COME©NWEAL,11 OF A USTRALIA

DEPARTMENT OF NATOONAL DEVELOPMENT

eo. cps./

3

RALEAU SOU GEOOGY INDMZ, EC)

Drought and Groundwater in theAustralian Capital Territory

11^'

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DROUGH1 AND GROUNDWATER IN flit AUSTRALIAN CAPITAL TERRITORY

by

G.M. Burton

Record 19603

(Paper presented at the Symposium:"THE HYDROLOGICAL ASPECTS OF DROUGHT - with particular

reference to the A.C.T. & environs" held at Canberra, May 1969 2

and organized by the Hydrological Society of Canberra)

The information contained in this report has been obtained bythe Department of National Development as part of the policy of theCommonwealth Government to assist in the exploration and developmentof mineral resources. It may not be published in any form or usedin a company prospectus without the permission in writing of theDirector, Bureau of Mineral Resources, Geology and Geophysics.

CCIT2ENTS

Eam.SUMMARY

INTRODUCTION

GROUNDWATER DROUGHT^ 1

GROUNDWATER IN THE A.C.T.^ 2

Observation bores^ 4

Groundwater hydrographs^ 5

THE 1965-1968 DROUGHT^ 5

Catchnents in drought^ 7

CLIMATIC CHANGE^ 7

Lake George^ 8

ACKNOWLEDGEMENTS^ 8

REFERENCES^ 8

APPENDIX : PROGRAMME OF SYMPOSIUM

FIGURE 1: Hydrological Cycle in A.C.T.

2 : Climatological Data Canberra-Qneanbeyan Area

3 : Groundwater provinces of Australian CapitalTerritory

4 : Groundwater level observation bores 1, 2, 7, 8, 10

5 : Hydrographic data, A.C.T. & Environs

6 : Fluctuation in water level, Lake George, N.S.W.1819-1968

7 : Annual Approximate Water Balance, Lake George, N.S.W.

8 : Lake George Hydrological Data 1958-1968

TABLE 1 : Regional Groundwater Observation Bores, A.C.T.& Environs

(NOTE: This paper should be read in conjunction with the otherpapers of the symposium (see Appendix). Copies of allpapers have been lodged as a volume in the Bureau ofMineral Resources Library / Canberra)

stimmay

The nature of a drought is defined and the important differences

in both the character and duration of surface and groundwater droughts are

stated. The occurrence of groundwater in the Canberra area is explained,

and the role-of-groundwater in maintaining the base flow of rivers and

springs is stated.

The 1965-1968 drought started with groundwater storage at a

high level: groundwater was able to sustain the flow of rivers and

springs during the severe shortage of rainfall in 1965 and ameliorated

the severity, of the early stages of the drought. Groundwater storage

declined progressively and was unable to sustain the flow of most springs

and rivers in the very dry summer of 1967/68. The yield of bores was

little affected-by the drought and the bores continued through the

drought to supply badly needed farm water supplies.

The importance of observation bores in hydrological networks is

stressed. Attention is drawn to the importance of the hydrograph of Lake

George that forms ane_of the few long term hydrolagical bench marks of the

Canberra area; its interpretation will yield valuable guides to possible

climatic changes.

INTRODUCTION

This paper deals specifically with the behaviour of groundwater

in the Australian Capital Territory during the drought which commenced in

1965. It also contains supplementary information on the drought gather-

ed during water balance studies in the Lake George catchment adjoining

the A.C,T.

Before the 1965 drought can be considered in detail it is

necessary to define a groundwater drought, and describe the normal

groundwater regime in the A.C.T.

GROUNDWATER ]OUGHT

I propose to define drought as the state of strain imposed on

the natural environment and human culture of a specified area by an

appreciable reduction in the natural supply of moisture.

I would consequently define a groundwater drought in a speci-

fied area as a drought in which normal periodic or seasonal recharge

becomes insufficient to maintain groundwater at a level where it will

carry out its normal natural, and reasonable developed functions in that

area. These functions in any area may be several of the following-.-

To maintain base-flow of any effluent rivers,

to supply reasonable bore outputs,

to maintain springs,

to supply phreatorphytes by direct contact; and

to promote growth of limited areas of pasture by slow seepage

through soil.

