This invention relates to the control of water flow and more specifically to a method and apparatus for distributing water. Water distribution systems are a vital part of modern life and now that so many homes and factories are connected to a mains water supply, the challenge of providing a sufficient quantity of water of good quality, at a reasonable cost and meeting legislative requirements is greater than ever.

The form of a water distribution system will vary according to the sources of water available, the possible sites for a treatment plant and options available through natural or artificial means to convey water from its source via a treatment plant to a user. In a typical case water collected in a reservoir may be pumped through pipes and/or passed along a river or canal to a treatment plant from where it may be passed via other storage reservoirs to end users, with pumps again being provided where necessary. There are a multiplicity of different , paths for the water from the initial collection point to the end user and the flow of water is controlled by opening and closing valves and switching pumps off and on. The main cost in such a system is the cost of the electrical power required to run the pumps. In a typical pumping station there will be a plurality of pumps, only

some of which may be operating at any one time. Turning pumps on is a costly exercise and an attempt is therefore made to.rationalize the running of the pumps to prevent them being switched on and off too often, and to run the pumps at times when electricity is less expensive. At the same time, however, allowance must be made for example for breakdown of a pump or any sudden or unexpected change in demand. Thus, simply the control of the pumps in a pumping station is complicated. It is an object of the invention to provide an improved method and apparatus for distributing water.

According to a irst aspect of the invention there is provided a method of distributing water via a water distribution system in which there is at least one reservoir to store water and at least one pump or valve to control transfer of water from one part of the system to another, wherein a central control station is provided at a location remote from parts of the system, the central control station receiving a plurality of input signals and being capable of automatically processing the incoming signals together with data stored in a memory at the control station to produce an operational programme for the system and of generating and transmitting a plurality of output signals in accordance with the operational programme, one of the input signals being information relating to the level of water in the reservoir and one of the output signals being a signal for controlling operation of the pump or valve.

The invention provides a central control station which is able to control many different parts of the system even though they may be remote from one another. In view of the complexity of a water distribution system and the cost of linking together the different parts of the system, the invention might be seen as likely to be disadvantageous. We have found, however, that there are considerable benefits from providing a central control station which is connected to provide a closed loop control of the system. Allowance can be made at such a station for a variable in a first part of the system that has an effect on a second part remote from both the first part and the control station. For example, in the case of a water distribution system supplied from two reser- voirs via respective pumping stations, the number of pumps operating or the period for which they operate in a pumping station associated with the first reservoir may be increased automatically in the event of a deleterious change in quality of the water in the second reservoir. The increase in complexity is not a problem given the power of modern computers and the increased cost of connecting together all the separate parts of the system is far outweighed by the savings in electricity consumption that can be achieved by operating the system more efficiently.

In a water distribution system, water will typically be distributed from its collection point to a multiplicity of end users, which may for example include

thousands of domestic homes as well as factories and other businesses, via a water treatment plant. The central control station may control the flow of water right from its collection point to the end user but alternatively it may control the flow of water either from its collection point to a water treatment plant or from a water treatment plant to the end user.

The "reservoir" referred to above will usually be a service reservoir (storing treated water) or a reservoir of raw water, but it may be any collection of water that serves the purpose of a reservoir, for example, water in a river or in an underground storage means.

Preferably one of the input signals received at the control station is a signal indicative of water quality in the system. Various tests for measuring water quality are known and those tests per se do not form part of the invention and will not be described further. There may for example be a monitor at a reservoir or elsewhere in the system monitoring the quality of the water and transmitting a signal indicative of water quality to the central control station. The signal may merely indicate whether the quality is above or below a threshold level or a quantitative measure of the quality may be provided in the signal. Whilst it has been common practice to test water quality it is an especially distinctive and advantageous feature of preferred embodiments of the present invention that they provide for measurement of water quality to be taken into account automatically as

an integral part of the control system, directly affect¬ ing the operation of the system. The test of water quality may involve testing just one variable or several variables: for example the pH, electrical conductivity and/or chlorine content may be tested.

Usually there are a plurality of pumps and the input signals received at the control station include signals indicative of whether or not each pump is operating and/or whether or not each pump is able to operate. At least some of the pumps may be connected in parallel with one another.

