GROUNDWATER MONITORING REVIEW AND RATIONALISATION … · caused by negligence or otherwise, or any loss, however caused, arising from reliance on, or the use or release of, this information

GROUNDWATER MONITORING REVIEW AND RATIONALISATION 2000-2012:

TOOLIBIN LAKE CATCHMENT

Jasmine Rutherford, Ronan O’Brien and Jackson Carr

DEPARTMENT OF PARKS AND WILDLIFE

HYDROLOGY REPORT

WCP-HR-2017-002

June 2017

For more information contact:

Jasmine Rutherford Senior Hydrologist Wetland Conservation Program Department of Parks and Wildlife (DPaW) 17 Dick Perry Avenue Kensington, Western Australia 6151

Disclaimer

While all reasonable care has been taken in the preparation of the information in this document, the Chief Executive officer of the Department of Parks and Wildlife and its officers and the State of Western Australia accept no responsibility for any errors or omissions it may contain, whether caused by negligence or otherwise, or any loss, however caused, arising from reliance on, or the use or release of, this information or any part of it.

Copyright © Department of Parks and Wildlife, 2017

Recommended Reference

The recommended reference for this publication is:

Rutherford, J.L. O’Brien, R. and Carr, J. (2017). Groundwater Monitoring Review and Rationalisation 2000 - 2012: Toolibin Lake Catchment. Prepared for the Wheatbelt Region by the Wetlands Conservation Program, Science and Conservation Division, Department of Parks and Wildlife, Kensington, Western Australia.

Acknowledgements

The following are acknowledged for their assistance at various stages during the development of this review: Ray McKnight, Maria Lee, Adrian Pinder, Richard George, Neil Milligan, Peter Lacey, Shawan Dogramaci and Darren Farmer.

Cover photo of bore TL26 courtesy Mariajose Romero-Segura; Toolibin Lake 2014

Table of contents

1. Background ......................................................................................................................................... 7

2. Purpose and Scope .............................................................................................................................. 8

3. Methodology ....................................................................................................................................... 8

3.1 Groundwater data sourcing .......................................................................................................... 8

3.2 Aquifer mapping and assignment to monitoring bores ................................................................ 8

3.3 Error sources and limitations ........................................................................................................ 9

3.3.1 Infrastructure ......................................................................................................................... 9

3.3.2 Timing and frequency of data collection ............................................................................... 9

3.3.3 Data collection and quality assurance protocols ................................................................. 11

3.4 Conceptual ideas and frameworks to assess groundwater level trends .................................... 11

4. Hydrograph analysis ...................................................................................................................... 13

4.1 Qualitative assessment ............................................................................................................... 13

4.1.1 Toolibin hydrograph generator ............................................................................................ 13

4.1.2 Trend classes ........................................................................................................................ 13

4.2 Objective assessment ................................................................................................................. 14

4.2.1 Statistical tools ..................................................................................................................... 14

4.2.2 Hydrograph classification ..................................................................................................... 14

4.3 Limitations ................................................................................................................................... 14

4.4 Results – hydrograph trends ....................................................................................................... 14

4.4.1 Data trends – qualitative approach ..................................................................................... 15

4.4.2 Data trends – objective approach ........................................................................................ 15

5. Spatial trends ................................................................................................................................ 16

6. Aquifer response – quantifying change to assess risk .................................................................. 17

7. Review discussion ......................................................................................................................... 19

7.1 Limitations ................................................................................................................................... 21

8. Monitoring recommendations ...................................................................................................... 21

8.1 Rationalised groundwater monitoring program ......................................................................... 21

References ............................................................................................................................................ 24

Tables

Table 1 Frequency of groundwater measurements in the TLC............................................................. 10

Table 2: Hydrograph trends for the 230 shallow bores assessed in the TLC ........................................ 15

Table 3: Hydrograph trends for the 86 deep bores assessed in the TLC .............................................. 15

Table 4: Number and percentage of deep and shallow bores within the three main classes of rainfall CDFM response (2000 to 2012) ............................................................................................................ 18

Table 5: Number and percentage of deep and shallow bores within the three main classes of rainfall CDFM response (2000 to 2012) ............................................................................................................ 19

Table 6: Groundwater Management Zones showing monitoring trends, current and predicted risks under the current climate and major groundwater processes. ........................................................... 23

Figures

Figure 1: TLC monitoring bores assessed in this groundwater monitoring review and rationalisation .............................................................................................................................................................. 26

Figure 2: Number of discrete groundwater level measurements (1977 to 2012). ............................... 27

Figure 3: wickepin BOM weather Station (010654); a. annual rainfall 1912 to 2013 (from muirden and coleman 2014); b. wickepin rainfall CDFM (1911 to 2012) and c. . ............................................... 27

Figure 4: Bore TL28 hydrograph, water level data overlain on rainfall CDFM...................................... 29

Figure 5: Toolibin hydrograph generator, showing information for bore TL06 ................................... 29

Figure 6A and B: Maps of idealised shedding and receiving areas shown in context to the 1980’s “Toolibin Flats” valley floor model (6A) and recent slope mapping using LIDAR data (6B) ................. 30

Figure 7: Map displaying shallow and deep bore hydrograph trends overlying LIDAR slope <1degree .............................................................................................................................................................. 31

Figure 8: Map displaying shallow bore hydrograph trends overlying LIDAR elevation <310mAHD ..... 32

Figure 9: Map displaying deep bore hydrograph trends overlying LIDAR elevation <310mAHD ......... 33

Figure 10: Monthly rainfall CDFM showing superimposed drying (blue) and wetting (light red) trends and monthly water level data collected from bore TL22 ..................................................................... 34

Figure 11: Map showing changes in groundwater levels (2000 to 2012) for deep and shallow bores that exhibit a rainfall CDFM trend. ....................................................................................................... 35

Figure 12: Map showing changes in groundwater levels (2000 to 2012) for deep and shallow bores that exhibit a rising or rainfall CDFM-rising trend ................................................................................ 36

Figure 13: Map showing average rates of groundwater level rise in deep and shallow bores (2000 to 2012). .................................................................................................................................................... 37

Figure 14: Map showing the location of Groundwater Management Zones, TLC rationalised monitoring program -shallow bores trends (2000 to 2012), valley floor extent and uplands riparian zone (<1 degree slope); TLC dpaw estate monitoring shown in blue bordered inset .......................... 38

Figure 15: Map showing the location of Groundwater Management Zones, TLC rationalised monitoring program -deep bores trends (2000 to 2012), valley floor extent and uplands riparian zone (<1 degree slope); TLC dpaw estate monitoring shown in blue outlined inset .................................... 39

HYDROLOGY GROUNDWATER MONITORING REVIEW AND RATIONALISATION 2000-2012 – TOOLIBIN LAKE NDRC

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Executive Summary

Toolibin Lake is a Ramsar listed wetland and the lake’s vegetation community is also classified as a threatened ecological community under the Commonwealth Environment Protection and Biodiversity Conservation Act (1999). Due to changes in the water balance induced by land clearing in the 1800’s the lake’s fresh water status is threatened as well as the health of the vegetation. In 1994 the Toolibin Lake Catchment (TLC) Recovery Plan set a hydrological criterion on groundwater levels beneath Toolibin Lake and the Toolibin Flats, which saw the rise in the number of monitoring bores installed to measure the efforts of groundwater, recharge reduction strategies. Many of the current 460 monitoring bores are nearing the end of life or are not designed to directly provide data relevant to the original management goal. This study will review groundwater data and trends and identify bores that are now redundant. The output will be a provisional rationalised groundwater monitoring program that is focused on the original management goal and can be updated following the completion of the upcoming new conceptual and numerical groundwater models.

