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West Kimberley Grain Project
Summary
The rivers of the West Kimberley region have considerable potential for irrigation
based on capturing the wet season flows. Based on a 1964 report updated for long
term rainfall data, this region could produce 8.4 million tonnes per annum of grain – a
production level equivalent to that of WA’s wheat crop. The fully developed capital
cost will be less than the cost of cropland in the State’s southwest in terms of capital
cost per annual tonne of production. Fully developed, the Kimberley region has the
potential to double WA’s agricultural production.
Catchment Area Rainfall Yield Grain
sq. km. mm. GL/annum mtpa
Barker River 2,253 1125 529 0.6
Isdell River 4,662 1234 1357 1.6
Lennard River 2,072 980 352 0.4
Fitzroy River 16,835 1052 3172 3.6
Central Fitzroy 10,619 744 786 0.9
Leopold River 5,439 762 471 0.5
Margaret River 12,303 635 670 0.8
Total Grain Production 8.4
Table 1: West Kimberley Catchments, Water Yield and Potential Grain
Production
This table is derived from a report by John Lewis in 1964 for the Public Works
Department of Western Australia entitled “The Fitzroy River Plan (W.A.)”. Rainfall
records used in that report have been superseded by modern rainfall data. Grain
production is based on irrigated sorghum yielding 8 tonnes/ha with a water
requirement of 7 megalitres/ha. To grow 8.4 million tonnes per annum on two crops
per year would require an irrigated land area of 524,000 ha. This area is equivalent to
a square with sides of 71 km. Each crop requires 700 ml of irrigation. This
requirement might be reduced by the first crop utilising soil moisture from the wet
season. Sorghum is used as the example as it is already grown in the West Kimberley
region. Wheat and cotton are also likely to be successfully grown.
West Kimberley Grain Project David Archibald, December 2011
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Figure 1: West Kimberley River Catchments
West Kimberley Grain Project David Archibald, December 2011
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Figure 2: Ord River Scheme Lake Argyle Storage Levels 1980 – 2011
A dam on the Ord River in the East Kimberley was completed in 1972 to provide
irrigation water downstream. A expansion of the irrigated area of the scheme is
currently underway. There is considerable potential for further expansion of the area
under irrigation. This graph shows the last 30 years of storage history for Lake
Argyle. The Ord River is approximately 650 kilometres long and drains a catchment
area of approximately 55,000 square kilometres. The mean annual flow of the Ord
River at its mouth is estimated to have been 4,500 GL before the river was dammed.
Water demand for Ord Stage 1 was only 300 GL per annum.
A weir on the spillway of the Lake Argyle dam was installed in 1996 in order to make
possible a 30 MW hydro power station. The power from this dam has displaced most
diesel use for power generation in the Kununurra area.
West Kimberley Grain Project David Archibald, December 2011
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Irrigation Area Capital Grain Capital Cost/ Capital Cost/
Cost of Production Tonne Hectare
Dams mtpa inc. centre pivot inc. centre pivot
Lennard Group $900 m. 2.6 $602 $9,630
Fitzroy Group $600 m. 4.5 $383 $6,122
Leopold + Margaret $900 m. 1.3 $940 $15,041
Total $2,400 m. 8.4 $536 $8,571
Table 2: Capital Costs and Capital Intensity of the Wester Kimberley Grain
Project
The proposed dams in the West Kimberley naturally group into three areas. Dams on
the Isdell, Barker and Lennard Rivers would service the broad, flat plain of the
Lennard River downstream from Lennard Gorge. The dam with the greatest potential
because of the size of its catchment and rainfall is the Dimond Gorge Dam on the
Fitzroy River upstream from Fitzroy Crossing. Combined with a barrage on the
Fitzroy River just downstream from Fitzroy Crossing, this system will produce grain
at a rate equivalent to half the WA wheat crop at a modest capital costs. The capital
costs in the table above only include the cost of the dams and do not include the cost
of water distribution and centre pivot irrigation. Including indicative costs for the
latter, the capital cost per annual tonne of grain production will be about half of the
cost of prime wheat growing acreage in the southwest of WA.
The Dimond Gorge Dam will provide water as far downstream as Camballin, as well
as completely mitigating the flood risk from Fitzroy Crossing to Camballin. The
prime irrigation area for the dams on the Fitzroy River will be Alexander Island,
produced by the River bifurcating just south of Fitzroy Crossing. The Island is 48
km. long.
Dams on the Leopold and Margaret Rivers would irrigate the black soil plains on
Fossil Downs station in the first instance.
West Kimberley Grain Project David Archibald, December 2011
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Figure 3: Grain Prices 2001 – 2011
Rice has steadily increased in price over the last ten years relative to the other major
grain crops and could very well be a high margin crop in the West Kimberley region.
Figure 4: The Dimond Gorge Damsite on the Fitzroy River
West Kimberley Grain Project David Archibald, December 2011
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Figure 5: Barker River Damsite
Figure 6: Idsell River Damsite
The Idsell River flows north to be waste in the Timor Sea. A dam at this location and
a 5 km diversion tunnel will turn its waters south to the Barker River.
West Kimberley Grain Project David Archibald, December 2011
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Figure 7: Damsites in the Catchment of the Leopold River
Building two dams upstream on gorges will be cheaper than one downstream just
above the irrigation areas. The Leopold River does need to be dammed for flood
mitigation as well as irrigation.
