Unfolding the Plan
0NE third of the continent of Australia has a climate whichproduces sufficient rainfall to warrant and support a highly-developed agriculture.Within this area there are great stretches of completely undeveloped land that arecrying out and demanding attention and development.
If we are to produce a real Australian type of agriculture thatis safe and permanent and which will preserve all that is best in our natural environment(an environment which in its totality is unlike that of any other country in theworld and which contains everything except a good agricultural climate), then wemust overcome this climatic drawback and regard it as offering our greatest opportunity.We could, by careful and realistic planning, produce in a few years on our undevelopedcountry, farms and grazing properties which would be permanent and safe from ourpresent land troubles. They would also have more individuality than our best propertiesof today. Because this poor agricultural climate extends over so much of this landwhich is available for development, it is ever in the background of these discussionsand it is therefore selected as the theme in the presentation of the planning techniquesof Keyline.
These subsequent descriptions are typical of my actual experiencebut will be more readily appreciated if they are made to apply to a fictitious propertyunder an assumed name. I have called it "Yonaroo".
In planning the agricultural development of any land, its climate(or weather), placed first on the Keyline scale, must be known. The general functionof climate has been described in Chapter V, entitled "Climate", but tobe more specific, the following paragraph completes the climatic picture chosen forthe area of land we call "Yonaroo".
The average annual rainfall is assumed to be 24 inches. Thereis a little more rain in the winter months of June, July and August, though the floodrains do not usually occur at this time of the year. Heavy rainfalls are more likelyto occur in the summer months of December, January and February. The summer can beextremely dry and hot. Good run-off occurs in practically every year, but on occasionsthe rainfall may vary from ten to nearly fifty inches, with consequently much greaterrun-off. There are frosts each winter but snow is never heavy enough to lie on theground.
Land shape is second on the Keyline scale, and for our purposesis taken to include all the land forms that are likely to be present on land whichis between 1400 to 1800 feet above sea level. The soil of the property is of twotypes, clays from slates and a lighter soil from a granitic area. The property mustbe described in some detail as the description proceeds to enable a clear pictureto be seen of its development.
"Yonaroo" contains 1800 acres. Except for a smallarea all the land can be travelled with farm equipment. To describe the land further,it is assumed that there are two secondary valley systems which form small intermittentlyflowing creeks and which join on the property and flow to a larger creek. This largercreek, which rises several miles beyond the property, flows alongside and forms partof the property boundary. There is another secondary valley, but smaller than theother two, which forms on the property but flows away from the other drainage systemsand is unconnected with them. The land is tree and brush covered but well cut over,with most of the good milling timber trees removed. Agriculturally this propertywould carry a few sheep or cattle in a good season and offers only a poor type ofsheltered winter grazing. There is no permanent stock water, but holes in the creekretain water for most of the winter except in the droughts.
There are two general means of examining "Yonaroo"preparatory to planning. First, we may produce a suitable contour map of the propertyand develop from it a Keyline map with all planning lines and land shapes displayed.The map would have a scale of one inch equal to five chains (110 yards), with contoursat 20-foot vertical intervals.
The second method of land examination for planning purposesis by visual means on the land itself.
The land divisions of "Yonaroo" are those alreadymentioned, namely, two secondary watershed areas each containing several primaryvalleys, and these two secondary valleys which, joining on the property, form a creekwhich, in turn, joins a larger creek and becomes part of the property boundary. Severalprimary valleys flow to this boundary creek and the combined land area of these latterprimary valleys is the third land division. Another valley area, not associated withany of these three areas, forms on and flows from "Yonaroo" without joiningthe other systems. It is the fourth main division. To repeat, there are four mainareas of land--the two secondary valley systems, the area of the group of primaryvalleys falling into the boundary creek, and the fourth valley or watershed divisionnot associated with the other three.
The next step in planning is to select the land division whichwill be developed first and to determine. the relationship between its various primaryvalleys. In order that the full pattern of the water supply scheme for the farm maybe determined, it is necessary to know whether the keypoints of the primary valleysrise into the rising country.
Water supply is third on the Keyline scale of permanence, andit is designed according to the dictates of climate and land shape.
The rainfall feature of the climate of "Yonaroo" indicatesthat the plan of development should aim to conserve all the rain that falls. Landshape discloses that there is ample opportunity to do so in various types of storages.
Looking at the contour map we can spot almost at a glance thelocalities of all the most suitable dam sites. Where each contour line crosses avalley it could be the water line of a dam, and by drawing a line across the loopof a contour the dam can be "seen". On the map an examination is made ofthe primary valleys that fall to the secondary valley area which was selected forthe start of the work. Beginning with the lowest primary valley falling on one sideof the secondary valley, its keypoint is located, i.e., the point of changein the slope of the primary valley at the bottom of the first steeper slope. Nexton the map the nearest contour to the first keypoint is followed around to the nextvalley in the general direction of the rise of the land. If the keypoints of thevalleys have the usual rising relationship into the rising country the contour followedwill cross the next primary valley at a point lower than this valley's keypoint.Now the keypoint of the secondary primary valley is selected and the nearest contouron the map is followed in the rising land direction to the next valley, and so onuntil the highest primary valley in this system at the head of the secondary valleyis reached. The primary valleys falling from the other side and into the secondaryvalley are examined in like manner.
These primary valleys vary in size. Therefore, they are appraisedfirst from their significance in water conservation. The first or lowest primaryvalley flowing to the secondary valley is found to be too small a form to consider.The planning examination then considers the next primary valley, which is assumedto be of water conservation significance.
