Eucalyptus Management on Water Catchments inSouth-eastern Australia

F. R. MOULDS (*)

The natural distribution of Australia's major forests is tied to regionsof dependable rainfall, usually within 100 miles of the coast. Apartfrom the extra-tropical rain forests of the north-east coast of the maín-Jand, the predominant species are of the genus Eucalyptus. The treelinc is located at about 5,800 ft. above which are grassy plains. ThereL:;no permanent snow and therefore no glaciers. Average persistenceof snow above the tree line would be five to six months, depending uponaltitude and exposure. The highest elevation is at Mt. Kosciusko, 7328 ft.on the east coast mountain chain.

In very simple terms the Australian mainland has a wet east andsouth-east coast and an extensive, dry interior. Because of the smallproportion of the total land area which receives a reasonable rainfall,questions relating to water supply and water use assume a very importantrole in many aspects of government policy and largely constitute thebasic determinants in location of industry and distribution of the people.

It has frequently been stated that availability of water wiU ultima-tely determine the upper limit of Australia's population, which could beof the order of 30 millions. The Water Research Foundation of Aus-tralia has recently estimated that only two to three percent of the totalrun-off of approximately 200 million acre feet is used at present andthat 30 million acre feet per annum is the maximum run-off which couldconceivably be made available under present conditions. There is noutilizable run-off where rainf'all is less than 20 inches per annum, whichis the situation applying to approximately 75 percent of the totalland mass.

The total probable water use in the near future for agriculture,industry, power generation, stock and domestic supply, at the level requi-red to maintain present living standards, is about one acre foot per personper annum. It is evident that, if the limit of population referred tois even to be attained, much less exceeded, close attention will need tobe paid to achieving the greatest economies in the use of water foragriculture, to reclamation and re-use of water wherever practicable, andto a research programme leading to the economic de-mineralization of

("') Forest Commis: ...io n. Vtctori«. Au st ruliu .

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underground and sea water to supplement surface run-off. At the pre-sent time, many miles of unlined channels are used for conveying irri-gation, stock, and domestic water into low rainfalI areas: such chan-nels together with shalIow lakes used for storage and regulation, resultin high losses through seepage and evaporation.

The eucalypt which occurs at highest elevations is snow gum (E.poucütora var alpina), a multi-stemmed from not used for commercialtimber production. At elevations extending from approximately 2,000'to 4,500' are hygrophyllous (temperate moderate rainfall) forests ofmountain ash, (E. regnans) and more open stands of alpine ash (E. dele-gatensis), brown barrel (E. fastigata) and shining gum (E. nitens).On the foot-hills and lower country occur stands composed of a widevariety of eucalypt species such as blackbutt (E. pilularis), grey iron-bark (E. paniculata) and various stringybarks, peppermints and gums.On the drier slopes occur extensive stands of slow growing, durabletimber species such as bloodwood (E. gummifera), red ironbark (E.sideroxylon) and box. Along the main water courses and flood plainssubject to periodic inundation from flood waters are riverain forests ofred gum (E. camaldulensis).

There are major differences between these broad categories of euca-lypt types. The mountain species occur in areas of relatively highrainfall (more than 40 inches per annum and subject to some wintersnow falI) generalIy on good quality soils, and are associated with anunderstory of shade tolerant non-eucalypt species, often hygrophylIousand dense near permanent water. The mixed eucalypts at elevationsbelIow those of the mountain forests are subject to lower rainfall (25 to40 inches per annum) and occur principalIy on sedimentary soils,although they grow equally well on basaltic and granitic soils. Becauseof the drier conditions the undergrowth is relatively sparse and in manyareas almost non-existent or limited to grasses and bracken. Many ofthe streams rising in the foothill country favoured by these mixed fo-rests flow only during the winter months and immediately after rain.The irombark and box forests which occur generally on poorer sedi-mentary soils with lower rainfalI (15 to 25 inches per annum) carrylittle or no undergrowth; streams rising within these forests flow onlyfor short periods throughout the year. The riverain red gum forestswhich exist in areas of low rainfall and are dependant upon seasonalinundation can be entirely excluded as far as catchment considerationsare concerned.

The Government forest services (Commonwealth and State), whichcontrol most of the forested areas throughout Australia, pursue a policyof multiple purpose management for water supply, timber production,and recreation, except in a few small isolated instances where domesticwater supply or public recreation are overrinding considerations.