West Kimberley Grain Project David Archibald, December 2011
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Figure 8: Lennard River Damsite
A dam on this popular sightseeing spot will significantly enhance its amenity.
Figure 9: Margaret River Damsite
This is another ideal damsite in the West Kimberley region.
West Kimberley Grain Project David Archibald, December 2011
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Fertiliser Demand
Taking wheat as an example, nutrient removal from a farm per tonne of wheat is
~23kg/t nitrogen, 3kg/t phosphorus and 4kg/t potassium and 1.5kg/t sulphur.
Nitrogen application is at the rate of 25 kg per tonne of wheat. At that rate, the urea
requirement for the Kimberley Grain Project would be 450,000 tonnes per annum.
That demand level would justify building a urea plant on one of the coal deposits of
the region. The capital cost of that plant would be of the order of $900 million,
taking the total investment for the project to beyond $5.5 billion.
Recommendation
The West Kimberley Grain Project will be of enormous benefit to Western Australia
and the Nation. This project, if it resulted in producing 8.4 mtpa of rice at the current
rice price, would increase national income by $5.0 billion per annum.
Planning for this project should begin immediately. Construction of the roads into the
major damsites should also begin immediately.
David Archibald
Perth, December 2011
West Kimberley Grain Project David Archibald, December 2011
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Appendix 1
THE FITZROY RIVER PLAN W.A.
PRELIMINARY REPORT JAN. 1964
Contents PAGE
1. Introduction 2
2. The Camballin Scheme 3
3. Topography 4
4. Hydrology 4
(a) Annual Flows 4
(b) Floods 6
(c) Sediment 7
5. Land Resources 7
6. Order of Development 8
7. Details of Damsites 10
(a) Dimond Gorge Dam 10
(b) Go Go Barrage 12
(c) Margaret River Dam 12
d) Leopold River Dam 13
(e) Mt. Krauss Barrage 13
8. Current Investigations 14
9. Associated Schemes in West Kimberley 15
10. Conclusions 16
Plans
1. Catchment Areas, Isohyets, Water Resources
2, Damsites and Irrigation Areas,
5. Detail of Camballin Irrigation Area.
West Kimberley Grain Project David Archibald, December 2011
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THE FITZROY RIVER PLAN W.A.
PRELIMINARY REPORT JAN. 1964
1. Introduction
Over a period of years there has been interest in the development of the Fitzroy River
as a multipurpose project primarily for irrigation, but with some benefits in both flood
control and hydro-electric power.
The plan proposed in this report consolidates current Departmental thinking and
would harness all the natural resources of the Fitzroy. It involves building a large
multiple purpose dam on the main branch of the Fitzroy at Dimond Gorge, two lesser
dams on the Margaret and Leopold Rivers, and two diversion dams near Go Go
Station on the Fitzroy and near Mt. Krauss below the confluence of the Margaret and
Watery Rivers. The plan can be implemented in stages with progressive development
of the irrigation areas over a period of time. Flood control and power generation
would also increase progressively as the head works are developed.
This report is purely an engineering and agricultural feasibility plan. Insufficient data
is available to attempt any estimates of cost nor any discussion of likely crops and
economics. The plan has been prepared at this stage for guidance and use of
Departmental personnel engaged in various phases of investigation and design. The
plan would also be useful to officers of CSIRO and Department of Agriculture in their
phases of investigation and development. It is to be hoped that various suggestions
and improvements can be made if all Departments are working towards a known
objective in a definite order of priority,
The first real attempt to utilise the Fitzroy waters was by Mr. K.M. Durack who set up
a small property at Camballin on behalf of Northern Developments Pty. Ltd.
Originally water was simply pumped from a large billabong on Uralla Creek, which is
a branch of the Fitzroy. This scheme was begun in 1951, and has been improved and
enlarged over the years. A statement of the present position follows in Section 2.
The proposal to place a weir on the Fitzroy to divert water into Uralla Creek by
gravity came from Departmental and Consulting Engineers in about 1954 and
construction was completed in 1961.
In about 1952 the late Mr, C.M. Dimond, then Engineer for the North West, initiated a
survey of the Margaret River Damsite and in 1955 flew over and selected the damsite
on the Fitzroy River now bearing his name. The late Mr. W. MacDonald of Fossil
Downs knew the river extremely well and was a keen advocate of damming both the
Margaret and Fitzroy Rivers and gave much help to Departmental Engineers.
West Kimberley Grain Project David Archibald, December 2011
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2. The Camballin Scheme
A small irrigation scheme has been developed at Camballin some 75 miles from the
port of Derby. This scheme derives its water from the Fitzroy River by means of a
diversion structure known as the Fitzroy Barrage which is a weir equipped with
shutters capable of collapsing automatically in flood time and being raised
mechanically to divert streamflow into an improved natural channel, leading to the
irrigation area. Something like £l,000,000 has been invested in this weir and
associated distribution structures such as the Uralla Creek Dam and spillway,
channels, levees, measuring structures, pumps, roads, etc.
The Camballin scheme suffers two major deficiencies. Firstly, the area is located on a
flood plain and all structures and crops are liable to damage of varying severity each
wet season according to the intensity of flooding. Secondly, the gross storage of the
Fitzroy Weir and Uralla Creek Dam is only about 7,700 ac. ft. of which a great deal is
lost in evaporation. Since the river normally ceases to flow in about May or June
depending on the season, the Camballin Scheme is limited largely to wet season run
of river operation. When storage is built upstream and water can be released down the
river, this trouble will be overcome.