The failure of adequate recharge may occur by the complete

absence of recharge in one annual recharge season or by the cumulative

effect of below-average recharge over a number of seasons. A groundwater

drought can usually be considered in terms of years rather than weeks or

months. It generally will not develop until a year or more after the

onset of a long agronomist's or meteorologist's surface drought, and may

not end for several years afterwards. Not all agronomist's droughts lead

to groundwater droughts.

2

The severity of the groundwater draught will be measured by the

degree of strain imposed on the environment and culture. Only one of

the functions of groundwater, such as the flow of high-level springs,

may fail in a mild drought; in severe drought major streams may cease to

flow as well as the high-level springs.

Recharge or replenishment of groundwater depends on many

factors, the more important of which are rainfall, evaporation, landform

(including soil distribution), geology, and vegetation. The areal

extent of a , groundwater drought will be controlled by the local influence

of rainfall and evaporation on the other factors. _We may have a severe

local groundwater drought in a belt of limestone country, such as Wee

Jasper, while immediately adjoining country in volcanic rocks is not as

seriously-affected. The cause of this difference is the much higher

permeability and easier drainage of the limestone than the volcanics;

the specific yield of both rocks would not differ greatly.

Before detailed discussion on the 1965-1968 drought, it is•,

important to consider briefly the general occurrence and behaviour of

groundwater in the A.C.T.

GROUNDWATER IN THE A.C.T.

Groundwater in the A.C.T. and environs occurs mainly in frac-

tures, joints and weathered zones of crystalline rocks such as porphyry,

granite,. limestone and metasediments (Fig.1). Alluvial aquifers are

restricted to the Lake George basin and small areas along mature sections

of the Molanglo and Murrunbidgee Rivers. Very minor perched aquifers

occur in a few small areas of special soil or scree.

The Canberra region is part of the headwaters catchment of the

Miirrumbidgee River. Cainozoic faulting has led to rejuvenation along

most major rivers and many minor streams: the drainage network is dense,

in keeping with the relative youthfulness of the major streams, which are

only two to four miles apart. The rejuvenated streams are effluent and

discharge groundwater moving in the neighbouring crystalline rocks for

most of almost every year. host groundwater does not travel fart from

the recharge areas (which usually are areas of thin skeletal soils an the

Fig. IHYDROLOGICAL CYCLE

i n A.C.T.

1 V,'\\ . \ \ \IW\ !1 \\\

^

• ' \ Precip4a;ion \ 1^, 11

^. \\ ''AVt \\' \\^\ \\

^

\6 'll . \\\ ' ))1\1\ .^l '^•

. 1 '°01 \ '0 1 \ 61\\

by trees^

I \^\

Groundwater infiltrationI along fractures

ea."'Wt■it 'Or' P..! A_ mer a',

-,.....Piezometric +6^+ + +^',Spring

surface^ 1..(Water table)^"1"..^+^+ +^+^ f.,T

+ + + + + + + + +^\+ + + Granite + + + + +V.....

Sod^ (Little fractured but deeply weathered)^+%. 1--"•"---y., ---,^-^"......^

i/A^/ + + + + + + + + + + + + \ , 7 ) i ,7. 1 I

ifi^1 4-7,1-- ivi

' -A ',, .-7 + + -4- + 4- + 4- + + + + ++ + + + 4- + + + + + ++ + +.1.< L.' Gr'u:+rolZfrefrrXo:,a 'n s 'L u pd,,,aser ' 1- 11- V^'''

'' >4<4', AL

,...1,

> s( + + ++ + + + + + + + + + ++ + + + + + + ++ + + + + +‘\ )" 7 L 1 > r 1 4 : 7 L 1 discharge, +^>

^

> L.^r_-I. < P.

