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Estimating potential costs and gains from an aquifer storageand recovery program in Australia

Shahbaz Khan a,b,c,*, Shahbaz Mushtaq b,c, Munir A. Hanjra a,b, Jurgen Schaeffer d

aCommonwealth Scientific and Industrial Research Organization, Land and Water, Wagga Wagga, NSW, Australiab International Centre of Water, Charles Sturt University, Wagga Wagga, NSW 2650, AustraliacCooperative Research Centre for Irrigation Futures, AustraliadGHD Pty Ltd., Locked Bag 5 Morwell, Vic. 3840, Australia

a r t i c l e i n f o

Article history:

Received 11 June 2007

Accepted 5 December 2007

Published on line 31 January 2008

Keywords:

Groundwater

Artificial storage and recovery

Murrumbidgee

Deep aquifers

Drought

Water allocation

a b s t r a c t

Artificial recharge of aquifer storage can provide water during drought periods, reverse

falling groundwater levels and reduce water losses associated with leakage and evapora-

tion, as compared with surface water storage. We examine the technical and economic

potential of artificial storage and recovery for drought mitigation in the Murrumbidgee

Region of New South Wales, Australia. Potential locations for infiltration basins and injec-

tion/recovery wells are identified according to criteria such as water availability, aquifer

suitability, recharge potential, and potential to provide a usable resource. The estimated

annual artificial recharge potential is 180,000 ML through a combination of injection wells

and infiltration basins. The cost estimates for artificial recharge vary from AU$ 62 ML�1 to

AU$ 174 ML�1 depending on the choice of recharge method. Underground storage capacity

can be developed at less than half the cost of surface storage facilities without undesirable

environmental consequences or evaporation losses. The estimated benefits of artificial

through infiltration basins are three to seven times the costs, during

Water pricelow allocation years.

storage and recovery

# 2007 Elsevier B.V. All rights reserved.

1. Introduction

Australia encompasses a range of climatic zones, including

wet tropics, cool temperate zones, and deserts. Rainfall

varies from an average of several meters per year, to areas

averaging less than 200 mm. Australia’s climate is variable

over time, with substantial variation in average annual

rainfall (Khan et al., 2007; Kokic et al., 2007). Indeed, the

term ‘average rainfall’ has little meaning in Australia,

where rainfall variability and high levels of evapotranspira-

tion produce a land of ‘droughts and flooding rains’

(Proust et al., 2007). The sporadic spatial and temporal

distribution of rainfall motivates interest in managing water

* Corresponding author at: Charles Sturt University, International CentrAustralia. Tel.: +61 2 6933 4933; fax: +61 2 6933 2647.

E-mail address: shahbaz.khan@csiro.au (S. Khan).

0378-3774/$ – see front matter # 2007 Elsevier B.V. All rights reservedoi:10.1016/j.agwat.2007.12.002

supply through storage to match the demand (Keller et al.,

2000).

The recent drought and the increase in concerns about

climate change have highlighted the need to manage

Australia’s water resources sustainably. Greater storage is

needed to minimize the negative impacts of drought (Botzan

et al., 1999; Khan et al., 2004a,b). Artificial recharge can provide

water during drought periods for irrigation and environmental

needs, and reverse falling groundwater levels (Khan et al.,

2008). Storage in aquifers also prevents water losses due to

leakage and evaporation from surface storage (Pratt Water,

2004a; Donovan et al., 2002; Khan et al., 2004a; Barnett et al.,

2000; Dudding et al., 2006).

e of Water for Food Security, Building 24, Wagga Wagga, NSW 2650,

d.

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8478

Aquifer storage and recovery, known also as managed

aquifer recharge, is the process of artificially recharging

aquifers by infiltrating water through permeable media or

by direct injection through tubewells. The goal is to store water

in a suitable aquifer during times when water is available, and

recover water from the same aquifer when it is needed (Dillon,

2005; Pyne, 1995; Dudding et al., 2006). Large volumes can be

stored underground, reducing or eliminating the need to

construct surface reservoirs and minimizing evaporation

losses. Aquifer storage and recovery (ASR) has been utilised

throughout the world to enhance local and regional water

resources (Khan et al., 2004a).