The first problem of seasonal sheet flooding at Camballin can be partly overcome by
building large flood control storages upstream and partly by building an extensive
levee from Nura Nura Ridge to Grant Range to keep the river out. The latter measure
is too expensive to consider at the present stage of development at Camballin.
The area resumed for irrigation at Camballin is only 20,000 acres but surveys have
shown that this could probably be doubled at least. Actual irrigation results so far
have been disappointing for a number of reasons in addition to the two problems
already mentioned. The development of the irrigation area itself is in the hands of a
single private Company under an agreement for joint co-operation with the State
Government. This Company showed great courage in being the first to pioneer
irrigation development on farm scale in the Kimberleys. The risks were great and the
unknowns on the agricultural side proved a formidable barrier. The Company chose to
base its efforts on rice growing and milling for export. If yields of two tons or more to
the acre could have been achieved consistently, the enterprise may have succeeded,
but yields have never approached this figure over the whole crop. Often the crops
have looked promising but some new trouble has occurred each year.
In recent years with development of other crops on the Ord, Camballin has turned to
cotton, linseed, safflower, sudan grass and others on a small scale to gain wider
experience and improve the adverse economic situation. The Company has also
bought a controlling interest in Liveringa Station and is having some success with
broad irrigation of natural grasses for grazing sheep. While this may prove a good
solution to the Company's problems, it is of little assistance in developing an intensive
irrigated agriculture which must be proved if costly major projects are to be justified.
It is essential for full scale agricultural research to proceed in conjunction with the
engineering investigations now being carried out. Without this, no plan can succeed
and it would be foolish to rely too heavily on results coming from the Ord.
West Kimberley Grain Project David Archibald, December 2011
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3. Topography
The main tributary of the Fitzroy is the Hann River which rises within fifty miles of
the sea in very rugged and inaccessible country. From here the river flows inland
making a wide semicircular sweep of almost 500 miles before it finally reaches the
sea in King Sound at Langey Crossing near Derby.
The attached plans show the Fitzroy River and its major tributaries the Hann, Adcock,
Traine, Leopold, O‘Donnell, Margaret and Mary Rivers and Christmas Creek. Also
shown are the respective catchment areas at known damsites and potential irrigation
areas. It cannot be readily shown in the plan, but the Fitzroy Catchment is broken up
into two very distinct topographical areas by the Oscar, Sparke and other small
Ranges all running more or less north west to south east across the catchment. The
Fitzroy above the Oscar Range and the Margaret above the Sparks Range, both have
rugged catchments characterised by parallel ridges of quartzite mostly very bare
supporting only spinifex and a few stunted trees. In the valleys between the ridges,
there is some heavier country with a sparse cover of trees and natural perennial
grasses.
The upper perimeter of the catchment is at an elevation between 1500 and 2500 feet
and as the river level at the storage damsites is of the order of 400 feet, there are
considerable slopes from the ridges into the tributary streams. The lower part of the
Fitzroy below the Oscar Range and the Nargaret below the Sparks Range and
Christmas Creek further south all traverse extremely flat country with very little
topographical relief apart from the watercourses. The fall of the Fitzroy River from
Fitzroy Crossing to Langey Crossing near Derby is only 280 feet in a distance of 212
miles or just over one foot per mile. There are no obvious sites for storage dams in
these lower catchments, although if it proved feasible and economic to store water at
Go Go Barrage, this would be most valuable.
The Fitzroy and Christmas Creek have flood plains up to 50 miles wide at their
confluence and the greater part of all the best irrigable soils are subject to sheet
flooding under several feet of water. The rivers meander through the flood plain and
have many anabranches and billabongs indicating old watercourses or new courses
developing. In locating a diversion structure on this flood plain, great care has to be
taken to avoid disturbing the natural regime of the river too much and causing a
sudden switch in its course. This was the main reason for the automatically collapsing
shutter weir at Camballin.
4. Hydrology
(a) Annual Flows
The water resources of the Fitzroy River are only vaguely known at present due to the
small number of gauges and short term of record. It is unfortunate that major storage
dams can only utilise about l3,400 square miles out of a total catchment of 55,000
square miles, but the runoff characteristics of the mountainous upper catchment would
undoubtedly be better than those of the very flat and generally sandy lower catchment.
The rainfall isohyets in the attached plan show that the Hann River, which is the
farthest upstream tributary of the Fitzroy, rises in a 40 inch rainfall area and most of
West Kimberley Grain Project David Archibald, December 2011
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the 6,500 square mile catchment up to the Dimond Gorge Damsite has over 25 inches
of rainfall with the average being about 28.75 inches.
The Ord River by comparison has a catchment of 17,800 square miles at the Main
Damsite, but the average annual rainfall is only 21 inches.
It has been shown on the Ord Catchment that total runoff varies with about the 2.5
power of rainfall so that on direct comparison, the relatively small catchment at
Dimond Gorge could have an annual flow of the order of 0.80 times that of the Ord,
i.e. about 1.8 million acre feet per year, assuming the catchments have similar runoff
characteristics. (Using median rather than arithmetic mean to avoid distortion due to
cyclonic floods, and Ord median 2.25 million acre feet per year.)