These matters are very simply determined on the contour mapby examining the contour loop next below the keypoint of the valley against whatis considered a suitable depth of water for effective water conservation. This lattermatter, the suitable water depth of dams, must also be determined. Effective waterconservation capacity for irrigation, or stock and irrigation, as distinct from purelystock water dams, should, in my opinion, be determined as a minimum of ten acre feet,approximately two and a half -million gallons. A twenty-foot depth of water shouldbe accepted as a suitable depth for these Keyline dams. Confirmation of this figurewill not be found in agricultural literature because it is a recommendation basedon the results of my own experiences. By way of illustration, a dam with a depthof 24 feet of water at the lockpipe has generally been found to be double the costof a dam on the same site but having a depth of 20 feet. If the contour loop immediatelyat or just below the keypoint of a valley can be joined by a straight line acrossthe valley shape, thereby representing the wall of a dam, and just touches the topof the next lower contour loop, then a twenty-foot dam is represented. The capacityof the proposed dam is simply calculated by determining the acreage area boundedby the contour loop and the wall line, and multiplying by nought point four (0.4)times the depth. For instance, if the area of the dam is two acres and the depthof water is twenty feet at the lockpipe, the capacity of the dam is sixteen acrefeet. The average depth of such a dam is thus generally 40% of the full depth ofwater at the lockpipe. In this manner the sizes can be determined against each valleyand those valleys without value in water conservation potential in true keyline damsare disregarded in the first or general stage of the planning of "Yonaroo".
Now, there are two general approaches to the way in which thefarm may be developed. Either it may be developed as a complete project in whichall the work of the final plan is completed as one quick undertaking or, and muchmore usually, the work will be done over a longer period of time as finance becomesavailable from the results and profits of each stage of the development of the farm.Whichever approach is chosen the full final plan is prepared or at least understoodbefore proceeding at all. On "Yonaroo" the design of the water supply setsthe pattern for the whole of the development work.
While it may be assumed that the annual run-off is of the orderof three to four inches there are occasions when the run-off in one year exceedsten inches. There may be a run-off of even twelve inches in a short period in floodmaking rains.
In these circumstances of run-off all the better dam sites justbelow the keypoints of the primary valleys could be used. These dams will be filledby water conservation drains which follow the gently rising keylines of the land.
From prior knowledge of the uniform geological structure ofthe underlying rock of the secondary valley and from the examination of the contourmap it will have been seen that the dam sites in each primary valley are progressivelyhigher, permitting the use of keyline drains to feed water to each dam and to allowoverflow water from each dam to flow into the keyline water conservation drain ofthe next lower dam or into the catchment above this keyline drain. Thus, all thewater from the high country is controlled so that none escapes until all the keylinedams are filled. The keyline water conservation drains with the dams themselves areto become the most permanent structures of all the work that will be done on theproperty.
If the work is to proceed progressively there must first bepermanent water. Under these circumstances the sites for all the projected dams andothers to be discussed, are examined to select the dam that will best supply theearly needs. Not only should the first dam be one that will fill quickly and providelow cost water, but it must be consistent with a site which will enable the waterto be used for irrigation on a piece of land that can readily be cleared and developedfor crops or pasture. Any one of the dam sites from the highest down may be chosenand built first so long as it is in its right place in relation to all other selectedsites when the full plan finally emerges.
The capacity of all the true keyline dams will usually be filledfrequently enough by the water conservation drains, but where there are many goodcapacity sites the average run-off rain for one and a half years from the areas abovethe dams and water conservation drain may be assumed as a limit to the capacity ofthe true keyline dams. A run-off of four inches per annum will be reduced, perhapsappreciably, by the soil developed in Keyline absorbing and holding more moisture,but the effect is less significant in periods of heavier run-off.
We have dealt with only the series of high-level dams, the truekeyline dams. There are two further types of dams to be considered in this generalclimate and land form : they are reservoirs and lower valley dams.The reservoir site is looked for firstly in the area of the secondary valley belowthe highest dam of the keyline series. The reservoir or reservoirs may, in theirheight position in the secondary valley, lie below the level of the lowest of thekeyline dams, but not necessarily so. A reservoir site could be just above the breakof the land that marks the first formation of the small creek of the first secondaryvalley. The reservoir is kept high for preference and with some consideration beinggiven to the area of its catchment excluding that of the keyline dams above it. Thereservoir catchment is suitably related to its capacity if two years usual run-offwill fill it. If a larger than necessary catchment is available two or more reservoirsare considered, the higher site being used before the others.
The lower valley dam or dams of this particular natural landarea is sited at or near the point where the land form of the secondary valley finishesand becomes part of another division. In Keyline the lower valley dam is sited anddesigned to hold all the run-off from its catchment area for three years or moreof average run-off.
This then is the general pattern of the water supply for thefull development of the land in the area of the selected secondary valley.
While there is a pattern to the siting of dams, there is alsoa particular pattern developed in Keyline for the use of the conserved water. Forinstance, the pattern of use with all dams filled commences with irrigation fromthe true keyline dams immediately irrigation is advantageous or profitable. The lowerdam also comes into use at this time to irrigate its own special irrigation area,but the reservoirs are left filled while there is ample water still in the true keylineand the lower dams.
There is one other aspect of the overall water supply on "Yonaroo"to be considered. This relates to the whole farm and to the creek which is formedand fed by the joining of the two smaller watercourses of the two secondary valleysand which in turn join the boundary creek. It will be assumed that each small creekhas a water catchment area of approximately 400 acres.