C. > <^..' 1 -'^r ' + + + + + + + + + + + + + + + Docile volcanics^-.1.).r‘.r 7 4 -T r 1 4

7^1 < ,^A- 4 + 4 .4 4 + 4 4 4 4 4. ± 4 4 4 \ (Well fractured and weathered)^< v < j.,› < v L

^To accompany Record 1969/r3^155/A167427

evaporation

Plant transpirationand evaporation

IntercePti" ' 44*

AftitrumbicigeeRiver

3

higher ground and non-perennial water courses on the upper and some of the

lower slopes) to springs along the major effluent streams; the distance.

is commonly only one to four miles.

The aquifer in the crystalline rocks is generally the upper

mantle of open-jointed and weathered rock. This mantle follows approxi-

mately the form of the local topography: the most permeable and porous

part of the aquifer is only about 15 to 100 feet thick. Because the

-porosity occurs only in fractures and weathered material the specific

yields are very low - possibly only about 0.0 to 0. Transmissibility

is low - commonly about 100 to 400 gallons/day/foot. Most importantly :

however, the aquifers have a marked natural slope: commonly about 1 in

40 in the ridges and , plain country, and about 1 in 4 to 1 in 10 in the

ranges.

Hence we may summarize: our effluent streams are fed mainly by

short thin dipping aquifers of low permeability and very low specific

yield. It does not take long to dewater almost completely the main

part of the aquifers, which really owe their efficiency to the very .

great regularity of rainfall in the autumn, winter, and spring (Fig.2).

Some faults and shear zones that form thicker parts of the aquifer, and

'certain geomorphological restrictions, maintain a long slow supply to

major streams even after dewatering in a long drought.

' The process of recharge is . as follows:

In autumn the moisture-deficient soils start to receive appreciable mois-

ture as evaporation decreases in the cooler months (Fig.2); colder

temperatures slow 'down plant growth and their moisture consumption;

precipitation continues at approximately the same rate throughout the

year.. The length of the recharge season and quantity of recharge depend

very much on the late April and May and especially, the spring

precipitation.. Particularly important is frequent steady low to medium

intensity rainfall that penetrates rather than runs off soil. Absence

of rain in the spring and autumn has a two-fold effect - it increases the

length of the groundwater discharge (or recession) season-and shortens

the recharge. Hence groundwater droughts commonly originate, in these

months.

Summer

Winter

HydrologicalSeasons

CANBERRA

111111111IIII35 40 45 50

5

1111,111i

0 5^10 15 20

30 40

OUEANBEYAN10^

1671-1966

- Fig.2

Climatological DataCanberra - Queanbeyan Area

MEAN RAINFALL AND EVAPORATION

1-CC crirCra CC ...WUJSC-7_0.111).DM VD03

4z-10E0ZZ

a.tucPwto 2°

EVAPORATION

MI RAINFALL

ANNUAL RAINFALL HISTOGRAMS

Rainfall in inches

Bureau of Mineral Resources, Geology and Geophysics. To accompany Record /969/73

155/A16/436

4

The Canberra region is only about 1,000 square miles in area,

-but the natural environment varies markedly across the region. Different

combinations of geology, landform, elevation, rainfall, evaporation and

vegetation have led thel.Bureau of Mineral Resources to divide the region

into six groundwater provinces (Fig.3), which are only slight modificat-

ions of Griffith-Taylor's physiographic subdivision of the Territory.

Observation bores

Groundwater observation bOres are a normal part of a well-

designed hydrologic network. However, they are commonly one of the last

parts of the network to be established. This is understandable because

they can be.expensive_to.construct, the design of a network requires con-

siderablelhydibgeClogical knowledge and experience, and commonly some

experience in systems design, if maximum efficiency and economy are to be

achieved.

As part of a policy of assessing the groundwater resources of

the Canberra region and gathering basic hydrogeologic data for its

various provinces, the Bureau has progressively established a small

network of observation bores over the last 12 years.

Ecanomy has been achieved by using Bureau drills in short slack

periods. Several graziers have also made their private bores available.

The Bureau has kept liaison with officers of the Department of Works and

Bureau of Meteorology, the Forestry and Timber Bureau and other

organizations in order to close the important groundwater gap in the data

of the network covering the local hydrologic cycle. Exchange of data

during the recent drought suggests substantial progress in our knowledge

of the cycle.