To achieve this aim groundwater data were sourced and compiled from an archived HYDSTRA database, aquifers assigned to bores, error and limitation issues identified, groundwater hydrographs produced and trends assessed, volumetric changes in groundwater levels examined spatially, redundancy identified and a subset of monitoring bores compiled to form the provisional rationalised monitoring program.

Bores were assigned a shallow aquifer (<12 metres below ground level) and deep aquifer (>12 metres below ground level) status, with the main potential sources of error and interpretation limitations identified as bore construction, maintenance, the timing and frequency of data collection and the potential for the introduction of human error.

Hydrograph and spatio-temporal trends were interpreted and compared with predictions made by previous researchers. These mainly focused on determining if groundwater level increases related to ‘past’ recharge events, incident rainfall or incident rainfall supplemented with surface water sourced locally and/or from upgradient areas (taking into consideration constraints introduced by landscapes and anthropogenic features (e.g. roads)).

The timing and frequency of groundwater data collected made them best suited to a qualitative hydrograph analysis, with data compared against a rainfall CDFM model. Results identified seven main trends; rainfall CDFM, rising, discharge, pump affected bores, dry, stable and no trend. Low sampling frequency, too few sample points and erroneous data limited the number of bore sample being assessed to 316 in number, with rainfall CDFM being the dominant trend in shallow bores (68%) and rising being the dominant trend in deep bores (49%).

Spatio-temporal results validate some of the conceptual model ideas presented by Cattlin (2006) and all ideas tested in DEC-DAFWA (2008), with roads having a localised affect compared to the broader influence of incident rainfall. Valley floor aquifers (shallow and deep) were found to display a dominant rainfall CDFM response and deep aquifers in the upper valleys and hill slopes generally show a rising trend. Where the rainfall CDFM trend is present, groundwater levels have been decreasing since 2000, the magnitude of this decrease ranging from 1-2, or 2-3 metres.

The rates of rise observed in deep aquifers in upland areas and risk of groundwater discharge is different in the east compared with the north and western areas. In the east the average rate of rise


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to the east is around 0.2m/yr and depth to groundwater between 7 to 13 metres below ground level, resulting in discharge at the 2m extinction depth within the next 25 years. Shallow aquifers to the west and north are rising at rates between 0.1 and 0.3 m/yr, shallower groundwater exists with average depth to groundwater around 4 metres below ground level in low slope areas. Perennial discharge predicted to occur in the next 10 to 20 years at the current rates of rise.

In Toolibin Lake groundwater levels in shallow aquifers tend to exhibit limited pumping effects, showing a dominant rainfall CDFM trend that has maintained a groundwater level maximum of around 1.5 to 2.5 metres below ground level. Deeper bores located within 50 metres from pumping bores show more pronounced, but generally short lived, pumping effects.

Information from this groundwater review shows the Toolibin Catchment displays common trends within a simple two aquifer (shallow and deep) and landscape characterisation (valley floor and uplands), with more complex aquifer responses in and around Toolibin Lake. Some of the variation in the valley floor is likely to relate to data measurement error as well as processes outlined by Cattlin (2006).

A total of 74 bores were selected to be part of the provisional rationalised groundwater monitoring program, with optimal bores firstly prioritised bores within DPaW Estate (located mainly in the valley floor) followed by suitable bores located upgradient that can provide information on potential water and salt fluxes.


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1. Background Toolibin Lake is a Ramsar listed wetland and the lake’s vegetation community is also classified as a threatened ecological community under the Commonwealth Environment Protection and Biodiversity Conservation Act (1999). The Lake is a perched wetland, a hydrological setting that encourages vegetation to flourish with the periodic inundation of fresh to brackish water. The clearing of native vegetation in the 1800’s altered the catchment water balance and provided more water for groundwater recharge, which filled aquifers and encouraged groundwater discharge. This change in dynamics resulted in the widespread death of vegetation due to waterlogging and salinisation, particularly in the valley floor where Toolibin Lake is located.

In 1994 the Toolibin Lake Catchment (TLC) Recovery Plan developed a set of hydrological criteria to guide management actions and measure progress towards achieving goals (Toolibin Lake Recovery Team and Toolibin Lake Technical Advisory Group 1994). One of the important hydrological criteria for groundwater was to ensure the minimum depth to the water table beneath Toolibin Lake and Toolibin Flats in spring (when the lake is dry) was at, or below, 1.5 metres from the ground surface. This required groundwater levels to be lowered by enacting management actions that would reduce groundwater recharge. In the TLC this involved revegetating areas up gradient and within the lake, designing engineering structures to divert surface water and abstracting groundwater beneath the lake and piping it south to Lake Taarblin for disposal.

Groundwater, surface water and entrained salts in the TLC move from east and west tributaries and aquifers into a north-south trending central valley where Toolibin and other lakes are positioned. Groundwater monitoring bores have been installed in the lake and broader catchment to understand these variable fluxes as well as assess the performance of the revegetation, groundwater pumping and the surface water diversion.

The installation of groundwater monitoring bores commenced in the 1970s and over the past forty years over 460 monitoring bores have been installed to measure the success of different recharge reduction strategies. As a result bore field design, construction and information collected during and after bore installation is highly variable.

Many monitoring bores are now redundant due to aging infrastructure, the completion of projects and changes in resourcing. This project has been designed to review groundwater data trends and identify bores that are now redundant and produce a provisional rationalised groundwater monitoring program that is focused on the original management goal and will be updated following the completion of the upcoming new conceptual and numerical groundwater models.


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2. Purpose and Scope The main objective of the work undertaken in this report is to assess broad scale groundwater monitoring trends and develop a provisional rationalised groundwater monitoring program.

To achieve this aim the following tasks were undertaken;

1. source and compile groundwater monitoring data, 2. review lithology and assign aquifer, 3. identify sources of error and interpretation limitations, 4. produce groundwater hydrographs and assess trends, 5. examine change in groundwater levels over two static time periods and interpret spatial

trends, 6. identify areas where there is redundancy in the groundwater monitoring network and 7. select a suitable subset of monitoring bores to form a rationalised TLC monitoring network.

3. Methodology 3.1 Groundwater data sourcing

Groundwater data for the Toolibin Lake Catchment (TLC) are archived in the industry standard database HYDSTRA (http://kisters.com.au/hydstra.html).

Bore information and monitoring data used in this project were sourced from a Hydstra Site Table and spreadsheet of time series data prepared for the August 2011,Toolibin Lake NDRC Groundwater Data Review (Coleman and Wroe 2011). Additional groundwater data, from August 2011 to December 2013, were provided by the Great Southern District and entered together with the HYDSTRA time series dataset into a single Excel spreadsheet where data were graphed and analysed.

The TLC HYDSTRA database contains groundwater records for 456 bores. A subset of 316 bores had sufficient monitoring data to allow their assessment in this project. The locations of these bores are shown in Figure 1; relative to DPaW Estate, the distribution of ephemeral drainage channels and lakes and other features resolvable on a February 2011 airphoto mosaic at 1:140000 scale and catchment management boundaries developed by Cattlin (2004).