Three different types of dams have been discussed: (1) The truekeyline dams located at the head of the second slope of the primary valleys. (2)Reservoirs, lower in height, and located in the upper part of the secondary valleybeneath the highest of a series of keyline dams or just below the junction of oneof the highest of the primary valleys with the secondary valley or in the lower endof a larger primary valley before its junction with the secondary valley--there maybe one or several reservoirs in a secondary valley area. (3) Lower valley dams, whichare located in the secondary valley at a site located above the junction of the watercourseformed by the two secondary valleys. When the boundary of a property crosses a secondaryvalley, the site of a lower dam is chosen so as to ensure that it will catch allrun-off from the land below the other dams and also the overflow of these dams. Wehave seen that these three types of dams are simple and obvious against the backgroundof the undulating country of "Yonaroo." Where there is sufficient variationin height over a property, the factors which relate to these three types of dam generallyapply.
Getting back to the creek formed by the junction of the flowof the two secondary valleys, conservation of water here is not entirely in the handsof the farmer. In Australia, Government authorities generally control or administerthese matters. A dam constructed across a defined and confined watercourse requiresthe permission of such authorities, since consideration must be given to the rightsof owners of land below through whose property the creek later flows. There is alsosomething less than law but still of some consequence which says that a farmer hasthe inalienable right to as much as he can store of the rainfall which actually fallson his own land. Even if all the rainfall which formerly was lost in run-off is nowconserved in the soil and in farm dams by the farmer, he is still not holding allthe water. Quantities of water would be continuously moving into the earth belowthe farm and so replenish ground water supplies. Springs which thus form are theonly constant flow water of the creeks and rivers. The more water the farmer conservesthe more water moves underground as seepage from his soil and from his dams. Morewater will also evaporate over his land.
Generally then, before these dams on creeks may be built, applicationhas to be made to the appropriate Government authority, who cause a notice to beinserted in a suitable daily newspaper giving information of the proposed dam tothose who may be interested. Other farmers have the right to object to the dam ifthey consider it is detrimental to their own lands. If such objection be lodged thematter is heard by an authority but with the rights of appeal, if necessary, determinedby such court as the Land and Valuation Court. When authority is given the farmeris not released in any way of responsibility for the dam. The deciding authorityin permitting the construction of the dam does not assume any responsibility forthe effectiveness of the dam. This general procedure, in instances which have concernedme, is a source of inconvenience and delay on a matter that should never be unnecessarilydelayed.
Here again, it seems to me, is a purely agricultural matterthat should be determined quickly by the agricultural officer on the spot. He maybe the local agronomist, dairy officer, or any other. An alternative procedure couldbe that the farmer first contacts his neighbour below and acquaints him of the projectas a matter of courtesy and expedition, and then informs the local agriculturalistwho accepts the farmer's application by word of mouth or telephone and immediatelycalls to inspect the proposed site. The agricultural officer should not be in anyway responsible for the site selection, design or construction of the dam, but shouldbe capable of offering effective advice if requested to do so by the farmer. Theofficer, who in all probability knows the farm well, should merely appraise the creekflow, if any, and then decide if the dam would detrimentally affect the neighbouror neighbours in the next two-mile length of the creek. The creek may be a constant-flowtype, which would flow to the same capacity after the construction of the dam formost of the time, but on the other hand if in his opinion it could cease to flowin a drought where formerly it did not, the agricultural officer may then suggestto the two or three concerned that the farmer owning the dam should release. a certainspecified flow in drought times when there was still water remaining in the dam.If this is agreed he could issue a notice to each recording his inspection of thecreek and the stipulation referring to drought flow. The dam could then be builtbut it would remain the farmer's sole responsibility. He is responsible for damages,if any, if the dam fails, and while there is water in the dam above the level ofthe original bed of the creek at the site, the farmer in dry times would releasethe equivalent of the drought flow. There will be concern in the minds of only thosewith little knowledge of these matters at the possible loss of water caused by adam on one farm to the land of the property below. Generally, the more water thatis conserved and used on farms the more constant and reliable is the flow in thecreeks below. However, the rights of neighbours must be fully protected, and indeed,Keyline enhances them.
A dam constructed below the junction of our two creeks of thesecondary valleys may be of relatively large capacity and of low-cost storage. Itwould have a natural catchment on "Yonaroo" of 800 acres, including thecatchment area of all the other dams. In the present planned water storage schemeit would appear to have little chance of filling even in substantial floods. Underusual circumstances, the influence of the greater water storages above, the constantuse of the water on the irrigation areas, and the continuous partial and completerecharging from each rain of the dams of the primary and secondary valleys, wouldcause the natural and intermittent flow of the creek to become a considerable constantflow. This effect may take two years before it starts to function.
In my opinion the matter resolves itself into a somewhat optimisticappraisal of the circumstances relating to filling capacity, cost of constructionand use of the water. As there are still areas of "Yonaroo" below the projectedcreek dam it may be possible to use the water from the creek dam by flow methodsof irrigation. In these methods of water conservation all dams are constructed withlockpipe controls. In the construction of dams in flowing creeks in this type ofcountry the lockpipe system makes what is with other methods always a difficult andcostly job, now a simple and easy one.
