Water The Forest
Pattern and Flood-flo are the names which were bestowed on thetwo original Keyline irrigation procedures. They suit forest and farm.
In the first attempts to use for irrigating the water whichwas in such a hurry to get off our farm, costs, in time and money, won easily. Notlooking to irrigate a potato patch or a few acres of grass, it had to pay for growingbeef; so all the water available was needed and it had to be stored in dams first.There were no difficulties building them; that was already an experience in miningwork.
At that time government departments showed little interest infarm dams for irrigation. Critics described our dams as huge and useless. They saidour soil was no good for anything but why cover with water the little good soil wehad in the (primary) valleys in order to irrigate worthless shale ridges? Only creekand river flats were worth irrigating!
Such opinions were universal then, but passengers flying southwardsof Sydney today will see evidence of the reversal of this view in the concentrationof these dams so close to the metropolis. All were constructed years after we establishedtheir practicability and they are for irrigating land formerly believed unsuitablefor the purpose.
We used both flood and spray systems of irrigation. The rateof water flow was doubled from 25,000 to 50,000 gallons an hour which was more thandouble spray rates at the time. Still the money flowed the wrong way.
While new ideas for irrigating were constantly being tried otherexperiments to improve soil were going forward. In theory and on paper a way hadbeen devised for cultivating the land to slow down the run-off rainfall from theprimary ridges and drift it toward the centre of the ridge, and to make the waterdrift outwards from the centres of the primary valleys. It was called Keyline 'pattern'cultivation, and now we would try it out.
A hundred acres were plowed 'pattern' on dry land with an implimenthalf way between the later chisel plows and a road ripper. Some months later it rainedduring a weekend stay on the farm and an inspection was made of the 'pattern' cultivation.Where I entered the paddock it looked good. The rain was heavy, the run-off was heldup nicely and spreading evenly and not concentrating anywhere. A dam some distanceaway was overflowing down a small primary valley. The water was doing exactly whatin theory it had to do but it was hardly believable. Instead of flowing as it wouldnormally do, about 12 feet wide, a foot or more deep in the centre of the valleyand fast, the 'pattern' had taken complete control. The sheet of water was flowing180 feet wide, covering from boundary to boundary the entire primary valley shape.The water out near the side limits of the valley, three and four feet higher thanthe centre of the valley, was the same depth as in the valley bottom. What I wasseeing was a flow of water ten times greater than we had used, moving uniformly downwardover a strip of land which sloped in three different directions. Keyline 'pattern'was a breakthrough!
Pattern irrigation is based on pattern cultivation which inturn is based on the pattern of the contours of the various shapes of the land, (Chapter4). Contours, which by nature are a uniform vertical distance apart, are parallelto each other on the vertical plane only. Marked in on the land with its varyingslope planes, contours are not parallel to each other.
Therefore if lines are made parallel to a contour on one sideof it--on paper or on the land surface--the lines are not contours but have a slope.if other lines are made parallel to the same contour, but on the other side of it,they also would be sloping lines but their slope direction would be opposite to thoseof the first group of parallel lines.
When the parallel lines are the hundreds of small furrows ofchisel plowing they will influence water to spread or drift in one direction or theother, according to which side of the particular contour--upwards toward the highercountry or downward toward the creek--the plowing has been done. Pattern cultivationis simply done parallel to a marked-in contour line in the direction away from itwhich will drift and spread flowing water in the opposite direction to its normalpath; towards the centre of the primary ridge instead of towards the centre of theprimary valley.
The water for pattern irrigation usually comes from on-farmstorages of two general types: firstly, from a large dam in a primary valley--atthe Keyline or lower down--or a dam on a creek or other water course which has sufficientland below it for irrigation; secondly from a smaller dam sited high enough to whichwater is lifted by pump from a large lower dam or other source of supply. This dammay hold only sufficient water to irrigate once and then be filled for the next irrigation.
The water flows from an outlet pipe in the dam directly intoan irrigation channel which is wholly within the ground like a shallow trench. Thechannel is about 50 inches wide and 25 inches deep, and usually has a gradient ofone in 300.
Present outlets beneath the walls of dams, consist of two pipelines,one small inside a larger pipeline. The small line is one and a half inch bore tosupply filtered drinking water from near the surface of the storage. It operatesindependently of the large steel pipeline--12 inches or 25 inches diameter--throughwhich the irrigation water is released. This is in part of description of our LockpipeSystem which is protected by various patent applications and designs registrationsthroughout the world.