3.2 Aquifer mapping and assignment to monitoring bores In the TLC Tertiary to Quaternary age valley floor sediments identified in drilling programs in the 1990’s became target aquifers for both monitoring and abstracting groundwater due to their higher hydraulic conductivities and transmissivities. These inset valley sediments have been deposited by different processes (dominant fluvial and lacustrine) and they are located where the crystalline basement rock is incised or has low variation in relief. Tertiary aged sediments (Pliocene and Miocene in age; ~20 to 2 Ma) are characterised by fluvial sands (coarse to fine), silts and sandy clays and lacustrine clays (De Silva 1999a & Dogramaci 1999). Regolith materials overlying these sediments are generally thin and unsaturated comprising of aeolian sands, mixed alluvial clayey sands and lacustrine clays (Verboom 2003).

Aquifers within the weathered crystalline basement rock (saprolite) generally have lower hydraulic conductivities compared with the overlying sediments. Physical and chemical data collected from saprolite aquifers in the Toolibin Lake catchment confirm their bulk properties allow them to store high volumes of water and salt, but their low permeability’s prohibit high water and salt yields (De

http://kisters.com.au/hydstra.html


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Silva 1999b). Higher hydraulic conductivities are localised and may occur in areas of extensive geological faulting, near the basement contact or where thicker saprolite profiles have been stripped by erosion on valley flanks and rises (e.g. George and Bennett 1995). There are few nested bores measuring the connectivity between the saprolite aquifers and sediments, but where there is information data indicate that the aquifers are connected where thick lacustrine clay sequences are absent.

In the TLC, the mapping of aquifers within the saprolite and overlying deep and surficial sediments commenced in the 1970’s and over the past forty years has been the subject of around 19 drilling and several aquifer testing programs (Rutherford et. al.., 2016). Data and information on aquifers collected from drilling programs is often missing, which complicates the assignment and grouping of bores for hydrograph analysis and the development of reliable 2D or 3D aquifer maps.

Bores with lithological information show that in the valley floor most shallow bores intersect a thicker sequence of sediments than bores located on valley rises, with screened sections in the valley floor being on average ten metres below ground level. This conceptualisation was used in Dogramaci et. al. (2003) and is applied in this project to address the lack of spatial and point source lithological and hydrogeological information. Monitoring bores are grouped into two broad classes;

• shallow aquifers (bores with a base of aquifer screen at a depth < 12 metres below ground level) and

• deep aquifers (bores with a base of aquifer screen at a depth >12 metres below ground level.

More detailed geological and hydrogeological mapping using recent airborne and borehole geophysics will be completed in the production of a TLC conceptual model (Rutherford in prep), which will then be incorporated into a numerical groundwater model.

3.3 Error sources and limitations 3.3.1 Infrastructure Error may be introduced into groundwater monitoring measurements where bore infrastructure hasn’t been constructed according to criteria outlined in “Minimum Construction Requirements for Water Bores in Australia” (NWC, 2012a). If these criteria are followed the effective life for bores that receive minimal or no maintenance is estimated at 25 years, for bores constructed of steel materials, and 50 years for those constructed from PVC (NWC, 2012b).

Most monitoring bores in the TLC program are constructed from PVC and generally comply with NWC (2012a) criteria but are noted to deviate in relation to bore sealing, development and headworks (Romero-Segura and Rutherford, 2016). A review of drilling notes and a subsequent field audit identifies potential sources of error introduced to measurements due to bore development times being short, few bores are grout sealed, bore collars don’t provide adequate protection from vertical leakage within the annulus and PVC casing extending above ground is not always protected from potential damage (NWC, 2012a). Selecting cheaper options has allowed the TLC programs to install more bores that as a consequence may not provide accurate monitoring data. This was considered in the interpretation of hydrograph and spatial data in Sections 4, 5 and 6.

3.3.2 Timing and frequency of data collection An important limitation on interpreting groundwater level trends is the timing and frequency of collecting groundwater measurements.


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Groundwater monitoring data are collected across the TLC and over the length of the programme the number of discrete measurements has generally increased as more monitoring bores were installed. Figure 2 shows the number building to a peak in the 1990’s, with small reductions in measurements occurring approximately every five years.

Of the 316 bores examined in this study, 285 were associated with a monitoring program where data were collected on a regular basis. The frequency of data collection is detailed in Table 1 below; showing almost 80% of measurements are biannual or quarterly, with the 17% of monthly measurements restricted to a small part of the catchment, Toolibin Lake.

TABLE 1 FREQUENCY OF GROUNDWATER MEASUREMENTS IN THE TLC

A number of physical properties influence net groundwater recharge and groundwater level responses, including the intensity of local incident rainfall, the specific yield/water retention characteristics of soils, antecedent soil moisture, depth below the ground/natural surface to the water table, groundwater gradients, rainfall interception by vegetation and delivery of and/or proximity to surface water conveyances and/or topographic depressions. Most of these processes would require daily, or in some cases hourly, monitoring data to be collected to begin to understand and quantify the significance of different physical processes on the water balance.

The majority of groundwater level data collected in the TLC are discrete manual measurements and their frequency of collection is fit for purpose to assess seasonal (biannual) aquifer recharge and discharge. This requires groundwater level minimum and maximum levels to be measured (e.g. end of summer minimum water levels (March/April) and end of winter maximum water levels (Sept/Oct) and trends compared against local rainfall data.

Dogramaci and others (2003) undertook hydrograph analyses in the TLC and compared groundwater level trends for fourteen bores (data collected between 1989 to 2000) against rainfall data from Bureau of Meteorology (BoM) Wickepin weather station (Station 10654, located ~18 km from Toolibin Lake) (http://www.bom.gov.au/climate/data/). Results showed that the sample number and frequency of data collection were both sparse, but sufficient to interpret seasonal trends and the dominant groundwater processes driving aquifer responses.

The work in this project follows a similar methodology to Dogramaci et. al. (2003). Daily rainfall from the BoM Wickepin weather station were sourced and a rainfall cumulative deviation from the mean (CDFM) model produced. Groundwater monitoring data were then overlain and compared with the CDFM trend. Rainfall CDFM is the common metric used for this purpose (Yesertener, 2005; Ali et. al.., 2010). Information on drying and wetting climate trends within the CDFM, identified as respective negative and positive slopes within the time series, were also noted (Figure 3).

The application of the rainfall CDFM method follows the idea is that there is a good relationship between groundwater levels measured at a bore and surplus incident rainfall. Deviation from this relationship indicated that other hydrological processes are important, such as surface water interaction/contribution, groundwater pumping and groundwater throughflow. For example, Figure 4 shows monitoring data from bore TL28 overlain on the rainfall CDFM series (Wickepin rainfall, monthly mean 1969 to 2013). There is a good relationship between the rainfall CDFM and the


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discrete monitoring data, which indicates incident rainfall is the major driver of groundwater recharge.

3.3.3 Data collection and quality assurance protocols To have confidence in interpreting the TLC groundwater measurements archived in the HYDSTRA database they need to be supported by metadata that details how they have been collected and quality assured. It is essential that data is collected using appropriate standard operating procedures (SOPs), collated and quality assured by trained hydrologists and managed within a suitable (industry standard) database.

In the TLC there have been a number of stakeholders responsible for the installation of bores and the collection, quality assurance and management of groundwater data. Changes in custodianship of infrastructure and data can affect data quality, with error introduced through limited training, a different interpretation of SOPs, incorrect or modified use of equipment and poorly maintained equipment and infrastructure. To combat this problem spatio-temporal trends are examined in Section 5 and 6 to assess the quality of data collection and quality assurance.