In the Murrumbidgee Region of New South Wales,

Australia, up to 350,000 ML of water per year are lost from

the system due to evaporation, supply and storage inefficien-

cies, and on farm losses (Khan et al., 2004c). Through the

development of an ASR scheme, current storage could be

utilised to augment the groundwater system, thus increasing

water in storage in the region. During periods of drought or low

rainfall, groundwater could be utilised for maintaining some

security of water supply. During periods of plentiful rainfall

artificial recharge would replenish the groundwater system

and potentially help to restore groundwater dependent

ecosystems within the region.

The aim of this paper is to examine the technical and

economic potential of ASR for drought mitigation in the

Murrumbidgee Region. We evaluate potential water avail-

ability, water quality, and potential locations for ASR in the

study area. We estimate the cost of artificial storage and

recharge schemes using infiltration basins and injection wells.

We develop a hypothetical scheme that demonstrates the

potential of artificial storage and recovery for drought

mitigation at the regional scale.

2. Literature review

Aquifer storage and recovery is a relatively recent develop-

ment. The first investigations of injecting potable water into

saline aquifers were conducted about 50 years ago (Ceder-

strom, 1957). In early trials the injected water formed a lens or

bubble of potable water within the saline groundwater.

Current methods of artificial recharge include surface

spreading, infiltration pits or basins, and injection wells

(Bouwer, 1989; EPA South Australia, 2004; Sheng, 2005; Dudding

etal.,2006;Pavelicetal.,2007).Surfacespreadingandinfiltration

pits and basins allow water to infiltrate into an aquifer largely by

passive means, requiring less energy. However, there must be a

good hydraulic connection between the surface and the aquifer,

with no impermeable layers separating the two (Dillon, 2005).

Injection wells are used in areas where impermeable strata

between the surface and the aquifer make recharge by surface

infiltration impractical or in areas where land for surface

spreading is limited (Pavelic et al., 2007).

A key factor in the operation of an ASR well is its recovery

efficiency, defined as the percentage of water volume stored

that is subsequently recovered, while meeting a target water

quality criterion in the recovered water (Pyne, 1995). Recovery

efficiency tends to improve with successive cycles when the

same volume of water is stored in each cycle because the

residual water not recovered in one cycle becomes a transition

or buffer zone of marginal quality surrounding the stored

water in the next cycle (Pyne, 1995). Indications from ASR sites

around the world suggest that in saline aquifers efficiency can

reach 85% (Reese, 2002), while in non-saline aquifers efficiency

can approach 100% depending on the nature of the ground-

water system. Hydro-geological and design factors are

important to the recovery of non-saline water from within a

saline aquifer (Reese, 2002).

The potential benefits of ASR and artificial recharge, as

adapted from Pyne (1995) and Pratt Water (2004a) include:

� s

easonal, long term and emergency storage,

� r

estoration of groundwater levels,

� m

aintenance of distribution system pressure and flow,

� im

provement of water quality,

� p

revention of saltwater intrusion,

� r

eduction of environmental effects of streamflow diver-

sions,

� a

gricultural water supply,

� n

utrient reduction in agricultural runoff,

� e

nhancement of wellfield production,

� d

eferred expansion of water facilities,

� c

ompensation for surface salinity barrier leakage losses,

� r

eclaimed water storage for reuse, soil aquifer treatment,

� h

ydraulic control of contaminant plumes,

� m

inimisation of surface storage costs and evaporative

losses, and

� s

torage capacity losses.

The costs of ASR programs vary with location and depend

primarily on land acquisition, water pre-treatment, environ-

mental regulations and permitting, design and construction,

and operation and maintenance costs (Pitman, 1999; Topper

et al., 2004). The estimated initial capital cost of a 100 ML ASR

program in South Australia is about AU$ 2000 ML�1 (Dillon,

2005). The estimated capital cost of a 200 ML ASR program in

Salisbury, Australia is AU$ 625 ML�1 (Pitman, 1999).

Employing a comparative benefit–cost analysis, using cost

assessment simulation and employing weighted coefficients

rather than market prices, Botzan et al. (1999) show significant

benefits from artificially recharging the aquifer adjacent to the

San Joaquin River in California. Similarly, Donovan et al. (2002)

report net savings of about $700 per year during a 20-year period

of recharging an aquifer in the Las Vegas Valley. Acharya and

Barbier (2000) use a production function approach to value

groundwater recharge in northern Nigeria. A 1 m decrease in

groundwater recharge (from 6 m to 7 m), reduces welfare in

households growing vegetables by an estimated 7.6%. As 77% of

the households produce vegetables and wheat, this might have

significant implications for equity. Hussain et al. (2004) provide

similar evidence for the upper Indus Basin.