There are a few instances in which areas not under the control offorest authorities are managed solely for domestic water supply. Wheresuch conflicts of management policies have arisen, there are usuallyunderstandable historic reasons. Australia being a young country in sofar as white settlement is concerned, with a history of not much more

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than 100 years, has not long passed the usual pioneering stage of exces-sive uncontrolled logging operations. It was during this phase of «cut-out and get-out» towards the latter part of the last century that actionwas taken to reserve certain areas and vest them in the water supplyauthorities to preserve the efficiency of the catchments. At this timeforestry was little in evidence and alternative timber resources wereundoubtedly abundant. A strong public feeling has been built up, thatthis is the best way to ensure the protection and preservation of domesticwater supply catchments.

In view of this difference of opinion and at the request of the tim-ber industry, which is now becoming short of saw-logs, a StandingCommittee of Parliament recently instituted enquiry into the utilizationof timber resources on catchments in the State of Victoria. The prin-cipal recommendations made following that enquiry are summarised asfollows:

1. It is essential for all forested catchments to be adequately providedwith access roads for fíre-protectíon purposes, both in and around thecatchments.

2. The policy of excluding timber mills from locating in forest areas berigorously adhered to.

3. Uncontrolled logging should not be permitted in any catchment area.4. Controlled logging based on the established silvicultural and regenera-

tive management practices of the Forests Commission of Victoria bepermitted under strict supervision in all catchment areas.

5. All logging operations should be carried out on the basis laid downby the Forests Commission subject to the following amendment toclause 8 of the principIes contained therein (see later reference)to read:

"It is essential that logging operations be supended in smalland vulnerable portions of large catchments during and imme-diately following heavy rainfall".

6. A Joint Research Committee, responsible to the Minister for Conser-vation, should be set up to study and report on the effect of varioustypes of activities and management which occurr on Victorian catch-ments from which town water supply or alternatively water for hu-man consumption is drawn.

It is clear that this all-party Parliamentary Committee (by a 5 to1 majority) favors multiple purpose management of all catchment are asincluding those at present managed for water supply alone, under con-trols similar to those aIready being implemented by the forest authority ,

Research work is proceeding in calibrating a number of smallcatchments in mountain forests and in mixed eucalypt forests for waterquality and water yield. A series of different forest managementpractices wiIl then be applied over a period of years to ascertain theeffects on water characteristics.

The approach to utilization operations in forest areas within cat-chments varies considerably according to the principal uses e. g ., waterfor irrigation, hydro-electric power or domestic purposes. Particular

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attention is paid to the planning and control of operations where do-mestic water supply is involved. In Victoria principIes of domestic watercatchment management within State Forests have been enunciated andspecific prescriptions of management drawn up for a considerable num-ber of such catchments. The princíples of management are set out inApprendix A and an example of a set of management prescriptions nowin effect for one such catchment which is the source of important írri-gation and domestic water supply is given in Appendix B.

The forests on this catchment are mixed eucalypts, the predominantspecíes being E. obliqua, E. viminau«, and E. radiata together with E.rubuia, E. diues, E. aromaphloia, E. ovata and E. macrorrh.uncha, Eitherthe Selection or the Group Selection System is considered to be satísf'ac-tory for the management of this class of forest. However within therange of the mixed species type on the foothill country, there is consi-derable variation in the form and characteristics of the species. Forinstance, with the exception of the ash group, eucalypts coppice freelyand it is possible to operate many of these mixed forests under a Coppiceor Coppice with Standards System. This is not applicable to the highforest ash types. Furthermore in the ash types the species are less tole-rant of shade and a Selection System cannot be applied. The ash spe-cies have many of the attributes of a fire climax in their natural range.AlI important stands of these species are even aged and apparently ori-ginated from past fires, even before white settlement was effected. Theusual system of management adopted is clear felling with retention ofseed trees and, in the absence of fire, this has not always resulted incomplete regeneration of cut-over areas. Recent investigations indicatethat regeneration can satisfactorily be achieved without the use of firewhich, on catchments from which domestic water is derived, is fraughtwith many problems. The main consideration in relation to ash specieson water catchments is that wider openings in the canopy are essentialfor natural regeneration of these species. This means careful controlof logging operations at all stages to ensure successful regeneration andto prevent surface soil movement despite the greater exposure necessaryon the steeper slopes of mountain forests.

