Hydro-electric Power Scheme Letter 1920

A.M.I.C.E., A.M.I.E.E.

26th, March 1920

Sir Andrew Russell,


Hydro-electric Power.

We have the honour to report as follows on the proposal to develop the waterpower on the Otukarara [Otekarara] Stream to supply your district with electric light and power.

The report is accompanied by two plans, No. 1 showing in outline the various ways of harnessing the stream, and No. 2 the location of the stations and settlers houses, and the outline of the transmission and distribution system.

Power requirements.
We shall consider first the amount of power to be provided. We assume that the eight stations and the thirty-two settlers will all be consumers, and that, due to increased settlement, an additional ten houses will be supplied.

It will be found that only about one third of the total number of lights installed, (which we estimate will be eight hundred of fifty candle-power each), will be switched on simultaneously. This will require at the power station an output of twenty-seven horse-power.

Electric Irons.
Ultimately there will be about sixty irons connected of which number one half will be in use simultaneously during the day and one quarter in the evening. These will increase the demand on the power station, at those times, by twenty-eight and fourteen horsepower, respectively.

A.M.I.C.E. A.M.I.E.E.

These will not be so generally used as the electric irons, but we estimate that they will increase the load during lighting hours, at certain seasons, by about ten horsepower.  [Handwritten – 1 H.P. each]

The high cost of installation will restrict the general use of current for cooking. The demand on the power station for this purpose will, we estimate, be fifty horsepower during lighting hours and twenty horsepower at other times.   [Handwritten 30/40½ complete]

A five horsepower motor will provide the individual consumer with all the power required for an eight-stand shearing plant, and other farm purposes. The output of an electric motor is limited by heating, and it can carry, temporarily, an overload of 100% without losing speed appreciably. The demand for power will be heaviest during the shearing season, and will be proportional to the total number of stands in operation, at the same time, throughout the district. We consider it will not exceed fifty horsepower, and will not overlap the demand for lighting.

The maximum load during the day will be due to the coincidence of the demand for power (50 H.P.), for heating (28 H.P.), and for cooking (20 H.P.) and will amount to ninety-eight horse-power. The maximum load on the power station during the evening will be due to the coincidence of the demand for lighting (27 H.P.) for heating (24 H.P.) and for cooking (50 H.P.) and will amount to one hundred and one horsepower.

If, however, electric cooking, is not attempted the maximum demand at any time need not exceed fifty horsepower provided that most of the ironing, during the shearing season, is done in the evening, and that the number of shearing stands in operation, simultaneously, is arranged not to exceed seventy.

A.M.I.C.E. A.M.I.E.E.

These estimates of the power to be provided we consider are liberal. The maximum demand for current by Havelock North, for instance, does not exceed fifty horsepower, while their average consumption is about seven to eight horsepower. There is not much current used there, however, for power or heating.

Power Development.
The two waterfalls investigated on the otukarara Stream are about half a mile apart. The first commences at the Patea Road and extends over a distance of fifteen chains providing a total fall of eighty feet. The second has a fall of forty-four feet, most of which occurs in one drop. The volume of water below this fall was measured, on the 8th. inst, over a gauging weir, and found to be two hundred and ten cubic feet per minute. The amount of water at the upper falls is slightly less. Two hundred and ten cubic feet of water per minute will develop in an efficient turbine three-tenths of a horsepower for every foot of fall. It is evident that it will be necessary to conserve the water by means of a dam built across the stream. Without a dam the water would be running to waste except for the few hours per day during the periods of maximum demand. With a dam this water would be conserved for use, later on in the day, to meet a much greater maximum demand. In a large hydro-electric station where the number of turbines in operation is varied in accordance with the power required, the addition of a dam will permit the output to be increased in the same ratio as the maximum demand bears to the average. But in a small non-attendant plant where the capacity of the generating machinery is not adjusted to suit the demand the same high efficiency cannot be obtained. For the amount of water consumed by a large turbine during the night when practically no current is required is much greater than that taken by a small turbine of a capacity commensurate with the power required. For this reason we do not consider it advisable to instal a turbine of greater capacity than two and a half times the average power available from the fall.