3. Study area

Benefit–cost analyses of aquifer storage and recovery pro-

grams in Australia are rare. Our goal is to provide such a study

for the Murrumbidgee catchment, which extends from the

Snowy Mountains in the east to the juncture of the

Fig. 1 – Murrumbidgee catchment and Lower Murrumbidgee Groundwater Area.

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8 479

Murrumbidgee River with the Murray River in the west (Fig. 1).

Pratt Water (2004c) has identified a major portion of the Lower

Murrumbidgee Groundwater Area (LMGA) as being suitable for

aquifer storage and recovery.

The Murrumbidgee catchment has a climate that varies

from high country in the eastern portion to irrigation areas of

the Lower Murrumbidgee in the west. Annual rainfall varies

from more than 1500 mm in the eastern portion to less than

400 mm in the Lower Murrumbidgee area. Annual evaporation

ranges from 1000 mm to 1800 mm, respectively, for the same

regions. In 2002–2003 annual evaporation in the Murrumbid-

gee area was 2240 mm, the highest ever recorded.

3.1. Water management

In the Murrumbidgee catchment, a rigorous regulatory frame-

work is used to determine water allocations. The amount of

water that irrigators have access to for any 1 year is based on

seasonal water allocation announcements during the irriga-

tion season. A water allocation is defined as a percentage of a

license holder’s entitlement and is determined by the amount

of storage in two main reservoirs behind the Burrunjuck and

Blowering dams, and minimum expected inflows. The

reservoirs have capacities of 1,026,000 ML and 1,631,000 ML,

respectively. Irrigation entitlements for the two main irriga-

tion areas in the Murrumbidgee Valley, the Murrumbidgee

Irrigation Area (MIA) and the Coleambally Irrigation Area (CIA)

are 1,213,000 ML and 503,000 ML, respectively. In a given year,

depending on storage levels of dams and inflows, water is

allocated according to the following list of priorities:

� E

nvironmental water provisions;

� L

icensed domestic and stock requirements;

� L

ocal water utility requirements;

� A

ny water carried forward in water accounts;

� H

igh security; and

� G

eneral security.

Water for irrigation purposes is provided after satisfying

environmental, domestic and carryover requirements. Irriga-

tors with high security water for permanent crops usually

receive 100% of their entitlement, irrespective of water

availability in the reservoirs. General security water alloca-

tions accumulate gradually during the irrigation season, and

are determined by the volume of water in the Burrinjuck and

Blowering reservoirs at the start of the agricultural year (July to

August), and the minimum expected inflows. Recent droughts

have caused substantial reductions in general security water

allocations in the Murrumbidgee Valley (Table 1). Water is set

aside also for conveyance inside the irrigation corporations (in

accordance with their licenses), and to account for losses in

delivery of allocated water.

The estimated average natural recharge to the lower

Murrumbidgee Aquifers is 335,370 ML year�1 (Kumar, 2002).

During the last 10 years, the local imbalance between

groundwater recharge and discharge has resulted in about

10 m to �20 m of residual drawdown in deep aquifers over

large areas between Darlington Point and Hay.

The estimated annual value of irrigated agricultural

production in the Murrumbidgee catchment is AU$ 408

million. Major crops include wheat and other cereals, grapes,

rice, and vegetables. The Murrumbidgee catchment accounts

for 80% of the carrots and 90% of the potatoes produced in New

South Wales. Good water management is essential to ensure

that this significant agricultural industry continues to provide

economic and social benefits.

3.2. Regional geology

The Lower Murrumbidgee Groundwater Area (LMGA) occurs

within the eastern Riverine Plains province of the Murray

Geological Basin, a large saucer-shaped structure that

covers about 300,000 km2 in southeastern Australia. The

Murray Basin extends over the States of New South Wales,

Victoria, and South Australia and consists of a sequence of

mostly semi-consolidated to unconsolidated, flat lying

sedimentary deposits that began accumulating during the

Early Eocene. The sediments have a maximum thickness of

about 600 m in the central area near Mildura (Lawson and

Webb, 1998).