A creek dam built recently on "Kencarley", at Orange,flowed the water of the creek, which carried a constant flow, through the wall viathe lockpipe installation during the construction of the dam. As part of the generalsite preparation work, the lockpipe, 140 feet total length, was laid in a preparedbulldozer trench at the level of the creek bottom and a little to one side of thecreek bed where the water originally flowed. Immediately a full bulldozer blade loadof good wall material was pushed over the lockpipe near its inlet end and acrossthe flow of the creek, the water entered the lockpipe and flowed there and rightthrough the wall, where it continued to flow during the building of the wall. Therewas no water and mud to cause trouble and the work proceeded in the same orderlymanner as though the construction was in a dry primary valley.
There are many circumstances, where, while there is no suitableland for flow irrigation below the lockpipe level of such a dam, there is suitableland for this purpose below the level of the high water of the dam. In these circumstancesa pipe from the lockpipe outlet to a suitable higher point between the levels ofthe lockpipe outlet and the top-water line can discharge water into a suitable irrigationdrain and may employ the lowest cost method of irrigation for half the depth of thewater in the dam. Much more than half the water capacity of the dam is containedin the top section. In such circumstances the dam, as it were, has two levels, topwater level and irrigation drain level. In a large dam of this type the land lyingbetween these two levels and covered with water when the dam is filled and at othertimes dry, may be prepared for special crop production. This type of dam and otherspecial purpose dams are discussed in later chapters.
There remains the smaller catchment area of the property, whichis actually the small top section of a secondary valley and which is planned to itsown particular development capacity. The only area on the property presumed to betoo steep for mechanical clearing lies near the head of this valley. The flattertop section is cleared and the steep section is left for possible later hand work.The lower area is planned and developed as are the other secondary valley areas.
The creek flowing to the property from higher lands and forminga part of the boundary of "Yonaroo" may now be considered. Several landowners could have an interest in the part of this creek that is on the property.
In general, where creeks form property boundaries, the centreline of the creek is presumed to be the boundary. However, the fenced boundary isa give-and-take arrangement, which provides suitable exclusive access to the creekfor each party. Apart from the right of owners lower down, a dam on this creek wouldcover part of the adjoining neighbour's land and therefore could be constructed onlyon a mutual basis. After satisfying the land-owner lower down, a dam may be consideredin which all details, including proportions of cost and particular rights of waterusage, would need to be embodied in a formal legal document acknowledging permanentright of each area of land on the other. Water may be taken from such a creek bythe various owners provided the reasonable rights of all others are protected. Thewater that is most significant generally is that which is above normal flow and upto flood flow. Small inexpensive weirs may divert water to a water race or waterconservation drain, which would follow the general fall of the land to provide irrigationby flow methods. However, the only time during which this water is readily availableis when it is not likely to be critically needed. Good creek flow is a feature onlyof good seasons. So the best use of the available water may be by the conservationof the water from the creek when flow is good, via a suitable drain into an off-the-creekstorage. It may be brought into dams already a part of a primary or secondary valleystorage or into a dam to be constructed in a special new site. If the creek watercan be diverted to a previously constructed reservoir the use pattern for the waterof the reservoir could then be changed to suit its new faster and more frequent fillingcapacity. It could become a special purpose dam and all its water used by flow methodsas soon as irrigation was advantageous. With this matter suitably decided the fullwater conservation capacity in surface storage sites available on "Yonaroo"is now finalised.
I have suggested that dams for farm irrigation be limited tothose with a capacity of a minimum of 2-1/2 million gallons, or ten acre feet. Thelimiting of a farm irrigation dam to this minimum size should be consequential tosite, limitations and represent the amount of the water storage capacity of the sitewith a wall 23 feet high and water depth at the lockpipe of 20 feet. Dams of ten-acrefeet capacity are generally the highest cost water storage with costs running to£200 per million gallon, i.e., £50 per acre foot, or the equivalentof four shillings per thousand gallons of storage capacity. In the past I had considered£30 per acre foot as a satisfactory cost figure, but now am not inclined toset any cost limit to the value of storage capacity. In Keyline the storage capacityof dams is a permanent asset. The cost of the water as distinct from the water storagecapacity relates to the storage cost divided by the number of times the water ofthe storage capacity is used. If the water is used twice a year for twenty yearsthe cost of water from the most unfavourably sited farm dams is very low. The smallerfarm dam also costs relatively more for the reticulation of the water, and in flowirrigation the cost of the lockpipe system and the irrigation drain, which constitutesthe full irrigation system, will add approximately 66% to the earth cost of the dam.In a large farm dam of, say, 400 acre feet the cost of the lockpipe and the reticulatingdrain and irrigation system may add only 10% to the earthworks cost of the wall.The three costs are: (1) earthworks on the site and in the wall; (2) lockpipe system;(3) conservation and irrigation drains.
It can be understood that while all these decisions on the overallplanning and the water supply scheme can be determined very quickly with the aidof the special contour map, the absence of the map changes things considerably. Thenthe same decisions must be made from direct observations on the land, in which mattersdetermined almost at a glance on the map, without the map now involve much walkingand some measurements and levels. A start is made as before at the lower limit ofthe secondary valley above the point where it junctions with the creek of its companionsecondary valley. The nearest primary valley is the first one inspected. The valleyis tree covered and it is necessary to walk up the centre of this primary valleyto locate the keypoint of the valley. This presents little difficulty. Then it mustbe decided whether or not the valley is of significance in the planning which isbased on water supply. If there is some doubt on this matter a more thorough examinationof the valley will be necessary. This is done with the aid of a level, and in treecovered country our Bunyip level provides the quickest means. The examination firstascertains the "valley floor slope". Over my twenty years of experience,experiments on the siting and the design and the construction of many dams, valleyfloor slope emerges as one of the important design considerations for all farm dams.My farms dams are described fully in later chapters, but some points may need tobe mentioned briefly as the development of "Yonaroo" unfolds.