Alternatively, a rainfall runoff correlation for Fitzroy Crossing suggests a median
annual flow of 2.43 million acre feet at that point. Again utilising the 2.5 power
relationship to distribute the combined flow, the median annual flow at Dimond
Gorge is estimated at 1.55 million acre feet. However, estimates based on Fitzroy
Crossing gaugings could be low as two anabranches bypass the gauge and higher
flows are no doubt grossly under-estimated.
By the same reasoning, the Margaret and Leopold River catchments are in much
lower rainfall areas and not only would the total runoff be less, but it would be
considerably less reliable from year to year. Christmas Creek has a fairly large
catchment but flows from semi desert areas of only l4 inch rainfall and its annual
runoff would be fairly small, despite the fact that it produces major flooding every
few years when subject to intense cyclonic rainfall of short duration. Topographically,
there are no known damsites on Christmas Creek (but this has not been thoroughly
investigated) and its water resources have been discounted in this examination.
Unfortunately this means that is ability to cause flood in damage downstream of its
confluence with the Fitzroy cannot be controlled.
The first river gauging station in this basin was established at Fitzroy Crossing in
1956. Flow records commenced in February, 1957 and combine the flow of the
Fitzroy and Margaret Rivers. Another gauging station was set up at Dimond Gorge
and recording began at the end of 1962. The record is too short yet to draw
conclusions.
A gauge was established on the Margaret River at Fossil Downs towards the end of
1957, but was affected by backwater levels from the Fitzroy and never rated.
Investigations are being made to establish a new station in the vicinity of the Margaret
River Damsite.
Thus in the future it will be possible to assess the flow in the Leopold and Margaret
Rivers by subtraction of the Dimond Gorge flow from that at Fitzroy with due
allowance for the catchment in between. So far however it is only possible to split
the Fitzroy flows in accordance with rainfall and catchment areas using the 2.5 power
relationship of rainfalls which seems to be valid for the Fitzroy as for the Ord.
The estimated median annual discharges are tabulated hereunder.
West Kimberley Grain Project David Archibald, December 2011
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Fitzroy River at Dimond Gorge 1.80 million acre feet
Leopold River 0.27 million acre feet
Margaret River 0.38 million acre feet
Central Fitzroy 0.45 million acre feet
Fitzroy Crossing Total 2.90 million acre feet
The important conclusion of these preliminary assessments is that the flow at Dimond
Gorge is (64%) of the combined flow at Fitzroy Crossing, although the catchment is
only 37% of the total. On the other hand, the Margaret with 27% of the total
catchment only 13% of the flow.
(b) Floods
Estimation of flood flows presents considerable difficulty because high floods at
Fitzroy Crossing are not contained by the current meter section. It is thought that a
large quantity of flood water by passes the branches on the south side. Furthermore
Dimond Gorge gauging station has not been established for long enough to have
metered significant floods although an extrapolated rating curve indicates a flood
peak of approx. 230,000 cusecs in February, 1961 and again in February, 1963.
It seems that a flood of the order of 300,000 cusecs might be expected at Dimond
Gorge with approximately a ten year recurrence interval. The catchment at Fitzroy
Crossing is some 2.75 times the area at Dimond Gorge and a higher ten year flood
would be expected although bank overflow would have a reducing effect. In the seven
years of recorder operation at the Crossing, the highest flood indicated by the
extrapolated rating curve is 210,000 cusecs.
However the rating curve does not account for flow by-passing the cableway. It seems
unlikely that a ten year flood at Fitzroy Crossing could be much below 400,000
cusecs.
The peak rate of discharge probably decreases down the river from Cherrabun to
Langey Crossing because although the catchment increases, a large amount of flood
storage is provided by bank overflow. The time delay in passage of 5 high flood peaks
down the river between Fitzroy Crossing and Langey Crossing varies between 5 and 7
days which, in storms of normal or short duration, generally allows down-stream local
peak runoff to pass before the main flood comes.
Obviously a great deal of hydrological work needs to be done on this river and its
tributaries before major works can be undertaken, but at present it seems that a
storage dam at Dimond Gorge without.flood control would need to be designed for a
discharge of the order of 1,000,000 cusecs. The Go Go barrage is more difficult to
assess for discharge capacity, but even accepting that flood regulation will be
provided upstream, it would seem that a similar flood peak discharge must be passed
by this structure under maximum design storm. This fortunately is markedly less than
required on the Ord River structures. However the main waterway of the Fitzroy is
relatively shallow and consequently the irrigable levee lands are much more prone to
flooding than on the Ord. It is therefore very desirable that the Dam at Dimond Gorge
should have provision for flood control as well as storage within the limits of normal
economics.
West Kimberley Grain Project David Archibald, December 2011
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While the dam at Dimond Gorge can control two thirds of the annual flow (based on
median values) up to Fitzroy Crossing, it is most improbable that this dam could
control two thirds of the flooding problems. This is because large floods result from
intense cyclonic rains of only a few days duration and so far as is known at present
those could occur in almost equal intensity on any part of the catchment and bear little
relation to the pattern of annual rainfall isohyets. On this basis flood control at
Dimond Gorge may only reduce high floods by 20% but smaller floods may be
reduced by greater amounts and the normal three year frequency of flooding now
existing could be greatly decreased.
(c) Sediment
The final important hydrological aspect is that of sediment. There is ample evidence
in the streambed that considerable quantities of sand and shingles are transported as
bedload. It is also evident in flood flows that a considerable amount of suspended
sediment is transported. Despite appearances, depth integrated samples taken from
the cableway at Fitzroy Crossing indicated average suspended sediment of less than
0.2%. This is very much lower than the Ord and is probably explained by the fact that
no serious erosion is occurring on the upper catchments.