Table 1 – Water entitlements in the Murrumbidgeecatchment

Category Volume (ML)

Basic landholder rights 4,560

Local water utility access licences 23,403

Domestic and stock access licences 35,572

High security 298,021

Murrumbidgee irrigation (conveyance) 243,000

Coleambally irrigation (conveyance) 130,000

General security 2,043,432

Source: Khan et al. (2004c).

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8480

The sedimentary deposits in the LMGA can be subdivided

into three regional geological formations (Fig. 2): the Shep-

parton Formation, Calivil Formation, and the Renmark Group

(Evans and Kellett, 1989). These sedimentary deposits reach a

maximum thickness of about 400 m, near Balranald.

4. Methodology

4.1. Hydrologic modelling

We use the regional MODFLOW/MT 3D model developed by

Khan et al. (2004a,b). This model was further refined and

customised with the proposed pumping and recovery using a

1.25 km � 1.25 km grid size (Fig. 3). The model can represent

both the radial and vertical flow components that usually

occur from pumping boreholes in layered aquifers. We

characterize the Upper Shepparton, Lower Shepparton,

Calivil, and Renmark Formations covering a total area of

618,750 ha with 3960 (60 � 66) cells in each layer. The flow and

transport models were run with periodic cycles (stress

periods) of 6 months each, during a 10-year period.

The spatial variation of hydraulic conductivities, specific

yield, and specific storage in different model layers have

been defined using harmonic means, based on average soil

Fig. 2 – North–south and east–west sections through

properties and bore log data (Punthakey et al., 1994). The

numbers of bore logs used to derive the hydraulic properties of

individual layers are 442, 405, 177 and 113 for the Upper and

Lower Shepparton, Calivil, and Renmark formations, respec-

tively. The interactions between model layers are specified

using vertical leakage terms in MODFLOW. Vertical/horizontal

anisotropy ratios of 1:20–1:100 are used to calculate vertical

hydraulic conductivities. The vertical leakage for each cell is

calculated from vertical hydraulic conductivities and layer

thicknesses, as described in McDonald and Harbaugh (1988).

The groundwater balances for different zones and clusters

of farms are obtained by calibrating the groundwater flow

model. A trial and error procedure was adopted to calibrate the

hydraulic parameters and recharge, to match piezometric

water level hydrographs. We used groundwater pumping data

from 616 observations from the Upper Shepparton, 221 for the

Lower Shepparton, 27 for the Calivil, and 25 for the Renmark

formations for 1999–2001. We used 43 hydrographs to calibrate

the model—14 in the Upper Shepparton, 12 in the Lower

Shepparton, 8 in the Calivil, and 9 in the Renmark formation.

We compare the computed and observed drawdowns for

10-year periods at one of the piezometers, as an example, in

the upper Shepparton aquifer (Fig. 4). The model replicates the

pumping test data during 467 days with a pumping rate of

28.5 ML day�1 at observation points at 10 m, 959 m, 3564 m,

4054 m and 5157 m depths. Records of possibly blocked

piezometers or boreholes were not considered for comparison

with the predicted groundwater heads. Six-monthly data for

winter stress periods were used as model inputs. The

simulation was run for the period covering two irrigation

seasons (September to March) and three non-irrigation

seasons (March to September), using a time step of 10 days.

Observations for March 1999 were used as initial conditions for

model runs. Based on initial estimates of parameters, ground-

water heads were predicted and compared with the observa-

tion records. Adjustments to recharge values were made for

each stress period to obtain reasonable agreement between

observed and predicted values.

the Murray Basin (after Evans and Kellett, 1989).

Fig. 3 – Lower Murrumbidgee Groundwater Model.

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8 481

4.2. Cost modelling

The cost of an artificial storage and recharge system depends

on many factors such as site conditions, type of recharge

system (infiltration basin or injection well), water treatment

processes, the cost of acquiring and transmitting source

water, land costs, and regulatory standards (Donovan et al.,

2002; Topper et al., 2004). The fixed or capital cost includes the

well, pump, pipe, filtration system, basin construction and

land acquisition cost, while variable costs include basin

cleaning (once in 5 years), basin skimming (twice in a given

year), pumping costs, the opportunity cost of water, and

supervision (Hafeez et al., 2008; Botzan et al., 1999). The fixed

cost was converted into an annual capital cost by considering

the useful life of the basin, pumps, engine and accessories, and

Fig. 4 – Observed and calculated hydrographs: Piezometer

12379 Model Layer = Upper Shepparton Piezometer.

Location = Easting 385956 (m) Northing 6143058 (m).

interest rates. We use a 20-year life for the well and an interest

rate of 7%.