A valley floor slope of one in twelve is too steep a site generallyfor a dam unless the rest of the valleys are similar or steeper. One in twenty isa satisfactory slope and one in thirty or flatter is considered good for a true keylinedam site.
In the first primary valley a point is selected one to two feetlower than the keypoint of the valley and the first staff is stood up. From thispoint and another point fifty feet away (the full length of the water tube of theBunyip level) and down the centre of the valley the readings on the two staffs ofthe level are taken to determine the height difference. The difference in the levels,as read off the two staffs of the Bunyip Level for the fifty feet distance apart,determines the valley floor slope. A difference of one foot in the reading of thestaffs indicates a valley floor slope of one in fifty, which is better than may usuallybe expected for a true keyline dam. If the valley floor slope is too steep the valleyis not considered any further at this stage. Apart from a satisfactory valley floorslope, the valley needs a suitable "shape", which again is determined withthe level. From the point previously pegged just below the keypoint, the Bunyip levelis used to run out a true contour in both directions, marking points along the contouras conspicuously as possible; and so is determined the shape of the top water lineof the possible dam. Here again classifications and determinations of my own mustbe mentioned. The length of a dam is the distance from the water line at the middleof the wall up the valley to the top water line of the dam near the keypoint. Ifthe length of the proposed wall (a line across the water level contour) and the lengthof the dam are equal, then the site satisfies what I consider minimum requirements.But if the wall length is longer than the length of the dam, then the site is rejectedfor water storage.
A dam length twice as long up the primary valley as the lengthof its wall is of good shape. It is assumed that the first primary valley has a valleyfloor slope of one in eleven and would require a wall of 300 feet long to containa depth of twenty feet of water at the lockpipe. These figures indicate that thelength of the dam would be the depth in feet multiplied by the slope (20 x 11 = 220feet). This figure could be further checked by taking levels from the peg placedoriginally just below the keypoint, down the valley twenty feet vertically lower,and from this point measuring back to the original peg. The wall of the proposeddam is longer than the dam, so the site is abandoned. But this dam site also failson minimum requirements in another direction, that of capacity, which can be quicklychecked by the following means: The water surface area of the proposed dam can becalculated by taking two-thirds of the area found by multiplying the length of thewater line at the wall and the length of the dam measured at right angles to thewall (300 x 200 x 2/3 = 44,000 square feet = 1 acre approximately). Again, assumethat the average depth is nought point four (0.4) times the water depth of 20 feet,which is 8 feet. The capacity of the proposed dam is therefore approximately 8 acrefeet, against our general minimum capacity recommendation for a farm irrigation damof 10 acre feet.
Continuing the inspection from the first primary valley whichis suitable for water conservation in a dam , it is then necessary to run a nearcontour or rising keyline to the next primary valley up land. As the country is treecovered, the line will need to be marked in a manner that will permit of being locatedagain later. This type of work is continued on the land generally as done on themap, but it takes considerably longer to obtain an appreciation of the land shapeand the valley relationships. For the real work to proceed and whether a contourmap is available or not, the marking out of these keylines must eventually be completedon the ground. Without the map, trial lines will sometimes be necessary to obtaina first understanding of the primary valley inter-relationships.
To summarise these early planning points. First, obtain an overallpicture of the relevant larger agricultural land units and, as seen so far on "Yonaroo",these are four. Second, select one as the first for development, considering perhapsaccessibility and uniformity of shape. Third, as water conservation in farm damsis determined to be of prime importance (judging from the climate and the land shape),examine the primary valleys of this first development area and ascertain both theirsignificance in water conservation and their relationships, i.e., whetherthey possess the general "rising relationship".
In general land development such as at "Yonaroo",where the conservation of all run-off water is planned, the keylines are lines risingwith the rising country. As soon as their positions are determined, and marked withsuitable pegs, clearing of the trees and brush may commence.
The keylines themselves are first cleared by a bulldozer, followingthe pegged line and forming a definite cleared line which will represent also theboundary between cleared and uncleared land. A strip or tree belt is to be left alongthe keyline and may be either above the keyline or below it. In the conditions herewhere water conservation is vital it will be better for the tree strip to be leftabove the keyline. The first cleared run of the 'dozer along the keyline representsthe top boundary of a strip of cleared land or land to be cleared which lies belowthe keyline. The timber belt itself is left standing above the keyline.
Any belts of trees left to form part of the permanent landscapeshould be wide enough for good forest condition to be pertinent. Strips which aretoo narrow tend to die out in about the same time that single trees take to die,but in conditions that resemble those in the natural forest, trees live longer andnatural regeneration also takes place, thus preserving the tree belt in perpetuity.I have found that a width of twenty-five yards of trees in approximately these conditionsappears to promote good conditions for timber-tree life and growth. This is the distancesuggested as a minimum, and thirty yards as a general width. The first tree beltthen is located by marking a strip of land twentyfive yards wide in the trees abovethe keyline, a line uphill and parallel to the keyline.
The next permanent line of importance that may be preservedin a treed belt is the irrigation drain. Whether it is to be or not be used by theimmediate construction of the dam, its site should be located at once if a stripof trees is to be left above the irrigation drain. The keyline tree strip works satisfactorilywhether it is above or below the keyline drain. I prefer it above, so that in crossingthe valley it does so above the dam, and thereby protects the dam from wind whichcauses wave erosion and the trees also retard evaporation; but the tree strip ofan irrigation drain is located always above the drain, so that water does not flowthrough the trees when irrigating the paddock.
