgradient as discussed above) and hence the riverine ecosystem is already somewhat adapted to groundwater. However the balance will change and there is not much detail in the current ecosystem reports. This is one of the main focuses in the detailed ecosystem report.
13. The environmental flow regime to be released from the storages will be designed to reflect the natural features of the in-flows to the storages in magnitude, frequency, rate of rise and fall, seasonality, duration and variability. How will the natural inflows be determined when they are being radically modified by reduced baseflows and run-of-river transfers?
The proposed groundwater transfer volumes (maximum 50 ML/day) are small in comparison with the volume of rainfall runoff and Shoalhaven transfers. It is not expected that periods of groundwater pumping and its transfer via the rivers will influence the environmental flow regime for releases from the dams. However the rates and volumes of pumping will be known and, if significant, can be taken into account in setting the environmental flow release rules
14. The reports expose quite divergent figures and timeframes for proposed pumping regimes and yields. What constitutes the sustainable yield? Is this the rate and volume of groundwater that can be sustainably extracted, or does it relate to an acceptable level of ecological sustainability associated with a volume and rate of extraction? It should be clearly spelt out that the water extraction licence will contain provisions to ensure that pumping is always sustainable and will not continue if drought conditions go beyond three years
Sustainable yield (in aquifer management terms) is generally referred to as the long-term recharge to a regional groundwater source given a particular planning timeframe. It also is assessed on the basis of social and economic criteria. It is usually expressed as a volume per annum. The term includes both water for the environment and water for consumptive uses (and there is a priority of use approach for different consumptive uses). The specific management requirements that will apply to any borefield development will be determined by DNR on the basis of the scientific studies completed to date, and any additional studies and longer term testing that is undertaken. The licence would reflect all requirements considered necessary to ensure sustainability.
15. Given the high levels of uncertainty an adaptive management approach is vital. Page 53 of the technical report indicates that the operation of the bores will be informed by pumping then modelling, and continued monitoring of borefield performance. Will it also be informed by environmental information, for example if pumping is found to impact swamps and creeks?
Yes, monitoring of ecosystem health will also be an important aspect of the adopted borefield monitoring approach. A key issue will involve separating ecosystem impacts that are related to severe drought from impacts that are directly related to borefield operation
16. The report states that the actual number of licensed bores in use is unknown – will this be verified to determine social impact? Will the number of unlicensed bores also be identified?
SCA is planning to commission a property survey in the coming months to locate existing bores (both licensed and unlicensed), abandoned bores, bores in use (purpose and to what extent - frequency and volume of use). The study may also be extended to include springs, dams and creeks that are spring fed
17. What investigations will be undertaken in regard to artificial recharge?
As this preliminary stage, the only study that has been commissioned is a desktop study that investigates the feasibility of artificially recharging fractured rock aquifers. This relates to the technologies that may be appropriate for this type of groundwater system in this setting given the local water sources and water quality that are available.
18. As groundwater is a ‘drought’ contingency and not an augmentation of supply, will it only be accessed in conjunction with at least the continuation of existing water restrictions?
Yes, groundwater use is only proposed in cases of severe drought and it is unlikely to be used in advance of the dam storage levels reducing below 40%. Other measures including announced water restrictions are key to reducing the water demand.
19. Is the action “to investigate the construction of borefields if the total volume of the SCA storages falls to around 40% of capacity” permitted under Part 5 of the EP&A act, or will it only occur after the formal environmental assessment and public exhibition phase?
Investigations can continue to be assessed using the existing SEPP and under part 5 of the EP & A act. If the Government decides to proceed with borefield development, then the planning approval process will involve a Part 3a application under the EP&A Act followed by an environmental assessment report and formal exhibition period to allow for further public consultation and submissions.
20. At what stage does the proposal require a water extraction license?
It is expected that once the study proceeds beyond the investigation stage and full borefield development is proposed that an amendment to SCA’s water management supply license under Part 9 of the Water Act will be required. This will occur in parallel with the formal planning approval process.
Ian Tonking
14/7/06
1. It appears that no information has been assembled as to local usage of groundwater, either actual, projected or otherwise. This is of concern given the statement that “basic landholder rights (stock and domestic) and indigenous purposes are afforded the highest level of protection”. (2006 Metropolitan Water Plans, p.89 and Technical Overview Report p.47) Thus at p.44 of the Technical Overview there is a statement “there is little private development of deep groundwater in the upper catchment. There are around 50 licensed bores within 5 km [of the proposed bore field], however the actual number in use is not known.”
If the requirements of the Department of Natural Resources for sustainable use are to be observed, and there have already been embargoes placed on new bore licences in the Parish of Mittagong because of “over use” [ref introductory slides], how can any assessment of the likely local demand be made if current usage and likely trends have not been explored?
There are no reporting requirements to DNR under current bore licences regarding the status of bores and the actual use of groundwater. Within the next 6 months it is planned to conduct a property survey of all properties within a defined radius (probably 2kms) of the most likely borefield layout (advice required from CRG in this regard).
The DNR embargo on new bore licences applies to Commercial licences only – trends in stock/domestic use are not normally factored into this DNR management response
The DNR decision to embargo certain areas is also based on expected trends given the current volumes allocated (not to be confused with actual usage) (or likely to be allocated for basic rights, indigenous and drinking water purposes if these are likely to grow substantially)
SCA would be grateful for any private records regarding actual groundwater use in recent years from private bores – this data will be collected at the time of the proposed property surveys
2. While statistics concerning lower water usage in Sydney (as outlined in the 2006 Metropolitan Water Plan) are encouraging, it appears to be taken for granted that Sydney will continue to grow in the uncontrolled way that we have observed in recent years. Recently the NSW Government announced the release of 40,000 new home sites in Western Sydney as the first stage of a programme which appears to involve occupying the remaining farmlands of the Cumberland Plains with houses. At the rate of usage assumed in the Plan (426l per capita per day), assuming three persons per new house, this release would increase Sydney’s demand by 18.65bn litres a year, slightly more than the projected production from the Upper Nepean bore field. On one view the present proposal is designed to cater for the uncontrolled expansion of housing in Sydney and nothing else. Perhaps “uncontrolled” is the wrong epithet, since the increase is not only approved but promoted by the Government. No doubt it will be said that certain requirements or restrictions will be placed on the 40,000 new homes by way of tanks and restrictions, but there appears to be no suggestion that they will be self-sufficient, or anything approach it, in terms of water demand.
Issues here are broad strategies under the Government’s MWP. There is no specific question regarding groundwater, suffice to say that:
Groundwater is to be used as a severe drought water source only
Additional groundwater sources apart from the identified Upper Nepean and Leonay sources may be identified and developed some time in the future to provide additional water if the present initiative is successful