A.M.I.C.E. A.M.I.E.E.

We have carefully estimated the cost of developing the upper falls, shown as Proposal No. 1 on the accompanying plan; the lower falls, shown as Proposal No. 2; and of utilising the total fall available in the stream from the Patea Road to the junction of the stream with its other branch about three-quarters of a mile lower down. This development is shown as Proposal No. 3, and the total fall is one hundred an [and] seventy-eight foot.

No. 1 Proposal.
A concrete dam would be constructed just above the road and the water conveyed through eighteen inch pipes to a small concrete tank, near the old mill site, on the top of the right bank of the stream. Thence water would be fed through fifteen inch steel pipes laid in concrete across the bed of the stream to a turbine of fifty-five horsepower. This would be situated in a power house, built above flood level, at the bend at the foot of the falls on the left bank of the stream. The right side is subject to slips and is unsuitable as a site for a power house. The cost of this development, shown in detail in the attached schedule, we estimate, would be £7,299.

No. 2 Proposal.
The dam would be built on the natural weir of shell-rock about one and a half chains above the falls. A race out across the rocky point would convey the water to a turbine of thirty-five horsepower set in a concrete penstock about a chain and a half below the falls. We estimate that this development would cost £6,359.

No. 3 Proposal.
To allow the water to be carried in an open race across the flat above the left bank of the stream, it is necessary, not only to have the intake about seven chains above the road, but also to obtain additional elevation by means of a dam. It is advisable to convey the water for the first twenty-eight chains through concrete pipes to avoid not only damage by floods, but also danger from slips which would be accentuated by carrying an open water race along a bench such as would be necessary in this first

A.M.I.C.E. A.M.I.E.E.

section. Once the water is on the top it can be carried in an open race to a storage basin, excavated on the flat, where shown on the plan. Thence the water is fed to the turbine of one hundred and ten horsepower through a pipe line similar to that described in No. 1 proposal. The storage basin should be as close to the turbine as the natural conditions will allow, for then the water conduit, from the intake, is required to carry only the average, instead of the maximum rate of consumption of water by the turbine.

Additional fall is obtained by constructing the power house below the junction of the streams as shown. The estimated cost of this development, as shown in detail on the attached schedule is £10,293.

The capacity of any of these schemes could be increased considerably by the installation of a larger turbine and also of a small generating set of about 15 horsepower, which if run during the night would prevent the waste of water that occurs in running a large turbine on light load. The working expenses would be greater, as an attendant would have to be on hand to change the load from one machine to the other. As the additional power can be obtained more cheaply by utilising a greater fall, we consider that, at present, there is nothing to warrant the adoption of such means of increasing the output.

The dam in No. 2 Proposal is likely to lose much of its capacity through slips occuring in the gorge. This trouble would not be so serious in No. 1 proposal as the stream changes in character above the road. The dam in No. 3 proposal is required as a diverting weir and not for storage.

No standbye [standby] plant has been allowed for, as it is found that any “shutdowns” that occur are of such short duration that this additional expense is not warranted.

A.M.I.C.E. A.M.I.E.E.

All the schemes have been designed to run for long periods without attendance. A bi-weekly visit to the power station is found sufficient for the successful operation of similar undertakings. An engineer, however, will be required to manage and generally look after the installation, read meters, collect revenue, instal motors &o., make repairs when necessary &o. We have therefore debited half his salary against the cost of generation.

No. 2 proposal is suitable for lighting, and for [a] small motors, while No. 1 proposal would supply all requirements except cooking. No. 3 proposal would involve an additional annual charge of £216. The revenue derivable from cooking would certainly exceed this sum.