All the details of the water conservation and irrigation drainsof Keyline, including their sites, designs, construction and uses, are explainedin later chapters. However, to follow the course of the present development, it maybe appropriate at this juncture to briefly discuss the drains used in Keyline. Manyfarmers know drains from the anti-soil erosion approach, but the drains of Keylineare totally different. There are only two classes of drains in Keyline. The firstis the water conservation drain, which is for the express purpose of transportingrun-off rainfall into farm dams. The second is the irrigation drain, which providesfor the economical use of the irrigation water and generally, with the lockpipe,completes the irrigation equipment. The water conservation drains of Keyline mayfollow the keylines as we have discussed, or be located below the higher sectionof a property which does not include the complete land shapes of primary and secondaryland units. Where these land forms are large, the land of a property may be of sizeablearea and still only include a portion of one of these land systems. Again, the drainsof the Keyline plan are permanent features while those of soil conservation are not,since they are designed purely to overcome soil erosion problems, when, if the drainsare successful in their purpose, the problems no longer remain and the drains becomesuperfluous.
The first irrigation drain on "Yonaroo" is locatedfrom the position of the lockpipe outlet of the first proposed dam. These lockpipeoutlets are described in later chapters.
With the irrigation drain pegged in the down land directionfrom the outlet point the bulldozer clears the drain line. The tree strip is markedtwenty-five yards wide in the trees above the line and again marked by the bulldozerpushing the trees down along this line. There is now an area ready for clearing withits upper limit marked by the pushed-down path of the keyline and its lower limitby the top of the irrigation drain tree strip.
The best means of getting the trees down is by using two largebulldozers with a 400-foot or longer length of six-inch wire rope (about two inchesin diameter) or with a heavy chain. One bulldozer travels the top marked line, thekeyline, the second 'dozer travels in the same direction about 100 feet lower downin the trees. The first run pulls down a large area of trees quickly. The secondrun should be made with one 'dozer on the line above the tree strip of the irrigationdrain and the other in the trees 100 feet or so above it. After the first run, whichpulls down a strip below the keyline, and the second run, which pulls down a stripabove the irrigation drain tree belt, are both completed, the pattern of the workis clear. It is then a matter of pulling down the trees that are left in the centreof the land strip of what will be the first cleared paddock area. When pushing downand clearing are to be done with one bulldozer it should start by pushing down fromthe keyline into what will be the cleared strip and working right along the line.When this is done it pushes up into the area of clearing from the line above thetrees of the irrigation drain tree strip. This part of the work when properly supervised,leaves the job in a condition where mistakes in pushing down trees in the wrong placesare nearly impossible and supervision may be relaxed if necessary.
The keyline rising into the rising country from the keypointof a primary valley in which a dam is planned, may, if extended, cross the next primaryvalley well below its keypoint and even below a keyline dam site in the second valley.There are sometimes very interesting planning possibilities in this feature whichshould not be missed. For instance the keyline water conservation drain feeding run-offto the lower keyline dam of a series of keyline dams may, as it approaches the nextvalley higher up land coincide with the irrigation drain from its keyline dam. Itcould, in some cases, be much lower than this irrigation drain and coincide withthe extension of the irrigation drain of a keyline dam higher still. It may be suitable,in special circumstances, to continue the keyline tree strip of a lower primary valleyright through the land area of the secondary valley. All drains, both irrigationand water conservation drains rise into the general rise of the country or, the samething, fall with the general fall so that the slope of any drain line does not clashwith any later work.
The tree belts to be left in the clearing of "Yonaroo"take their pattern from the first four factors of the Keyline scale, namely, climate,land shape, water supply and farm roads. So far, in considering trees in relationto the water supply features, dams and drains, the first two factors of the scale,climate and land shape, which govern water supply, therefore are interpreted alsoin the tree lines. We now must consider farm roads in fixing tree-belt sites otherthan those along the keyline water conservation drains and irrigation drains. Someof the work roads will take their pattern from the two drains already mentioned,but the roads of particular significance at this stage in the planning are thosethat travel the main divides, on the property and the others branch roads from thesewhich lead down to the creek or the bottom of the secondary valley. Their preferredsite is down the neutral line of a suitable primary ridge. The road would then leavethe secondary watershed ridge, the main ridge, and turn down the neutral line ofthe primary ridge. Here it could have to cross a keyline drain and an irrigationdrain. Since this road provides access to the work roads or travel ways along thesedrain features it will probably be necessary to provide from one to three such primaryridge roads on both sides of the secondary valley. They will cross through the treelines, so far discussed, at approximately right angles. These first tree belts provideprotection from wind blowing in the general uphill or downhill direction of the primaryridge and primary valley, but they provide less effective protection in the directionof the general rise of the secondary valley. This latter protection is provided bya strip of trees left in the clearing of the land on one or other side of the primaryridge roads. A fence may follow the road on one side with the uphill and downhilltree strip on the other side of the road.
Summing up as far as we have gone with the tree landscape, wehave now a tree belt located by each of the keyline water conservation and the irrigationdrains and by the main road which generally follows the boundaries of the watershedof the secondary valley, and also by the roads down the selected primary ridges.These tree belts set the particular pattern for the whole of the clearing to be undertakenin this secondary valley.