We estimate the costs of artificial storage and recovery

systems at potential locations using surface spreading

(infiltration pits or basins) and injection wells. We use

published cost data, where available, and we have obtained

additional information from artificial recharge practitioners.

We estimate the cost of constructing a hypothetical artificial

recharge scheme.

5. Results and discussion

5.1. Groundwater pressure trends and regional flowsystems

Long-term variations in pressure trends indicate that across

the eastern part of the system there is a consistent decline in

groundwater levels imposed on the seasonal fluctuations. The

most significant changes are in the areas labeled as drawdown

area 2 (DDA2) and DDA3, with some change to the southwest

of Narrandera (Fig. 5). Changes in areas labeled DDA2 and

DDA3 are due to the groundwater system being unable to

recover during the winter recharge period. This has resulted in

a decline in groundwater pressure in excess of 10 m over an

area of about 5500 km2, indicating the potential for artificial

recharge. Based on the observed drawdowns, a storage

coefficient of 1.12 � 10�4 m�1 and an estimated average

thickness of 200 m, we estimate that about 2,000,000 ML of

groundwater might be stored in the deep aquifer systems of

the LMGA.

Long-term groundwater pressure trends in the Shepparton

Aquifer indicate a variable response to the reduction in

pressure in the Calivil Formation. Some piezometers indicate

Fig. 5 – Net changes in groundwater levels Renmark/Calivil Formations 1990–2000.

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8482

that water levels have decreased in the deeper Calivil

Formation, while other piezometers indicate that water levels

in the shallow Shepparton Formation continue to rise.

5.2. Groundwater recharge

The current or potential recharge areas for the Calivil and

Renmark Formations are shown in Fig. 6. Areas of low

groundwater salinity in both the shallow and deeper aquifer

can be associated with areas of freshwater recharge to the

deeper aquifer. In the shallow aquifer, areas of locally low

salinity are likely to be associated with a relatively high rate of

flushing of groundwater. This may be due to localised drainage

features, such as rivers, or good leakage into the underlying

aquifer. Areas of good water quality are associated with the

Murrumbidgee River and Yanco Creek. Total recharge to the

Fig. 6 – Probable and potential g

aquifers in the lower Murrumbidgee area is estimated to be

65,000 ML year�1 to the Shepparton and 335,000 ML year�1 to

the Calivil and Renmark.

This indicates that the Murrumbidgee River and Yanco

Creek are providing fresh water to the shallow groundwater

system that is not associated with high salinity due to elevated

water tables. This suggests that these areas might be

recharging the deeper aquifer. Water quality in the deeper

aquifer indicates a local source of freshwater recharge,

apparently associated with the Murrumbidgee River and

Yanco Creek.

5.3. Potential storage capacity of the aquifer systems

An aquifer’s storativity is a measure of the amount of water

that can be extracted per unit change in aquifer head.

roundwater recharge areas.

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8 483

Storativity is the product of aquifer thickness and what is

called the aquifer’s storage coefficient, which indicates the

confining nature of the aquifer. In the vicinity of Hay and

Balranald, storage coefficients are generally between

1 � 10�4 m�1 and 5 � 10�4 m�1, suggestive of confining aquifer

conditions. Along the eastern extents of the Renmark Group

and east of Hay the specific storage is higher (between

5 � 10�4 m�1 and 1 � 10�2 m�1) indicating semi-confined con-

ditions.

The potential storage capacity in the aquifer system is

subject to some uncertainty. As the aquifer is not fully

confined, increasing the pressure likely will cause elevated

groundwater levels in the shallow aquifer, and a worsening of

salinity problems. The maximum pressure in the aquifer is

limited by consideration of these problems. We consider

historical groundwater levels, prior to the intense pumping of

recent years, to be the maximum groundwater levels that

might be achieved through artificial recharge.

