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   0NE third of the continent of Australia has a climate which produces sufficient rainfall to warrant and support a highly-developed agriculture. Within this area there are great stretches of completely undeveloped land that are crying out and demanding attention and development.

   If we are to produce a real Australian type of agriculture that is 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 the world and which contains everything except a good agricultural climate), then we must 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 undeveloped country, farms and grazing properties which would be permanent and safe from our present land troubles. They would also have more individuality than our best properties of today. Because this poor agricultural climate extends over so much of this land which is available for development, it is ever in the background of these discussions and it is therefore selected as the theme in the presentation of the planning techniques of Keyline.

   These subsequent descriptions are typical of my actual experience but will be more readily appreciated if they are made to apply to a fictitious property under 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 function of climate has been described in Chapter V, entitled "Climate", but to be more specific, the following paragraph completes the climatic picture chosen for the area of land we call "Yonaroo".

   The average annual rainfall is assumed to be 24 inches. There is a little more rain in the winter months of June, July and August, though the flood rains do not usually occur at this time of the year. Heavy rainfalls are more likely to occur in the summer months of December, January and February. The summer can be extremely dry and hot. Good run-off occurs in practically every year, but on occasions the rainfall may vary from ten to nearly fifty inches, with consequently much greater run-off. There are frosts each winter but snow is never heavy enough to lie on the ground.

   Land shape is second on the Keyline scale, and for our purposes is taken to include all the land forms that are likely to be present on land which is between 1400 to 1800 feet above sea level. The soil of the property is of two types, clays from slates and a lighter soil from a granitic area. The property must be described in some detail as the description proceeds to enable a clear picture to be seen of its development.

   "Yonaroo" contains 1800 acres. Except for a small area 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 intermittently flowing creeks and which join on the property and flow to a larger creek. This larger creek, which rises several miles beyond the property, flows alongside and forms part of the property boundary. There is another secondary valley, but smaller than the other two, which forms on the property but flows away from the other drainage systems and 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 property would carry a few sheep or cattle in a good season and offers only a poor type of sheltered winter grazing. There is no permanent stock water, but holes in the creek retain 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 property and 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 contours at 20-foot vertical intervals.

   The second method of land examination for planning purposes is by visual means on the land itself.

   The land divisions of "Yonaroo" are those already mentioned, namely, two secondary watershed areas each containing several primary valleys, and these two secondary valleys which, joining on the property, form a creek which, in turn, joins a larger creek and becomes part of the property boundary. Several primary valleys flow to this boundary creek and the combined land area of these latter primary valleys is the third land division. Another valley area, not associated with any of these three areas, forms on and flows from "Yonaroo" without joining the other systems. It is the fourth main division. To repeat, there are four main areas of land--the two secondary valley systems, the area of the group of primary valleys falling into the boundary creek, and the fourth valley or watershed division not associated with the other three.

   The next step in planning is to select the land division which will be developed first and to determine. the relationship between its various primary valleys. In order that the full pattern of the water supply scheme for the farm may be determined, it is necessary to know whether the keypoints of the primary valleys rise into the rising country.

   Water supply is third on the Keyline scale of permanence, and it is designed according to the dictates of climate and land shape.

   The rainfall feature of the climate of "Yonaroo" indicates that the plan of development should aim to conserve all the rain that falls. Land shape 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 the localities of all the most suitable dam sites. Where each contour line crosses a valley it could be the water line of a dam, and by drawing a line across the loop of a contour the dam can be "seen". On the map an examination is made of the primary valleys that fall to the secondary valley area which was selected for the start of the work. Beginning with the lowest primary valley falling on one side of the secondary valley, its keypoint is located, i.e., the point of change in the slope of the primary valley at the bottom of the first steeper slope. Next on the map the nearest contour to the first keypoint is followed around to the next valley in the general direction of the rise of the land. If the keypoints of the valleys have the usual rising relationship into the rising country the contour followed will 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 contour on the map is followed in the rising land direction to the next valley, and so on until the highest primary valley in this system at the head of the secondary valley is reached. The primary valleys falling from the other side and into the secondary valley are examined in like manner.

   These primary valleys vary in size. Therefore, they are appraised first from their significance in water conservation. The first or lowest primary valley 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 assumed to be of water conservation significance.