3.4 Conceptual ideas and frameworks to assess groundwater level trends

Three main hypotheses on TLC groundwater level trends are reported in Dogramaci et. al. (2003), Cattllin (2006) and DEC-DAFWA TAG Meeting (2008). Major ideas put forward by these authors are outlined below and used as a reference to interpret results in Sections 5 and 6.

Dogramaci et. al. (2003) reported that aquifers are more responsive to incident rainfall and evapotranspiration than the lateral flow of groundwater and surface water. Three main hydrograph trends observed;

1. Steady groundwater rises tend to dominate the uplands due to a ‘past’ recharge pulse 2. Seasonal rainfall trends are common in shallow valley floor aquifers and 3. Stable trends in valley floor aquifers occur where water levels are near the land surface due

to compatible rates of evaporation and groundwater rise.

The conceptual model of Cattlin (2006) put forward ideas that expand on Dogramaci et. al. (2003) above that the “fluctuation of the watertable is caused through a combination of runoff distribution and catchment wide recharge processes”. In this work terrain analysis was deemed to be an important factor in analysing groundwater trends and recharge, with the two main landscape units being;

• rainfall-runoff (shedding); in upper slope areas, upgradient from the main drainage lines, characterised by high runoff/low recharge and slopes greater than one percent and,

• waterlogging and groundwater recharge (receiving); broad valley flats and valley floors, located downgradient from shedding areas and characterised by low runoff/high recharge and slopes of less than one or two percent.

Cattlin (2006) used a soil-landscape approach to attribute the shedding and receiving areas with information on the relative rates of surface water runoff or groundwater recharge respectively. To achieve this attribution a soil-hydrology map developed by Verboom (2003) was employed. The soil-


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hydrology map had been developed through ascribing hydrological processes to soil units interpreted from airborne radiometric data. It is important to note that the limitations of this form of soil-hydrology mapping is that they require extensive field validations and that without this the outputs are speculative as they have been developed with datasets that only sample the upper few centimetres of materials on the ground surface.

The three major water balance ideas presented by Cattlin (2006) were;

1. Water logging is dominant in the valley floor receiving areas due to the presence of lower permeability soil units (shallow duplex soils grading to grey clays).

2. Degradation of the valley floor, or grey clay areas, is the result of rising watertables that result from additional recharge provided by accumulated runoff derived from upslope shedding landscapes and,

3. Roads that cross flow paths form a barrier and promote local waterlogging and groundwater recharge.

A DEC-DAFWA technical advisory group meeting on the 31st July 2008 agreed that the major controls on aquifer responses were;

1. While wet years may cause runoff, catchment scaled flow does not occupy much of the landscape. Rainfall-recharge and local inundation and waterlogging is more significant as a source of recharge than ‘flooding’ and streamflow, with recharge from in-situ processes expected to be of the order of 5-10% rainfall. In contrast, streamflow is <2-3% of the water balance,

2. Valley floor aquifers in the lower landscape areas of the Wheatbelt catchments since 2000 are now at, or close to, hydrological equilibrium (watertables within 1-2 m). In other areas or in the upper catchment, the water balance is approaching a new equilibrium, with groundwater still rising under upper valleys and hill slopes, and

3. Reduced rainfall since 2000 has resulted in some areas exhibiting falling groundwater level trends. Groundwater levels noted to be decreasing in areas where there is variation in relief (e.g. hillsides). In these areas groundwater levels have decreased from around 1-2m to 2-3m below ground level.

Due to similarities between many of the Dogramaci et. al. (2003) and the DEC-DAFWA (2008) qualitative criteria, comparisons made against DEC-DAFWA in the following sections of this report can also be considered to be in agreement with Dogramaci et. al. (2003).


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4. Hydrograph analysis Hydrograph analysis of groundwater level data involves adopting a mathematical approach to separate groundwater recharge from rainfall from other water balance parameters such as throughflow and evapotranspiration. This can be undertaken quantitatively where high frequency data are available. Discrete data collection in the TLC are more suited to a qualitative assessment, which is completed here together with trial of an automated objective classification.

The qualitative assessment involved visual pattern matching of groundwater monitoring against the Wickepin rainfall CDFM data. Current average annual rainfall in the TLC is around 370mm and apart from summer storms, most rainfall is received in winter months (Figure 3A) (Muirden and Coleman 2014). Treatment of rainfall data to assess the behaviour of surface water is different to groundwater. High rainfall intensity of short lived summer storms creates more runoff/overland flow and stream flow, with major groundwater recharge occurring within ephemeral lakes and areas of low relief. Timeframes that influence aquifer recharge are longer; decadal and seasonal (winter) (Figure 3B and C, Appendix B).

4.1 Qualitative assessment 4.1.1 Toolibin hydrograph generator A groundwater monitoring graphing tool, Toolibin Hydrograph Generator, was developed for this project. The tool operates in MS Excel and displays basic bore information along with and X-Y graph showing the location of the bore (red dot in Figure 5) on an airphoto mosaic. A separate time series graph has two main data series;

• discrete groundwater level measurements, in metres below ground level, and • rainfall CDFM.

The generator provides a sense of landscape position by providing a spatial reference between the bore location, DPaW Estate / biological elements (yellow outline) and ephemeral drainage lines and lake outlines. Erroneous data can be more readily identified, as demonstrated by the outliers present for bore TL06 in Figure 5.

Provision was provided to note the hydrograph trend and relevant comments as well as update in the future and compare with previous interpretations.

4.1.2 Trend classes The seven classes were identified in this work are described below;

• Rainfall CDFM represents aquifers that display a similar relationship with the cumulative deviation from the mean (CDFM) rainfall time series.

• Rising trends show an increasing trend in relation to the rainfall CDFM. • Discharge represents bores where groundwater levels are consistently within the

evapotranspiration extinction depth, which for the TLC is two meters below ground level. • Pump affected bores occur on Toolibin Lake and exhibit trends where the groundwater

levels show sustained reduction in relation to other trends. Bores exhibiting these trends are normally within 100 meters from an operational pumping bore.

• Dry represents bores where groundwater levels are at the base of the bore apart from heavy rainfall events when seasonal aquifers develop.


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• Stable trends are categorised where the trends described above are not evident. • No trend classification is provided to bores where insufficient data exists to identify a trend.

4.2 Objective assessment 4.2.1 Statistical tools A statistical tool was developed to test the qualitative classification of the rainfall CDFM class in Section 3.2.2. Details on the method are outlined in Appendix A.

4.2.2 Hydrograph classification Two additional rainfall CDFM classes were included in this analysis.

• Rainfall CDFM/Rising trends have similar responses to the CDFM time series but also have an underlying rising trend in the groundwater levels.

• Rainfall CDFM (less than 40 samples) was added to cover bores where there was a weak relationship with the rainfall CDFM time series, but a definitive identification wasn’t possible due to a small number of observations (less than 40).

4.3 Limitations The qualitative approach was limited by the skill of the individual assessing the ‘goodness of fit’ between the groundwater and rainfall CDFM datasets. The low frequency data collection affected both the qualitative and quantitative approaches. The quantitative approach encountered the problems outlined below:

• Low sampling frequency; rainfall CDFM values are calculated monthly while, depending on the TLC monitoring program, sampling may occur monthly, three times a year, biannually or annually. The sampling does not always occur at the same time each month, or always as scheduled (months are missed for various reasons). As a result there is no standard time step between measurements to build a standard offset to calculate the best correlation coefficient for each bore. Instead the offsets have to be applied with variation built into them to account for the disparate sampling, for example the offset is 0 where groundwater sampling and the rainfall CDFM occur in the same month and 1 where sampling occurs the month following the rainfall CFDM value used to calculate the correlation coefficient. This results in increased error and a reduction in confidence on the quantitative method.