From fairly well established data overseas, the bedload is probably less than 20% of
the suspended load. As previously mentioned the gradient of the Fitzroy Crossing is
only just over one foot per mile. Combined with relatively shallow depths of flow,
this means that velocities above six feet per second are uncommon. Such velocities
do not transport large shingle and move small shingle very slowly. Deposits of shingle
for concrete making are very hard to locate in the river bed. Of course larger sizes can
sometimes be found in old courses of the river, presumably laid down when gradients
were higher than at present.
Downstream of Fitzroy Crossing, the catchment has suffered due to poor pastoral
practices and overgrazing by sheep as well as kangaroos. Some bad areas are subject
to erosion by wind and sheet flooding as has been evident in the Camballin Scheme
and once the grass cover is gone, the process is very difficult to stop. On the whole
however, the problem is not nearly as severe as in the Ord River.
5. Land Resources
The CSIRO has made a number of regional soil surveys which have revealed potential
irrigable areas as shown in the accompanying plan amounting to possibly 500,000
acres. All of this area is adjacent to the lower parts of the Margaret, Christmas Creek
and Fitzroy Rivers. A lot of it is subject to sheet flooding and no doubt a considerable
amount cannot be commanded conveniently by gravity from the proposed diversion
dams. Some of the area is dissected by small water courses, anabranches and
billabongs which would render it too rough for irrigation. After making allowances
for these factors it seems there is still about 300,000 acres left and this could be more
than adequate to utilise the water resources of the Fitzroy River system.
The easiest land to irrigate is probably the Alexander Island, Go Go Station and
Lower Christmas Creek areas. This is all quite compact and can be commanded by
West Kimberley Grain Project David Archibald, December 2011
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gravity channels from the proposed Go Go Barrage. The gross area surveyed to date
on three mile sections is 200,000 acres and the survey is far from complete. Alexander
Island alone contains 93,000 acres gross. The Department of Agriculture is carrying
out broad soil profiles as the survey proceeds to determine the extent and variation of
the several different soil types, of which there are at least four main classes. The black
soil similar to that occurring at Camballin is very common.
Mention has already been made of possible extensions of the Camballin Scheme and
this has been soil surveyed in some detail by CSIRO. (Churchward and Bettenay
1959). Good strips of land appear to exist at intervals all along the lower Fitzroy
River, one such strip being in the vicinity of Noonkanbah Station. These areas are not
large enough to warrant a large diversion dam but could possibly be served by
pumping or small collapsible weir such as that already built at Uralla Creek.
The remaining large tract of good land, perhaps the best in the whole valley according
to CSIRO is that around Fossil Downs Station mainly on the north side of the
Margaret River. Unfortunately none of this can benefit easily from construction of the
dam at Dimond Gorge or the Go Go Barrage. However it can be served by the waters
of the Margaret and Leopold Rivers, a possible diversion site for which exists in the
vicinity of Mt. Krauss.
Since the damsites on the Margaret and Leopold Rivers are not as good as that at
Dimond Gorge and also since the runoff will be less reliable, the Fossil Downs lands
may have to wait some considerable time for development. A possible alternative is
that the Go Go Barrage is likely to back up the Margaret River some appreciable
distance, and pumping into a channel running back along the Margaret may be
practicable. The gradient of the Margaret is very flat, being about the same as the
Fitzroy. This proposal would involve less pumping if some worthwhile storage can be
held at Go Go Barrage thus raising the expected water level in the Margaret.
It is not inconceivable that water released from Dimond Gorge could be pumped over
the northern end of the Geikie Ranges to the Fossil Downs area.
The passage is long and difficult but the lift may be less than 100 feet. The gross area
of potentially irrigable land around Fossil Downs is about 100,000 acres which is
enough to utilise the waters of the Margaret and Fitzroy Rivers, although this is not an
essential requirement, as any excess can be allowed down to the Go Go Barrage for
use in the main irrigation area commanded from there.
6. Order of Development
Assuming that the financial provisions are not too restricted in the early years, there is
a logical order of development which generally involves building headworks storage
before the diversion structures. This is for a three-fold reason. Firstly, the storage
ensures supply of water all the year round, secondly a considerable measure of flood
control is achieved thus reducing spillway costs and risks to the irrigation area, thirdly
less sediment will be carried into the diversion storage.
On the Fitzroy the second and third points are only partially achieved by a single
headworks storage as the remaining catchment is still uncontrolled. However, control
West Kimberley Grain Project David Archibald, December 2011
18
of the major contributor of floods and sediment at Dimond Gorge is still a marked
advantage.
The only point in favour of building Go Go Barrage first is that run of river water can
be supplied immediately without pumping in the wet season and fairly low lift
pumping in the dry season. This applied in the Ord River Project where the Diversion
was built first in order to get the scheme going on reasonable scale at limited cost,
The same may yet apply at Fitzroy but should be avoided if possible.
Bearing the foregoing in mind, the logical order of development is as follows:-
(a) Build the Dimond Gorge Dam on the main branch of the Fitzroy, complete
with gates for flood control. The size has yet to be determined but something
about the same size as the main Ord Dam is envisaged i.e. about 5 - 6 million
acre feet of active storage and at least as much again as flood control
surcharge. This is the heart of the whole Fitzroy Plan as it forms the largest
and most reliable storage in the valley.