   These matters are very simply determined on the contour map by examining the contour loop next below the keypoint of the valley against what is considered a suitable depth of water for effective water conservation. This latter matter, the suitable water depth of dams, must also be determined. Effective water conservation capacity for irrigation, or stock and irrigation, as distinct from purely stock 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 should be accepted as a suitable depth for these Keyline dams. Confirmation of this figure will not be found in agricultural literature because it is a recommendation based on the results of my own experiences. By way of illustration, a dam with a depth of 24 feet of water at the lockpipe has generally been found to be double the cost of a dam on the same site but having a depth of 20 feet. If the contour loop immediately at or just below the keypoint of a valley can be joined by a straight line across the valley shape, thereby representing the wall of a dam, and just touches the top of the next lower contour loop, then a twenty-foot dam is represented. The capacity of the proposed dam is simply calculated by determining the acreage area bounded by 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 depth of water is twenty feet at the lockpipe, the capacity of the dam is sixteen acre feet. The average depth of such a dam is thus generally 40% of the full depth of water at the lockpipe. In this manner the sizes can be determined against each valley and those valleys without value in water conservation potential in true keyline dams are disregarded in the first or general stage of the planning of "Yonaroo".

   Now, there are two general approaches to the way in which the farm may be developed. Either it may be developed as a complete project in which all the work of the final plan is completed as one quick undertaking or, and much more usually, the work will be done over a longer period of time as finance becomes available 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 understood before proceeding at all. On "Yonaroo" the design of the water supply sets the pattern for the whole of the development work.

   While it may be assumed that the annual run-off is of the order of three to four inches there are occasions when the run-off in one year exceeds ten inches. There may be a run-off of even twelve inches in a short period in flood making rains.

   In these circumstances of run-off all the better dam sites just below the keypoints of the primary valleys could be used. These dams will be filled by water conservation drains which follow the gently rising keylines of the land.

   From prior knowledge of the uniform geological structure of the underlying rock of the secondary valley and from the examination of the contour map it will have been seen that the dam sites in each primary valley are progressively higher, permitting the use of keyline drains to feed water to each dam and to allow overflow water from each dam to flow into the keyline water conservation drain of the next lower dam or into the catchment above this keyline drain. Thus, all the water from the high country is controlled so that none escapes until all the keyline dams are filled. The keyline water conservation drains with the dams themselves are to become the most permanent structures of all the work that will be done on the property.

   If the work is to proceed progressively there must first be permanent water. Under these circumstances the sites for all the projected dams and others to be discussed, are examined to select the dam that will best supply the early needs. Not only should the first dam be one that will fill quickly and provide low cost water, but it must be consistent with a site which will enable the water to be used for irrigation on a piece of land that can readily be cleared and developed for crops or pasture. Any one of the dam sites from the highest down may be chosen and built first so long as it is in its right place in relation to all other selected sites when the full plan finally emerges.

   The capacity of all the true keyline dams will usually be filled frequently enough by the water conservation drains, but where there are many good capacity sites the average run-off rain for one and a half years from the areas above the dams and water conservation drain may be assumed as a limit to the capacity of the true keyline dams. A run-off of four inches per annum will be reduced, perhaps appreciably, 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 true keyline dams. There are two further types of dams to be considered in this general climate and land form : they are reservoirs and lower valley dams. The reservoir site is looked for firstly in the area of the secondary valley below the highest dam of the keyline series. The reservoir or reservoirs may, in their height position in the secondary valley, lie below the level of the lowest of the keyline dams, but not necessarily so. A reservoir site could be just above the break of the land that marks the first formation of the small creek of the first secondary valley. The reservoir is kept high for preference and with some consideration being given to the area of its catchment excluding that of the keyline dams above it. The reservoir catchment is suitably related to its capacity if two years usual run-off will fill it. If a larger than necessary catchment is available two or more reservoirs are considered, the higher site being used before the others.

   The lower valley dam or dams of this particular natural land area is sited at or near the point where the land form of the secondary valley finishes and becomes part of another division. In Keyline the lower valley dam is sited and designed to hold all the run-off from its catchment area for three years or more of average run-off.

   This then is the general pattern of the water supply for the full development of the land in the area of the selected secondary valley.

   While there is a pattern to the siting of dams, there is also a particular pattern developed in Keyline for the use of the conserved water. For instance, the pattern of use with all dams filled commences with irrigation from the true keyline dams immediately irrigation is advantageous or profitable. The lower dam 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 keyline and 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 formed and fed by the joining of the two smaller watercourses of the two secondary valleys and which in turn join the boundary creek. It will be assumed that each small creek has a water catchment area of approximately 400 acres.