There may be a plurality of reservoirs and, then, the input signals preferably include respective signals from each of the reservoirs providing information relating to the level of water in the respective reservoirs.

Usually there are a plurality of valves which control the path of the water through the system. In that case the input signals preferably include respective signals from each of the valves providing information indicating the state of the valve, normally either open or closed. Even if the central control station sends command signals to the valves to change their states and therefore may be able to determine the valve states according to the command signals given, it is useful to have feedback signals from the valves to guard against malfunctions.

The input and output signals may be passed directly

to or from the central control station from or to each individual component (for example, a pump or valve) of the system or they may be passed via a relay station. For example the signals may pass along a common transmission line between the central control station and a relay station and through separate transmission lines from the relay station to the individual components. The signals may be transmitted by various means, for example wireless links using radio waves or microwaves, fibre optics, ordinary telephone lines or dedicated land lines. In addition to receiving information through input signals from different parts of the water control system, the central control station also receives other information and stores it as data in the memory. More particularly the central control station preferably receives meteorological data, which may be forecast information, and preferably generates a forecast of the demand for water. The forecast demand may for example cover the following 24 hours and may be provided frequently, for example at least once a week and prefer¬ ably every 24 hours or more often. The ability of the control station to take account of forecast variations in demand through a 24 hour period and furthermore to take account of changes in that forecast from one day to another is an especially advantageous feature.

The control station may also receive information regarding electricity costs. As has already been mentioned, the cost of electricity for pumps is the main

factor in determining the cost of running a typical water distribution system and it is therefore preferable to run the pumps at times when electricity is compara¬ tively cheap. Under some arrangements electricity costs are varied according to the time of day and/or the day of the week in a regular way and in that case the information regarding electricity costs can be supplied once and then not supplied again until the pattern changes, perhaps months or years later. Under other arrangements, however, electricity costs are varied, for example at hourly or even more frequent intervals, and they are decided only a short time in advance; for example, the costs may be set every day for the following 24 hours with separate costs being allocated to each half hour of the 24 hours; in that case it is preferable that the control station receives information regarding electricity costs frequently, preferably every 24 hours. In the case where the costs vary eight or more times per 24 hours it is preferable to convert the information regarding electricity costs into a notional tariff in which fewer than eight different costs are allocated per 24 hour period, and to provide the notional tariff as input information into the central control station. For example, the information regarding electricity costs may provide a separate figure for each of the 48 half hour periods of a day and that information may be converted into a national tariff where, say, only four different periods, having respective electricity costs allocated

thereto, are provided.

Usually the central control station transmits a plurality of output signals.

Where a plurality of pumps are provided, the output signals preferably include respective command signals for switching on and switching off each of the pumps. Where a plurality of valves are provided, the output signals preferably include respective command signals for opening and closing each valve. It should be understood that the term "valve" is used in the present specification for any device which is able to be altered from a condition in which it allows fluid flow through it to a condition in which it prevents such flow.

The control station in accordance with the first aspect of the invention is capable of operating entirely automatically with the plurality of output signals being transmitted in dependence upon the plurality of input signals and any other input information. It is, however, possible to allow a skilled operator to take part in determination of the output signals given the input signals. For example,- the central control station may produce automatically a proposed programme of operation for the system in accordance with the plurality of input signals and any other input information; it may then be possible for an operator to accept or modify the programme before instructing the central control station to transmit the output signals. Preferably the control station is able to produce a programme of operation

extending into the future for a plurality of hours.

The central control station is thus able to function as a simulator. An operator may suggest a certain proposal, for example to switch on one pump instead of another, or to vary the storage capacities of the service reservoirs or the minimum and maximum water levels in the reservoirs, and the central control station can then produce a programme of operation extending into the future for a plurality of hours based on the modified proposal. The central control station preferably provides an indication of the total estimated cost of electricity for the pumps of a programme of operation.

Thus, according to a second aspect, the present invention provides a method of simulating a water distribution system including at least one reservoir to store water, a plurality of electrically powered pumps to transfer the water from one part of the system to another and a plurality of valves controlling movement of the water in the system, in which a computer is provided with information regarding the operational characteristics of the pumps, minimum and maximum water levels in the reservoir, storage capacity of the reservoir and costs of electricity for the pumps, and the computer generates a programme for the operation of the pumps and the opening and closing of the valves and provides estimates of the electricity costs of running the pumps according to the programme.