• Too few measurements; results in the correlation analysis not being sufficiently robust to confidently classify a rainfall CDFM trend. These were classified as No Trend or rainfall CDFM (less than 40 samples).

• Erroneous measurements; due to multiple sources of error the groundwater monitoring data the data were not cleansed prior to undertaking the work in this project (see Section 2.2.4). Outliers will have affected the correlations achieved in this analysis.

4.4 Results – hydrograph trends The results from the trend analysis are discussed and tabulated below. Appendix B shows examples of the seven main classes described in Section 4.1.2 and Appendix C provides assessment details for individual bores.


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4.4.1 Data trends – qualitative approach Of the 316 bores examined, 230 were shallow and 86 deep (see Section 3.2). The classification demonstrated different processes were dominant in the shallow and deep aquifer systems. The distribution of the trends is shown in Tables 2 and 3.

TABLE 2: HYDROGRAPH TRENDS FOR THE 230 SHALLOW BORES ASSESSED IN THE TLC

TABLE 3: HYDROGRAPH TRENDS FOR THE 86 DEEP BORES ASSESSED IN THE TLC

Groundwater levels are rising in almost fifty percent of deep bores compared with around 2% of shallow bores. Relationships with rainfall CDFM is strong in both datasets, the shallow and deep data exhibiting trends of 68% and 30% respectively. It is important to note that for the shallow bore data almost 85% of the rainfall CDFM classifications had less than 40 sample points and therefore there is a need to collect and examine more data to validate the classification. The spatial distribution of areas with more data, and therefore more confidence, is discussed in Section 5.

4.4.2 Data trends – objective approach The quantitative approach was trialled but was found not to be successful due generally due to the lack of samples for individual bores and time lags evident in data where there is higher frequency monitoring (see Appendix B). Results from the qualitative and objective approaches are shown in Appendix C. It is likely that the methodology would be successful for monitoring bores in Toolibin Lake where monitoring frequency is higher and time lags for major changes in rainfall-recharge patterns could be identified and filtered to assess the main trends. This work was not undertaken as these relationships and other hydrological processes that influence net groundwater recharge are explored in more detail within a new conceptual and numerical model under development (Rutherford in prep).


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5. Spatial trends Hydrograph trends were examined within the current conceptual ideas and frameworks outlined in Section 3.4. Both Cattlin (2006) and DEC-DAFWA (2008) argue the importance of the valley floor and hill slopes in groundwater response. In Cattlin (2006) the valley floor receiving area also represents areas with lower permeability soils and was simplified for numerical modelling to capture lower landscape slopes at around one to two degrees in slope. Figure 6A shows the shedding and receiving areas, coloured yellow and blue respectively, with bore locations in red and the ‘Toolibin Flats’ as a dotted outline (McFarlane et. al.., 1989). Figure 6B depicts the same receiving area superimposed on slope derived from a 5m gridded LIDAR dataset.

To test the hydrograph trend relationships with landscape slope both shallow and deep bores were plotted on LIDAR derived slope data that had been clipped to less than one degree slope (Figure 7). Many of the deep and shallow bores in the TLC have been drilled within the riparian zone, which is characterised by low slopes. The expectation is that most bores will be located in lower slope areas, although it is evident in Figure 6B that drilling transects cover areas of variable slope up gradient of the main ephemeral drainage lines. Results presented in Figure 7 validate both models presented by Cattlin (2006) and DEC-DAFWA (2008). Groundwater rising and rainfall CDFM are the dominate trends, with discharge responses positioned where there is a change in slope, or in close proximity to anthropogenic features. The rainfall CDFM trends tend to be located in the lower landscape areas and up gradient rising trends are common.

To test these landscape relationships the shallow and deep bores were plotted independently on threshold elevation values that may represent and map where the lower landscape-valley floor aquifers are ‘full’ (e.g. they have reached maximum storage capacity). The value that best represented this threshold value is the LIDAR 310mAHD value and the trends for both shallow and deep bores are discussed in this framework, clipped to the catchment boundary, in Figures 8 and 9.

For the purpose of this study the less than 310mAHD LIDAR threshold elevation is classified as the Toolibin Catchment Valley Floor boundary.

Data displayed in Figures 8 and 9, show common hydrograph trends for the shallow and deep bores within and outside the Toolibin Catchment valley floor. For shallow bores up gradient of the valley floor rising trends are common in the west and drying trends in the east. The spatial variation in up gradient response is explained by the different hydrology. Compared to the east, aquifers in the west are thinner and groundwater levels and gradients are elevated, promoting overland flow and interflow.

Drilling data show aquifers in the east are generally thicker than those in the west, and depth to groundwater and groundwater gradients are both lower. Overland flow and interflow are likely to occur under the same rainfall events as the western subcatchments, however in the east the flow paths are often longer. Under the current drying climate trend (Figure 3) these factors reduce the likelihood and frequency of seasonal perched aquifers developing, which explains the prevalence of dry shallow bores.

Rising trends in the deeper bores (Figure 9) located up gradient of the Toolibin Catchment valley floor are the likely the result of contemporary and past recharge. The low hydraulic conductivity and transmissivity of the aquifers will produce a lag in responses and mixing of water, as groundwater


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recharge from the last 100 years and longer moves slowly towards the Toolibin Catchment valley floor.

Important to this study of hydrograph assessment is the development of an understanding of the connectivity of the shallow and deep aquifer systems. External to Toolibin Lake there is a lack of paired bore sites, which limits the opportunity to gain a better understanding of seasonal aquifer connectivity and water balance exchanges between the aquifers. Shallow and deep bores are in close proximity within and close to Toolibin Lake. Hydrograph trends in these bores indicate that overall shallow aquifers are maintaining a rainfall CDFM, dry or pumping trend, with some deeper bores exhibiting a variable response, rainfall CDFM or rising, that is likely to be the result of pumping efficiency, operational problems with pumps, or areas with higher storage and throughflow. Effects attributed to pumping are discussed in detail in Rutherford (in prep).

Paired bores near drains to the north of Toolbin Lake show different trends. Perched aquifers developing in road reserves near drains appear to be the common shallow bore trend, while deeper bores in the same area continue to respond to rainfall CDFM. This may indicate that water balance risks associated with waterlogging and recharge near drains is low under the current drying climate trend.

6. Aquifer response – quantifying change to assess risk The conceptual models discussed in Section 3.3 provided information on qualitative and quantitative trends. The DEC-DAFWA model suggested bores installed in aquifers that show a good relationship with rainfall CDFM would exhibit a decrease in groundwater levels since 2000, the decrease ranging from 1-2, or 2-3 metres. This is due to the dominant WA Wheatbelt post 2000 drying climate trend. Figure 10 shows the overall monthly mean rainfall CDFM for the Wickepin rainfall data series (1911 to 2014). The main post 2000 drying trends are highlighted in blue and shorter lived wetting trends in red.

In the TLC the current catchment groundwater level sampling program has not been designed to sample for a southwest Western Australian minimum (March/April) or maximum (Sept-Oct) water level, with bores on Toolibin Lake being the exception. Most monitoring bore suites have collected data for the months of December-January, which is approaching a water level minimum. In this review, where these data existed for December-January 2000 and 2012 they were extracted and the difference calculated. Spatial patterns were then examined (Figures 11 and 12).