   Three different types of dams have been discussed: (1) The true keyline 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 valley beneath the highest of a series of keyline dams or just below the junction of one of the highest of the primary valleys with the secondary valley or in the lower end of a larger primary valley before its junction with the secondary valley--there may be one or several reservoirs in a secondary valley area. (3) Lower valley dams, which are located in the secondary valley at a site located above the junction of the watercourse formed by the two secondary valleys. When the boundary of a property crosses a secondary valley, the site of a lower dam is chosen so as to ensure that it will catch all run-off from the land below the other dams and also the overflow of these dams. We have seen that these three types of dams are simple and obvious against the background of the undulating country of "Yonaroo." Where there is sufficient variation in height over a property, the factors which relate to these three types of dam generally apply.

   Getting back to the creek formed by the junction of the flow of the two secondary valleys, conservation of water here is not entirely in the hands of the farmer. In Australia, Government authorities generally control or administer these matters. A dam constructed across a defined and confined watercourse requires the permission of such authorities, since consideration must be given to the rights of owners of land below through whose property the creek later flows. There is also something less than law but still of some consequence which says that a farmer has the inalienable right to as much as he can store of the rainfall which actually falls on his own land. Even if all the rainfall which formerly was lost in run-off is now conserved in the soil and in farm dams by the farmer, he is still not holding all the water. Quantities of water would be continuously moving into the earth below the farm and so replenish ground water supplies. Springs which thus form are the only constant flow water of the creeks and rivers. The more water the farmer conserves the more water moves underground as seepage from his soil and from his dams. More water will also evaporate over his land.

   Generally then, before these dams on creeks may be built, application has to be made to the appropriate Government authority, who cause a notice to be inserted in a suitable daily newspaper giving information of the proposed dam to those who may be interested. Other farmers have the right to object to the dam if they consider it is detrimental to their own lands. If such objection be lodged the matter is heard by an authority but with the rights of appeal, if necessary, determined by such court as the Land and Valuation Court. When authority is given the farmer is not released in any way of responsibility for the dam. The deciding authority in permitting the construction of the dam does not assume any responsibility for the effectiveness of the dam. This general procedure, in instances which have concerned me, is a source of inconvenience and delay on a matter that should never be unnecessarily delayed.

   Here again, it seems to me, is a purely agricultural matter that should be determined quickly by the agricultural officer on the spot. He may be the local agronomist, dairy officer, or any other. An alternative procedure could be that the farmer first contacts his neighbour below and acquaints him of the project as a matter of courtesy and expedition, and then informs the local agriculturalist who accepts the farmer's application by word of mouth or telephone and immediately calls to inspect the proposed site. The agricultural officer should not be in any way responsible for the site selection, design or construction of the dam, but should be capable of offering effective advice if requested to do so by the farmer. The officer, who in all probability knows the farm well, should merely appraise the creek flow, if any, and then decide if the dam would detrimentally affect the neighbour or neighbours in the next two-mile length of the creek. The creek may be a constant-flow type, which would flow to the same capacity after the construction of the dam for most of the time, but on the other hand if in his opinion it could cease to flow in a drought where formerly it did not, the agricultural officer may then suggest to the two or three concerned that the farmer owning the dam should release. a certain specified 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 the creek and the stipulation referring to drought flow. The dam could then be built but 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 of the original bed of the creek at the site, the farmer in dry times would release the equivalent of the drought flow. There will be concern in the minds of only those with little knowledge of these matters at the possible loss of water caused by a dam on one farm to the land of the property below. Generally, the more water that is conserved and used on farms the more constant and reliable is the flow in the creeks 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 the secondary valleys may be of relatively large capacity and of low-cost storage. It would have a natural catchment on "Yonaroo" of 800 acres, including the catchment area of all the other dams. In the present planned water storage scheme it would appear to have little chance of filling even in substantial floods. Under usual circumstances, the influence of the greater water storages above, the constant use of the water on the irrigation areas, and the continuous partial and complete recharging from each rain of the dams of the primary and secondary valleys, would cause the natural and intermittent flow of the creek to become a considerable constant flow. This effect may take two years before it starts to function.