(b) Develop an Irrigation Area in the Alexander Island - Christmas Creek
Region complete with channels, drains and flood protection levees. A
pumping station would be needed initially until the Go Go Barrage can be
built. The Ord River Pumps will have become redundant by then and could be
adapted for this purpose quite well. This development, being the primary
object of the Fitzroy Plan, would extend over a large number of years.
(c) Enlarge the Camballin Project to its full extent and split it up into small
farms if necessary to hasten development. Provide flood control by
constructing a levee from Nura Nura Ridge along the Fitzroy River and back
into Grant Range near Liveringa Homestead. This will be about 15 miles long,
constructed of river sand as at Carnarvon and will need provision of inlet and
outlet structures for Uralla Creek. The height of this levee can be reduced
because of the flood control at Dimond Gorge and would be of the order of 10
feet although higher at Liveringa. This levee and structures will be costly but
will allow 50,000 acres of land to be irrigated under secure conditions and
would justify itself, The area has good soil and topography, is close to Derby
and already has considerable capital invested which must be made good. Local
water from Nemille Creek would still be of some nuisance value in the lower
areas. This phase of development could be concurrent with (b).
(d) Build Go Go Barrage to provide gravity command of the main rrrigation area
with left and right bank channels. The left channel runs right down to
Christmas Creek which is uncontrollled and which would need a siphon
crossing if further land had to be served. The right channel does not command
so much land but meets no known obstacles. It could serve Alexander Island
through a large barrel siphon under the Cunningham River which is the lesser
of the two branches of the Fitzroy. Alternatively, it may prove feasible to close
off the Cunningham completely and pass the flood controlled flows down the
Fitzroy alone. This would simplify the supply and access to Alexander Island
and reduce the cost of flood protection levees as these would be confined to
the one river instead of two, although naturally somewhat greater in height.
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(e) Build the Margaret River Dam complete with gates for flood control. The
size has yet to be determined but something of the order of 0.8 million acre
feet of active storage and at least the same amount of flood surcharge is
envisaged, depending on the nature of the dam and spillway solution in
relation to benefit cost economics.
(f) Build the Leopold River Dam complete with gates for flood control. This
could be constructed concurrently with the Margaret River Dam as both are
relatively small and serve the same irrigation area. The order of` size of this
dam is about 0.6 million acre feet of active storage and a similar amount of
flood surcharge depending on the same factors as above.
(g) Develop an Irrigat1on Area in the Fossil Downs – Mt Krauss Region complete with channels, drains and flood protection levees. A pumping station
would be needed until the Mt. Krauss Barrage could be built or became
economically justified. By this time the Go Go pumping equipment ex Ord
River, if still serviceable, should be available having become redundant at Go
Go after building that barrage.
(h) Build the Mt. Krauss Barrage to provide gravity command of the Fossil
Downs Irrigation Area on both left and right banks. The main supply channels
have n number of substantial creeks to cross and would probably need to
siphon under some of them. A fairly large irrigation area would be necessary
to justify a costly diversion against a small weir with pumping. It could well
be argued that the dam on the Leopold River could wait till last when
irrigation development actually needed it, but against this are the two points
that flood protection in (g) and spillway design in (h) will be more expensive
due to the lack of control on the Leopold River. Detail design and economic
analysis will determine the best order of development.
7. Details of Damsites
(a) Dimond Gorge
This is a magnificent damsite, perhaps the most impressive discovered so far in
the Kimberleys. The geology is simple comprising gently folded quartzite of large
blocky structure with fairly tight jointing. There is no sign of faulting, shear zones,
thin bedding or foreign intrusive in the vicinity of the dam. The foundations are
obviously solid parent rock, being almost completely exposed at the end of the dry
season.
The river bed is more or less flat across the bottom and the walls of the Gorge rise
abruptly and almost vertically. They are only three hundred feet apart at the
damsite and not badly weathered for quartzite. Since the dam will be over two
hundred feet high, a thin arch dam will have to receive serious consideration. In
this case the spillway would have to be cut in a narrow but long natural saddle
which has been located about two miles from the dam. The spillway could include
West Kimberley Grain Project David Archibald, December 2011
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the flood control gates or it could be uncontrolled whichever is cheaper. It is
possible that the Kariba-type spillway located in the arch dam some distance
below the crest would give adequate discharge.
An obvious solution is a hollow gravity type concrete dam with spillway gates on
top. It seems a pity to place a gravity dam in such a fine site but spillway problems
have dictated that this be done in similar sites previously.
Due to the high cost of concrete in this remote area (250 miles by road from
Derby) and the relative cheapness of rock excavation and rockfill, it is very likely
that a rockfill dam and rock cut spillway will be the most economic solution as at
the Ord Main dam. Unfortunately the lead from the spillway cut is rather long for
rockfill and it may be more economic to open up a quarry near the damsite.
Comparative designs and estimates for these various types of structure are being
carried out and when the most economic solution is found, a drilling programme
can be laid out for further site investigation in the dry season of 1965. Surveys of
the damsite and reservoir basin have been completed. Since the basin is so large, it
was necessary to cover the area by aerial photography and 10 foot contours have
been drawn by stereo-plotter. Basin volumes at different heights 1% have been
computed.
The effective flood storage has not yet been full determined, but it is fairly certain
that flood storage will be feasible and economic to a degree at least comparable to
the Ord. The damsite is in a most inaccessible part of the King Leopold Ranges.