Also,- Under a limited educational programme, a number of local

graziers have been, trained to record and understand groundwater levels in

their boresi ,Ialong'with their usual rain and stream measurements. This

should help the graziers to understand the full water-budget of their.^.properties. With experience they will be able to predict the failure

of springs or streams in time of drought.

The location of the observation bores are shown in Fig,3 and

details of the terrain, rainfall and bore data are given in Table 1.

GEORGE

REFERENCE

Groundwater Observalion Barewith reference number

Boundary olGroundwonwPromhse

s•=, Roads

Railways

Territorial Boundary

Topographic contours -interval 3000.

Milt

155/616/434

GROUNDWATER PROVINCES^

Fig.3

OF

AUSTRALIAN CAPITAL TERRITORY

TABLE I : Ri61011 11 61101111NATER °RV:RI/010H ^& ENVIRONS

Ref.No.

Bore Name &Lo catlon

Groundwat.FArPrbVin de.

(P1 atel i 2)

•a eliit I On :1;

bore: ft.a.s.l.

Nature e -;' Catehment ■' Depth to

water1/ 2/67

Maximumvariati on in

1 nvel s

-APP rm.yield

ofBore- .

•g.p.h.

Ann. Rai n fallin inches

Geology'

PhysiographyVeciegcico

Cul tireGaugingStarted

.

. )L.c,

Beloohnsn 5(Gribble'sFarm)

Ridges & Plain 2140 25 Porphyry-intrusive

Higher plcOes of lowdivide

Natural grassland Dec. 19 58 48.8 ft 22 ft r200

2 Belconnen 67 & 8(C.S.I.R.O.Farm) -^-

•1940(8) 25 Porphyry.

intrusiveSmall^perched basinwith granite bar

Grasslands, Partlypasture. improved

Dec. 1958 9,3(Bore 8)

.

10 1500(6)'20(7)900(8)

3

.......

Jeir 1(Jai r Station) a 1875 25 . Acid volcanics

- medium dipMargin of broadplain.^•^-•^-

Mainly-naturalgrassland. -•-• •

•Oct.^1961 19.7 5 $1 00

4 Beloonnen 13(BlackMountain)

"^e 2032.6 25

•

Si ltstone and 'Slate - stronglyfolded-

Iiiiiir -31 OPeS • Ofaircirig di vi ding•ri dge

Mai iil Y . natural .^-Eucalyptus forest

........^......

Mar, 1966

•

880

•

1 20

5

_

City 13( B.t. R.Fyihtii Of()

•1 895 25 Vol can 1 Cs and

sediments .strongly sheared

LOW 'ridge on roll ingplain^.

Natural grassland ..Parily .diiiilaped ailight industrial area

June 1966 19,7

.

6 >10,000

6 Lanyon 5("all poseVal 1 ey")

W. GourookHighland

2350 25 Porphyry bier sl OPes - Of . MajorPardlied-iilley partlyrejuvenated

Grassland ....Pastureimproved withclover^- .

Aug. 1960 36.9 13 100.

7 Tennent 1(HoneysuckleTrackingStation)

Gudgenby.

3520.8 35 Granite - deeplyweathered On^.poiiibl e line-ament

Lollar . S1 opeS . O1 deepl ydissected 'Valley^'

Mainly hiturat ..•Eucalyptus forest

April 1966 22.5

.

2 1 00

8 Cotter River 1(Corin DamRoad)^•

Bimberi Mt. &Paddy's River

4064,2 40 Granite ..! deeplyireitherid Ori " . .possible line-ament

MajOriaddle - in majordividing. raage.

Nitiiral EtIcalyptusforest^.

April 1966 1.2_ . 14 >100

9 Paddy's River(TidbinbillaTrabkingStation)

Paddy's River 2300(?) 30 Granite - somestrOngly foldedslate

Lamer slopes on marginof broad valley^.