   In my opinion the matter resolves itself into a somewhat optimistic appraisal of the circumstances relating to filling capacity, cost of construction and use of the water. As there are still areas of "Yonaroo" below the projected creek dam it may be possible to use the water from the creek dam by flow methods of irrigation. In these methods of water conservation all dams are constructed with lockpipe controls. In the construction of dams in flowing creeks in this type of country the lockpipe system makes what is with other methods always a difficult and costly 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 via the lockpipe installation during the construction of the dam. As part of the general site preparation work, the lockpipe, 140 feet total length, was laid in a prepared bulldozer trench at the level of the creek bottom and a little to one side of the creek bed where the water originally flowed. Immediately a full bulldozer blade load of good wall material was pushed over the lockpipe near its inlet end and across the flow of the creek, the water entered the lockpipe and flowed there and right through the wall, where it continued to flow during the building of the wall. There was no water and mud to cause trouble and the work proceeded in the same orderly manner as though the construction was in a dry primary valley.

   There are many circumstances, where, while there is no suitable land for flow irrigation below the lockpipe level of such a dam, there is suitable land for this purpose below the level of the high water of the dam. In these circumstances a pipe from the lockpipe outlet to a suitable higher point between the levels of the lockpipe outlet and the top-water line can discharge water into a suitable irrigation drain and may employ the lowest cost method of irrigation for half the depth of the water in the dam. Much more than half the water capacity of the dam is contained in the top section. In such circumstances the dam, as it were, has two levels, top water level and irrigation drain level. In a large dam of this type the land lying between these two levels and covered with water when the dam is filled and at other times dry, may be prepared for special crop production. This type of dam and other special purpose dams are discussed in later chapters.

   There remains the smaller catchment area of the property, which is actually the small top section of a secondary valley and which is planned to its own particular development capacity. The only area on the property presumed to be too steep for mechanical clearing lies near the head of this valley. The flatter top 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 forming a part of the boundary of "Yonaroo" may now be considered. Several land owners could have an interest in the part of this creek that is on the property.

   In general, where creeks form property boundaries, the centre line of the creek is presumed to be the boundary. However, the fenced boundary is a give-and-take arrangement, which provides suitable exclusive access to the creek for each party. Apart from the right of owners lower down, a dam on this creek would cover part of the adjoining neighbour's land and therefore could be constructed only on a mutual basis. After satisfying the land-owner lower down, a dam may be considered in which all details, including proportions of cost and particular rights of water usage, would need to be embodied in a formal legal document acknowledging permanent right of each area of land on the other. Water may be taken from such a creek by the various owners provided the reasonable rights of all others are protected. The water that is most significant generally is that which is above normal flow and up to flood flow. Small inexpensive weirs may divert water to a water race or water conservation drain, which would follow the general fall of the land to provide irrigation by flow methods. However, the only time during which this water is readily available is when it is not likely to be critically needed. Good creek flow is a feature only of good seasons. So the best use of the available water may be by the conservation of the water from the creek when flow is good, via a suitable drain into an off-the-creek storage. It may be brought into dams already a part of a primary or secondary valley storage or into a dam to be constructed in a special new site. If the creek water can be diverted to a previously constructed reservoir the use pattern for the water of the reservoir could then be changed to suit its new faster and more frequent filling capacity. It could become a special purpose dam and all its water used by flow methods as soon as irrigation was advantageous. With this matter suitably decided the full water conservation capacity in surface storage sites available on "Yonaroo" is now finalised.

   I have suggested that dams for farm irrigation be limited to those with a capacity of a minimum of 2-1/2 million gallons, or ten acre feet. The limiting of a farm irrigation dam to this minimum size should be consequential to site, limitations and represent the amount of the water storage capacity of the site with a wall 23 feet high and water depth at the lockpipe of 20 feet. Dams of ten-acre feet capacity are generally the highest cost water storage with costs running to £200 per million gallon, i.e., £50 per acre foot, or the equivalent of 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 to set any cost limit to the value of storage capacity. In Keyline the storage capacity of dams is a permanent asset. The cost of the water as distinct from the water storage capacity relates to the storage cost divided by the number of times the water of the storage capacity is used. If the water is used twice a year for twenty years the cost of water from the most unfavourably sited farm dams is very low. The smaller farm dam also costs relatively more for the reticulation of the water, and in flow irrigation the cost of the lockpipe system and the irrigation drain, which constitutes the 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 reticulating drain 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 overall planning and the water supply scheme can be determined very quickly with the aid of the special contour map, the absence of the map changes things considerably. Then the same decisions must be made from direct observations on the land, in which matters determined almost at a glance on the map, without the map now involve much walking and some measurements and levels. A start is made as before at the lower limit of the secondary valley above the point where it junctions with the creek of its companion secondary valley. The nearest primary valley is the first one inspected. The valley is tree covered and it is necessary to walk up the centre of this primary valley to locate the keypoint of the valley. This presents little difficulty. Then it must be decided whether or not the valley is of significance in the planning which is based on water supply. If there is some doubt on this matter a more thorough examination of the valley will be necessary. This is done with the aid of a level, and in tree covered country our Bunyip level provides the quickest means. The examination first ascertains the "valley floor slope". Over my twenty years of experience, experiments on the siting and the design and the construction of many dams, valley floor 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 to be mentioned briefly as the development of "Yonaroo" unfolds.