Irrigation proceeds in this manner--the area of course havingbeen pattern cultivated within the previous three or four years: The operator isusually equipped with a long handled shovel and has three irrigation flags of registereddesign. A flag is made of a large piece of water resistant cloth, and includes alight weight pipe-bar to hold it across the channel, and a chain and spikes to holdthe flag in position in the channel.
To irrigate, one flag is placed in the channel near the damand a second, 60 to 90 feet further along. The water is turned on full bore or tothe full capacity of the channel, to be blocked by the flag and spill down over theland. The operator follows a set drill, releasing the water by moving the flags leapfrogfashion along the channel, to water the land uniformly and quickly. Various layoutdesigns to suit all circumstances make pattern irrigation a one to three channelsystem, operated by one to two men to vary the rates of water application from tento 30 acres per hour.
For irrigating the City Forest on positively undulating landthe channels could be concrete lined, a little larger, perhaps with slightly moregradient, for the same two men to control four times as much water as from a cityof 200,000 people. The pattern 'cultivation' would be maintained forever, to spread.the water uniformly, by planting the trees in rows laid out on the appropriate pattern.
Pattern irrigation spreads water in large flows, uniformly,quickly, economically and it is a soil making process.
Flood-flo irrigation does the same things on gently undulatingand flatter lands but it is much faster and even more economical. For instance anormal rate of irrigation on pasture land for one man is 33 acres per hour, but itis almost as effortless to irrigate 50 acres each hour.
Flood-flo irrigation operates on these same principles of thenatural movement of water flow over various shapes of lands, only the emphasis givenby landscape design is different. For instance, on the more positively undulatingland the natural movements of water are too fast and it concentrates too quickly.Pattern irrigation slows it down and causes it to spread in the right direction.But on land which has very little slope, water travels too slowly, spreads too widelyand loses its togetherness and its power to move down the gentle slopes fast enough;too much water soaks into the land. Landscape design controls it but in a differentfashion.
The source of the water for flood-flo irrigation is similarto pattern irrigation. Because the landscape is flatter the dams are shallower andof much greater surface area and water holding capacity. The lockpipe system is alwaysthe larger size, 25 inch and they may be laid in duplicate. When the water is releasedit flows directly into an irrigation channel but the shape is different and thereis no gradient; it is a contour channel.
This is the design; the irrigation channel is constructed asa two feet or larger earth bank on a contour across the land, a mile or more long.The water flows on the land above the bank where it may be from 50 to 300 or morefeet wide according to the slope of the land it traverses. From the irrigation channelthe water is released on to the land below through sheet metal water gates six feetwide. The irrigation land 800 to 1,000 metres wide is divided into 'water fields'of ten or more acres each by "water-steering banks" which join up withthe irrigation channel and fall directly down the land.
The steering banks may be only a few inches high. They are placedon the surveyed lines of the maximum fall of the land.
The full flow of water is released via the water gates to eachwater field in turn. The steering banks hold the water together to flow gently butfaster than normal for flat country. Between irrigations, all water gates are leftopen.
Should flood rains occur, the heavy rain run-off from higherland is automatically controlled by the irrigation channel to be spread into allthe water fields through the open water gates.
Flood-flo would be also the system of irrigation chosen formuch medium undulating country, when the slopes are not too short.
The land for City Forests would more generally be suited byFlood-flo irrigation. The amount of water which one man could control in irrigationwould be three times greater than for pattern irrigation and 10 times greater thanfor any orthodox irrigation system.
The design of both water systems--pattern and flood-flo irrigation--automaticallydesign their own road systems for efficient forest management and, why not, for tourists.For instance a sizeable City Forest on some of Sydney's unattractive and not usednearby sandstone reserves, could be laid out on flood-flo water design. Roads withwide parking strips would cross the slope of the land at say 600 metre intervalsalongside the line of the irrigation channels. Other roads would follow the layoutof some of the steering banks up and down the slope.
The roads would divide the City Forest into separate areas asdid the farmscape and the cityscape design. These 'suburbs' of the City Forest couldbe adopted by schools or societies involved in landscape betterment--guardians ofthe environment. Children may like to 'people with trees' their own forest suburbsand watch the trees grow as they themselves grew up. My youngest son helped plantthe six leaf seedlings for a strip forest and saw them grow to 60 feet high beforehe grew to manhood. The trees grew well and we did not have to wait years to seesomething. In 12 months they were ten feet high and in two years the strip foreststransformed the landscape. But the City Forests, with the wonder-water of the cityto irrigate the trees, would grow much faster.