Above the keyline tree belts there will be further cleared paddockareas. These are located by deciding a suitable vertical height above the keylinefor the lower line of the next tree strip. The most suitable minimum vertical heightis estimated from the general approach that the tops of the highest trees of thelower tree strip, in this case the keyline strip, should be approximately on thesame level as the ground at the lower side of the timber strip next above. This isnot merely a matter of estimating the height of the highest trees. The average heightgain in the tree strip from the keyline to the top ground line of the trees in thestrip above it must be considered. For instance, if the taller trees are forty feethigh, and the slope of the land generally in the keyline tree belt is one in eight--12-1/2%grade--the minimum vertical interval of fifty feet six inches is obtained. The calculationis as follows: The keyline, the actual line itself which forms the water conservationdrain, needs to be ten feet clear of the tree belt above it so that equipment canbuild the drain without obstruction from trees; the tree belt is twenty-five yards(seventy-five feet) wide and the distance therefore is eighty-five feet minimum fromthe keyline to the higher edge of the timber belt just above it. The grade of theland--assumed one in eight--places the top edge of the keyline tree belt ten feetsix inches vertically above the keyline and which, added to the height of the trees--fortyfeet--gives a vertical interval of fifty feet six inches,.
In retarding the drying effect of winds that blow across theclearing, tree belts at this vertical interval apart provide a very powerful influenceon all the cleared land. The generally accepted relevant figure is that such a treebelt will appreciably retard wind velocity for a distance of 1,200 feet on the windwardside of the tree-belt windbreak; therefore the cleared area is appreciably affected.But another favourable factor also operates. A tree belt or windbreak also retardsthe velocity of wind on the leeward side of the windbreak for a distance of approximately200 feet under these conditions, and so provides greatly increased effect in thearea approaching a second tree belt where the protection afforded from the lowertree belt would be petering out. In my opinion this influence on wind alone makesclearing on this pattern more than fully justified; it should be considered imperativeon this type of land. It has been found also in all my experiences of these mattersthat the extra planning and supervision which is necessary in this method of plannedclearing so increases the interest of all concerned that added efficiency resultswhich in turn actually reduces clearing costs below those of other methods.
The position of the first tree belts above the keyline treebelt is determined by the foregoing methods and a strip of trees twenty-five yardswide is left as before. Generally the areas of cleared land above the keyline areabove the highest dams, and so there will be no grade lines needed. The belt of treesmay therefore follow a grade similar to the drains as before or be placed with thelower edge of the belt on a true contour. Whichever method is used, measurementswhich locate the tree line in reference to the lower belt are taken at near the middlepoint along the length of the keyline, the neutral line of the primary ridge. Whenthe area of land above the keyline tree strip, or above the strip next above it,is below the height referred to, then all the area above is cleared with the exceptionof trees which may be left along a road or a boundary fence line.
The first tree strip to be left below the irrigation drain treestrip conveniently follows the lowest boundary of the irrigation area. Irrigationpaddock boundaries are therefore considered and determined at this stage.
In Keyline flow irrigation which will be employed here, theirrigation area comprises a strip of land along and below the irrigation drain whichis limited in depth down the slope by the distance that irrigation water will travelin one hour over the particular land fall. The distance downhill or the width ofthe irrigation area is influenced by another important fact, peculiar to a Keylinedevelopment, which also requires brief explanation at this stage. It involves a summaryof a new approach to irrigation. Keyline techniques provide the widest control ofwater, including methods which control the movement of water over land surfaces forirrigation purposes. Low-cost irrigation is therefore eminently practical on landand land shapes and slopes that are seldom considered suitable for irrigation byorthodox methods where it is usually something which is considered with flatter andvery flat lands, including, in the undulating country, the creek and river flats.Keyline irrigation principles and methods usually apply to all such land in a moreeffective manner than do orthodox methods, but it also brings another and extremelyvaluable and as yet unrecognised type of land into the class of high-value irrigationcountry. This form of land embraces the hill country which is not so steep that itis incapable of being cultivated on Keyline methods by the farm tractor and implements.It also can include country that is considered somewhat steep. Where water can beconserved and flowed on to hill country, such land will become the highest valuedpasture and crop land, not excluding river flats. I realise that to most people sucha statement will require a lot of proof. I trust it will be found in this book.
Drainage is one of the ever-present problems of flat land irrigation.So water, which is our main lack, then destroys land by being over supplied. Thisis strange, but true. Keyline hillside irrigation (the methods are covered in detaillater), is designed for the highest efficiency in water use, which is in part accomplishedby irrigating as high on the land as practical by Keyline flow methods, and leavinga strip or paddock of unirrigated land below the irrigation area. The unirrigatedarea lies between the lower boundary of the irrigation paddock and the bottom ofthe secondary valley below. This particular design in Keyline immediately eliminatesdrainage as a problem of irrigation. The surplus water, if any, from the irrigationarea can only improve the dry or rain-only land below it. Therefore the bottom ofthe valley or flat land, the drainage problem land as normally irrigated, is segregatedfrom the general irrigation water by a dry area. The dry or rain-only area is improvedby the drainage, if any, of surplus irrigation water and improved by a moisture drift,which always develops later from the irrigated land. The secondary valley, oftentoo wet naturally, is also improved by the protection thus afforded from excess waterand further improved by Keyline soil development methods.