Access can be made from the south through Fossil Downs to the stream gauging
station which has a light airstrip and store hut nearby. However the four miles
from here to the damsite are accessible only by foot and will require quite heavy
roadworks in due course.
Access from the north through Glenroy and Mornington is comparatively good,
especially with the new beef road going through. This is the best access for
surveys, drilling and possibly construction, but it will become submerged under
the future reservoir.
Bypassing around the edge of the reservoir would be long and cut into hill slopes
making it very expensive. If permanent access is wanted from the north, a ferry
may be the best solution.
The reservoir will inundate some pastoral country which is not very valuable and
Mornington homestead will be under some 50 feet of water at normal storage
level.
The possible provision of hydro power will need close consideration. The head
will be greater than the Ord, being close to 200 feet at full storage and the
tailwater not nearly as high. Geological conditions appear good for tunnelling and
underground construction. The transmission route to the irrigation area
commencing at Go Go Barrage is 60 miles long and fairly rough, although vehicle
access could be established. In view of this and since the power needs will be
small for a number of years, it seems best to install local diesel plant until the
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demand builds up enough to justify development of the hydro plant. Diesel power
will be rather expensive in this area because low grade diesel fuel is not shipped
by tanker into Derby and the lead from there is 160 miles.
(b) Go Go Barrage
This site is 8 miles downstream of Fitzroy Crossing. It was located during the
floods of February, 1962 when a survey was made by helicopter to determine the
most suitable place for barrages and the extent of flooding of potential irrigable
lands. The Go Go site joins Alligator Hill on the right bank to Mt. Campbell on
the left bank. It is four miles between the abutments which may seem a long way,
but nevertheless this is the best site on the lower Fitzroy River.
The greater part of the Barrage could be built in earthfill and only the spillway
need be of concrete construction. Insufficient data is available to design the
spillway, but it will need to be about 1,000 feet long and fully gated in a similar
way to the Ord Diversion Dam. With such a narrow spillway there is some
freedom in choosing where it should be placed in the whole length of the barrage.
If the foundation conditions are not good in the existing river channel, then the
spillway can be built in excavation in a more favoured location. The limits to this
are that a new river entry and exit have to be excavated and due regard has to be
given to hydraulic conditions of the new river profile.
Only a single seismic section has been run between the two abutments so far but
this gives promise of finding reasonably competent sedimentary rock at shallow
depths of the order of 20 to 40 feet. More seismic work correlated with check
drilling may show up better profiles in due course. The important point for now is
that the foundations are not sand and shingle extending to great depth.
The Go Go Barrage is ideally situated to serve the main irrigation areas of
Alexander Island, Go Go and Christmas Creek. Mention has already been made of
the left and right bank channels, the possibility of closing off the Cunningham
River and flood protection levees along the Fitzroy downstream of the Barrage.
If possible it would be very desirable to have storage as well as diversion at Go
Go since it commands a lot of good catchment downstream of the three storage
dams. Surveys will show if this is feasible. If Fitzroy Crossing had to be moved,
this is no great problem and its importance would disappear in any event, as the
new highway would use the all weather access provided by the Barrage and a new
town would be needed nearer to the centre of the irrigation areas.
(c) Margaret River Dam
This site is a spectacular gap in the Barramundi Range. It is quite narrow and the
storage basin spreads out well making it an economic location. The rock is mainly
quartzite, strongly folded with some faulting. The joints are more open and the
surface more weathered than at Dimond Gorge. The foundations are no doubt
fairly sound rock, but they are deep as a long pool runs right through the Gorge.
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Probing and preliminary survey of the damsite has been completed. The basin has
been flown and 10 feet contours are being stereo-plotted. A ground survey to give
a quick guide to capacity was also done some years ago. Nothing of any value
would be inundated by this dam. Access to the site is quite good from Fitzroy
Crossing during the dry season. A light airstrip has been constructed near a
proposed river gauging station just downstream of the Gorge. The site does not
offer very stable control for stream-flow recording and construction of a cableway
has been delayed until alternative sites have been investigated.
No suitable saddles for a spillway cut have been located, but this has not been
proved exhaustively. If it is true, then a rockfill dam is not possible and the choice
of dam would be limited to hollow gravity with gates on top and the Kariba-type
arch with gates some distance below the crest. By the time this dam is built there
may be enough experience to encourage an arch design with deep overflow
springing clear of the crest. At present these designs are limited to shallow
overflows but have been used on quite high dams without excessive vibration.
Due to the lower priority of this dam in current planning, no preliminary designs
or estimates have been carried out nor can attention be given to them for some
years.
(d) Leopold River Dam
This has only been identified as a likely site from the air. No survey has been done
nor is it contemplated at present.
It is a pity that the one dam cannot harness both the Margaret and Leopold Rivers,
but this unfortunately appears to be so. It is also a pity that neither dam will serve
an irrigation area directly by channel or pressure pipeline, but such occurrences
are rare.
(e) Mt. Krauss Barrage
This has only been identified as CI possible site from the air. Others probably
exist and would serve the potential irrigation areas adequately. The right bank
channel would serve the best land around Fossil Downs. The left bank channel
would serve a more broken and lighter soil type down towards Go Go Station.
Both channels will encounter a number of difficult creek crossings probably
involving siphon structures.