The maximum drawdown that can be achieved or is

desirable in the aquifer also is uncertain. We use current

maximum drawdowns to calculate the potential storage

capacity of the aquifer. With careful management these

drawdowns might be increased further if sufficient recharge

were available during a flood/drought timescale (perhaps 5–10

years) to recharge the aquifer.

We assume that the potential storage capacity of the

aquifer is the difference between the drawdown that has been

induced in the aquifer, which has not been recovered by

winter recharge, and historical groundwater levels. Natural

recharge is not sufficient to return groundwater levels to those

that existed historically (Fig. 7). By using artificial recharge for

a higher pressure range between current and historical

recharge levels, a larger aquifer storage capacity can be

achieved.

The volume pumped in 2003–2004 was 240,000 ML, result-

ing in the observed groundwater drawdown. Recharge to

the system during the irrigation season is estimated at half the

annual recharge (i.e. 335,000 ML to 2 = 168,000 ML). The

amount extracted during the irrigation season is derived from

Fig. 7 – Historical and projected Calivil an

recharge during this period and the change in head. On the

basis of this a ratio between head change and volume

extracted can be derived (storativity). Assuming that the

currently unused capacity of the system could yield ground-

water at a similar rate per unit change in head, and using

gridded basin-wide drawdowns of the difference between

historical levels and current recovered levels, we estimate a

storage capacity of 180,000 ML year�1. The resulting estimated

annual yield is 414,000 ML. Sources of error in developing this

estimate include the process of gridding and contouring the

seasonal groundwater changes. In addition, there might be

discrepancies between actual and measured volumes pumped

from the aquifer.

5.4. Water availability

Potential sources of surface water for artificial storage and

recovery in the LMGA are:

� R

d R

iver flows (during high flow periods) resulting in an

effective increase in the capacity of en-route storage, which

allows greater efficiency, better control and more flexibility

in water management.

� R

eplacement or supplementation of current en-route

storage (and a reduction in evaporation losses), and

� S

ewage treatment plants.

Of these, both river flow and replacement or supplementa-

tion of current en-route storage (potentially 180,000 ML year�1)

are feasible. However due to their small outflow and discharge

to river systems, sewage treatment plants are not considered

feasible.

5.5. Available flows

Environmental flow rules pertaining to the Murrumbidgee

Catchment likely will constrain diversion volumes (Aquilina,

2003). Since 1979, water flow has exceeded the required

minimum environmental flow past Balranald Weir

enmark water levels (hydrograph).

Fig. 8 – The river flows past Balranald Weir.

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8484

(300 ML day�1,) on an average of 240 days per year (Fig. 8). In

2003, the required minimum flow was achieved or exceeded

on just 76 days. The excess volume can fulfill the environ-

mental flow component during low flow periods, or could be

stored en-route should additional storage capacity become

available.

5.6. Surface and ground water quality

A large zone of relatively fresh water (total dissolved salts less

than 1000 mg L�1) occurs in the eastern portion of the LMGA,

mainly close to the Murrumbidgee River, and the Mid-

Murrumbidgee groundwater inflow area. A much larger zone

of fresh water is also present near the center of the basin, but

east of Hay. This spread and increase in the volume of fresh

water indicates that additional fresh water is recharging the

system to the west of the eastern groundwater boundary. This

fresh water might flow from the Murrumbidgee River, and

Yanco Creek.

Groundwater salinity levels are generally low to the east of

the LMGA, except the discrete saline areas associated with the

CIA and MIA. Except these discrete saline areas, groundwater

quality gradually deteriorates to the west and the north.

Table 2 – Average water quality for the Murrumbidgee River d

Analysis Units Surface wa

N Mean Minimum

Nitrogen mg/L 15 0.4 0.3

Electrical conductivity @ 25 8C mS/cm 65 114 48.4

Oxygen dissolved Mg/L 93 9.5 5.9

pH Units 177 7.5 6.6

Phosphorous—total mg/L 57 0 0

Total suspended solids mg/L 58 34.7 4.0

Turbidity NTU 161 31.5 4.3

Total dissolved solids mg/L – – –

The quality of the surface water and ground water

seem similar (Table 2). High turbidity and suspended solids

in the surface water suggest potential fouling problems. In

some zones along the Murrumbidgee, river water is

currently recharging the deep groundwater systems.