Mainly EUcalYPtUs •fiest in sredhargeitibit.--reinSinder .natiiril-graisliiidi- .some lawn at Station

May 1987.^-

8,1^•(12/5/67)

1800

5

Groundwater hydrographs

The hydrographs from several of the observation bores are shown

in Fig.4. It is impossible to discuss each hydrograph in detail.

Several points, hotever, should be made.

The regularity of recharge in the cooler months can be - clearly

seen. Significant differences can be seen between the hydrographs.an

Bore 1 gives the best record; it is in/ideal situation on the groundwater

divide between Hall and Ginninderra Creeks. Here the water table is

deep; movements are obvious and large. This contrasts with Bore 2,

where the water table is shallow;, here the effects of use of water by

plants can be seen, but slight "noise" due to barographic changes affects

the record.

Figure 5 shows two of the hydrographs together with rainfall,

evaporation (data from Forestry and Timber Bureau), and minimum flow in

the Queanbeyan River (data from the Commonwealth Department of Works).

THE 1965-1968 DROUGHT

. I am Sorry that -so much has had to precede the main point of

this lecture.

. Reference to Figures 4 & 5 shows very clearly the course of

the groundwater drought. Several points stand out.

(1)Late winter and spring rain in 1964 brought groundwater to

record storage levels.

(2)During the severe surface drought of the first four months

of 1965 there was no groundwater drought.

(3)The abnormally high level of groundwater storage of January

and February kept many rivers and springs flowing more strongly than

would normally have been expected.

(4)The groundwater drought started about June when the poor.

autumn and winter rains failed to build up soil moisture after the

summer and caused an almost complete failure of recharge.

(5) The groundwater drought became progressively worse until

September 1966, when reasonable recovery occurred.

GROU DIARTE-P, LEVI OBSEPVRT ION BORE 102.13)

1961^1962^1963^1964^1993^1656^1967^1438:6.30

ftGROLADNPTF R LEV

GAO CNA T FR LEVr-L

1%9^1930 1936^1967^19681961^1957^1963^1%4^1935

OBSERVAT I ON BORE 8

/--"" \ \

\fr\'

1959^1960^1961^1662 1963^1964^1965^1966^1967^1968

OB5E-VAT ION BORE: 7

1630^196. 1^1932 196 4^1965 1936^1637^1968

G1-41JNDIARTER LEVEL OBSERVATION BORE 21462

A

Fl

•CP

GROLICIAPTER LEVEL OBEPVAT ION BORF 1

2W.)

1

1993^1960^1961^1962^1963^1964^1955^1936^1967^1958

To accompany Record 1969/73^ I 55/416/600^- F194

160

E^80...

- I 55 /A16/443

1959^1960^1961^1962^1963^1964^—1-965^1966^1967

HYDROGRAPHICDATA,

2100-- A. C . T. & ENVIRONS

re:5r:IngGROUNDWATER LEVEL

in2092- D'OgreSS OBSERVATION BORES

R.

L.

2084Belconnen N25

.T 1942_

1934 Belconnen Ne 7

NETT MOISTURE(RAINFALL-

POTENT. EVAPORATION)

(4-Weekly— Periods )Canberra

MINIMUM MONTHLY FLOW

Queanbeyan River

To accompany Record /969/73

6

(6)The low rainfalls of autumn and winter 1967 were dis-

astrous; the groundwater record started to show that recharge for 1967

was unlikely, and that base-flows of rivers in the summer of 1967/68

would be very low; Warnings were issued to various agencies of the

probable low flows.

(7)Substantial recharge occurred in 1968.

(8)The drought had a noticeable effect (change 715%) on , the

maximum rate of pumping of probably only about 10% of the bores in the

area; the effect was very noticeable (change .25%) in about half of this

10%. In all cases of changes in output that came to the Bureau's

attention it was possible to suggest simple changes in the pumping

programme so as to produce the same overall daily yield as before the

drought.

(9)For the past five or six years the Bureau has been able

to use the results from its observation bores to site and determine

the correct depth for bores so that droughts will have no appreciable

effect on their output.