Annual Expenditure for Generation.
As is shown in the attached schedule the annual generating expenses, including capital charges, attendance and maintenance are £654, £583, and £870 for Nos. 1, 2 & 3 proposals respectively, which is equivalent to £11.8, £16.6 & £7.9 respectively per horsepower of maximum output. The Govt’s price for electricity supplied in bulk to Power Boards [Handwritten –  from Hora Hora] will be £7.5 per horsepower per annum; and in the event of Waikaremaona [Waikaremoana] being harnessed, we consider that if electricity were bought in bulk by your district, the price would be at least £10 per H.P.L per year, owing to your distance from the main transmission line.

Transmission & Distribution.
Owing to the distance of transmission alternating current of standard frequency and pressure would be adopted. Ordinary galvanised fencing wire would make a suitable conductor for the current if transmitted at 11,000 volts.

The consumers would be supplied in groups from pole transformers, which would reduce the pressure to 230, volts for lighting and heating and 400 [?] volts for power.

A.M.I.C.E. A.M.I.E.E.

The route of the transmission line should follow generally the main coach road as shown on plan No. 2.

The cost of the transmission and distribution system, together with service connections and meters, we estimate, would be £12, 158. The annual expenditure for transmission and distribution would be £1086 as shown in detail in the attached schedule.

The total annual expenditure, including capital charges, maintenance and attendance would amount to £1,956.

Assuming that the current is generally and freely used for all purposes we estimate that a revenue equal to the expenditure can be obtained without adopting high charges.

The settlers houses could be supplied at £10 per year, and stations at £25. This would be equivalent to about 9d. per unit. To run four lights with a benzine generating set would cost £16 per annum for fuel alone. [Handwritten – plus installation about 2/5/- per light]

Irons could be supplied at £3 per annum, and radiators at £5 per annum.

The charges would be equivalent to the cost of cooking with gas.   [Handwritten – 12£ a year for for a small range   30£ for large]

Energy could be sold at £9 per H.P. per year, provided its use is generally adopted. In country districts supplied from Lake Coleridge the charge is £7 per H.P. per year for small motors.

Our estimate as shown by the attached schedule, for revenue is £2,000.

In an undertaking of this kind it is the amount of possible demand by any consumer on the generating plant that should be made the basis of the price charged. What is sold is not units of energy, but units of plant capacity, which have to be reserved for each particular consumer. We would therefore advise the adoption of

A.M.I.C.E. A.M.I.E.E.

what is known as the “telephone “system of charging for current. This consists of a fixed charge per annum depending on the capacity of the consuming devices that the consumer has connected to the mains, and in addition a small rate for all units consumed as registered by a meter.

Installation Costs.
The cost of wiring a house is usually estimated on the number of lights, controlled by an independent switch, that are installed. At present the price is about 45/- for each such point, with plain fittings and reflector.

Ovens range from £5 to £50 depending on the size. A 5 H.P. motor could be installed complete for £150.

In conclusion, we wish to point out that the cost of the transmission and distribution system is practically independent of the amount of current consumed, within the limits of all ordinary requirements and that the success of the undertaking will depend on the free and general use of the current for all purposes. A canvas of the district would give a conservative estimate as to what extent this condition would be realised.

Yours faithfully,
H.W. Climie & Son,
H R Climie
Assoc. M.Inst.O.E.

Original digital file


Non-commercial use

Attribution-NonCommercial 3.0 New Zealand (CC BY-NC 3.0 NZ)

This work is licensed under a Attribution-NonCommercial 3.0 New Zealand (CC BY-NC 3.0 NZ).


Commercial Use

Please contact us for information about using this material commercially.


Proposed power scheme location on the Otekarara (Otukarara on older maps) Stream (more commonly known as the Willowford Stream), on the corner of Napier-Taihape Road and Willowford Roads, Waiwhare. The property was owned by the Ensor family at the time; in 2020 owned by David and Linda Ward (“Wrekin”).

Business / Organisation

HW Climie and Son

Format of the original

Typed document

Date published

9 March 1920

Creator / Author

  • H Richmond Climie

Accession number


Do you know something about this record?

Please note we cannot verify the accuracy of any information posted by the community.

Supporters and sponsors

We sincerely thank the following businesses and organisations for their support.