The red lines on Figure 10 represent the static sample points (December-January 2000 and December-January 2012) for bore TL22, with the dashed line joining the samples selected to display the net change and the seasonal variation over this time period. Groundwater data from bore TL22, a shallow bore on Toolibin Lake, follow the main rainfall CDFM trends, with the magnitude of change exceeding three metres in 2004 and approaching three metres in 2012. Data for 2012 indicate that the aquifers have responded to a rainfall event in December which has elevated water levels. The increase in summer rainfall events complicates the selection of years to study, however it is noted that for bore TL22, the December-January sampling remains lower than for the same period in 2011.

Trends observed in the rainfall CDFM data validate the conceptual ideas put forward by DEC-DAFWA (Section 3.4), with decreases in groundwater levels since 2000 generally ranging from 1-2, or 2-3


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metres (Figure 11). Information in Table 4 confirms that most bores (94% and 40% of shallow and deep bores) fall into the minor change class, with groundwater levels dropping at or below one metre. To the north of Toolibin Lake, greater decreases, 1.01 to 2 and 2.10 to 3 or 4 metres, occur where bores are located near drains, the closer to the drain the greater the decrease.

In Toolibin Lake the largest decrease in groundwater levels (around 4 metres) is observed in deep bores TL29, TL30 and TL34, which maintain a rainfall CDFM trend but also exhibit localised pumping drawdown affects due to being located between 15 to 70 metres from production bores. Decreases greater than one metre in deep bores tend to occur near major geological faults, which are likely to respond differently to pumping (Rutherford in prep).

TABLE 4: NUMBER AND PERCENTAGE OF DEEP AND SHALLOW BORES WITHIN THE THREE MAIN CLASSES OF RAINFALL CDFM RESPONSE (2000 TO 2012)

Shallow bore rising trends are few in number and generally spatially restricted to the sub catchments located west and north of Toolibin Lake where aquifers are more responsive to small changes in rainfall (Figure 12). Deep and shallow rainfall CDFM-rising trends represent the major classes with a similar number (29 bores for each class) of bores exhibiting these trends (Table 5). The west and northern areas of the TLC have limited deep bores. The deep bore trends to the east show that the magnitude of change tends to increase with distance from the ephemeral drainage lines (Figures 12 and 13). Rainfall CDFM-rising trends are dominant in the northern area of Toolibin Lake as well as to the west of the lake, suggesting other sources of water contribute to increases in recharge, such as surface water overtopping of the Toolibin Lake weir and waterlogging to the west due to the diversion forming a barrier to flow. LT31 (rise >10m – coloured red in Figure 12) is an outlier due to questionable bore construction.


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TABLE 5: NUMBER AND PERCENTAGE OF DEEP AND SHALLOW BORES WITHIN THE THREE MAIN CLASSES OF RAINFALL CDFM RESPONSE (2000 TO 2012)

Information in Tables 5 and 6 and Appendix C indicate the following combined trends;

• Deep and shallow aquifers in the Toolibin Catchment valley floor follow a rainfall CDFM trend, with one metre decreases in groundwater levels between 2000 and 2012,

• Groundwater levels have shown a greater decrease where groundwater pumping and drains (that don’t form a surface water barrier) have been installed. The trends follow the rainfall CDFM with decreases on average of around three metres between 2000 and 2012. The magnitude of decrease increases with distance from pumps and drains,

• Deep groundwater levels are rising up gradient and to the east of the Toolibin Catchment valley floor, with the average rate of rise of around 0.2m/yr. Depth to groundwater in bores closest to the Toolibin Catchment valley floor (located 300 to 1300m up gradient) ranges from 7 to 13 metres below ground level. Based on the current rate of rise groundwater could discharge at the 2m extinction depth zone in these areas in the southeastern drainage within the next 25 years,

Shallow aquifers to the west and north exhibit rises between 0.1 and 0.3 m/yr, with average depth to groundwater around 4 metres below ground level in low slope areas. In the west, deeper unpaired bores show higher groundwater levels indicating upward hydraulic heads and discharge into the shallow aquifer. If current rates of rise continue perennial discharge and subsequent evaporation of deep and shallow groundwater could occur in the next 10 to 20 years.

7. Review discussion Work reported here demonstrates that there are different trends between deep and shallow aquifers in the valley floor and uplands, using a provisional depth classification between deep and shallow aquifers of ten metres (see Section 3.2).

Results presented in Sections 5 and 6 in this report validate some of the conceptual model ideas presented by Cattlin (2006) and all ideas tested in DEC-DAFWA (2008).


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For Cattlin (2006), increases in recharge due to anthropogenic barriers in the valley floor were observed locally west and north of the Toolibin Lake surface water diversion as well as the northern area of Toolibin Lake. Valley floor groundwater discharge and rising trends develop where and when surface water contributions and associated rainfall-runoff are high locally. This is observed where perched aquifers develop in road reserves near drains and could be influenced by the lower permeability near surface regolith materials promoting waterlogging. The spatial and temporal extent of shallow perched aquifers developing under the current drier climate and their role in the water and salt balance is not fully understood.

The DEC-DAFWA conceptual ideas tested in this study were confirmed. Valley floor aquifers display a dominant rainfall CDFM response and aquifers in the upper valleys and hill slopes generally show a rising trend. Where the rainfall CDFM trend is present, groundwater levels have been decreasing since 2000, the magnitude of this decrease ranging from 1-2, or 2-3 metres.

It is interesting that groundwater rising trends in the uplands remain dominant while average rainfall has shown declines since 1970 and more recently 2000. The rate of rise is noted to be less than 50% of the previous predicted rate in Dogramaci and others (2003). Rates of groundwater rise different in the eastern, compared to the west and northern TLC, with a risk of groundwater discharging within the extinction zone (two metres below ground level), within the next 25 or 10 to 20 years in the eastern and west and northern areas respectively. There is limited evidence that bores have stabilised and stopped rising, but these predictions are made with limited data. The current annual data collection frequency is acknowledged as coarse, but is sufficient to confirm that contemporary rainfall contributes to groundwater rises in these areas. The hysteresis of the groundwater system requires a more detailed assessment of the salt and water balance, which is beyond the scope of this project.

In Toolibin Lake groundwater levels in shallow aquifers tend to exhibit limited pumping effects, showing a dominant rainfall CDFM trend that has maintained a groundwater level maximum of around 1.5 to 2.5 metres below ground level. Deeper bores located within 50 metres from pumping bores show more pronounced, but generally short lived, pumping effects.

Two other important observations in this study include spatial variability of rates of groundwater rise and the mapping of shedding and receiving areas and their role in determining different recharge patterns.

For rates of groundwater rise, the rates observed in deep aquifers in upland areas and risk of groundwater discharge is different in the east compared with the north and western areas. In the east the average rate of rise to the east is around 0.2m/yr and depth to groundwater between 7 to 13 metres below ground level, resulting in discharge at the 2m extinction depth within the next 25 years. Shallow aquifers to the west and north are rising at rates between 0.1 and 0.3 m/yr, shallower groundwater exists with average depth to groundwater around 4 metres below ground level in low slope areas. Perennial discharge predicted to occur in the next 10 to 20 years at the current rates of rise.