According to a third aspect the present invention

provides a method of distributing water via a water distribution system in which there is at least one reservoir to store water, a plurality of pumps to transfer water from one part of the system to another and a plurality of valves to control flow of water from one part of the system to another, wherein a control means is provided for controlling operation of the system, information relating to the quality of the water in the system and to the level of water in the reservoir being transmitted automatically to the control means, the control means also receiving other information including information regarding the cost of electricity for the pumps and generating in dependence upon the received information a forecast of the demand for water and a programme of operation of the system.

The present invention also provides according to the first aspect a water distribution system comprising: at least one reservoir to store water, means for monitoring the level of water in the reservoir and for transmitting a signal containing information regarding the water level, at least one pump to transfer water from one part of the system to another, means for controlling the operation of the pump in accordance with a transmitted signal, a central control station at a location remote from parts of the system, the central control station includ¬ ing a memory for storing data regarding operation of the

system and being arranged to receive a plurality of input signals and to transmit a plurality of output signals, one of the input signals being from the monitoring and transmitting means and one of the output signals being for the pump controlling means, the central control station being capable of generating the output signals automatically in response to the various input signals and stored data.

The system preferably further includes a monitor for monitoring the water quality in the system and for transmitting a signal indicative of water quality to the control station. The signal may indicate whether the quality is above or below a threshold level.

There may be a plurality of pumps. The input signals received at the control station may include signals indicative as to whether or not each pump is operating. The input signals received at the control station may include signals indicative as to whether or not each pump is able to operate. There may be a plurality of reservoirs and the input signals may include respective signals from each of the ,■ reservoirs providing information relating to the level of water in the respective reservoirs.

There may be a plurality of valves which control the path of the water through the system and the input signals may include respective signals from each of the valves providing information indicating the state of the valve.

The central control station is preferably arranged to transmit output signals to both at least one pump and at least one valve. The output signals may include respective command signals for each pump and/or valve. The control station is preferably arranged to operate entirely automatically with the plurality of output signals being transmitted in dependence upon the plurality of input signals and the stored data.

The present invention also provides according to the second aspect an apparatus for simulating a water distribution system including at least one reservoir to store water, a plurality of electrically powered pumps to transfer the water from one part of the system to another and a plurality of valves controlling movement of the water in the system, in which a computer is arranged to receive information regarding the operational charac¬ teristics of the pumps, minimum and maximum levels in the reservoir storage capacity of the reservoir and costs of electricity for the pumps, and to generate from the information a programme for the operation of the pumps and the opening and closing of the valves and to provide estimates of the electricity costs of running the pumps according to the programme.

The present invention also provides according to the third aspect a water distribution system comprising: at least one reservoir to store water, means for monitoring the level of water in the reservoir,

means for monitoring the quality of water in the system, means for transmitting signals including information regarding the level of water in the reservoir and the quality of water in the system, a plurality of pumps for transferring water from one part of the system to another, means for controlling the operation of the pumps in accordance with received signals, a plurality of valves to control flow of water from one part of the system to another, means for controlling the operation of the valves in accordance with received signals, and control means arranged to receive signals from the transmitting means and information regarding the cost of electricity for the pumps, to generate a forecast demand for water and to transmit a plurality of output signals to the pump controlling means and the valve controlling means. The central control station comprises a computer programmed by appropriate software. The precise form of ,■ the software is not a part of the present invention and will not be described in detail. In Section 8.7 (pages 79 and 80) of Information Systems and IT for Managers written by Leonard Capper and published in 1991 by Open University (ISBN 0335 174043), an intelligent knowledge-based system is described and a system of that kind is suitable for use in carrying out the present

invention where the computer is required to store a great deal of information and to carry out operations which may be regarded as reasoning. Such systems are sometimes referred to as expert systems. By way of example certain embodiments of the invention will now be described with reference to the accompanying drawings, of which:

Fig. 1 is a diagram of a first water distribution system, and Fig. 2 is a diagram of a second water distribution system. The system shown in Fig. 1 comprises a first reservoir 1A, and an underground supply available at a borehole IB which in the terminology employed in this specification is also hereinafter referred to as a "reservoir", a pumping station 2, a river 3, a third reservoir 4, a second pumping station 5 and a water treatment plant 6. The various parts of the system are connected together by pipes 7 and valves 8 are provided to control the flow of water through the system.