One of the vital problems in both mixed eucalypts of the foothillsand in the mountain forests is that of fire protection. Several extensiveand disastrous fires have occurred at intervals through this century andit is only within the last 20 years that major advances in the form ofimproved access, early detection and efficient prevention and suppressionmeasures have reduced fire losses to acceptable figures.

The other management prescriptions referred to are reasonably self-explanatory and have presented no insurmountable problems in practice,although dose co-operation is at all times necessary between the forestauthority and forest industries. It is regarded as vital that the waterusing authorities be fully consulted in the preparation of the managementprescriptions for the catchment concerned and in relation to measuresfor their implementation.

The question might be asked as to whether there are any particulardisabilities in growing eucalypts on water catchments as compared with

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other hardwoods or more particularly conifers, as far as water qualityand water yields are concerned. Little information is available on thesepoínts and no controlled investigation work has been carried out, althoughwidely differing views have been expressed by water using authoritiesand others. Some important water authorities have converted eucalyptstands to or planted cleared areas with conifers, and no noticable diffe-rence in water quality or water yields has been reported. The samesituatian applies with regard to State forests of conifers on watercatchments. Conversions of hardwood to softwood stands have beenmade entirely on ecanamic grounds in relatian to the value of the resul-tant timber yield.

Soil litter and humus conditions under eucalypt forests are undoubte-dly different from those under broadleaved deciduous trees and undercanifers. It has been estimated (1) that accumulation of litter undera mature jarrah (E. marginata) forest is about 4,000 lbs. per acre perannum. This appears to be somewhat less than accretion reported inEuropean and American forests in temperate regions and considerablyless than reported in high rainfalI and tropical forests where annualaccretian up to 9,000 lbs. has been recorded.

It is known that certain differences exist in the quantities of variousnutrients returned to the soil by hardwoods and conifers, and it is alsosuggested by Lutz and Chandler (2) that the weight of forest floor(unincarparated farest debris) is greater under conifer stands than underhardwoods. In one series of experiments it was recorded that dry orga-nic matter averaged 100,000 lbs. per acre under various conifers and40,000 lbs. under hardwoads. Although these findings have not beentested as far as eucalypts are concerned, abservations tend to supportthem and suggest that there could be a greater run-off under eucalyptstands than under deciduous trees or conifers growing on the same site.There cauld also be a greater possibility of surface soil movement undereucalypts on steep slopes or on soils subject to erasion.

Another relevant question is that af the water using characteristicsaf eucalypts. In regians of frequent light rainfall, particular1y in sum-mer, eucalypts would not intercept as much water as deciduous treesor conifers.

Limited investigation of the amount of water transpired by eucalyptsin farest stands reveals (3) that larger quantities of water are used bya young mauntain ash crop than a mature stand and that larger amountsof water are used by dense immature stands than by lightly stocked orthinned stands. Lower transpiratian out-weighs higher evaporation fromexpased soil, so that the net effect is increased water availability in thefarm of water recovery from lightly stocked stands.

Eucalypts are not likely to be much different fram other forest cropsin their general effect on water quality and yield under most circumstan-ces. The combined effect of evapo-transpiration is undoubtedly such thatin regions of deep soil, dense vegetation and abundant rainfall, removalof the forest crop would reduce total evapo-transpiration losses andincrease water yields. Thinnings under these conditians should alsoincrease total water yields.

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It can generally be accepted that eucalypts are fairly prolific waterusers. Most species are shallow feeders and cause drying out of thesurface soil in their vicinity. One notable exception is the red gum (E.camalduleneis) which is a deep feeder. This factor would not be ofcritical importance on water catchments in high rainfall areas wherethere is normally a good cover of understorey and shrub species whichkeep evappration to a minimum. In lower rainfall areas however wheretree growth tends to be more open and undergrowth sparse, this canassume greater importance and should be borne in mind in consideringeucalypt plantation establishment. On soils with low permeability andwhere there is little undergrowth and relatively little soíl litter so thatconsiderable soil exposure occurs in the summer months, it is possiblethat the best contribution to surface soil stability may not be providedby eucalypts.

REFERENCES

Primary Production in Australia - B. J. Callinan. Unpublished paper - WaterResearch Foundation of Australía .