The shedding and receiving areas have been used to divide the catchment landscape into two areas that explain where runoff and waterlogging are higher Cattlin (2006). They potentially form the two main recharge zones. The digital elevation model used by Cattlin (2006) lacked the resolution of LIDAR data and as a result the slope maps didn’t resolve the complex distribution patterns of the low


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slope riparian zone across the TLC. In this study a landscape elevation threshold value (LIDAR derived 310mAHD), rather than slope, is used to map the valley floor and mark the division of the two main hydrogeological zones that exhibit different groundwater trends.

7.1 Limitations Limitations are discussed in detail in Section 3.3. The main limitation in the interpretation of groundwater data is the frequency and timing of data collection and errors introduced during data collection. The commitment to monitor a network of the size in the Toolibin NDRC is considerable. The trends reported in this review indicate that there is redundancy where areas display common trends, and where applicable, rates of rise. Recommendations for the rationalised monitoring program, selecting a representative subset of bores to be monitored around the same date and in some cases at a higher frequency are presented in the following section.

8. Monitoring recommendations Groundwater level monitoring data are required to provide confidence that the current management actions in the TLC are effective. Recommendations arising from the work undertaken in this review agree with those proposed by Dogramaci et. al. (2003), in particular the continued need to;

1. Maintain and improve surface and groundwater monitoring schedules and networks, 2. Assess the relationship between soil salinity and areas underlain by a shallow watertable, 3. Use a catchment water balance model to simulate the influence of changes in climate on rates of

water table rise and 4. Review available data to assess the effectiveness of the groundwater pumping against climate

variability.

8.1 Rationalised groundwater monitoring program Results from this review confirm that current groundwater monitoring network is extensive and should be reduced in size to improve the timing, frequency and quality of data collection. The rationalisation will also ensure the program is compatible with DPaW core business and available resourcing. The rationalised groundwater monitoring program outlined below is provisional and will be updated following the completion of a new conceptual and numerical groundwater model in 2018.

Information from this groundwater review shows the Toolibin Catchment displays common trends within a simple two aquifer (shallow and deep) and landscape characterisation (valley floor and uplands), with more complex aquifer responses in and around Toolibin Lake. Some of the variation in the valley floor is likely to relate to data measurement error as well as processes outlined by Cattlin (2006). This cannot be verified with the existing bore infrastructure and as groundwater recharge from flooding is less compared to that from incident rainfall under the current climate it would be advisable to explore this through episodic surface water monitoring as recommended by Muirden and Coleman (2014).

The importance of ensuring groundwater monitoring links effectively to landscape and surface water observations requires that catchment bores are mapped to both a catchment and landscape or landform unit. Surface water management units developed by Cattlin (2004) have been assigned


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corresponding groundwater management units and it is recommended these are used in reporting future monitoring trends (Table 6).

A total of 74 bores were selected to be part of the rationalised groundwater monitoring program and their locations in relation to the groundwater and surface water management zones are shown in Figures 14 and 15. The selection of optimal bores for the rationalised monitoring program firstly prioritised bores within DPaW Estate (Figures 14 and 15) (located mainly in the valley floor), followed by suitable bores located upgradient that can provide information on potential water and salt fluxes.

Table 6 outlines the major monitoring trends from selected optimal monitoring bores identified in this review, the current and predicted risks associated with these trends under the current climate and the groundwater processes driving those threats. However, it must be noted that variation in the valley floor may be in part due to the frequency and timing of previous groundwater data collected as well as limited information on aquifer connectivity due to a lack of paired bore sites (note that all operational paired bore sites have been included in the rationalised groundwater monitoring program).

Appendix D provides information for individual bores covering; recommended frequency of data collection, groundwater and hydraulic head trends, geomorphology (major and minor landforms), hydrogeological controls (mapped basement/shallow regolith and faults and dykes Rutherford in prep), major soil-hydrology mapping units (Verboom 2003) and influence of anthropogenic controls (roadside drains, agricultural drains, dams, pumps etc) including interpreted hydrograph surface water effects.

For the timing of groundwater level measurements it is recommended that;

• Water level data are collected for all bores on the same day if possible, • Quarterly and biannual measurements coincide with monthly measurements and • Biannual, quarterly and monthly measurements are collected to understand both minimum

(March/April) and maximum (Sept/Oct) groundwater levels.


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TABLE 6: GROUNDWATER MANAGEMENT ZONES SHOWING MONITORING TRENDS, CURRENT AND PREDICTED RISKS UNDER THE CURRENT CLIMATE AND MAJOR GROUNDWATER PROCESSES.


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References Ali, R., Emelyanova, I., Dawes, W., Hodgson, G., McFarlane, D.J., Varma, S., and Turner, J. (2010), Groundwater methods used in the South-West Western Australia Sustainable Yields Project. CSIRO.

Cattlin, T., D. Farmer, N. Coles and D. Stanton (2004). Surface Water Assessment for the Toolibin Lake Recovery Catchment, Engineering Water Management Group, Department of Agriculture Western Australia.

Cattlin, T. (2006), The Impact of Redistributed Surface Water and Spatially Distributed Recharge on Water Quality decline in the Toolibin Lake Catchment: a modelled approach to process management. Masters of Science Project Report University of Technology, Sydney Travis Cattlin 10007235 Autumn

Coleman, B. and Wroe, R. (2011), Groundwater Data Review Toolibin Lake Catchment, Hydrology Report 2011-004, Department of Environment and Conservation, Natural Resources Branch, Western Australia.

DEC-DAFWA Technical Advisory Group Meeting minutes (31st July 2008) Department of Environment and Conservation Western Australia.

De Silva, J. (1999a), Toolibin Catchment Airborne Geophysics Bore Completion Report, Water and Rivers Commission

De Silva, J. (1999b), Evaluation of Airborne Geophysics for Investigation Land and Water Salinisation in the Toolibin Catchment. Perth, Western Australia, Water and Rivers Commission

Dogramaci, S. (1999), Toolibin Lake Drilling Program - Bore Completion Report and Pumping Test Data. Hydrogeology Report 139. Perth, Water and Rivers Commission

Dogramaci, S. George, R., Mauger, G. & Ruprecht, J. (2003), Water balance and salinity trend, Toolibin catchment, Western Australia, Department of Conservation and Land Management, Perth.

George, R. and Bennett D. (1995). Toolibin Groundwater Management Program, Drilling Results, Explanatory Notes and Drill Logs, Completion Report to CALM. Bunbury, Western Australia.

McFarlane, D.J., Engel, R. and Ryder, A.T., (1989). The location of recharge areas responsible for valley salinity in the Lake Toolibin catchment, Western Australia. In M. Sharma (Editor) Groundwter Recharge. Balkema Publishing Company, Rotterdam: 255-267

Muirden, P. and Coleman, S. (2014). The Toolibin Natural Diversity Recovery Catchment, Review of Surface Water Monitoring. Department of Parks and Wildlife, Western Australia. Unpublished report NRB-HR-2013_010.

NARWRC (1978) Northern Arthur River Wetlands Rehabilitation Committee – Progress Report August, 1978, NAWWRC, Western Australia.

National Water Commission (2010), Groundwater bore deterioration: schemes to alleviate rehabilitation costs, GHD, Waterlines Report Series No 32, October 2010

National Water Commission (2012a), Minimum Construction Requirements for Water Bores in Australia, 3rd edition, National Uniform Drillers Licensing Committee, Australia.

National Water Commission (2012b), An assessment of groundwater management and monitoring costs in Australia, Sinclair Knight Merz, Waterlines Report Series No 90, September 2012


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Romero-Segura, M., Rutherford J. (2016), Toolibin Lake Catchment: Groundwater Monitoring Bore Census - 2014. Department of Parks and Wildlife, Perth.