   A valley floor slope of one in twelve is too steep a site generally for a dam unless the rest of the valleys are similar or steeper. One in twenty is a satisfactory slope and one in thirty or flatter is considered good for a true keyline dam site.

   In the first primary valley a point is selected one to two feet lower than the keypoint of the valley and the first staff is stood up. From this point and another point fifty feet away (the full length of the water tube of the Bunyip level) and down the centre of the valley the readings on the two staffs of the 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 the staffs indicates a valley floor slope of one in fifty, which is better than may usually be expected for a true keyline dam. If the valley floor slope is too steep the valley is not considered any further at this stage. Apart from a satisfactory valley floor slope, the valley needs a suitable "shape", which again is determined with the level. From the point previously pegged just below the keypoint, the Bunyip level is used to run out a true contour in both directions, marking points along the contour as conspicuously as possible; and so is determined the shape of the top water line of the possible dam. Here again classifications and determinations of my own must be mentioned. The length of a dam is the distance from the water line at the middle of the wall up the valley to the top water line of the dam near the keypoint. If the length of the proposed wall (a line across the water level contour) and the length of 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 rejected for water storage.

   A dam length twice as long up the primary valley as the length of its wall is of good shape. It is assumed that the first primary valley has a valley floor slope of one in eleven and would require a wall of 300 feet long to contain a depth of twenty feet of water at the lockpipe. These figures indicate that the length of the dam would be the depth in feet multiplied by the slope (20 x 11 = 220 feet). This figure could be further checked by taking levels from the peg placed originally 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 proposed dam is longer than the dam, so the site is abandoned. But this dam site also fails on minimum requirements in another direction, that of capacity, which can be quickly checked by the following means: The water surface area of the proposed dam can be calculated by taking two-thirds of the area found by multiplying the length of the water line at the wall and the length of the dam measured at right angles to the wall (300 x 200 x 2/3 = 44,000 square feet = 1 acre approximately). Again, assume that 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 acre feet, against our general minimum capacity recommendation for a farm irrigation dam of 10 acre feet.

   Continuing the inspection from the first primary valley which is suitable for water conservation in a dam , it is then necessary to run a near contour or rising keyline to the next primary valley up land. As the country is tree covered, the line will need to be marked in a manner that will permit of being located again later. This type of work is continued on the land generally as done on the map, but it takes considerably longer to obtain an appreciation of the land shape and the valley relationships. For the real work to proceed and whether a contour map is available or not, the marking out of these keylines must eventually be completed on the ground. Without the map, trial lines will sometimes be necessary to obtain a first understanding of the primary valley inter-relationships.

   To summarise these early planning points. First, obtain an overall picture 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 perhaps accessibility and uniformity of shape. Third, as water conservation in farm dams is 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 their significance in water conservation and their relationships, i.e., whether they 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 rising with the rising country. As soon as their positions are determined, and marked with suitable pegs, clearing of the trees and brush may commence.

   The keylines themselves are first cleared by a bulldozer, following the pegged line and forming a definite cleared line which will represent also the boundary between cleared and uncleared land. A strip or tree belt is to be left along the keyline and may be either above the keyline or below it. In the conditions here where water conservation is vital it will be better for the tree strip to be left above the keyline. The first cleared run of the 'dozer along the keyline represents the top boundary of a strip of cleared land or land to be cleared which lies below the keyline. The timber belt itself is left standing above the keyline.

   Any belts of trees left to form part of the permanent landscape should be wide enough for good forest condition to be pertinent. Strips which are too 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 and natural 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 conditions appears to promote good conditions for timber-tree life and growth. This is the distance suggested as a minimum, and thirty yards as a general width. The first tree belt then is located by marking a strip of land twentyfive yards wide in the trees above the keyline, a line uphill and parallel to the keyline.

   The next permanent line of importance that may be preserved in a treed belt is the irrigation drain. Whether it is to be or not be used by the immediate construction of the dam, its site should be located at once if a strip of trees is to be left above the irrigation drain. The keyline tree strip works satisfactorily whether it is above or below the keyline drain. I prefer it above, so that in crossing the valley it does so above the dam, and thereby protects the dam from wind which causes wave erosion and the trees also retard evaporation; but the tree strip of an irrigation drain is located always above the drain, so that water does not flow through the trees when irrigating the paddock.