Although Mt. Krauss has no obvious attractions as a storage site, this would bear
checking as its combined function of storage for the Margaret, Leopold and
Louisa Rivers plus diversion could be very useful and lead to earlier development
of the non-flooding Fossil Downs Area.
As previously mentioned if the Mt. Krauss Barrage proved very expensive, a
fairly large irrigation area would be necessary to justify it compared to the
alternative of a small weir with a pumping station. Also as noted earlier, the Go
Go Barrage may back water up far enough into the Fossil Downs area to render
such a weir unnecessary.
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8. Current Investigations
One of the most serious deficiencies at present is the lack of hydrological data
Fitzroy Crossing gauging station has been fully operative for some time but the
rating is inadequate at higher flows which are not contained. Dimond Gorge
gauge has not been long in operation and it is not yet rated for higher flows. The
gauge at Margaret River Damsite should be completed as soon as possible and a
gauge established on the Leopold River in due course.
Analysis of data already available is needed, especially concerning correlation of
runoff and rainfall for yield studies and production of a design flood hydrograph.
Daily rainfall records are available for some pastoral stations going back more
than 50 years.
For proper flood design of Dimond Gorge Dam at least one gauging station is
required upstream of the structure probably on the Hann River.
Further field information is needed on sediment load at different discharges. This
should not be neglected because the problem is less severe than on the Ord.
The second serious deficiency concerns soil surveys and agricultural research. The
location and extent of the best areas are now fairly well understood, but existing
levelling and sampling on three mile sections is not adequate to determine the best
layout of the irrigation scheme or the extent of each soil type. The next step
should be to level and sample on lines 20 chains apart as on the Ord. Finally this
would have to be closed up to a 5 chain grid for farm layouts, but the 20 chain
sections are adequate for design purposes.
A research station is needed as soon as possible in the Alexander Island -
Christmas Creek Area. This should combine the several predominant soil types
and be close to a large billabong for dry season water supply. A number of sites
have already been suggested and the final choice rests with the soil scientists.
The 20 chain sections will enable the left and right bank channels to be laid out
together with the major drainage system. It will enable a decision to be made as to
whether it is prudent to close off the Cunningham River. Together with
hydrological data and locally determined flood heights, the height and extent of
flood protection levees can be established.
Regarding the damsites, no more field work can be done at Dimond Gorge until
preliminary designs, now current, are prepared. When this is done, a full
geological investigation combined with diamond drilling and seismic testing can
be carried out in the dry season of 1965.
At Go Go Barrage site, only one section is available so far and in the 1964 dry
season a full coverage of levels, seismic testing and auger drilling will be obtained
to establish depths and soil properties of overburden and possible location of the
spillway section.
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Preliminary designs can then be made in the following dry season of 1965.
Diamond drilling can be carried out to determine the nature of the bedrock
especially in the concrete spillway section.
A suitable pumping station site will have to be selected to serve the irrigation area
in the early years before the Go Go Barrage is built.
As time permits, some design work should be done on an ultimate plan for
Camballin, including the levee from Nura Nura Ridge to Grant Range. The intake
structure for Uralla Creek through this levee could possibly combine a high level
supply channel to serve the full extent of the irrigable area east and north of the
present area. Low lift pumping will probably be required for this extension.
9. Associated Schemes in West Kimberley
The attached plan shows in faint lines some schemes other than the Fitzroy Plan
which are important in West Kimberley Development. These are the Lennard
River Dam and the Isdell River Dam with a tunnel diverting it into the Barker
River and thence to the lower reaches of the Lennard.
The Lennard River Damsite is not particularly good as the left abutment is well
back off the river and an extensive saddle embankment is required in a gap to the
north. The basin area has been flown and 10 foot contours are being produced.
The irrigation area downstream of the Napier Range is small but very attractive. A
preliminary reconnaissance has been made by CSIRO some years ago. Supply of
water to this area would require a diversion dam or pumping.
The Isdell River Damsite has only been identified from the air but is at the head of
a long deep gorge. There is little doubt that this is a good site with an extensive
basin behind it, and that water can be diverted through the King Leopold Ranges
by a tunnel only three or four miles long.
The catchment area of the Isdell is only about 1800 square miles but the annual
rainfall is about 34 inches and the estimated average annual runoff 770,000 ac. ft.
The main reason for diverting the Isdell is that it has no irrigable land in its own
valley whereas the Barker and Lennard are fairly well endowed and relatively
close to Derby.
Although little definite information is available, it is reasonably certain that
neither the Lennard nor the Isdell - Barker schemes would be as economic as the
Fitzroy Plan nor could they compete in scale which is important in northern
development.
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10. Conclusions
1. The first structure to be built in the Fitzroy Plan should be the Dimond Gorge
Dam complete with provision for maximum economic flood surcharge storage.
2. With water available at all times in the river, the main Go Go - Christmas Creek
irrigation area could be commenced in a small way using pumped water until
firmly established. The Ord pumps would suit this purpose on completion of the
main dam.
3. The Camballin Scheme could be brought up to its full potential of 50,000 acres
with all season water available. The area should be subdivided if necessary to
promote close irrigated development. If this is done, a flood control levee to keep
out flood waters would be warranted. (see attached plan)
4. Intensive agricultural research is required at both Camballin and Go Go —
Christmas Creek as soon as possible. Emphasis should be placed on farm scale
problems rather than fundamental research and close liaison should be maintained
with Kimberley Research Station on the Ord.
John G. Lewis
9/1/64