Rutherford J., Fergusson K., Horsfield N. & Romero-Segura, M. (2016), Hydrology Program Review 1977 - 2015: Toolibin Lake Catchment. Department of Parks and Wildlife, Perth

Rutherford J (in prep) Conceptual Hydrogeologial Model of Toolibin Lake and Catchment: Toolibin Lake Catchment. Department of Biodiversity Conservation and Attractions, Western Australia

Toolibin Lake Recovery Team and Toolibin Lake Technical Advisory Group (1994), Toolibin Lake Recovery Plan. Perth, Australia

Verboom, W., (2003). Soils of the Toolibin Lake Catchment, Report produced for CALM. Department of Agriculture and Food Western Australia.

Yesertener, C., (2008), Assessment of the declining groundwater levels in the Gnangara groundwater mound, Western Australia. Hydrogeological Record Series HG14


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FIGURE 1: TLC MONITORING BORES ASSESSED IN THIS GROUNDWATER MONITORING REVIEW AND RATIONALISATION


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FIGURE 2: NUMBER OF DISCRETE GROUNDWATER LEVEL MEASUREMENTS (1977 TO 2012).

FIGURE 3: WICKEPIN BOM WEATHER STATION (010654); A. ANNUAL RAINFALL 1912 TO 2013 (FROM MUIRDEN AND COLEMAN 2014); B. WICKEPIN RAINFALL CDFM (1911 TO 2012) AND C. .

A.


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B.

C.


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FIGURE 4: BORE TL28 HYDROGRAPH, WATER LEVEL DATA OVERLAIN ON RAINFALL CDFM

FIGURE 5: TOOLIBIN HYDROGRAPH GENERATOR, SHOWING INFORMATION FOR BORE TL06


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FIGURE 6A AND B: MAPS OF IDEALISED SHEDDING AND RECEIVING AREAS SHOWN IN CONTEXT TO THE 1980’S “TOOLIBIN FLATS” VALLEY FLOOR MODEL (6A) AND RECENT SLOPE MAPPING USING LIDAR DATA (6B)

A B


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FIGURE 7: MAP DISPLAYING SHALLOW AND DEEP BORE HYDROGRAPH TRENDS OVERLYING LIDAR SLOPE <1DEGREE


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FIGURE 8: MAP DISPLAYING SHALLOW BORE HYDROGRAPH TRENDS OVERLYING LIDAR ELEVATION <310MAHD


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FIGURE 9: MAP DISPLAYING DEEP BORE HYDROGRAPH TRENDS OVERLYING LIDAR ELEVATION <310MAHD


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FIGURE 10: MONTHLY RAINFALL CDFM SHOWING SUPERIMPOSED DRYING (BLUE) AND WETTING (LIGHT RED) TRENDS AND MONTHLY WATER LEVEL DATA COLLECTED FROM BORE TL22


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FIGURE 11: MAP SHOWING CHANGES IN GROUNDWATER LEVELS (2000 TO 2012) FOR DEEP AND SHALLOW BORES THAT EXHIBIT A RAINFALL CDFM TREND.


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FIGURE 12: MAP SHOWING CHANGES IN GROUNDWATER LEVELS (2000 TO 2012) FOR DEEP AND SHALLOW BORES THAT EXHIBIT A RISING OR RAINFALL CDFM-RISING TREND


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FIGURE 13: MAP SHOWING AVERAGE RATES OF GROUNDWATER LEVEL RISE IN DEEP AND SHALLOW BORES (2000 TO 2012).


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FIGURE 14: MAP SHOWING THE LOCATION OF GROUNDWATER MANAGEMENT ZONES, TLC RATIONALISED MONITORING PROGRAM -SHALLOW BORES TRENDS (2000 TO 2012), VALLEY FLOOR EXTENT AND UPLANDS RIPARIAN ZONE (<1 DEGREE SLOPE); TLC DPAW ESTATE MONITORING SHOWN IN BLUE BORDERED INSET


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FIGURE 15: MAP SHOWING THE LOCATION OF GROUNDWATER MANAGEMENT ZONES, TLC RATIONALISED MONITORING PROGRAM -DEEP BORES TRENDS (2000 TO 2012), VALLEY FLOOR EXTENT AND UPLANDS RIPARIAN ZONE (<1 DEGREE SLOPE); TLC DPAW ESTATE MONITORING SHOWN IN BLUE OUTLINED INSET


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Appendix A Hydrograph Analysis - quantitative method developed for a limited data series

A quantitative approach was trialled to see if a numerical approach would resolve similar trends. The method was contingent on a number of robust observations being available. Where this was the case this had the potential to remove some of the subjectivity of the qualitative approach. The quantitative approach tested assesses the change from the mean of both times series for each time step, taking into account the standard deviation of both the CDFM and groundwater data time series. The correlation coefficient is then calculated by summing each of the values calculated for each time step as shown in Equation 1.

𝑅𝑅𝑥𝑥,𝑦𝑦 = 1

𝑛𝑛 − 1∑ (𝑥𝑥𝑖𝑖 − �̅�𝑥)(𝑦𝑦𝑖𝑖 − 𝑦𝑦�)𝑛𝑛

𝜎𝜎𝑥𝑥𝜎𝜎𝑦𝑦 1

here R is the correlation coefficient, n is the number of observations, xi is the value of the first variable (CDFM for example) and yi is the value of the second variable (groundwater level) at time i, �̅�𝑥 and 𝑦𝑦� are the means of both variables and σx and σy are the standard deviation of both variables. An R value of 1 indicates that both variables are perfectly correlated and when one variable increases, the other increases in proportion to it. An R value of -1 describes the situation where the two variables are perfectly inversely correlated, meaning that when one variable increases the other variable decreases proportionally. An R value of 0 indicates no correlation.

Groundwater level is measured as metres below ground level (mbgl) in the Hydstra database site table used in this project. Therefore it is expected that a good correlation will be towards -1 as when the CDFM increases the groundwater level will approach the surface i.e. decrease in value in terms of mbgl and hence move in the opposite direction to the CDFM time series. If groundwater responded without delay to rainfall the offset (time between the cause, here rainfall, and the effect, here the change in groundwater level) would be zero. Because groundwater can take some time to respond to rainfall, the correlation coefficient is calculated separately for offsets of 0 to 12 months (following the CDFM of rainfall for the month being interrogated). Therefore the offset that corresponds to the lowest correlation coefficient (as the two time series should be inversely proportional to each other) indicates the lag between the CDFM and the groundwater level time series.

This approach was used to compare the CDFM values with the groundwater levels and also the compare the monthly Deviation From Mean (DFM) rainfall values with the groundwater levels. The DFM was also used to attempt to account for effect that using different starting times for the CDFM time series will affect the shape of the CDFM and hence the different correlation coefficient values.


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Appendix B: Qualitative hydrograph analysis – type trends

Rainfall CDFM (note time lags in major trend changes)

Rising (steady increase in groundwater levels that is insensitive to the rainfall CDFM)

Discharge (GWLs consistently less than or equal to 2 metres below ground level)

Pump (extended periods where groundwater levels are close to the ground surface (pumps off) followed by rapid decreases with sustained lower groundwater levels (pumps on)


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Dry (groundwater levels are generally just above or at the bottom of the bore)

Stable (no obvious trend for the length of bore record)

No trend (no obvious trend for the length of bore record)


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Appendix C: results of qualitative and objective hydrograph analysis


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Appendix D


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