   All the details of the water conservation and irrigation drains of Keyline, including their sites, designs, construction and uses, are explained in later chapters. However, to follow the course of the present development, it may be appropriate at this juncture to briefly discuss the drains used in Keyline. Many farmers know drains from the anti-soil erosion approach, but the drains of Keyline are totally different. There are only two classes of drains in Keyline. The first is the water conservation drain, which is for the express purpose of transporting run-off rainfall into farm dams. The second is the irrigation drain, which provides for the economical use of the irrigation water and generally, with the lockpipe, completes the irrigation equipment. The water conservation drains of Keyline may follow the keylines as we have discussed, or be located below the higher section of a property which does not include the complete land shapes of primary and secondary land units. Where these land forms are large, the land of a property may be of sizeable area and still only include a portion of one of these land systems. Again, the drains of 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 drains are successful in their purpose, the problems no longer remain and the drains become superfluous.

   The first irrigation drain on "Yonaroo" is located from the position of the lockpipe outlet of the first proposed dam. These lockpipe outlets are described in later chapters.

   With the irrigation drain pegged in the down land direction from the outlet point the bulldozer clears the drain line. The tree strip is marked twenty-five yards wide in the trees above the line and again marked by the bulldozer pushing the trees down along this line. There is now an area ready for clearing with its upper limit marked by the pushed-down path of the keyline and its lower limit by the top of the irrigation drain tree strip.

   The best means of getting the trees down is by using two large bulldozers with a 400-foot or longer length of six-inch wire rope (about two inches in diameter) or with a heavy chain. One bulldozer travels the top marked line, the keyline, the second 'dozer travels in the same direction about 100 feet lower down in the trees. The first run pulls down a large area of trees quickly. The second run should be made with one 'dozer on the line above the tree strip of the irrigation drain and the other in the trees 100 feet or so above it. After the first run, which pulls down a strip below the keyline, and the second run, which pulls down a strip above the irrigation drain tree belt, are both completed, the pattern of the work is clear. It is then a matter of pulling down the trees that are left in the centre of the land strip of what will be the first cleared paddock area. When pushing down and clearing are to be done with one bulldozer it should start by pushing down from the 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 the trees 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 places are nearly impossible and supervision may be relaxed if necessary.

   The keyline rising into the rising country from the keypoint of a primary valley in which a dam is planned, may, if extended, cross the next primary valley 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 which should not be missed. For instance the keyline water conservation drain feeding run-off to the lower keyline dam of a series of keyline dams may, as it approaches the next valley higher up land coincide with the irrigation drain from its keyline dam. It could, in some cases, be much lower than this irrigation drain and coincide with the 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 valley right through the land area of the secondary valley. All drains, both irrigation and water conservation drains rise into the general rise of the country or, the same thing, fall with the general fall so that the slope of any drain line does not clash with 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 relation to 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 also in the tree lines. We now must consider farm roads in fixing tree-belt sites other than those along the keyline water conservation drains and irrigation drains. Some of 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 those that travel the main divides, on the property and the others branch roads from these which lead down to the creek or the bottom of the secondary valley. Their preferred site is down the neutral line of a suitable primary ridge. The road would then leave the secondary watershed ridge, the main ridge, and turn down the neutral line of the primary ridge. Here it could have to cross a keyline drain and an irrigation drain. Since this road provides access to the work roads or travel ways along these drain features it will probably be necessary to provide from one to three such primary ridge roads on both sides of the secondary valley. They will cross through the tree lines, so far discussed, at approximately right angles. These first tree belts provide protection from wind blowing in the general uphill or downhill direction of the primary ridge and primary valley, but they provide less effective protection in the direction of the general rise of the secondary valley. This latter protection is provided by a strip of trees left in the clearing of the land on one or other side of the primary ridge roads. A fence may follow the road on one side with the uphill and downhill tree strip on the other side of the road.

   Summing up as far as we have gone with the tree landscape, we have now a tree belt located by each of the keyline water conservation and the irrigation drains and by the main road which generally follows the boundaries of the watershed of 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 undertaken in this secondary valley.