(10)Thus although I would say the surface drought of 1965-

1968 was very severe I would say the groundwater drought was only

moderately severe. Groundwater continued to supply most bores with

their normal outputs; it continued to maintain the base flows of

rivers and springs in the early stages of the drought and only failed

to maintain useful flows in most of these in the summer of 1967/68.

(11)I would still hesitate to say that the groundwater

drought ended completely in 1968. I believe the rainfall of May and

June 1969 will be the deciding factor.

The importance of farm bores can be seen from the foregoing

points. Apart from their normal uses they are a safeguard against

the complete failure of farm water supplies during the severe droughts

that occasionally occur in the Canberra area and cause most surface

water supplies:to dry up.

7

The hydrographs show the importance of observation bores. They

give an added certainty to interpretation of river hydrographs. In a

river hydrograph light winter rains and shallow perched springs may mask

the main base-flow which comes from the main deep aquifer; the observat-

ion bore, however, records the occurrence of recharge and helps in

prediction up to five months or so ahead.

Catchments in drought

The behaviour of catchments in drought is interesting.

The Cotter is a long narrow catchment. Much of the aquifer

supplying base-flow dips steeply into the valley and has quite open

joints. The ratio of the area of discharge to general area of storage

is surprisingly large. In normal times the aquifer is regularly re-

charged by the excellent rainfall of the catchment and the aquifer pro-

vides an excellent continuous base flow. However, in the rare lengthy

near-total absence of rain the storage of the aquifer rapidly declines

and base flow declines rapidly also.

CLIMATIC CHANGE

I draw attention to Lamb's (1966) hypothesis of a major

climatic change in 1960. I believe that some of the local hydrologic

records, including Lake George, support it.

One can see how even a small change in our autumn and spring

rainfalls, or an increase in their variability, could affecf our water

resources management.

The more complete are our hydrologic networks recording all

elements of the hydrologic cycle the-more easily will we be able to

detect long term variations in climate and measure their effect an each

element of the cycle.

Lake George, which has one of the longest hydrologic records

. in Australia, may be a very useful tool in the examination of such

climatic changes.. We still need, however, to know much more about the

behaviour of the lake in its lower stages.

8

Lake George

Figure 6 shows the hydrograph of Lake George since 1819.

The Bureau has tried to gather carefully measurements of the

lake during 1965-1968 drought, and these are shown in Figure 8. The

graphs show the mean of rainfallfrom the Bureau of Meteorology's stations

at Bungendore and. Collector, the temperature of the water, and salinity

(total dissolved salts in parts per million). Since the lake has

shallowed the salinity has fluctuated rapidly; it will be understood

that one inch of rainfall or evaporation makes a marked change on the

salinity of 6 inches of water near the western shore: wind and waves

will ultimately mix the shallow component with deeper water to the east.

When one looks at Figure 8 one wonders if the 1965 drought did

end in 1968. The trend has not changed substantially. .

ACKNOWLEDGEMENTS

I gratefully acknowledge the considerable help of colleagues

in the Bureau of Meteorology, Commonwealth Department of Works, Forestry

and Timber_Bureau, and Land Research, C.S.I.R.O., in supplying data and

helpful discussion.

The co-operation of local graziers has been outstanding. Of

particular note is the help of Mr T. Gribble, Gribble Estate, Dr R.

Reader, "Melrose Valley", Jeir Station Pty Ltd,Ear J. Gorman, "Taliesin",

Mr P. Osborne, Grantham Park and Mr S. Smith, Leonia.

Hydrologic records would not be gathered without dedicated

Technical Assistanb6 and_I have been grandly served by mine. The •

encouragement of senior -officers is always an aid and I have had this

both in the Bureau and the Department of National Development.

REFERENCES

LAMB, H.H., 1966^Climate in the 1960fs.^Geogr. J., 132(2), 183-212

NOAKES, L.C., JENNINGS, J.N., & BURTON, G.M., 1964. - Notes an the

Lake George and Lake Bathurst Excursion, in Geological ExcuriDion3

Canberra District, Bur. Miner. Resour.