Together, this implies that, the high turbidity of surface

water might constrain ASR opportunities. Surface water

and groundwater quality data are required to determine

the level of treatment needed, prior to use in aquifer

recharge.

5.7. Potential artificial storage and recovery locations

We identify potential locations for infiltration basins and

injection/recovery wells based on water availability, aquifer

suitability, recharge potential, and recovery efficiency (Fig. 9).

The estimated annual artificial recharge potential of about

180,000 ML for the LMGA can be achieved through a combina-

tion of injection wells and infiltration basins, receiving treated

water from en-route storage and/or dedicated wetlands. The

resulting estimated annual yield is 414,000 ML for the MGA

that could be used to augment water allocation by about 10%

during drought years.

ownstream of Gogeldrie Weir

ter Groundwater

Maximum S.D. N Mean Minimum Maximum S.D.

0.5 0.2 33 0 0 0.3 0

231 52 13 238.1 182 335 34.5

12.1 1.3 – – – – –

8.7 0.4 13 7.1 6.5 7.8 0.4

0.1 0 – – – – –

264 46.6 – – – – –

250 30.3 – – – – –

– – 3 100 100 100 0

Fig. 9 – Potential artificial storage and recovery locations.

Table 3 – Estimated aquifer storage and recovery costs at potential sites at different recharge rates

Recharge capacity Potential aquifer storage and recovery sites

Infiltration basinnear Tombullen

storage

Injection wellBarrenbox Swam

Infiltration basinnear Lake

Urana and Area

Injection wellnorth of Yanco

Creek

Injection wellsMurrumbidgee

east of Hay

90,000 ML year�1 or400 ML day�1 ha�1

60,000 ML year�1

6 ML day�1 ha�190,000 ML year�1

400 ML day�1 ha�190,000 ML year�1

8 ML day�1 bh�1b90,000 ML year�1

8 ML day�1 bh�1a

Cost items (in AU$)

Capital costsb

Well – 34,000,000 – 36,000,000 36,000,000

Pump 10,000,000 6,000,000 4,000,000 3,000,000 3,000,000

Pipe 200,000 56,000,000 37,000,000 60,000,000 60,000,000

Filtration system – 500,000 – 500,000 500,000

Basin construction 1,000,000 – 1,000,000 – –

Land acquisition

(not included)

2.4 ha – 2.4 ha – –

Operating costs

Basin cleaningc 1,000,000 – 1,000,000 – –

Basin skimmingd 75,000 – 150,000 – –

Pumping power and

opportunity cost

of water

24 ML�1 0 ML�1 24 ML�1 60 ML�1 60 ML�1

Supervision 10,000 40,000 10,000 40,000 40,000

Total recharge costs 40 ML�1 174 ML�1 76 ML�1 171 ML�1 171 ML�1

Total extraction cost

(using existing bores)

22 ML�1 – 28 ML�1 –

Total extraction cost

(using new bores)

52 ML�1 174 ML�1 58 ML�1 171 ML�1 171 ML�1

Annual recharge is estimated based on available water supplies and probable local capacity of the aquifer based on the aquifer total.a bh = borehole.b AU$ 1.00 = US$ 0.80 (as of March 2007).c After 5 years of interval.d Twice a year.

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8 485

Fig. 10 – Hypothetical life cycle of aquifer storage and recovery scheme.

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8486

5.8. Cost of artificial storage and recovery

The cost of aquifer storage and recovery depends on the

opportunity cost of water, groundwater depth, extraction rate,

pumping distance and height, and the aquifer recharge

method (Topper et al., 2004). Conventional recharge methods

include surface spreading, infiltration pits or basins, and

injection wells. Surface spreading and infiltration basins allow

water to infiltrate into an aquifer largely by passive means,

saving energy. Injection wells are useful where impermeable

strata between the surface and the aquifer make recharge by

surface infiltration impractical, or in areas with limited land

for surface spreading. We consider infiltration basins and well

injection/recovery as suitable methods for recharge of deeper

aquifers within the LMGA.