Consideration of these new factors, then, assists in determiningthe width of the irrigation paddock below the irrigation drain toward the bottomof the secondary valley. My own experience of these matters generally indicates thatsuch an irrigation area should be at least twice the length along the irrigationdrain as its width downhill from the drain. On short to medium length land, as definedin Chapter VI, "Land Shape", there will be sufficient space down' the lengthof the land, i.e., the length of the primary valleys and primary ridges, foronly one such irrigation area from each irrigation dam. The width of the irrigationpaddock could be such that half the land lying under the irrigation drain to thesecondary valley bottom below is irrigation land and half rain-only pasture or cropland. The longer the irrigation areas, then, the larger generally will be the rain-onlyarea below which will be improved by eventual moisture drift from the irrigationland. Circumstances applying in medium length land may provide a general width abovethe keyline water conservation drain of 230 to 300 yards to conserve water to anirrigation dam, and perhaps 400 yards width of land below the irrigation drain, ofwhich half the width would be irrigated and the remainder comprise the rain-only'area. However, these circumstances are determined only by the land shape as it exists.The farmer can, however, always do the best with what he has.
In longer-slope country it may be suitable to plan alternatestrips of irrigated and rain-only land. For instance, on one section of "Kencarley",at Orange, the natural land shape and length of land permits flow-irrigated stripsfairly high up on the land. Down the slope below the first strip of irrigated landthere is a 25-yard-wide tree belt and a cleared rain-only area for pasture and crops.This is followed down the length of the land by two other tree belts, irrigated areas,and rain-only areas; in all three irrigated areas with, alternate rain-only areasbelow each of them.
There are other considerations which help to finalise the decisionas to the most advantageous width for the irrigation area. These are discussed later.
We may assume that on "Yonaroo" this first area isa little longer than short slope land, and that the first irrigation area is twelvechains wide along and below the irrigation drain. The lower boundary of the irrigationarea may be either planned from a true contour line or another grade line fallingwith the general fall of the land, as do all grade lines or drains. In this decisionthere are two factors to be considered. A grade line on the same fall as the irrigationdrain will not generally enclose an area of uniform width below the irrigation drain.There is a tendency for such land as that of the irrigation area to flatten slightlywith the general fall of the land (the fall of the secondary valley), causing theirrigation strip to widen in the down land direction. This is usually not a problem,since the area of rain-only land below the irrigation area always widens considerablyby the fact that contours in the down land direction move away from the bottom ofthe secondary valley. If the possible increasing width of the irrigation area isa definite disadvantage (as the irrigation drain is followed down land), a lowerirrigation area boundary on the contour has a compensating effect by the fact ofthe irrigation drain's slight fall approaching a little this lower contour.
However, in the circumstances on "Yonaroo" we willdecide on "no contours" and mark the lower boundary of the irrigation areaas a grade line falling down land.
We may now mark out the tree belt below the irrigation paddockand clear the timber from this area and from the land below it down to the bottomof the secondary valley.
Our discussion on clearing has been confined to only one ofthe primary land units with its primary ridge and primary valley form. The keylinesof the remainder of the primary land units in the secondary valley area are markedand the clearing is completed for the whole of this first of the four distinct majorland units of "Yonaroo".
We are now in a position to assess the progress of the work.The general situation may be that while all the future dam sites, their conservationdrains, irrigation drains, and irrigation areas have been decided and, with the farmroads, influenced the plan of clearing, one dam site only has been determined forimmediate construction. As the property cannot operate satisfactorily until permanentwater supply has been obtained it is advisable that the first dam be constructedas soon as its site is selected and cleared.
The clearing down the length of any primary ridge at this stagediscloses: (1) A keyline tree belt with cleared land above and below it. (2) A treebelt in the areas above the keyline trees with cleared land above it to the top ofthe watershed or main ridge. (3) A tree belt along the main road on the watersheddivide or main ridge. (4) A tree belt along the upper side of the irrigation drainwith rain-only pasture or crop land above it and irrigation land below. (5) A treestrip along the lower boundary of the irrigation area with the irrigation countryabove it and rain-only land below it to and including the bottom of the secondaryvalley. If the land above the keyline rises to legs than fifty feet six inches highervertically than the keyline there will be no timber belt above the keyline treesother than trees which may be left along the main ridge road.
The line of the tree strip from the lower primary valley andridge units are continued up land through the other land units according to how theywork out in the planning of each unit in turn. Some reasonable adjustment may bemade but otherwise each primary unit is designed individually. In my experience thereare always lines which, when continued. up land, fit the higher primary land units.
The lower tree strip, which approaches the bottom of the secondaryvalley is preserved as a tree strip crossing the valley into the primary land uniton the other side of the secondary valley. Other than the tree strip which crossesa valley when continued to plan, all trees should be cleared from both primary andsecondary valley bottoms. Trees left in the valleys will always tend to limit thefull development from the increased soil fertility and productiveness that rapidlyfollow the greatly improved environment from the Keyline planning and management.The secondary valley may be improved to such an extent that a portion of the brokenland at the first formation of the confined stream bed may later be smoothed overto a form where cultivation may cross the old break.
There are many who recommend the leaving or planting of treesalong a broken stream course or an erosion gully in the bottom of a primary or secondaryvalley to protect the land from soil erosion. In the great majority of cases in ourclimate and soil conditions, all that the trees "protect" is the permanenceof the gully. They will prevent the easy smoothing over of the break when smoothingmay be warranted. They will also screen the immediate area of the break in the landfrom the repairing effects of the improving environment.
Apart from the lines of the four of five tree belts runninggenerally across the land, across the primary valleys and primary ridges, there arebelts of trees along the roads down two of the primary ridges.
With both sides of the secondary valley area (secondary landunit), which includes the several primary valleys running into it, now completedand. one dam built with its water conservation drain installed, (a true keyline damwas selected as the first to be built), it is as well to go on immediately with workto develop the soil and pastures of the property. We begin with burning off and cultivation.This is the work of the next chapter.