   Above the keyline tree belts there will be further cleared paddock areas. These are located by deciding a suitable vertical height above the keyline for the lower line of the next tree strip. The most suitable minimum vertical height is estimated from the general approach that the tops of the highest trees of the lower tree strip, in this case the keyline strip, should be approximately on the same level as the ground at the lower side of the timber strip next above. This is not merely a matter of estimating the height of the highest trees. The average height gain in the tree strip from the keyline to the top ground line of the trees in the strip above it must be considered. For instance, if the taller trees are forty feet high, 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 calculation is as follows: The keyline, the actual line itself which forms the water conservation drain, needs to be ten feet clear of the tree belt above it so that equipment can build 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 from the keyline to the higher edge of the timber belt just above it. The grade of the land--assumed one in eight--places the top edge of the keyline tree belt ten feet six inches vertically above the keyline and which, added to the height of the trees--forty feet--gives a vertical interval of fifty feet six inches,.

   In retarding the drying effect of winds that blow across the clearing, tree belts at this vertical interval apart provide a very powerful influence on all the cleared land. The generally accepted relevant figure is that such a tree belt will appreciably retard wind velocity for a distance of 1,200 feet on the windward side of the tree-belt windbreak; therefore the cleared area is appreciably affected. But another favourable factor also operates. A tree belt or windbreak also retards the velocity of wind on the leeward side of the windbreak for a distance of approximately 200 feet under these conditions, and so provides greatly increased effect in the area approaching a second tree belt where the protection afforded from the lower tree belt would be petering out. In my opinion this influence on wind alone makes clearing on this pattern more than fully justified; it should be considered imperative on this type of land. It has been found also in all my experiences of these matters that the extra planning and supervision which is necessary in this method of planned clearing so increases the interest of all concerned that added efficiency results which in turn actually reduces clearing costs below those of other methods.

   The position of the first tree belts above the keyline tree belt is determined by the foregoing methods and a strip of trees twenty-five yards wide is left as before. Generally the areas of cleared land above the keyline are above the highest dams, and so there will be no grade lines needed. The belt of trees may therefore follow a grade similar to the drains as before or be placed with the lower edge of the belt on a true contour. Whichever method is used, measurements which locate the tree line in reference to the lower belt are taken at near the middle point along the length of the keyline, the neutral line of the primary ridge. When the 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 exception of trees which may be left along a road or a boundary fence line.

   The first tree strip to be left below the irrigation drain tree strip conveniently follows the lowest boundary of the irrigation area. Irrigation paddock boundaries are therefore considered and determined at this stage.

   In Keyline flow irrigation which will be employed here, the irrigation area comprises a strip of land along and below the irrigation drain which is limited in depth down the slope by the distance that irrigation water will travel in one hour over the particular land fall. The distance downhill or the width of the irrigation area is influenced by another important fact, peculiar to a Keyline development, which also requires brief explanation at this stage. It involves a summary of a new approach to irrigation. Keyline techniques provide the widest control of water, including methods which control the movement of water over land surfaces for irrigation purposes. Low-cost irrigation is therefore eminently practical on land and land shapes and slopes that are seldom considered suitable for irrigation by orthodox methods where it is usually something which is considered with flatter and very 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 more effective manner than do orthodox methods, but it also brings another and extremely valuable and as yet unrecognised type of land into the class of high-value irrigation country. This form of land embraces the hill country which is not so steep that it is 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 be conserved and flowed on to hill country, such land will become the highest valued pasture and crop land, not excluding river flats. I realise that to most people such a 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. This is strange, but true. Keyline hillside irrigation (the methods are covered in detail later), is designed for the highest efficiency in water use, which is in part accomplished by irrigating as high on the land as practical by Keyline flow methods, and leaving a strip or paddock of unirrigated land below the irrigation area. The unirrigated area lies between the lower boundary of the irrigation paddock and the bottom of the secondary valley below. This particular design in Keyline immediately eliminates drainage as a problem of irrigation. The surplus water, if any, from the irrigation area can only improve the dry or rain-only land below it. Therefore the bottom of the valley or flat land, the drainage problem land as normally irrigated, is segregated from the general irrigation water by a dry area. The dry or rain-only area is improved by 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, often too wet naturally, is also improved by the protection thus afforded from excess water and further improved by Keyline soil development methods.