Table 3 shows the cost of ASR schemes using infiltration

basin and injection wells at five potential locations. We

calculate ASR costs using the above recharge estimates,

Fig. 11 – Comparison of cost of aquifer storage and recov

assuming full use of the local aquifer recharge capacity. Less

than full use will increase the cost per ML. The estimated cost

of an ASR scheme using surface infiltration basin ranges from

AU$ 62 ML�1 to AU$ 134 ML�1, whereas it ranges from AU$

171 ML�1 to AU$ 174 ML�1 using injection wells. The costs are

indicative only, as these are not estimated spatially for each

plot of land, but are based on the likely costs for each recharge

location. Also, the cost of land acquisition is not included. In

general, surface methods are preferable due to lower capital

costs, greater simplicity, and lower operation and mainte-

nance costs.

We conclude that aquifer storage capacity can be devel-

oped at a lower cost than en-route storage (AU$ 326 ML�1) and

without adverse environmental consequences or evaporation

losses (Pratt Water, 2004b). In general, the cost of ASR is less

than half the capital cost of conventional water supply

alternatives, especially those involving the development of

new reservoirs, treatment facilities, or extensive pipelines.

ery cost with water trading and surface water price.

a g r i c u l t u r a l w a t e r m a n a g e m e n t 9 5 ( 2 0 0 8 ) 4 7 7 – 4 8 8 487

5.9. A Hypothetical artificial storage and recovery scheme

We develop a hypothetical ASR scheme at one of the potential

ASR locations in the LMGA to help understand the effective-

ness of ASR in mitigating drought. We assume that a water

allocation of 100% denotes a normal year, while an allocation

less than 25% denotes a dry year. We estimate that during a

normal year, a recharge of 90,000 ML can be achieved, based on

an ASR scheme with a potential of 180,000 ML but operating

only in a portion of the total area. Assuming 85% recovery

efficiency, 77,000 ML of water can be recovered during a peak

requirement period every year or stored for a longer period

and drawn during a drought. Fig. 10 shows the life cycle of an

ASR scheme. The cumulative volume indicates the changes in

aquifer storage with the storage and recovery of water.

We compare the cost (both upper and lower bounds) of an

ASR scheme using an infiltration basin with the market prices

of water (Fig. 11) obtained from water exchange (http://

www.waterexchange.com.au/). Assuming a smoothly func-

tioning water market, temporary water trading prices reflect

the opportunity cost of water. During drought periods such as

2002–2003 and 2006–2007, water allocations were very low

(<20%) whereas the temporary water trading prices were very

high (around AU$ 450 ML�1). The comparison of ASR costs

with temporary water trading prices indicate additional

benefits of ASR schemes during drought periods. During good

allocation years the ASR costs are higher than the cost of

supplying surface water or temporary water trading prices.

However, during dry years, the ASR scheme has a potential to

deliver benefits that are three to seven times larger than

associated costs or temporary water trading prices.

6. Conclusions

Water availability in the Murrumbidgee Region is dependent

on climatic cycles that vary from year to year. Irrigation

enterprises in the region, especially in the Lower Murrum-

bidgee Groundwater Area, which rely on groundwater pump-

ing, can utilise artificial storage and recovery by storing water

in underground storage during winter, high allocation periods,

and withdrawing water during dry, low allocation periods.

Underground storage can thus serve as a water bank for

augmenting water supplies during drought periods.

We estimate that at least 180,000 ML can be stored each

year in the Lower Murrumbidgee Groundwater Area through

the combination of injection wells and infiltration basins. If

the predicted recharge rates are achieved, the long-term

annual yield of the Murrumbidgee Groundwater Area might be

as much as 400,000 ML.

The estimated cost of a recharge scheme involving

90,000 ML year�1 (on part of the study area) using an

infiltration basin range from AU$ 62 ML�1 to AU$ 134 ML�1

while the cost estimates for injection wells range from AU$

171 ML�1 to AU$ 174 ML�1. Underground storage capacity can

be developed at a significantly lower cost than surface storage

facilities without undesirable environmental consequences or

evaporation losses.

Artificial storage and recovery can be used as a water

management tool for reducing the impacts of droughts in the

Lower Murrumbidgee Groundwater Area. During low water

allocation years, artificial storage and recovery can provide

benefits that are three to seven times larger than the costs.

Acknowledgements

We wish to acknowledge funding support from Pratt Water Pty

Ltd. Comments from anonymous reviewers helped improve

the overall presentation of our work.

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