In operation of the system raw water is collected in the first and second reservoirs 1A and IB, for example from a river flowing into them, ground water draining off hills and/or water in the ground, and is pumped by one or more of pumps 2A, 2B, 2C and 2D into the river 3. Raw water is taken out of the river at a position downstream of where it enters and is either passed directly to the water treatment plant 6 or pumped by one or more of pumps

5A, 5B and 5C into the reservoir 4 from where it passes to the water treatment plant 6. After passing through the water treatment plant the water passes through a further distribution system, for example as shown in Fig. 2, to the end users.

A control unit 9 comprising a computer is sited at the water treatment plant 6 and receives input signals and transmits output signals through a radio transmitter/ receiver 10. The input signals received by the transmitter/receiver 10 are as follows:

(i) signals transmitted from respective level measuring devices 11 in each of the reservoirs 1A, IB and 4 indicating the level of raw water in each reservoir, (ii) signals from respective water quality monitors 12 in each of the reservoirs 1A, IB and 4 and also in the river 3 indicating whether the raw water is above or below a threshold level of quality ("quality" being measured by one or more of the conventional tests used for checking water quality) , (iii) signals from each of the valves 8 indicating the state of each valve, the indication being valve open, valve closed or fault, (iv) signals from each of the pumps 2A to 2D and 5A to 5C indicating the state of each pump, the indication being that a pump is operating, that a pump is capable of operating or that a pump

is not operating and is incapable of operating either because of a fault or because maintenance is being carried out. The signals received by the transmitter/receiver 10 are transmitted by radio transmitters. In the drawing tlie level measuring device and water quality monitor of each reservoir are shown with their own transmitters but of course they may share a common transmitter (relay station) if that is more convenient. Similarly each pumping station has a single transmitter/receiver (relay station) . The transmitter/receivers of the valves are not shown in the drawing but it is to be understood that the valves are connected to either their own respective transmitters/receivers or a transmitter/receiver associated with a pumping station, a reservoir or another valve.

The output signals transmitted by the transmitter/ receiver 10 are as follows:

(i) signals to each of the valves 8 indicating the state to which the valve should change or in which it should remain, (ii) signals to each of the pumps 2A to 2D and 5A to 5C indicating the state to which the pump should change or in which it should remain. All the signals are transmitted over a radio transmission link. It is of course also possible to transmit any of the signals along a cable but in many cases the distances involved are many miles or kilometres

and wireless transmission is preferable.

The control unit 9 also receives and stores, in a memory, data comprising other information regarding the system at the time that the system is first set up. Some of that information is only likely to change in the long term whilst other information will change in the short term. Examples of received information that is likely to change only in the long term are:

(i) the minimum and maximum water levels that can be allowed in each of the reservoirs 1A, IB and 4, (ii) the capacities of the reservoirs at different levels, (iii) characteristics of the river including in particular the time taken for water to flow along the river from its point of introduction to its point of departure, (iv) the output of each pump, and the outputs of given combinations of pumps (m ³ /hour) - if two pumps are operated simultaneously at a pumping station their combined output will be less than the sum of the outputs of each when operating alone and it is therefore necessary to know the outputs of different combinations of pumps, (v) the power consumption of each pump (kW) ,

(vi) the maximum number of pumps at a single pumping station that can be operated at one time (the number may be limited for example because of

the limits on the electricity supply to the pumping station) . Examples of received information that is likely to change in the short term are: (i) the cost of electricity at the pumping station over the next 24 hours, (ii) meteorological information regarding rainfall, temperature, etc. , which may be used to determine water catchment and water replenish- ment information for the next 24 hours, and

(iii) indications of the pumps that will be out of service in the short term for repair or maintenance. The computer is programmed to process all the information it receives and to generate a forecast of the demand for water consumption and a programme of operation for the following 24 hours. The computer can be operated in any one of three modes.

