Toowoomba South Basalts (Zones 1 & 2)

Groundwater Status Review 2020

Contents of this presentation1. Key messages2. Map of the area3. Review groundwater levels4. Proposed Limitations5. Opportunities for further discussion

Steven Williams, Water Services,Toowoomba

Groundwater Status Review 2020Key Messages

• The Toowoomba South Basalts has been broken up into two zones to reflect the differences in aquifer response and to improve management decisions.

• There has been a slight reprieve for landholders with above average rains in January and February 2020 – with some local positive water level response.

• Recent rains may have also reduced the short-term demand on groundwater.

• Generally across the southern basalt area, longer-term aquifer storage has declined to levels nearing lowest on record.

• Should average (or above average) rainfall not occur over winter 2020 and summer 2020-21, further limitations are very likely for the 2021-22 water year.

Groundwater Status Review 2020

• Limitations are based upon a number of considerations• Information of sustainable yield of the aquifer such as:

• Long-term storage depletion• Expected recovery time after rainfall and recharge events• Comparison of current water levels to aquifer intake zones (i.e. areas of

higher permeability such as fractures/weathered layers)• Water level trends• Water demand and extraction• Forecast seasonal conditions• Balancing access to the resource for multiple stakeholders (e.g.

irrigators, town water supply, stock and domestic users)

• Zone 1 has 388 water licences totalling a volume of 15,889 ML of entitlement.

• Three main catchments in Zone 1 based on watershed drainage. These being: Hodgson Creek Westbrook Creek Linthorpe valley and uplands

• The monitoring bore hydrographs that were selected for each area show a typical aquifer response within the catchment.

• Three main aquifer layers are present across most of Zone 1 which are typically found at 0-20m; 50-60m and 70-100m. These are made up of weathered, fractured and vesicular (honeycomb) basalts.

Toowoomba South Basalts – Zone 1

• The Toowoomba South Basalts are within the green outline on the map.

• There is a total of 17 monitoring bores located in Toowoomba South Basalts which are dipped quarterly each year.

Toowoomba South Basalts – Zone 1

SWL (March 2020): -7.85 m

Depth of basalt: 54m

WL trend: Declining since 2013; recovery of +0.47m in response to February rain.

WL change since Jan 2019: +0.15m.

Note:Measurement Units – metresRN = Registered NumberSWL = Standing Water LevelWL = Water Level

RN 42231597 Cambooya Felton Rd

SWL (March 2020): -18.92m

Depth of bore: 143m

WL trend: Declining – levels have fallen 13m since winter 2013. Water levels below millennium drought levels in 2009.

WL change since Feb 2019: +1.08 m rise

RN 42231592 Watts Siding Rd (Greenmount)

SWL (March 2020): -7.22m

Depth of basalt: 95.3m

WL trend: Stabilising since 2018 however at levels lowest in recorded history.

WL change since Feb 2019: -0.15m

RN 42230972A Umbiram Banchory Rd

SWL (March 2020): -40.15m

Depth of basalt: 106.7m

WL trend: Declining – bore heavily impacted by nearby pumping. Consistent winter recovery levels for past 3yrs

WL change since Feb 2019: -2.5m

RN 42230969A Umbiram Rd (Wyreema)

SWL (March 2020): -45.85m

Depth of bore: 106.7m

WL trend: Sharp decline however responds quickly to rainfall events.

WL change since Feb 2019: +2.7m.

RN 42230963A FGG Couper Rd (west of Westbrook)

SWL (March 2020): -16.26m

Depth of bore: 126.0m

WL trend: Decline however good response to rainfall event in February 2020

WL change since Feb 2019: -2.0m

RN 42231596A Linthorpe Valley Rd

Toowoomba South Basalts – Zone 2

• Zone 2 (west of Toowoomba) – 176 water licences totalling a volume of 12,018 ML

• Similar formation to Toowoomba North Basalts area. Two main aquifers: Formations above 30m (contain upper weathered and fractured segments) Formations between 30m – 100m (contain the lower semi-confirmed

segments)

• Two main areas that were of similar groundwater geology characteristics:• Mt Irving area – lower aquifer groundwater levels (30m-70m) • Aubigny area

• The monitoring bore hydrographs that were selected for each area show a typical aquifer response within the catchment.

Toowoomba South Basalts – Zone 2

Mt Irving area SWL (January 2020): -13.69m

Bore depth: 56.1m

Aquifers: 22.2m to 24.1m41.0m to 42.3m

WL trend: Sharp decline during 2013-2019; approaching lowest levels on record.

WL change since March 2019: -0.54m

RN 42230981A – Jondaryan Mount Tyson Rd

SWL (March 2020): -10.22m

Bore depth: 61mAquifer: 32.0m to 35.0m

WL trend: Decline

WL change since February 2019: -0.67m

RN 42230936 – Jondaryan Mount Tyson Rd

SWL (March 2020): -12.87m

Bore depth: 37.9m

Aquifers: 12.5m to 27.7m

WL trend: Decline since 2013

WL change since February 2019: -0.81m

RN 42230937A – Jondaryan Mount Tyson Rd

SWL (March 2020): -12.87m

Bore depth: 37.9m

Aquifers: 12.5m to 27.7m

WL trend: Decline since 2014

WL change since February 2019: -0.81m

RN 42230938A – Toowoomba Cecil Plains Rd

Aubigny AreaSWL (March 2020): -18.15m

Bore depth: 110m

WL trend: Gradual decline

WL change since February 2019: -0.73m however there was 1.0m rise due to recent rain in Feb 20.

RN 42231593A – Oakey Crosshill Rd

Groundwater Status Review 2020Summary for Zones 1 & 2

• Generally across the Toowoomba South basalts, longer-term aquifer storage has declined in both upper and lower aquifers.

• Monitoring bores within Zone 1 indicated sharp water level responses (+0.5m –3m) to the recent creek flows in all three catchments.

• Typically, most of the shallow basalt aquifers in Zone 2 take 3 – 6 months after good rainfall events to respond and the deeper aquifers up to 12+ months.

• In some areas it appears as there is still a good saturated depth of the aquifer but this does not necessarily correlate with how much supply is remaining.

• Little to no water level response in bores located in the mid to upper slopes across both zones with depleting bore yields as a result.

• Above average rainfall will be required to see any aquifer recovery in these areas.

Groundwater Status Review 2020Proposed Limitations• Current groundwater limitations are: Zone 1 - 60% and Zone 2 - 70% • Proposal to CHANGE the limitations for the 2020-21 water year:

• Zones 1 & 2 - 60% of the nominal entitlement on your water licence.• Pumping times: 2 days x 12 hour periods commencing at 5pm on

Tuesday – 5am Wednesday and 5pm on Thursday – 5am Friday (total 24 hours).

• Licensees can apply for an Individual Notice (IN) to either install a meter, or demonstrate a need to have different pump days/hours (max 24 hours).

• Until licensees receive an IN they must comply with the general limitations notice.

• Existing IN holders need to reapply every year.• New limitations notice release date - late June 2020.• Limitations do not apply to the take of water for Stock and Domestic purposes

The department would value your feedback on

the limitations consultation via a short feedback

survey on the website.

Thankyou

To request additional information or make a time to discuss your specific situation please call the departmental on:

Phone - 4529 1394