State Development Committee Report (1960) - Victoria - Government. Printer.Forests Commission of Victoria - Bulletin No. 11. (1960). Victoria - Govern-

ment Printer.(1) W. R. Wallace & A. B. Hatch - Effect of leaf litter on surface soi! pro-

perties of the Jarrah forest. Australian Forestry XVI No. 1 (1952).(2) Lutz & Chandler Forest Soils. Wiley N. Y. p. p. 140-160.(3) Brookes J. D. - Relation of vegetative cover to water yield in Victorian

mountain watersheds. Unpublished thesis. University of Melbourne.

APPENDIX A

FORESTS COMMISSION OF VICTORIA

OPERATIONS ON TOWN WATER SUPPLY CATCHMENTS

PRINCIPLES TO BE OBSERVED WHEN FORMULATINGMANAGEMENT PRESCRIPTIONS

1) Management practice will be so designed that openings in the ca-nopy are kept to minimum size consistent with silvicultural re-quirements.

2) Location of roads, snig tracks and log landings is to be plannedto reduce erosion potential to a minimum.

3) Every endeavour shall be made to conduct snigging operations insuch manner as to avoid siltation of any running stream and par-ticularly to avoid drainage of surface run-off along snig tracksdirect into watercourses.

4) Streams must be kept clear of heads of felled trees, logs, and si-milar material resulting from forest operations. Any tree likelyto fall into a stream or water race shall not be fellel.

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5) A strip of a minimum width of one-half chain is to be reserved alongeach bank of all permanent streams for a distance of not less than10 chains upstream from the inlet to any diversion weir, storagereservoir, pipe-line or water race. Felling and snigging of timberare to be completely excluded from such reserved stríp, and anytree which cannot be felled and removed without encroachingthereon shall not be felled.

The views of the water authority shall be taken into conside-ration in relation to any operations adjacent to any water raceor channel.

6) Utilization operations will not be permitted within such distanceof any storage reservoir, diversion weir or similar installationlocated within the catchment as may be determined by the Com-mission.

7) On completion of logging operations, appropriate measures shallbe taken to prevent erosion of snig tracks and log landings andto divert or disperse drainage from the latter.

8) It is desirable that extraction operations on relatively small cat-chments and on the more vulnerable portions of larger catchmentsbe suspended during the winter period. Where complete suspen-sion is not practicable, operation should be restricted to a minimumand confined to sections of the catchment which are least liableto erosion and where soil disturbance will cause minimum streamturbidity.

9) Where it is necessary for tractors or other vehicles to cross runningstreams, satisfactory crossings shall be constructed.

10) Burning operations within the catchments shall be kept to a mini-mum consistent with effective protection. No burning shall beconducted within the areas from which utilization operations areexcluded in accordance with paragraphs 5 and 6. All burningcarried out must be strictly controlled.

11) In the event of a catchment being damaged by fire, any salvagelogging operations necessitated thereby must not be commencedwithout the prior sanction of the Commission.

12) To the maximum extent practicable, utilization operations are tobe controlled by tree marking.

13) No camps 01' other living quarters, whether temporary or perrna-nent, shall be established within the catchment except by expressapproval of the Commission.

14) In the case of licenced logging, the foregoing provisions are to beincluded in conditions of allotment specific to the area.

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APPENDIX B

FORESTS COMMISSION OF VICTORIA

COLIBAI'T - CAMPASPE CATCHMENT SUPPLYING BENDIGO,CASTLEMAINE, & OTHER NORTHERN TOWNS

TRENTHAM FOREST DISTRICT

(Approxim.ate area o] catch.ment 90,000 acres of which app'roximate7y25,000 acres in wpper reaches is State Eorest )

MANAGEMENT PRESCRIPTIONS WITH RESPECT TO STATE FORESTWITHIN THE CATCHMENT

1) The Silvicultural system of management shall be the selection sys-tem with a felling cycle of not less than 10 years except that, inthe event of the stand sustaining damage, the system may bechanged in order to rehabilitate the forest and produce un uneven-aged crop with a spread of age classes approximating normalityas soon as practicable. Sclection fellings to improve stand qualityor to remove forest produce other than mill logs shall be conductedso far as possible in conjunction with, or immediately following,the felling and remova I of mill logs.

2) Utilization operations shall be controlled by departmental treemarking.

3) Snigging and cartage operations shall be totally suspended duringwinter, dates of commencement and termination of such suspensionperiod in any year to be determined by the forest officer in chargeafter consultation with the Divisional Forester. Temporary sus-pension of such operations shall also be imposed by the forest officerin charge during heavy rain and for such period thereafter as inthe opinion of the forest officer in charge such operations wouldbe detrimental to water supply or forest interests.