Fully automatic mode In this case the computer receives the input signals and automatically generates output signals in accordance with its predetermined programme of operation. In the event that input signals to the computer arriving while the predetermined programme of operation is proceeding indicate that there is a deviation in the predetermined programme, for example because an input signal shows that the level of reservoir 1A is lower than expected, then

the computer will automatically generate a revised programme of operation which may for example involve taking more water from reservoir IB and less from reservoir 1A or taking some water from reservoir 4 and less from reservoir 1A. Similarly if one of the pumps 2A to 2D or 5A to 5C breaks down the programme of operation can automatically be altered.

Semi-automatic mode

In this case the computer receives the input signals and generates a proposed programme of operation which is displayed to an operator, for example on a VDU and/or a print-out, but does not automatically generate output signals to carry out the programme of operation. If an operator is satisfied with the desired programme of operation then he can instruct the computer to carry out that programme, but if he wishes he may alter an element of the programme, for example to avoid using a particular pump that he knows will require maintenance in the next 24 hours or to raise the amount of water in the river because of some leisure event (for example, canoeing) taking place by increasing the flow along it, and instruct the computer to recalculate an appropriate programme of operation. Once the operator is satisfied with the revised programme of operation, he can instruct the computer to carry out the programme.

In an alternative arrangement, the output signals are not sent by the computer but are sent under the

direct control of the operator in accordance with the programme of operation proposed by the computer.

Off-line mode

In this case the computer is used to simulate operation of the system. The computer may be asked to find the most effective programme for running the system over the next 24 hours or over a longer period such as a week or a month and to generate estimates of the cost of electricity for the pumps. The computer may also be asked to generate a programme for a hypothetical situa¬ tion such as when the electrical supply to a pumping station fails, in order to see for how long the system can continue to meet the demand for water and to what extent the cost of electricity for the pumps is increased. In the off-line mode it is also possible to investigate how the running of the system would be affected if certain pumps were added in place of or in addition to others having different ratings and what effect that would have on the cost of electricity. Thus in the off-line mode the computer can act as a very effective aid to planning and design of the system.

In either the automatic or semi-automatic mode, an operator may at any time obtain information via a VDU and/or a print-out of the current status of all the parts of the water system showing for example which pumps are operating, which valves are open or closed and which

pumps and valves are inoperable because they are being serviced or are faulty. The operator can also obtain historical information relating to any part of the system and/or showing an estimate of the cost of the electricity consumed by the pumps and can obtain a forecast for the future costs of operation over a chosen period.

Fig. 2 shows another water distribution system. Whereas the system of Fig. 1 ends at the water treatment plant, the system of Fig. 2 begins at the water treatment plant and ends at the end user which in this case is an industrial estate.

The system shown in Fig. 2 comprises a pumping station 20 having four pumps 20A, 2OB, 20C and 20D, a further pump 21, and service reservoirs 22, 23A and 23B. The various parts of the system are connected together by pipes 24 and valves 25 are provided to control the flow of water through the system. In operation of the system treated water from a water treatment plant 26 is supplied through pipe 24A either to the pumping station 20 or to the reservoir 22. Water from the pumping station is passed to one of the reservoirs 23A and 23B or directly along the pipe 24B to the industrial estate. Water from reservoir 22 is pumped by the pump 21 to one of the reservoirs 23A and 23B or directly along the pipe 24B to the industrial estate.

A control unit 29 comprising a computer is sited at the water treatment plant 26 and receives input signals and transmits output signals through a transmitter/

receiver 30. The input signals received by the transmitter/receiver 30 are signals relating to reservoir levels, water quality and the states of the pumps and valves and the output signals transmitted to the transmitter/receiver 30 are command signals for the vaives and pumps, as described with reference to Fig. 1.

The operation of the system of Fig. 2 is clearly analogous to Fig. 1 and will not be described further. The water distribution systems described above ensure a reliable water supply at relatively low opera¬ tional costs. The systems are able to take advantage of the knowledge and experience of skilled operators in the setting up of the control centre but are not thereafter dependent upon those operators. The control centre can react immediately and automatically to any unexpected events such as a failure in a pump or a burst pipe to present a modified programme of operation. In the uncommon event that the control centre is unable to propose a programme of operation meeting its minimum requirements (for example because all water supplies are of inadequate quality) it will draw the attention of an operator who can manually modify the operation plan.

The control centre can be used not only on-line but also off-line using data from its internal database to simulate certain conditions.