1 Pig.6

FLUCTUATIQk -PLWATER LEVEL LAKE GEORGE N.S.W. 1819-1968

A111111111111111111MM ^laril

1111110111111111101111111111111111111LTIM11111lIWWArraTIONAINIMMOMMOMMINCIA , 111111111111116,MOO

WM, • tr 114 La*W 11.11.11^d Soft Uri tamale. Lauft 0.0.0 gi Mira emonnall

•

• Ci

Amended from: NoakeseTenninge & Burton (1964) : 1

\

LAKE CATCHMENT-60SO MiLES(1-11-63)-4

E..p...tion a °bold45 depth (mainly Nov. to APril)

0

LAKE GEORGE, N.S.W^ .Fig' 7

ANNUAL APPROXIMATE WATER BALANCE

\\^

\ \ \ \ \ \\\ \\ \ \ \ \ \ \ " \ \\

,

\ \ \ \ \ \ \ , ,^, \ \^ ,,

. \ \ \ \ \ \ \\\, \ \ \ \ \TO\TA\L\CA\ TC\ AIH \ EN\ T\IN\CL\UO\IN6‘ LAKE - 360 SO. MILES -\\^ V\

^VT CATCHMENT-300 SO MILES 0-1/-671\ .,

\\\\\V\^\\\\\\ '\\ h \ \\\\\\\\\ \\\^\\Roinfoll 7 .Dout26\\\\ \‘,.\\'‘.

\ \ \\ \\\\\\\ \ \\ \\\ \\ \ \\ \\\ \\ .

1 Per colationr I rainfall ,,^\ /iv, oh\

\ "

\ \\

\\\ \\\

\\\\\\ .. . ._

,

\' \62r

Olaiwi\\\EC7=\\‘'11°'\°1\52\:(3\\':\\: \'\\

‘ \

\^I^\\ s

',......4.' ,'I

^\ ‘ \^\^1••••.„..",...^Use in for dams etc

\\^

\ ' \ \^'\

o

sz^Rainfall ".4 about26" depth on lake

To accompany Record 1969/73

Itl. Spring

............ f.... .^LoSS to shore line evaporation

PALAEOZOIC and use by humans, stock,Scree, doses, • ---_---- —'''' 17-7.7 ....^ ond fauna - very small

METAMORPHIC^allaviamawaanes "s '7 -___.= Thick cloy7Ihd --- _ _^ ' -^_ impermeable cloy floor (negligible\ ---=— sand beds ^._ - Postage of water too' from lake)

B E DR 0 C K^ \^ —.-- ---5tOID. Weathered rock

"- Slow mMor groundwater movement•^ main& to Lochlon River

0, ,,no Catchment areayellf, as lake rises or foils

- Lake area

Ratio =5 1-11-63

Ratio =8 / - 3-69

and hence depth of run- in will vary even though depth of run-off is the same IS5/416/505

1

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- APPENDIX

PROGRAMME OF SYMPOSIUM

09.30 Opening Address - Minister for Interior, Mr Nixon

09.45 Meteorological aspects of the 1965-68 Drought in the A.C.T.

V.J. Bahr, M.E. McCawley and K.J. O'Loughlin, Met. Bureau

10.30 Morning Tea

11.00 Hydrology of Canberra's major water storages in the 1965-68- Drought.^-

Fitzgerald, Commonwealth Department of Works

11.30 Agriculture and Rural water supplies in the A.C.T. duringthe 196568 Drought.^-

T. Taylor, Commonwealth Department of Interior

12.00 Drought and the A.C.T. Forests.

A.J. Marthur and R. Thistlethwaite Forestry ResearchInstitute

• 12,30. Luncheon

14.00 Drought and. Groundwater in the A.C.T.

• G.M. Burton, Bureau of Mineral Resources

1430 Rainfall.analysis techniques and Drought

J. Maher, Bureau of Meteorology

15.00 SimulatiOn techniques for the water balance in a droughtsituation

J. McAlpine, C.S.I.R.O. Division of Land Research

15.30 Afternoon tea

16.00 Open discussion on drought and symposium summary

Discussion Leader: A.I. McCutchan, Department of NationalDevelopment.