4) Snigging or cartage of forest produce through any running stream,spring or swampy confluent shall be prohibited and extraction shallbe planned accordingly. As far as practicable snigging shall beacross the slope to ridges trafficable by log trucks. Downhill snig-ging shall not be permitted. Strict attention shall be paid to dis-posal of drainage from roads, snig tracks and log landings to obvíateerosion and the direct discharge of silt into stream channels. Nolog landing shall be constructed in a position likely to cause drainagedirect into streams. Any abandoned snig track or cartage routewhich is liable to collect or channel surface run-off shall be breachedor barred to prevent erosion commencing and so that silt is notdeposited directly into stream channels. Abandoned log landingsshall be levelled.

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5) Where it is necesary for tractors or other vehicles to cross runningstreams, satisfactory crossings shalI be constructed in such a mannerthat the stream banks remain undisturbed.

6) No tree growing within any swampy section or within Yz chain ofany running stream or spring or which is liable to falI into theseareas shalI be marked for removal. Any heads of trees, logs orsimilar debris falling into streams or the foregoing areas as aresult of forest operations shall immediately be removed.

7) Burning operations shall be restricted to a minimum consistentwith the protection of the are a from fire and so far as practicableshall be confined to ridge tops and road-side stríps, All burningoperations shalI be carried out departmentally and shall be strictlycontrolIed .

8) At any log landing or depot intended to be used for more than 4consecutive weeks a pit type earth closet shalI be instalIed but nosuch landing or depot shalI be established within 5 chains of anystream, spring or dam.

9) The establishment on reserved forest of any sawmill or of anyindustry for the purpose of converting timber to manufacturedproducts shalI be prohibited.

10) The establishment of living quarters other than any already exis-ting or of any camp on reserved forest shalI be prohibited.

11) Any application for grazing rights on reserved f'orest shalI be con-sidered on its merits, and approval or otherwise shalI be the subjectof a Commission determination.

The prescriptions shalI remain in force until amended by authorityof the Commission and any departure from the prescriptions shall onlybe with the express approval of the Commission.

AMÉNAGEMENT DE L'EUCALYPTUS DANS LES VERSANTESUD·EST DE L'AUSTRALIE

Résumé

Dans les termes les plus simples, l'Australie est surtout constituée par unerégion côtíêre humide, à 1'est et au sud-est, et par un vaste intérieur seco Enraison de Ia petite proportion de Ia surface totale qui réçoit une raisonnableprécipitation pluviométríque, Ies questions concernant 1'approvisionnement d'eauet son usage ont une fonction importante dans beaucoups d'aspects de I'admí-nistration publique et determinent, en grande partie, de façon basique Ia loca-lisation des industries et distribution des populations.

En vie d'éviter les dégats qui decouleraient d'une consommation immoderéed'eau, des instructions spécíales ont été établies par Ia Commission Forestiérede Victoria.

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ORDENAMIENTO DEL EUCALIPTO EN LAS VERTI ENTESDEL SUDESTE DE AUSTRALIA

Resumen

En términos más simples, Australia está constituida, principalmente, al Estey Sudeste por una región costera húmeda y por un extenso interior seco. Acausa de Ia pequeiía área total, que recibe una caída pluviométrica razonable,los problemas que se refieren al aprovisionamiento de agua y a su uso, de-sempeiían un importante papel en muchos de 10s aspectos de Ia administraciónpública y en gran parte constituyen, Ias determinantes básicas para Ia Iocali-zación de industrias y distribución de su pueblo.

Para evitar Ios daiíos que resultarían de un gasto inmoderado deI agua,fueron establecidas instrucciones especiales por Ia Comisión Forestal de Victoria.

ORDENAMENTO DO EUCALIPTO NAS VERTENTES DO SUDESTEDA AUSTRÁLIA

Resumo

Nos têrmos mais simples, a Austrália é constituída, principalmente, poruma região costeira úmida, a leste e sudeste, e por um extenso interior sêco.Por causa da pequena proporção da área total que recebe uma razoável quedapluviométrica, as questões a respeito do suprimento de água e seu uso desem-penham importante papel em muitos dos aspectos da administração pública econstituem, em grande parte, as determinantes básicas da locação das indús-trias e distribuição das populações.

Para evitar os danos que resultariam dum gasto imoderado da água, ins-truções especiais foram estabelecidas pela Comissão Florestal de Vitória.