   Consideration of these new factors, then, assists in determining the width of the irrigation paddock below the irrigation drain toward the bottom of the secondary valley. My own experience of these matters generally indicates that such an irrigation area should be at least twice the length along the irrigation drain as its width downhill from the drain. On short to medium length land, as defined in Chapter VI, "Land Shape", there will be sufficient space down' the length of the land, i.e., the length of the primary valleys and primary ridges, for only one such irrigation area from each irrigation dam. The width of the irrigation paddock could be such that half the land lying under the irrigation drain to the secondary valley bottom below is irrigation land and half rain-only pasture or crop land. The longer the irrigation areas, then, the larger generally will be the rain-only area below which will be improved by eventual moisture drift from the irrigation land. Circumstances applying in medium length land may provide a general width above the keyline water conservation drain of 230 to 300 yards to conserve water to an irrigation dam, and perhaps 400 yards width of land below the irrigation drain, of which 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 alternate strips 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 strips fairly high up on the land. Down the slope below the first strip of irrigated land there 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 areas below each of them.

   There are other considerations which help to finalise the decision as to the most advantageous width for the irrigation area. These are discussed later.

   We may assume that on "Yonaroo" this first area is a little longer than short slope land, and that the first irrigation area is twelve chains wide along and below the irrigation drain. The lower boundary of the irrigation area may be either planned from a true contour line or another grade line falling with the general fall of the land, as do all grade lines or drains. In this decision there are two factors to be considered. A grade line on the same fall as the irrigation drain 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 slightly with the general fall of the land (the fall of the secondary valley), causing the irrigation 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 considerably by the fact that contours in the down land direction move away from the bottom of the secondary valley. If the possible increasing width of the irrigation area is a definite disadvantage (as the irrigation drain is followed down land), a lower irrigation area boundary on the contour has a compensating effect by the fact of the irrigation drain's slight fall approaching a little this lower contour.

   However, in the circumstances on "Yonaroo" we will decide on "no contours" and mark the lower boundary of the irrigation area as a grade line falling down land.

   We may now mark out the tree belt below the irrigation paddock and clear the timber from this area and from the land below it down to the bottom of the secondary valley.

   Our discussion on clearing has been confined to only one of the primary land units with its primary ridge and primary valley form. The keylines of the remainder of the primary land units in the secondary valley area are marked and the clearing is completed for the whole of this first of the four distinct major land 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 conservation drains, irrigation drains, and irrigation areas have been decided and, with the farm roads, influenced the plan of clearing, one dam site only has been determined for immediate construction. As the property cannot operate satisfactorily until permanent water supply has been obtained it is advisable that the first dam be constructed as soon as its site is selected and cleared.

   The clearing down the length of any primary ridge at this stage discloses: (1) A keyline tree belt with cleared land above and below it. (2) A tree belt in the areas above the keyline trees with cleared land above it to the top of the watershed or main ridge. (3) A tree belt along the main road on the watershed divide or main ridge. (4) A tree belt along the upper side of the irrigation drain with rain-only pasture or crop land above it and irrigation land below. (5) A tree strip along the lower boundary of the irrigation area with the irrigation country above it and rain-only land below it to and including the bottom of the secondary valley. If the land above the keyline rises to legs than fifty feet six inches higher vertically than the keyline there will be no timber belt above the keyline trees other than trees which may be left along the main ridge road.

   The line of the tree strip from the lower primary valley and ridge units are continued up land through the other land units according to how they work out in the planning of each unit in turn. Some reasonable adjustment may be made but otherwise each primary unit is designed individually. In my experience there are always lines which, when continued. up land, fit the higher primary land units.

   The lower tree strip, which approaches the bottom of the secondary valley is preserved as a tree strip crossing the valley into the primary land unit on the other side of the secondary valley. Other than the tree strip which crosses a valley when continued to plan, all trees should be cleared from both primary and secondary valley bottoms. Trees left in the valleys will always tend to limit the full development from the increased soil fertility and productiveness that rapidly follow 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 broken land at the first formation of the confined stream bed may later be smoothed over to a form where cultivation may cross the old break.

   There are many who recommend the leaving or planting of trees along a broken stream course or an erosion gully in the bottom of a primary or secondary valley to protect the land from soil erosion. In the great majority of cases in our climate and soil conditions, all that the trees "protect" is the permanence of the gully. They will prevent the easy smoothing over of the break when smoothing may be warranted. They will also screen the immediate area of the break in the land from the repairing effects of the improving environment.

   Apart from the lines of the four of five tree belts running generally across the land, across the primary valleys and primary ridges, there are belts of trees along the roads down two of the primary ridges.

   With both sides of the secondary valley area (secondary land unit), which includes the several primary valleys running into it, now completed and. one dam built with its water conservation drain installed, (a true keyline dam was selected as the first to be built), it is as well to go on immediately with work to develop the soil and pastures of the property. We begin with burning off and cultivation. This is the work of the next chapter.